Department of Pathology,

Faculty of Veterinary Medicine,

Zagazig University, Egypt.

Pathology of Veterinary DiseasesBY

Mohamed Hamed Mohamedmohamedelariny@yahoo.com

+20124067373

2011

Avian PathologyAvian Inflammation:

It is characterized by:

1-The reaction is rapid in birds, usually within 36 hours

2-Leakage of fibrin and fibrinogen are common in early exudate

3-Intense granulomatous reaction and the birds respond with

granulomatous inflammation to many insults: The granuloma was

consists of

-Coagulated eosinophilic debris

-Degranulating heterophils.

- Macrophages and giant cells

4-Macrophages, heterophils and thrombocytes are active phagocytes

5-Pus is caseous but liquefaction can occur.

6-Acute inflammatory reactions in birds involve edema, congestion

and vascular changes mediated by basophils and mast cells.

7-Chronic reaction usually with caseation, macrophages, giant cells

and granuloma formation.

Cells involved in inflammation

1-Heterophils: have lance-shaped granules, lack myeloperoxidase and

alkaline phosphatase, have b -glucuronidase and acid phosphatase :

Very phagocytic

Granules tend to round up in tissues, difficult to identify

2-Eosinophils: have spherical granules.

Function is not known; but it present in hypersensitivity and associated

with eosinophilic enteritis in turkeys due to ascarids.

3-Basophils: contain histamine, involved in acute inflammation.

4-Thrombocytes: small round to oval cells with clear cytoplasm and

small round nucleus (looks like small lymphocyte), phagocytic

5-Monocytes: precursors to cells of MPS, phagocytic, can fuse together

to form multinucleated giant cells and make monokines; IL-1, IL-2,

TNF, G-CSF, gamma interferon.

6-Lymphocytes: various morphologies involved in subacute

inflammation including plasma cells.

Avian Bacterial Diseases1-Avian Coliform Infection:

It is a variety of disease resulted from infection of poultry with

pathogenic serotypes of E. coli. The infection may be:

1-Colisepticemia (Systemic)

2-Coligranuloma (Hjarre’s disease)

3-Egg-Peritonitis

4-Omphalitis/yolk sac infection

Lesions:A- Colisepticemia: affects 4-12 weeks old birds.

1-Fibrinous pericarditis, airsacculitis and perihepatitis (caseous

deposits on serous membranes).

2-Congestion of the liver, spleen, lungs and kidneys.

3-In young birds show unabsorbed yolk sac

4-Fibrinous exudate replaces the white pulps of spleen and

fibrinous thrombi in the hepatic sinusoids.

B-Coligranuloma (Hjarre’s disease): affects adult birds (sporadic cases).

1-Hard yellow nodules or granulomas (similar to TB) in the ceca,

intestine and liver.

2-These nodules consist of central necrosis surrounded by

macrophages, lymphocytes and giant cells.

C-Egg Peritonitis:

-Peritonitis, salpingitis and impaction of the oviduct with yolk

debris.

-Inspissated yolk, caseous or milky fluid is seen in the abdominal

cavity.

D-Omphalitis (Mushy Chick disease): affects hatched chicks

(contamination of eggs) and induce 100%mortality during the first week

-Navel is inflamed, moist and necrotic.

-Septicemic lesions (congested and enlarged liver, kidneys, lungs

and spleen).

Arthritis: frequently affect the hock joint after colisepticemia.

-The affected joints are swollen (synovitis).

Colisepticemia: Severe pericarditis, perihepatitis and airsacculitis.

Omphalitis (inflammation of navel).

Coligranuloma: multiple nodular lesions in the ceca.

Egg peritonitis with acute peritonitis.

2-Salmonellosis:Large group of acute, subacute or chronic diseases caused by one or more members of

bacterial genus Salmonella: Pullorum disease in poultry, S. pullorum. Typhoid disease in

poultry, S. gallinarum. Paratyphoid in poultry, ducks, pigeons, wild birds, psittacines,

passerines. Arizonosis in turkey poults, S. arizonae

Lesions

Pullorum/Typhoid: In chicks:Acute Cases:

-Septicemic lesions of omphalitis with persistent yolk sac (contain creamy or

caseated material.

