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MD-022A.jpg

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gross image

  • firm swelling: subcutaneous

Leg, subcutaneous tissue

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In some cases of Marek's disease, large subcutaneous lymphomas may be observed throughout the body (shown here in the leg on the left). A normal leg is shown on the right for comparison.

MD-004A.jpg

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clinical sign

paralysis (legs), dyspnea

  • dyspnea
  • paralysis: whole body

Leg

Marek's Disease

chicken (Gallus gallus)

Clinical Description

The most common form of Marek’s disease is the lymphoproliferative syndrome, wherein mononuclear infiltrates develop in peripheral nerves and organs. The clinical signs associated with this condition are non-specific and relate to the location of the lesions. A variety of neurologic signs can develop including spastic paralysis of the limbs, exhibited here. This chicken is also gasping, a sign associated with the paralysis of the respiratory and digestive systems.

MD-021A.jpg

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gross image

  • crusts, skin
  • hyperemia: skin
  • ulcer: skin

Leg, skin

Marek's Disease

chicken (Gallus gallus)

Clinical Description

“Alabama red leg” is a Marek's disease syndrome associated with tumors in broiler breeders and roosters. Lesions consist of severe hyperemia of the skin of the shanks that can eventually become ulcerated and have brown crusts.

MD-003A.jpg

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clinical sign

Paralysis, paresis (legs)

  • paralysis: whole body
  • paraparesis

Leg

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Paresis and paralysis are usually asymmetrical, reflecting the asymmetrical peripheral nerve involvement of Marek’s disease. This clinical sign often manifests itself with the bird stretching one leg forward and one leg backward, as seen here.

MD-114A.jpg

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gross image

  • enlarged feather follicles: skin

skin

Marek's Disease

Unknown

Clinical Description

In Marek's disease, the skin around the feather follicles may become raised and roughened (shown here), due to epithelial cell proliferation.

pullet2close

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clinical sign

Paralysis (legs)

  • paralysis: whole body

Leg

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Spastic paralysis of the legs associated with peripheral nerve involvement in Marek's disease.

MD-016A.jpg

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gross image

  • enlarged feather follicles: skin

skin

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In some cases of Marek’s disease, only a few feather tracts may be affected, as shown here. In advanced cases, most of the feather follicles of the entire body may be affected due to lymphoid infiltration.

MD-005A.jpg

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clinical sign

opisthotonus

  • opisthotonus

head, neck

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In Marek's disease, opisthotonus (backwards extension of the head and neck), torticollis (lateral twisting of the head and neck), and other nervous signs are sometimes observed.

MD-116A.jpg

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gross image

  • enlarged feather follicles: skin

skin

Marek's Disease

Unknown

Clinical Description

Detailed view of the lymphoproliferative skin lesions associated with Marek’s disease.

Copy of LAYER

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clinical sign

Torticollis (head and neck)

  • torticollis

head, neck

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Neurologic signs in Marek's disease may include torticollis, shown here.

MD-120A.jpg

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gross image

  • enlarged feather follicles: skin

skin

Marek's Disease

Unknown

Clinical Description

Detailed view of the lymphoproliferative skin lesions associated with Marek’s disease.

Broilertorticolis

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clinical sign

torticollis (head and neck)

  • torticollis

head, neck

Marek's Disease

chicken (Gallus gallus)

Clinical Description

This chicken, infected with Marek's disease virus, is exhibiting torticollis, a lateral twisting of the head and neck.

MD-020A.jpg

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gross image

  • enlarged feather follicles: skin

skin

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek's disease may involve individual feather follicles, as observed in this chicken exhibiting swelling of the follicles.

MD-221A.jpg

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clinical sign

paralysis (neck)

  • paralysis: whole body

neck

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Other nervous signs associated with Marek’s disease may include neck paralysis, shown here.

MD-019A.jpg

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gross image

  • nodules: skin

skin

Marek's Disease

Unknown

Clinical Description

In Marek's disease, skin lesions may coalesce into large patches of tumors.

MD-108A.jpg

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clinical sign

paralysis

  • paralysis: whole body

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In Marek's disease, transient paralysis can occur and is caused by temporary vasculitis and edema in the brain. The condition typically persists for 1-2 days, after which time the chickens will experience a rapid and total recovery. Later, infected chickens may develop MD lymphomas with clinical signs reflecting tissue involvement.

MD-006A.jpg

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clinical sign

Paralysis (legs, neck), ataxia

  • ataxia
  • paralysis: whole body

Leg, neck

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In transient paralysis syndrome, a form of Marek’s disease, chickens may exhibit ataxia and flaccid paralysis of the neck and limbs.

MD-012A.jpg

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gross image

  • abnormal iris pigmentation
  • abnormal pupillary shape

eye, iris, pupil

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Ocular lesions, sometimes associated with Marek's disease, is usually due to lymphoid infiltration of iris that causes white discoloration. The pupil is often irregular (as shown here) and does not respond to changes of light. A normal eye is on the left.

MD-024A.jpg

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gross image

  • abnormal iris pigmentation
  • abnormal pupillary shape

eye, iris, pupil

Marek's Disease

Unknown

Clinical Description

Marek's disease infiltration of the eyes. A normal eye is shown in the center for comparison. Note, the eyes on the left and right have lighter colored irises and the iris/pupil shape is irregular. Both findings are related to lymphoid infiltration of the iris.

SILKY2

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clinical sign

wings, legs

  • paralysis: whole body

Leg, Wing

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Paralysis of the legs and wings caused by lymphomas involving the peripheral nerves, resulting from Marek's disease infection.

MD-031A.jpg

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gross image

  • white infiltrates: peripheral nerves

peripheral nerves

Marek's Disease

Unknown

Clinical Description

In Marek's disease, lymphomatous infiltrates may occur in any peripheral nerves. These infiltrations can be somewhat subtle at times and comparing the right and left sides of the paired nerves is often helpful.

MD-109A.jpg

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clinical sign

Paralysis, paresis (legs)

  • paralysis: whole body
  • paraparesis

Leg

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Paresis and paralysis are usually asymmetrical, reflecting the asymmetrical peripheral nerve involvement of Marek’s disease. This clinical sign often manifests itself with the bird stretching one leg forward and one leg backward, as seen here.

MD-105A.jpg

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clinical sign

depression, diarrhea

  • diarrhea
  • generalized depression

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Some chickens with Marek's disease may exhibit vague clinical signs such as depression, anorexia, weight loss, and diarrhea, as shown here. These signs are often related to visceral infiltrations of neoplastic cells.

MD-026A.jpg

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gross image

  • enlargements: peripheral nerves

peripheral nerves

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Often the nerve plexi are involved in lymphoid infiltration in Marek's disease. Look for lesions in the ischiadic/sciatic and brachial nerve plexi. Here the left ischadic plexus is asymmetrically enlarged. Comparing the symmetry of the paired right and left nerves is often the best way to distinguish such abnormalities.

MD-018A.jpg

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clinical sign

nodules and ulcers (skin)

  • enlarged feather follicles: skin
  • ulcer: skin

skin

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In Marek's disease, affected feather follicles can become roughened and develop ulcers. These ulcers may develop secondary infections, exacerbated by the immunosuppressive nature of Marek’s disease.

MD-071A.jpg

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gross image

  • white infiltrates: peripheral nerves

peripheral nerves

Marek's Disease

chicken (Gallus gallus)

Clinical Description

On post-mortem examination, gross lesions may be found in peripheral nerves. Here, the vagus nerve on the bottom (black arrow) has a grossly evident focal enlargement caused by Marek’s disease virus.

MD-027A.jpg

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gross image

  • enlargements: peripheral nerves
  • yellow discoloration, peripheral nerves

peripheral nerves

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Peripheral nerves with Marek’s lesions may have edema, loss of cross-striation, and a grey or yellow discoloration. Compare the affected nerve on the left with the glistening white unaffected nerve on the right.

MD-013A.jpg

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clinical sign

swelling (wattles)

  • swelling: wattles

wattles

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Swelling of the wattles (shown here) and combs can also occur in Marek's disease if the lymphomas infiltrate the subcutaneous tissue of these nonfeathered areas.

silkysciaticnervesmd

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gross image

  • enlargements: peripheral nerves
  • yellow discoloration, peripheral nerves

peripheral nerves

Marek's Disease

chicken (Gallus gallus)

Clinical Description

The sciatic nerve on top is enlarged and has a yellow discoloration, while the nerve on the bottom is normal and is shown for comparison.

MD-008A.jpg

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clinical sign

abnormal pupil shape, abnormal iris color

  • abnormal iris pigmentation
  • abnormal pupillary shape

eye, iris

Marek's Disease

chicken (Gallus gallus)

Clinical Description

A comparison between a normal chicken on the right and a chicken infected with Marek's disease on the left. The eye on the left shows how neoplastic cellular infiltration of the iris can produce an abnormal iris shape and color.

MD-025A.jpg

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gross image

  • enlargements: peripheral nerves
  • yellow discoloration, peripheral nerves

peripheral nerves

Marek's Disease

chicken (Gallus gallus)

Clinical Description

The sciatic nerve of a bird infected with Marek's disease has been removed and shown on top with a normal nerve on the bottom for comparison. The affected nerve is enlarged, yellowish, translucent and has a loss of cross-striations.

MD-007A.jpg

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clinical sign

abnormal pupil shape, abnormal iris color

  • abnormal iris pigmentation
  • abnormal pupillary shape

eye, iris, pupil

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek’s disease may be associated with unilateral or bilateral ocular abnormalities. The most common signs observed are changes in iris color and shape of iris/pupil (shown here), caused by lymphoid infiltration.

silkybraquialplexus

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gross image

  • white infiltrates: peripheral nerves

peripheral nerves

Marek's Disease

Unknown

Clinical Description

The sciatic (ischiadic) nerve on the left has an enlarged sciatic plexus, while the corresponding nerve on the right is normal.

MD-009A.jpg

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clinical sign

miosis (pupil)

  • miosis

eye, pupil

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Lymphoid infiltration of the iris may interfere with normal pupil dilation and constriction. The miotic pupil, shown here, prevents accommodation to changes in lighting conditions.

MD-033A.jpg

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gross image

  • white infiltrates: peripheral nerves

peripheral nerves

Marek's Disease

chicken (Gallus gallus)

Clinical Description

The peripheral nerves have been fully removed to allow a comparison between normal (top) and nerves (bottom) in a chicken infected with Marek's disease.

MD-034A.jpg

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gross image

  • enlargement: spinal cord

spinal cord

Marek's Disease

chicken (Gallus gallus)

Clinical Description

The dorsal root ganglia from bird with Marek's disease may be enlarged, but examination requires careful dissection of the spinal cord and its nerve trunks.

SILKY1

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clinical sign

paralysis

  • paralysis: legs

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Leg paralysis associated with peripheral nerve involvement in Marek's disease.

MD-042A.jpg

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gross image

  • white infiltrates: lungs
  • white neoplastic infiltrates: heart

heart, lungs

Marek's Disease

chicken (Gallus gallus)

Clinical Description

The more virulent strains of Marek’s disease can be associated with lymphomas on virtually any visceral organ. Here, the heart and lung of an infected chicken is shown on top and compared to the corresponding normal organs on the bottom. When examining a flock of birds infected with the visceral form of Marek’s, usually multiple organs or tissues are involved.

Copy of LUNG1

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gross image

  • white infiltrates: lungs

lungs

Marek's Disease

Unknown

Clinical Description

In this photo, taken from a bird infected with Marek's disease, multiple lymphomatous lesions are visible in the lungs.

MD-154A.jpg

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gross image

  • white infiltrates: lungs

lungs

Marek's Disease

Unknown

Clinical Description

Marek's disease tumors in the lungs.

MD-152A.jpg

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gross image

  • white infiltrates: lungs

lungs

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek's disease tumors in the lungs.

MD-036A.jpg

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gross image

  • white infiltrates: oropharynx

oropharynx

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek's disease tumors in the oropharynx.

MD-044A.jpg

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gross image

  • white focal lesions: liver
  • white infiltrates: lungs
  • white infiltrates: spleen

liver, lungs, spleen

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Lymphomas can develop on virtually any organ. Here the liver, lungs, and spleen all show white Marek’s lesions.

MD-230A.jpg

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gross image

  • pale areas in muscle wall: proventriculus

proventriculus

Marek's Disease

chicken (Gallus gallus)

Clinical Description

White Marek’s disease lesions in the wall of the proventriculus.

MD-231A.jpg

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gross image

  • white infiltrates: proventriculus

proventriculus

Marek's Disease

Unknown

Clinical Description

The proventriculus has been opened to show the nodular lesions in the muscle wall of a bird infected with Marek's disease.

MD-062A.jpg

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gross image

  • white infiltrates: proventriculus

proventriculus

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In this bird infected with Marek's disease, there is a more diffuse infiltration of the mucosa of the proventriculus.

MD-047A.jpg

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  • proventriculus

proventriculus

Marek's Disease

chicken (Gallus gallus)

Clinical Description

A nodular lymphoma in the mucosa of the proventriculus (organ on the left).

MD-057A.jpg

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gross image

  • pale areas in muscle wall: gizzard

ventriculus (gizzard)

Marek's Disease

Unknown

Clinical Description

A focal lymphoma in the incised wall of the gizzard caused by Marek's disease.

MD-049A.jpg

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gross image

  • nodule: gizzard

ventriculus (gizzard)

Marek's Disease

Unknown

Clinical Description

A lymphoma lesion in the wall of the gizzard in a bird infected with Marek's disease.

MD-276A.jpg

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gross image

  • white focal lesions: liver

liver

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek's disease tumors in the liver.

MD-065A.jpg

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gross image

  • enlargement: kidneys
  • pale discoloration: kidneys

kidney

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek’s disease visceral lymphoma can also produce a more diffuse lesion. Organs, such as this kidney, may become diffusely enlarged, are sometimes firm on palpation, and may have white to grey areas of discoloration, as seen here.

MD-060A.jpg

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gross image

  • white infiltrates: kidneys

kidney

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek's disease tumors in the kidneys.

Copy of kidneytumor+urol

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gross image

  • enlargement: kidneys
  • white infiltrates: kidneys

kidney

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Lymphomatous lesions in the kidney caused by Marek's disease.

MD-066A.jpg

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gross image

  • white infiltrates: kidneys

kidney

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In this photo, taken from a bird infected with Marek's disease, MD tumors are visible in the kidneys.

MD-236A.jpg

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gross image

  • atrophy: thymus gland
  • enlargement: spleen
  • premature atrophy: bursa of Fabricius

bursa of Fabricius, spleen, thymus gland

Marek's Disease

chicken (Gallus gallus)

Clinical Description

The degree of visceral tumor involvement in Marek's disease varies by virus strain and the genetic line of chicken. In this image the spleen, bursa, and thymus of 3 chickens infected with different strains of MD is shown. A normal control is shown on top for comparison. Note that the more virulent strain, presented on the bottom row, was associated with a greater degree of bursal and thymic atrophy.

MD-043A.jpg

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gross image

  • enlargement: spleen
  • white infiltrates: spleen

spleen

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Here, a comparison of a normal spleen and a spleen affected by Marek’s disease shows splenic enlargement as well as the characteristic white lymphoma lesions scattered throughout the organ.

SPLEENC2

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gross image

  • enlargement: spleen
  • white infiltrates: spleen

spleen

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Splenomegaly with lymphomatous lesions caused by Marek's disease.

MD-138A.jpg

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gross image

  • abnormal color: spleen

spleen

Marek's Disease

chicken (Gallus gallus)

Clinical Description

A detailed view of a spleen infiltrated by Marek's disease lymphomas, giving the organ a mottled white appearance.

MD-141A.jpg

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gross image

  • white infiltrates: spleen

spleen

Marek's Disease

chicken (Gallus gallus)

Clinical Description

in Marek's disease, organ infiltrates can be focal, as seen in this spleen.

MD-142A.jpg

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gross image

  • white infiltrates: spleen

spleen

Marek's Disease

Unknown

Clinical Description

Alternatively, organ infiltrates can be more diffuse, as seen in this spleen from a bird infected with Marek's disease.

MD-064A.jpg

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gross image

  • nodules: ovary

ovary

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek's disease tumors in the ovary.

MD-054A.jpg

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gross image

  • white neoplastic infiltrates: heart

epicardium, heart

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In this photo, taken from a bird infected with Marek's disease, MD tumors are visible in the epicardium of the heart.

MD-050A.jpg

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gross image

  • white infiltrates: intestines

intestine

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek's disease tumors distributed throughout the entire gastrointestinal tract.

MD-103A.jpg

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gross image

  • white infiltrates: intestines

intestine, jejunum

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In this photo, Marek's disease tumors have infiltrated the jejunum and surrounding mesentery.

MD-051A.jpg

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gross image

  • nodules: intestines

intestine

Marek's Disease

chicken (Gallus gallus)

Clinical Description

This intestinal lesion, caused by Marek’s disease, demonstrates a nodular type of lymphoma. When nodular tumors occur, their borders are firmly associated with the surrounding tissue.

Copy of Image001

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gross image

  • white infiltrates: pancreas

pancreas

Marek's Disease

Unknown

Clinical Description

A large number of tumors in the pancreas of a bird infected with Marek's disease.

MD-101A.jpg

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gross image

  • white infiltrates: intestines

intestine

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Marek's disease tumors in the intestines.

MD-160A.jpg

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gross image

  • white infiltrates: pancreas

pancreas

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In this photo, Marek's disease tumors have infiltrated the pancreas.

MD-039A.jpg

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gross image

  • white infiltrates: pectoral muscles

pectoral muscles

Marek's Disease

Unknown

Clinical Description

Marek's disease tumors found in the pectoral muscles.

MD-246A.jpg

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gross image

  • atherosclerosis: vessels

vessels

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Atherosclerosis (fatty proliferation on vessels) may occur in chickens infected with some strains of Marek's disease. This image shows artherosclerosis of blood vessels on the surface of the gizzard.

MD-069A.jpg

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gross image

  • nodules: ovary

kidney, ovary

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In Marek's disease, as the nodules on organs enlarge, as shown on this kidney and ovary, the normal architecture of the organ is destroyed and sometimes areas of tissue necrosis can occur.

MD-068A.jpg

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gross image

  • nodules: ovary

ovary

Marek's Disease

Unknown

Clinical Description

Marek's disease tumors in the ovary.

Bursalatrophy

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  • premature atrophy: bursa of Fabricius

bursa of Fabricius

Marek's Disease

chicken (Gallus gallus)

Clinical Description

There is premature atrophy of the bursa induced by Marek's disease virus.

MD-073A.jpg

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gross image

  • premature atrophy: bursa of Fabricius

bursa of Fabricius

Marek's Disease

chicken (Gallus gallus)

Clinical Description

In Marek’s disease, bursal atrophy is often noticeable in young birds. This finding is not pathognomonic for MD, since it may occur in many other diseases. The bursa on the right is from a normal bird while the bursa on the left is from an MD infected bird.

MD-074A.jpg

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gross image

  • focal infiltration: bursa of Fabricius

bursa of Fabricius

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Tumors may occasionally occur in the Bursa in Marek's disease. These tumors are diffuse in nature, involving the entire plicae. The Bursa on the left has a diffuse tumor involving several plicae, with focal areas of necrosis that should not be confused with a focal tumor. The Bursa on the right is from a normal bird.

MD-196A.jpg

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gross image

  • enlargement: testes

testes

Marek's Disease

chicken (Gallus gallus)

Clinical Description

The teste in the bottom of this photo shows a tumor, resulting from Marek's disease, causing asymmetrical enlargement of the gonad.

MD-190A.jpg

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gross image

  • enlargement: testes

testes

Marek's Disease

chicken (Gallus gallus)

Clinical Description

MD tumors in the testes.

MD-083A.jpg

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  • pectoral muscles

pectoral muscles

Marek's Disease

chicken (Gallus gallus)

Clinical Description

Large lymphoid tumor in the deep pectoral muscle of this chicken infected with Marek's disease.

MD-070A.jpg

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gross image

Marek's Disease

other

Clinical Description

Marek’s disease virus is primarily transmitted from chicken-to-chicken through inhalation of contaminated dust and dander as well as direct contact between chickens. However, darkling beetles (Alphitobius diaperinus) can be a carrier of Marek’s disease virus in the poultry house.

CoelomicCavity1

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normal

heart, liver

Normal Reference

chicken (Gallus gallus)

Clinical Description

With the bird in dorsal recumbency, the walls of the right atrium and ventricle are positioned on top. After death, the atria often expand with blood and can appear quite enlarged. The great vessels can be seen entering the base of the heart. The heart muscle should be reddish-brown in color. A variable amount of fat will be present in the coronary grooves. If the bird is emaciated, this fat may be absent or have undergone serous atrophy, resulting in a gelatinous, wet appearance. Look for any external lesions on the epicardial surface of the heart or on the surrounding fat.

CoelomicCavity3

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normal

heart

Normal Reference

chicken (Gallus gallus)

Clinical Description

With the bird in dorsal recumbency, the walls of the right atrium and ventricle are positioned on top. After death, the atria often expand with blood and can appear quite enlarged. The great vessels can be seen entering the base of the heart. The heart muscle should be reddish-brown in color. A variable amount of fat will be present in the coronary grooves. If the bird is emaciated, this fat may be absent or have undergone serous atrophy, resulting in a gelatinous, wet appearance. Look for any external lesions on the epicardial surface of the heart or on the surrounding fat.

Heart1

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normal

heart

Normal Reference

chicken (Gallus gallus)

Clinical Description

The heart muscle should be reddish-brown in color. A variable amount of fat will be present in the coronary grooves. If the bird is emaciated, this fat may be absent or have undergone serous atrophy, resulting in a gelatinous, wet appearance. Look for any external lesions on the epicardial surface of the heart or on the surrounding fat.

Heart3

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normal

heart

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the left side of the heart.

Heart7

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normal

heart

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the apex of the heart.

Heart11

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normal

heart

Normal Reference

chicken (Gallus gallus)

Clinical Description

The bottom 1/3 of the apex of the heart has been removed. This view allows the thickness of the ventricular walls and septum to be assessed. The right ventricular free wall should be approximately 1/3 to 1/2 the thickness of the intraventricular septum and the left ventricular free wall. In the normal heart, the lumina of the ventricles should be small and there should be negligible space between the walls of the ventriculae and the septum. In cardiac diseases, such as pulmonary hypertension or congenital defects, this space will be widened.

Heart8

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normal

heart, right atrioventricular valve

Normal Reference

chicken (Gallus gallus)

Clinical Description

In this view, the chambers of the right atrium and ventricle have been opened by making a cut up the right ventricular free wall. Once opened, the right atrioventricular valve and endocardium are exposed. The septal leaf of the right valve is normally very muscular.

Heart9

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normal

heart, left atrioventricular valve

Normal Reference

chicken (Gallus gallus)

Clinical Description

In this view, the chambers of the left atrium and ventricle have been opened by making a cut up the left ventricular free wall. The left atrioventricular valve is normally thin and smooth.

Heart10

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normal

aortic valve, heart

Normal Reference

chicken (Gallus gallus)

Clinical Description

The aorta has been opened by inserting scissors under the left atrioventricular valve and cutting upward. The normal lumen of the aorta, as seen here, is creamy white and the leaflets of the aortic valve are uniform and very thin.

18_liver

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liver

Normal Reference

chicken (Gallus gallus)

Clinical Description

The liver is separated into a right and left lobe, as seen here, attached at the base. The right hepatic lobe is slightly larger than the left and the liver margins should come to a thin crisp edge.

liver2

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liver

Normal Reference

chicken (Gallus gallus)

Clinical Description

In domestic birds, the left lobe has a fissure running along its surface, dividing it into 2 parts.

liver1

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liver

Normal Reference

chicken (Gallus gallus)

Clinical Description

The liver is separated into a right and left lobe, as seen here, attached at the base. The right hepatic lobe is slightly larger than the left and the liver margins should come to a thin crisp edge.

liver3

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liver

Normal Reference

chicken (Gallus gallus)

Clinical Description

The overall size of the liver is variable, often extending beyond the edge of the sternum. To identify hepatomegaly, look at the liver margins. Blunted or thickened margins are a sign of an enlarged liver.

liver4

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liver

Normal Reference

chicken (Gallus gallus)

Clinical Description

Healthy hepatic parenchyma should be somewhat firm on palpation and have a smooth and glistening appearance. The color of the liver can vary depending on the nutritional state of the bird. Generally, the liver is reddish-brown but it can be light brown or even slightly yellow, depending on the fat content in the diet. However, a very yellow liver is an abnormal finding, except in chicks between 1 to 5 days of age.

liver5

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liver

Normal Reference

chicken (Gallus gallus)

Clinical Description

Healthy hepatic parenchyma should be somewhat firm on palpation and have a smooth and glistening appearance. The color of the liver can vary depending on the nutritional state of the bird. Generally, the liver is reddish-brown but it can be light brown or even slightly yellow, depending on the fat content in the diet. However, a very yellow liver is an abnormal finding, except in chicks between 1 to 5 days of age.

gallbladder1

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gallbladder

Normal Reference

chicken (Gallus gallus)

Clinical Description

The gallbladder is located on the visceral surface of the right hepatic lobe. It is normally dark green in color, due to the bile located within the lumen of this thin-walled structure. During autolysis, bile pigments may leak out of the gallbladder, staining the adjacent hepatic tissues yellow to green. This bile inbibition is a normal part of autolysis and should not be confused with a lesion. Similar staining can also occur in the ascending duodenum, adjacent to the area where the bile and pancreatic ducts empty. The size of the gallbladder is variable and may be enlarged in birds that are off-feed.

gallbladder2

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gallbladder

Normal Reference

chicken (Gallus gallus)

Clinical Description

The gallbladder is located on the visceral surface of the right hepatic lobe. It is normally dark green in color, due to the bile located within the lumen of this thin-walled structure. During autolysis, bile pigments may leak out of the gallbladder, staining the adjacent hepatic tissues yellow to green. This bile inbibition is a normal part of autolysis and should not be confused with a lesion. Similar staining can also occur in the ascending duodenum, adjacent to the area where the bile and pancreatic ducts empty. The size of the gallbladder is variable and may be enlarged in birds that are off-feed.

liver6

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liver

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the liver on cross section. As seen here, the color and texture should be uniform. Focal or regional changes may indicate a lesion. It’s normal for a small amount of blood to ooze from the cut surface of the liver.

39_lungs

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lungs

Normal Reference

chicken (Gallus gallus)

Clinical Description

The lungs are tightly adhered to the dorsal rib cage. Their color should be bright pink in a fresh bird but will become increasinly more congested, wet, and dark red with autolysis, as seen here. To assess the lungs, do not over-interpret their color but rather, use a combination of visual inspection and palpation to assess the health of this tissue.

19_air_sacs

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air sacs

Normal Reference

chicken (Gallus gallus)

Clinical Description

The air sacs are thin membranes distributed throughout the body. In a fresh healthy bird, air sacs should be transparent but, as seen here, the membranes will become slightly cloudy after death. In over-conditioned birds, fat may be present on the air sac membranes. Inflammation of the air sacs can result in thickened membranes, opacities, or fibrin deposition. Fluid, foam, or exudate can accumulate between the air sac membranes.

CoelomicCavity2

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proventriculus, ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

The proventriculus is the glandular stomach that lies between the esophagus and the gizzard. It is lined with mucosal glands that secrete digestive enzymes important in food break down. On close inspection, these glands can be seen through the serosal surface, giving it a “honeycomb-like” texture. On palpation the proventriculus should feel turgid and, its surface should be shiny tan. Look for abnormalities such as hemorrhagic lesions or neoplastic infiltrates on its surface.

Proventriculus1

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proventriculus, ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

The serosa of the proventriculus is normally shiny, tan, and has a fine vascular pattern. In a fresh bird, on close inspection, the glands can be visualized through the mucosa. The muscular wall of the proventriculus should feel uniformly turgid. Flaccidity or dilatation of the organ might indicate an improper diet or feeding program, infection, or neuromuscular dysfunction. The external features of the ventriculus, or gizzard, should consist of alternating bands of dark red and light red smooth muscles, forming a roughly circular shape. These muscles may be covered by a thick layer of fat, as seen here. On palpation, the gizzard should be extremely firm. Thinning or laxity in the muscles may indicate inflammation, an improper diet or feeding program, or neuromuscular problems.

Proventriculus3

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proventriculus

Normal Reference

chicken (Gallus gallus)

Clinical Description

The proventriculus in situ.

Pancreas3

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proventriculus, ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

The serosa of the proventriculus is normally shiny, tan, and has a fine vascular pattern. In a fresh bird, on close inspection, the glands can be visualized through the mucosa. The muscular wall of the proventriculus should feel uniformly turgid. Flaccidity or dilatation of the organ might indicate an improper diet or feeding program, infection, or neuromuscular dysfunction. The external features of the ventriculus, or gizzard, should consist of alternating bands of dark red and light red smooth muscles, forming a roughly circular shape. These muscles may be covered by a thick layer of fat. On palpation, the gizzard should be extremely firm. Thinning or laxity in the muscles may indicate inflammation, an improper diet or feeding program, or neuromuscular problems.

Proventriculus6

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proventriculus, ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the serosal surface of the proventriculus and gizzard (ventriculus).

Proventriculus9

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proventriculus

Normal Reference

chicken (Gallus gallus)

Clinical Description

Close-up of the glands of the proventriculus as seen through the outer wall.

Proventriculus10

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proventriculus

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the glands of the proventriculus as seen from the mucosal surface.

Proventriculus11

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proventriculus

Normal Reference

chicken (Gallus gallus)

Clinical Description

Close-up view of the glands of the proventriculus as seen from the mucosal surface.

28_proventriculos

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proventriculus

Normal Reference

chicken (Gallus gallus)

Clinical Description

The contents of the proventriculus can vary from mucoid and creamy to more formed pieces of ingesta, depending on how recently the bird ate.

Proventriculus8

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proventriculus, ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the serosal surface of the proventriculus and gizzard (ventriculus).

Ventriculus5

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ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

The external features of the ventriculus, or gizzard, should consist of alternating bands of dark red and light red smooth muscles, forming a roughly circular shape. These muscles may be covered by a thick layer of fat, as seen here.

Proventriculus7

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proventriculus, ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the left side of the proventriculus and gizzard.

31_gizzard_contents

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ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

The consistency of the gizzard contents will vary depending on the stage of digestion. Generally, it contains fibers and portions of seeds. Additionally, small pebbles, ingested to facilitate the break up of food, may also be present.

Ventriculus6

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ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

The mucosa of the gizzard is covered by a sturdy layer of protein called koilin, which aids in food digestion. The koilin layer should be smooth and uniform. The color may vary from white, to yellow, to green depending on the diet and the degree of bile staining.

Ventriculus7

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ventriculus (gizzard)

Normal Reference

chicken (Gallus gallus)

Clinical Description

Close-up view of the koilin layer of the gizzard (ventriculus).

Spleen1

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spleen

Normal Reference

chicken (Gallus gallus)

Clinical Description

The spleen is located dorsal to the gizzard.

Spleen4

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spleen

Normal Reference

chicken (Gallus gallus)

Clinical Description

On very close inspection, the spleen as a slight stippled pattern.

29_spleen

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spleen

Normal Reference

chicken (Gallus gallus)

Clinical Description

On very close inspection, the spleen as a slight stippled pattern.

Spleen5

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spleen

Normal Reference

chicken (Gallus gallus)

Clinical Description

On very close inspection, the spleen as a slight stippled pattern.

Spleen6

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spleen

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the cut section of the spleen. On cross section, the spleen may appear slightly granular due to the variations in red and white pulp.

Duodenum1

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duodenum

Normal Reference

chicken (Gallus gallus)

Clinical Description

The duodenum has a descending and ascending loop, arranged in a U-shape. The loops are held together by a thin strip of mesentery and surround the pancreas. The appearance of the intestine can vary greatly depending on the post-mortem condition of the bird. In a fresh bird, the serosa of a healthy intestine is usually pink, smooth, and glistening. As the post-mortem interval increases, the intestinal walls will become congested, as seen here, and eventually, even a healthy loop of bowel may appear dark red. However, if the serosa has a dull granular appearance, this can be evidence of inflammation. The normal appearance of the pancreas is pale red or slightly yellow. On close inspection, its glandular nature is evident. Swelling of the pancreas can be recognized if the organ extends beyond its normal location between the loops of the duodenum.

Duodenum4

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duodenum

Normal Reference

chicken (Gallus gallus)

Clinical Description

The walls of the duodenum should be smooth and uniform and offer little resistance to incision. In the proximal duodenum, the ingesta is normally mucoid and pale tan to yellow. Distal to the bile ducts, the ingesta becomes more green in color.

Duodenum3

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duodenum, pancreas

Normal Reference

chicken (Gallus gallus)

Clinical Description

The duodenum has a descending and ascending loop, arranged in a U-shape. The loops are held together by a thin strip of mesentery and surround the pancreas. The appearance of the intestine can vary greatly depending on the post-mortem condition of the bird. In a fresh bird, the serosa of a healthy intestine is usually pink, smooth, and glistening. As the post-mortem interval increases, the intestinal walls will become congested, as seen here, and eventually, even a healthy loop of bowel may appear dark red. However, if the serosa has a dull granular appearance, this can be evidence of inflammation. The normal appearance of the pancreas is pale red or slightly yellow. On close inspection, its glandular nature is evident. Swelling of the pancreas can be recognized if the organ extends beyond its normal location between the loops of the duodenum.

Duodenum2

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duodenum

Normal Reference

chicken (Gallus gallus)

Clinical Description

The duodenum has a descending and ascending loop, arranged in a U-shape. The loops are held together by a thin strip of mesentery and surround the pancreas. The appearance of the intestine can vary greatly depending on the post-mortem condition of the bird. In a fresh bird, the serosa of a healthy intestine is usually pink, smooth, and glistening. As the post-mortem interval increases, the intestinal walls will become congested, as seen here, and eventually, even a healthy loop of bowel may appear dark red. However, if the serosa has a dull granular appearance, this can be evidence of inflammation. The normal appearance of the pancreas is pale red or slightly yellow. On close inspection, its glandular nature is evident. Swelling of the pancreas can be recognized if the organ extends beyond its normal location between the loops of the duodenum.

Pancreas4

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pancreas

Normal Reference

chicken (Gallus gallus)

Clinical Description

The normal appearance of the pancreas is pale red or slightly yellow. On close inspection, its glandular nature is evident. Swelling of the pancreas can be recognized if the organ extends beyond its normal location between the loops of the duodenum.

24_pancreas_texture

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pancreas

Normal Reference

chicken (Gallus gallus)

Clinical Description

On close inspection, the pancreas has a fine glandular texture.

MeckelsDiverticulum1

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Mekel's diverticulum

Normal Reference

chicken (Gallus gallus)

Clinical Description

After 10 days of age, the only remnant of the yolk sac is a small tag of scar tissue, called Meckel’s diverticulum. This tag, located on the antimesenteric side of the intestine, contains lymphoid tissue and is part of the GALT, or Gut Associated Lymphoid Tissue. Meckel’s diverticulum is also an important anatomical landmark, as it is located at the junction between the jejunum and the ileum. Being able to differentiate the jejunum from the ileum is important to generating differentials for intestinal diseases. Some infections, such as coccidiosis, have a predilection for the jejunum and other diseases target the ileum.

MeckelsDiverticulum2

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Mekel's diverticulum

Normal Reference

chicken (Gallus gallus)

Clinical Description

After 10 days of age, the only remnant of the yolk sac is a small tag of scar tissue, called Meckel’s diverticulum. This tag, located on the antimesenteric side of the intestine, contains lymphoid tissue and is part of the GALT, or Gut Associated Lymphoid Tissue. Meckel’s diverticulum is also an important anatomical landmark, as it is located at the junction between the jejunum and the ileum. Being able to differentiate the jejunum from the ileum is important to generating differentials for intestinal diseases. Some infections, such as coccidiosis, have a predilection for the jejunum and other diseases target the ileum.

Cecum1

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ceca

Normal Reference

chicken (Gallus gallus)

Clinical Description

At the junction between the ileum and the descending colon, are two blind-ended sacs known as the ceca. In domestic poultry, the cecae are large structures that bend over themselves, with their apices pointing caudally. The walls should be thin and semi-translucent, allowing the greenish-colored intestinal contents to be visualized within. If the walls are opaque, thin or irregular, infection should be suspected.

Ileum1

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ceca

Normal Reference

chicken (Gallus gallus)

Clinical Description

At the junction between the ileum and the descending colon, are two blind-ended sacs known as the ceca. In domestic poultry, the cecae are large structures that bend over themselves, with their apices pointing caudally. The walls should be thin and semi-translucent, allowing the greenish-colored intestinal contents to be visualized within. If the walls are opaque, thin or irregular, infection should be suspected.

CecalTonsil1

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cecal tonsil

Normal Reference

chicken (Gallus gallus)

Clinical Description

At the base of the ceca, near the junction of the ileum and the descending colon, are 2 important lymphoid structures called cecal tonsils. The tissue here bulges outward slightly as it is thicker and slightly more granular.

CecalTonsil2

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cecal tonsil

Normal Reference

chicken (Gallus gallus)

Clinical Description

At the base of the ceca, near the junction of the ileum and the descending colon, are 2 important lymphoid structures called cecal tonsils. The tissue here bulges outward slightly as it is thicker and slightly more granular.

CecalTonsil3

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cecal tonsil

Normal Reference

chicken (Gallus gallus)

Clinical Description

As demonstrated here, the cecal tonsils should be opened and the mucosa examined closely. This is a common location for lesions to be detected. In inflammatory or neoplastic diseases, the tonsils may be come enlarged and mottled red and tan. In some viral infections, the lymphoid tissue may become necrotic, causing the tonsils to become red.

33_cecaltonsil_mucosa

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cecal tonsil

Normal Reference

chicken (Gallus gallus)

Clinical Description

The cecal tonsil has been opened to show the mucosa. It’s important to examine this area closely for lesions. In inflammatory or neoplastic disease, the cecal tonsils may become enlarged and mottled red and tan. In some viral infections, this lymphoid tissue may become necrotic, causing the tonsils to become red.

CecalTonsil4

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cecal tonsil

Normal Reference

chicken (Gallus gallus)

Clinical Description

As demonstrated here, the cecal tonsils should be opened and the mucosa examined closely. This is a common location for lesions to be detected. In inflammatory or neoplastic diseases, the tonsils may be come enlarged and mottled red and tan. In some viral infections, the lymphoid tissue may become necrotic, causing the tonsils to become red.

Cecum2

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ceca, ileum

Normal Reference

chicken (Gallus gallus)

Clinical Description

The serosa of the ileum should be shiny, tan, and smooth, with no thickening or bulges. Be careful not to over-interpret the color of the intestinal walls as post-mortem congestion and autolysis can quickly turn the intestinal walls red or black. Because the intestinal walls are semi-translucent, look for areas of proliferation or mucosal exudate which can sometimes be visualized through the intestinal wall. At the junction between the ileum and the descending colon, are two blind-ended sacs known as the ceca. In domestic poultry, the cecae are large structures that bend over themselves, with their apices pointing caudally. The walls should be thin and semi-translucent, allowing the greenish-colored intestinal contents to be visualized within. If the walls are opaque, thin or irregular, infection should be suspected.

34_intestinal_lumen

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intestine

Normal Reference

chicken (Gallus gallus)

Clinical Description

The quality of intestinal ingesta can yield important clues about the functional status of the intestines. If the ingesta is normal, as seen here, regardless of the appearance of the intestinal wall, the intestines were likely functioning normal at the time of death. If the content is abnormal, intestinal dysfunction is present. Keep in mind that as the ingesta moves though the intestines, its color and consistency will change. In the jejunum, pictured here, the ingesta becomes slightly thicker and yellow tan in color.

colon1

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ceca

Normal Reference

chicken (Gallus gallus)

Clinical Description

Distal to the ceca, the intestines continue as a short straight tube known as the descending colon. These walls should be smooth and uniform. Look for any dilatations which may indicate an obstruction due to a mechanical blockage, a scar, or another disease process.

35_cloaca

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cloaca

Normal Reference

chicken (Gallus gallus)

Clinical Description

The cloaca is the common chamber for the gastrointestinal, urinary, and reproductive tracts. Here the cloaca has been opened. By the time ingesta enters the cloaca, it should have the normal color and consistency of feces and will be mixed with urates from the urinary system.

Cloaca1

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bursa of Fabricius, cloaca

Normal Reference

chicken (Gallus gallus)

Clinical Description

On the dorsal wall of the cloaca is a diverticulum called the Bursa of Fabricius. This structure is an important lymphoid organ. The shape of the bursa varies with species. In the chicken, it is roughly pear shaped. In ducks, geese and turkeys it is more spindle shaped. The size varies with the age of the bird. It typically reaches its maximum size between 4 to 12 weeks of age, at which time it can weigh up to 4 grams. Normally, the bursa begins to involute when the bird is approximately 3 months of age. By the time the bird reaches sexual maturity, it may no longer be evident on gross examination.

Cloaca2

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bursa of Fabricius

Normal Reference

chicken (Gallus gallus)

Clinical Description

On the dorsal wall of the cloaca is a diverticulum called the Bursa of Fabricius. This structure is an important lymphoid organ. The shape of the bursa varies with species. In the chicken, it is roughly pear shaped. In ducks, geese and turkeys it is more spindle shaped. The size varies with the age of the bird. It typically reaches its maximum size between 4 to 12 weeks of age, at which time it can weigh up to 4 grams. Normally, the bursa begins to involute when the bird is approximately 3 months of age. By the time the bird reaches sexual maturity, it may no longer be evident on gross examination.

Bursa2

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bursa of Fabricius

Normal Reference

chicken (Gallus gallus)

Clinical Description

On the dorsal wall of the cloaca is a diverticulum called the Bursa of Fabricius. This structure is an important lymphoid organ. The shape of the bursa varies with species. In the chicken, it is roughly pear shaped. In ducks, geese and turkeys it is more spindle shaped. The size varies with the age of the bird. It typically reaches its maximum size between 4 to 12 weeks of age, at which time it can weigh up to 4 grams. Normally, the bursa begins to involute when the bird is approximately 3 months of age. By the time the bird reaches sexual maturity, it may no longer be evident on gross examination.

Bursa1

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bursa of Fabricius

Normal Reference

chicken (Gallus gallus)

Clinical Description

On the dorsal wall of the cloaca is a diverticulum called the Bursa of Fabricius. This structure is an important lymphoid organ. The shape of the bursa varies with species. In the chicken, it is roughly pear shaped. In ducks, geese and turkeys it is more spindle shaped. The size varies with the age of the bird. It typically reaches its maximum size between 4 to 12 weeks of age, at which time it can weigh up to 4 grams. Normally, the bursa begins to involute when the bird is approximately 3 months of age. By the time the bird reaches sexual maturity, it may no longer be evident on gross examination.

36_bursa

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bursa of Fabricius

Normal Reference

chicken (Gallus gallus)

Clinical Description

The bursa of Fabricius has been opened to show its mucosal surface. The normal mucosa consists of many folds of tissue, which are pale white to pink or tan and slightly firm on palpation.

Vent1

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vent

Normal Reference

chicken (Gallus gallus)

Clinical Description

The vent, located just beneath the tail, is the external orifice of the urinary, genital and gastrointestinal systems. The normal vent is free of fecal and urate staining, swelling, redness, or evidence of trauma.

37_ovary

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ovary

Normal Reference

chicken (Gallus gallus)

Clinical Description

This image shows the normal ovary of a sexually immature female, approximately 10 weeks of age. Here, the ovary is small and inactive.

Ribs1

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rib bone

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the dorsal aspect of the ribs. Note that the ventral ribs have been removed from the field.

38b_kidney_chain

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kidney

Normal Reference

chicken (Gallus gallus)

Clinical Description

The kidneys consist of a right and left chain, with each chain being made up of 3 lobes. The lobes are tightly embedded in the bone of the synsacrum. They are normally red to dark mahogany brown in color and have a slightly granular texture.

38a_kidney_texture

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kidney

Normal Reference

chicken (Gallus gallus)

Clinical Description

This image shows a detailed view of the normal texture of the kidneys.

40_ishradic_nerve

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peripheral nerves

Normal Reference

chicken (Gallus gallus)

Clinical Description

The nerves should have a creamy-white color and a slightly striated texture on close inspection. This image shows a normal ishiadic plexus in the caudal coelomic cavity.

ThyroidGlandLeft2

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thyroid gland

Normal Reference

chicken (Gallus gallus)

Clinical Description

The thyroid glands should be smooth, oval, and reddish-brown in color. On very close inspection, the thyroid glands have a very fine granular appearance.

07_beak_articulation

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beak

Normal Reference

chicken (Gallus gallus)

Clinical Description

A properly formed beak, shown here, is bilaterally symmetrical and the upper and lower halves should form a smooth line where they articulate.

beak2

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beak

Normal Reference

chicken (Gallus gallus)

Clinical Description

A properly formed beak is bilaterally symmetrical and the upper and lower halves should form a smooth line where they articulate. Nutritional imbalances may result in beak malformations. The color of the beak depends on the bird’s coloration, with lighter birds typically having yellow beaks. However, beak color can also be influenced by physiologic factors. For example, yellow pigment in the beak may be lost as the chicken produces more eggs.

choana1

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oropharynx

Normal Reference

chicken (Gallus gallus)

Clinical Description

The oropharynx should be examined for any lesions. Note that birds do not have a soft palate or a discrete boundary between the oral cavity and the pharynx. The color of the oral mucosa will vary with lighter birds tending to have a pink mucosa while darker birds will have more pigment. Look for ulcers, erosions, opacities, diptheritic nodules, or other lesions.

tongue1

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tongue

Normal Reference

chicken (Gallus gallus)

Clinical Description

A bird’s tongue is supported by the hyobranchial apparatus, making it somewhat inflexible.

09_oral_mucosa

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oropharynx

Normal Reference

chicken (Gallus gallus)

Clinical Description

The color of the oral mucosa will vary with the overall coloration of the bird. However, the mucosa should be free of ulcers, erosions, opacities, diptheritic nodules, and other lesions.

tongue3

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tongue

Normal Reference

chicken (Gallus gallus)

Clinical Description

The dorsal surface of the chicken tongue should be smooth and pink. There is a row of large papillae near the caudal attachment of the tongue. Inspect the tongue for any lesions such as ulcers or nodules.

08_tongue

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tongue

Normal Reference

chicken (Gallus gallus)

Clinical Description

The dorsal surface of the chicken’s tongue is smooth and there is a row of large papillae near the caudal attachment. When inspecting the tongue, look for ulcers and erosions.

choana2

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choana

Normal Reference

chicken (Gallus gallus)

Clinical Description

On the roof of the oropharynx is a fissure, called the choana, which opens into the nasal cavity. Inspect the area around the choana for ulcers. The choana is also a good place to find respiratory exudate. Birds do not form liquid pus and inspusated exudate tends to accumulate in the choanal orifice. If exudate is present, you can collect a swab sample from the choana. The choana is surrounded by ridges and rows of sharp well-demarcated papillae that point caudally. A variety of diseases can damage the papillae, resulting in blunting.

13_infundibular_cleft

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infundibular cleft

Normal Reference

chicken (Gallus gallus)

Clinical Description

Just caudal to the choana is the infundibular cleft. This is the opening to the Eustachian tube and it is surrounded by ridges and rows of sharp well-demarcated papilla that point caudally.

pharynx1

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oropharynx, tongue

Normal Reference

chicken (Gallus gallus)

Clinical Description

The tongue, esophagus, and trachea have been removed as one unit. This view allows the structures of the structures of the caudal oral cavity and pharynx to be examined more closely.

pharynx3

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oropharynx

Normal Reference

chicken (Gallus gallus)

Clinical Description

The tongue, esophagus, and trachea have been removed as one unit. This view allows the structures of the caudal oral cavity and pharynx to be examined more closely.

crop1

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esophagus

Normal Reference

chicken (Gallus gallus)

Clinical Description

The esophagus runs down the length of the neck and, in domestic species, is interrupted by a diverticulum called the crop. The esophagus continues down the neck and empties into the proventriculus. The esophagus and crop are thin-walled and located just below the skin. Their outer surfaces should be pale tan and smooth.

crop2

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esophagus

Normal Reference

chicken (Gallus gallus)

Clinical Description

The esophagus runs down the length of the neck and, in domestic species, is interrupted by a diverticulum called the crop. The esophagus continues down the neck and empties into the proventriculus. The esophagus and crop are thin-walled and located just below the skin. Their outer surfaces should be pale tan and smooth.

crop3

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crop, esophagus

Normal Reference

chicken (Gallus gallus)

Clinical Description

The mucosal surface of the esophagus should be smooth and glistening. The cranial portion contains many glands and the caudal portion has numerous longitudinal folds. The color along the entire length should be pale tan to pink. The presence of proliferative lesions may indicate a viral infection or a dietary imbalance. You can gently wash away any food material from the walls of the crop with some water but do not scrape the mucosa. Food material should wash away easily while fibrin and exudate will stick to the mucosa. Look for ulcers and erosions, which appear as red or pale depressions in the mucosa.

26_esophagus_folds

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esophagus

Normal Reference

chicken (Gallus gallus)

Clinical Description

The caudal portion of the normal esophagus has numerous longitudinal folds, as seen here.

crop4

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crop

Normal Reference

chicken (Gallus gallus)

Clinical Description

You can gently wash away any food material from the walls of the crop with some water but do not scrape the mucosa. Food material should wash away easily while fibrin and exudate will stick to the mucosa. Look for ulcers and erosions, which appear as red or pale depressions in the mucosa.

crop5

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crop

Normal Reference

chicken (Gallus gallus)

Clinical Description

You can gently wash away any food material from the walls of the crop with some water but do not scrape the mucosa. Food material should wash away easily while fibrin and exudate will stick to the mucosa. Look for ulcers and erosions, which appear as red or pale depressions in the mucosa.

Trachea3

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trachea

Normal Reference

chicken (Gallus gallus)

Clinical Description

The trachea should be uniform in color, ranging from pale pink to tan or white and the external surface should be smooth. Upper respiratory disease may produce tracheal lesions that are sometimes visible on the outer surface. Look for discoloration, nodules, or irregularities in the tracheal cartilages.

palate2

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trachea

Normal Reference

chicken (Gallus gallus)

Clinical Description

The trachea is a thin tube completely encircled by small cartilagenous rings. The trachea should be uniform in color, ranging from pale tan to white and the external surface should be smooth. Look for discoloration, nodules, or irregularities in the tracheal cartilages.

21_trachea_cartilage

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trachea

Normal Reference

chicken (Gallus gallus)

Clinical Description

The trachea is a thin tube completely encircled by cartilagenous rings. The trachea should be uniform in color, ranging from pale pink to tan or white and the external surface should be smooth. Upper respiratory disease may produce tracheal lesions that are sometimes visible on the outer surface. Look for discoloration, nodules, or irregularities in the tracheal cartilages.

Syrinx1

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syrinx, trachea

Normal Reference

chicken (Gallus gallus)

Clinical Description

At the terminal end of the trachea lies the syrinx, a flattened area at the junction of the trachea and the primary bronchi. The syrinx is responsible for generating vocal sounds.

20_syrinx

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syrinx

Normal Reference

chicken (Gallus gallus)

Clinical Description

Since the diameter of the syrinx is significantly smaller than that of the trachea, examine this area closely for occlusions caused by exudate, fungal mats, or parasites.

Syrinx2

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syrinx

Normal Reference

chicken (Gallus gallus)

Clinical Description

Since the diameter of the syrinx is significantly smaller than that of the trachea, examine this area closely for occlusions caused by exudate, fungal mats, or parasites.

Trachea4

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trachea

Normal Reference

chicken (Gallus gallus)

Clinical Description

View of the inside lumen of the trachea.

Jugular1

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jugular vein

Normal Reference

chicken (Gallus gallus)

Clinical Description

The left jugular vein of the bird, seen here, is much larger than the right.

Jugular2

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jugular vein

Normal Reference

chicken (Gallus gallus)

Clinical Description

The left jugular vein of the bird, seen here, is much larger than the left. The vagal and glossopharyngeal nerves are closely associated with the veins.

22_jugular_and_nerve

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peripheral nerves

Normal Reference

chicken (Gallus gallus)

Clinical Description

The vagal and glossopharyngeal nerves run parallel with the jugular veins.

ThyroidGlandLeft1

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thyroid gland

Normal Reference

chicken (Gallus gallus)

Clinical Description

The thyroid glands are located on each side of the neck, medial to the jugular vein and cranial to the origin of the subclavian and common carotid arteries.

23_thyroid_parathyroid

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thyroid gland

Normal Reference

chicken (Gallus gallus)

Clinical Description

The glands should be smooth, oval, and reddish-brown in color. On very close inspection, the thyroid glands have a very fine granular appearance.

ThyroidGlandRight2

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thyroid gland

Normal Reference

chicken (Gallus gallus)

Clinical Description

Just caudal to the thyroid glands are the small pale pink parathyroid glands. The right parathyroid gland, seen here, lies directly adjacent to the right thyroid gland. The left parathyroid gland is slightly separated from the left thyroid gland.

Thymus1

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thymus gland

Normal Reference

chicken (Gallus gallus)

Clinical Description

The thymus is a bilateral chain of structures, located in the lateral neck region. each side is composed of 4 to 7 lobes. In chickens less than 17 weeks of age, the thymus should be visible but normally regresses around the time of sexual maturity.

Thymus2

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thymus gland

Normal Reference

chicken (Gallus gallus)

Clinical Description

The lobes of the thymus, normally present only in immature birds, are pale tan to pink in color.

VIT E-SELENIUM - 019A.jpg

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brain

Normal Reference

chicken (Gallus gallus)

Clinical Description

The avian brain has a smooth surface, with no gyri or sulci. Its cortex should appear smooth and glistening and the right and left sides should be symmetrical.

44_brain

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brain, cerebrum

Normal Reference

chicken (Gallus gallus)

Clinical Description

This image shows a detailed view of the surface of the normal cerebrum.

PectoralMuscles1

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pectoral muscles

Normal Reference

chicken (Gallus gallus)

Clinical Description

The 3 muscles involved in flight in the bird, called the pectoral muscles, lie on either side of the keel bone. These muscles are very large, making them ideal for body muscle assessment. The muscles should be smooth and have a relatively uniform texture.

PectoralMuscles2

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pectoral muscles

Normal Reference

chicken (Gallus gallus)

Clinical Description

The pectoral muscles can be removed from the keel and ribs in order to examine them more closely. Look for areas of necrosis, inflammation, or hemorrhage.

PectoralMuscles3

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pectoral muscles

Normal Reference

chicken (Gallus gallus)

Clinical Description

With the muscles removed, look for areas of necrosis, inflammation, or hemorrhage. A series of parallel cuts through the muscle bellies can facilitate this assessment.

eyes1

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comb, eyelid, wattles

Normal Reference

chicken (Gallus gallus)

Clinical Description

The eyelids should be free of swelling or exudate from ocular discharge.

eyes2

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eyelid

Normal Reference

chicken (Gallus gallus)

Clinical Description

The eyelids should be free of swelling or exudate from ocular discharge.

10_eye_insitu

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eye

Normal Reference

chicken (Gallus gallus)

Clinical Description

The cornea should be clear and convex and the sclera white. Iris color will vary with the breed and color of the bird however, look for abnormalities of the iris such as redness, anterior synechia, or exudate in the anterior chamber. The shape of the iris and pupil should be uniform and round.

12_conjunctiva

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conjunctiva

Normal Reference

chicken (Gallus gallus)

Clinical Description

The conjunctiva is a mucous membrane. It should be light pink in color and free of any redness, swelling, or exudate.

15_eye_front

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eye

Normal Reference

chicken (Gallus gallus)

Clinical Description

The eye has been removed from the skull showing the full extent of the orbit.

11_ear

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ear

Normal Reference

chicken (Gallus gallus)

Clinical Description

The ears in the bird are simple ostea, with no external pinna. The openings should be free of swelling, exudate, or other material.

beak1

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comb, wattles

Normal Reference

chicken (Gallus gallus)

Clinical Description

The comb and wattles are outgrowths of skin that are highly vascularized, making them a useful way to assess the bird's overall health. They are normally bright red but their color will quickly fade after death. However, they should remain firm and uniform on palpation. look for abnormalities such as edema, petechiae, necrosis, cyanosis, papules and ulcers.

14_sinus

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infraorbital sinus

Normal Reference

chicken (Gallus gallus)

Clinical Description

The infraorbital sinuses are triangular-shaped cavities, located rostroventral to the eyes. The sinuses are air-filled lumens, with one opening into the nasal cavity and the other into the caudal nasal cavity.

06_leg_conformation

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Leg

Normal Reference

chicken (Gallus gallus)

Clinical Description

As seen here, the legs bones of the should be straight and symmetrical.

limb1

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leg bones

Normal Reference

chicken (Gallus gallus)

Clinical Description

The leg bones should be straight and symmetrical. Palpate the bones for fractures and calluses and the joints for swelling or effusion. Flex and extend all the joints to assess range of motion, keeping in mind the effects of rigor mortis.

integument1

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skin

Normal Reference

chicken (Gallus gallus)

Clinical Description

The skin on the limbs is covered by scales that are normally dry, flat, and slightly overlapping. Some parasites live beneath the scales of the legs. Some infectious diseases can cause keratinous outgrowths from this skin.

integument2

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skin

Normal Reference

chicken (Gallus gallus)

Clinical Description

The skin on the limbs is covered by scales that are normally dry, flat, and slightly overlapping. Some parasites live beneath the scales of the legs. Some infectious diseases can cause keratinous outgrowths from this skin.

integument3

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digits, foot pads

Normal Reference

chicken (Gallus gallus)

Clinical Description

Digital pads cover the plantar surface of the birds’ feet. These pads are composed of thick skin and adipose tissue. In the center of the foot, there is a large central metatarsal pad. The pads should be soft, free of scabs, swellings, edema, hemorrhages, or other lesions.

pad2

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foot pads

Normal Reference

chicken (Gallus gallus)

Clinical Description

In the center of the foot, there is a large central metatarsal pad. The pads should be soft, free of scabs, swellings, edema, hemorrhages, or other lesions.

01_claw

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claws

Normal Reference

chicken (Gallus gallus)

Clinical Description

In birds housed on the floor, claws will normally come to a blunt tapered end, as seen here. Claws may be somewhat sharper in birds housed in cages. Curling or fraying claws are abnormal findings.

feathers1

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feathers

Normal Reference

chicken (Gallus gallus)

Clinical Description

Birds have several types of feathers distributed across various regions of their body including down, body feathers, and flight feathers. Look for abnormalities in feather conformation such as warping or malformed barbs and barbules. Make note of any body regions that are missing feathers. Feathers are normally distributed along tracks on the body, called pterylae. These tracks are interspersed with featherless tracts called apteria. Keep in mind, that not all feather loss is abnormal. Seasonal feather molting is a normal physiologic process. Additionally, females who are incubating eggs may have an area on their abdomen lacking feathers, called the brood patch. In non-pathologic feather loss, the skin will appear healthy. In cases of pathologic feather loss, such as excessive feather picking by the bird, or its cage mates, the skin will be traumatized.

04_down_feather

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feathers

Normal Reference

chicken (Gallus gallus)

Clinical Description

This image shows a typical “down” feather.

integument4

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skin

Normal Reference

chicken (Gallus gallus)

Clinical Description

The skin in the chicken is normally very thin and the amount of pigment varies from pink to black, depending on the coloration of the bird. The skin should be free of exudate and have little or no scale. Look for any lesions or evidence of ectoparasites.

05_apteria

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feathers

Normal Reference

chicken (Gallus gallus)

Clinical Description

Feathers are normally distributed along tracks on the body, known as pterylae, seen here. These tracks are interspersed with featherless areas called apteria. Patches of feather loss may be due to normal physiologic processes, such as seasonal molting. Pathologic feather loss can result from trauma and infection and is associated with skin lesions.

feathers2

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feathers

Normal Reference

chicken (Gallus gallus)

Clinical Description

Pay attention to the feather sheath, the area where the feather emerges from the follicle. Swelling in this location can be indicative of several types of infection.

feathers3

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feathers

Normal Reference

chicken (Gallus gallus)

Clinical Description

Pay attention to the feather sheath, the area where the feather emerges from the follicle. Swelling in this location can be indicative of several types of infection.

Uropygealgland1

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uropygeal gland

Normal Reference

chicken (Gallus gallus)

Clinical Description

The uropygial, or preen gland, is located dorsal to the base of the tail. This cutaneous gland secretes an oily substance that birds spread over their feathers during preening. These secretions help maintain normal healthy feathers.

Uropygealgland2

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uropygeal gland

Normal Reference

chicken (Gallus gallus)

Clinical Description

The body of the gland is located subcutaneously and its two lobes can sometimes be visualized beneath the skin, as seen here. The gland’s duct exits externally through a small papilla. Infected glands may result in swelling and reddening of the surrounding skin.

42_cartilage

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cartilage

Normal Reference

chicken (Gallus gallus)

Clinical Description

Cartilage should be smooth, shiny, and white with a slightly blue tinge, as seen here. Look for degenerative changes and roughed, discolored areas.

43_bone_marrow

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leg bones

Normal Reference

chicken (Gallus gallus)

Clinical Description

In a young bird, cut the long bone of the leg lengthwise to examine the epiphysis. Nutrient or mineral deficiencies can lead to poor mineralization of the bone. Look for widening of the epiphyseal plate or generalized hypoplasia of the bone.

Marek's Disease

Marek's Disease

Marek's Disease

Etiology

Marek's disease (MD) is a transmissible neoplastic disease, primarily affecting chickens. The disease is caused by a cell-associated herpesvirus, containing double-stranded DNA. There are three serotypes of MDV but oncogenicity is only associated with serotype 1 MDVs. Within this serotype however, there are many strains of MDV, whose pathogenicity varies widely. Subsequently, clinical signs in infected chickens vary from asymptomatic infection to neurologic disease, skin disease, and ocular lesions.

Host Range

Marek's disease is primarily a disease of commercial chickens, but it can also affect turkeys. MD often occurs in 2-5 month-old (sexually immature) chickens but can also occur after the onset of egg production. This form of the disease is referred to as

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  • Avian Encephalomyelitis
  • Erythroblastosis
  • Genetic Grey Eye
  • Histomoniasis
  • Lymphoid leukosis
  • Myeloblastosis
  • Myelocytomatosis
  • Newcastle Disease
  • Ovarian Carcinoma
  • Reticuloendotheliosis
  • Riboflavin Deficiency
  • Tuberculosis