-Liver is enlarged, friable and with necrotic foci.

-Catarrhal enteritis with white diarrhea.

-Peritonitis, necrotic typhlitis, pericarditis, splenitis, pneumonia, synovitis,

nephritis and opthalmitis.

Chronic cases: Pale yellow nodules in myocardium (histiocytes), intestine and gizzard.

In adults:-Oophoritis (hemorrhagic or atrophied), salpingitis, peritonitis (ascites), and orchitis

-The liver is enlarged, bronzy color (hemosiderosis) and show necrotic foci (typhoid)

-Enteritis (ulcerative duodenitis).

-Grayish nodules in the lungs, liver, intestine heart, gizzard, spleen.

Microscopic Pictures: The salmonella sp. Induces granulomatous

reaction of macrophages, giant cells and lymphocytes in the liver

besides coagulative necrosis.

Paratyphoid:Etiology: S. typhimurium most important

In different species of birds: similar to acute septicemic lesions of

pullorum and typhoid.

In pigeons: brain, bone, and gonads often involved.

-S. enteritidis can cause septicemic lesions in chicks.

Arizonosis: in turkey poults and caused by S. arizonae.

Clinical Signs:

Diarrhea, paralysis and twisted neck beside pasty vent.

The diseased bird site on their hocks and huddle together.

Lesions:

-Septicemic lesions, meningitis and ophthalmitis.

-Caseated material in abdominal cavity

-Enlarged liver with necrotic foci.

Pullorum: Focal necrotic foci on the liver surface.

Fowl typhoid: Ovaritis with misshaped ova in the ovary.

3-Fowl Cholera (pasteurellosis):It is septicemic disease of birds with high mortality and morbidity

Etiology: P. multocida. It is most common in turkeys, chickens, wild

waterfowl. Other birds such as geese, quail, pheasants, raptors,

psittacines, passerines, zoo birds, etc., are susceptible.

Lesions

Acute Form:-Petechial hemorrhages on viscera, serous and mucous membrane, fat

and on the gizzard.

-Hemorrhagic enteritis (duodenitis)

-Enlarged liver with numerous necrotic foci (corn meal liver).

-Serofibrinous pericarditis and airsacculitis.

Chronic Form (Localized):

1-comb and wattle form: The comb and wattles are swollen and

edematous.

2- Articular form: Arthritis and synovitis.

3- respiratory form: Fibrinous pneumonia, sinusitis and conjunctivitis.

4-Nervous form: Otitis and osteomyelitis of cranial bones due to

localization of Pasteurella in the middle ear and the base of brain inducing

torticollis and nervous signs (only in turkey).

Fowl Cholera: swollen liver with multiple small focal

areas of coagulative necrosis in acute form

4-Infectious Coryza:It is disease primarily of young chickens caused by Haemophilus paragallinarum. It is

characterized by upper respiratory tract infection.

Lesions:In uncomplicated cases:

1-catarrhal rhinitis and sinusitis with nasal discharge.

2-edema of face.

3-Conjunctivitis with adherence of eyelids or with cheesy exudate in

conjunctival sac.

In complicated cases:

1-Mucopurulent sinusitis and conjunctivitis (bacterial)

2-Catarrhal tracheitis, bronchitis and airsacculitis (viral as IB).

3-Fibrinous pericarditis, and perihepatitis (E. coli or mycoplasma).

4-Edema of face.

Remark:

Turkey Coryza (Bordetellosis): Caused by Bordetella avium

It is upper respiratory tract infection primarily of young turkey poults; swollen

sinus, collapsed trachea, watery discharge from eyes, tracheitis: deciliation,

squamous metaplasia, and lymphoplasmacytic inflammation.

NB.: B. avium can be a significant pathogen in young broiler chickens, ratites,

passerines and psittacines (lock jaw).

Infectious Coryza: Soft swelling eyes and face.

Infectious Coryza: Soft swelling eyes and face.

5-Mycoplasmosis:It is important economic diseases of poultry caused by M. gallisepticum, M. synoviae, M.

meleagridis, M. iowae 14-20 or more Mycoplasma sp. are known isolated from chickens,

turkeys, pigeons, raptors, ratites, wild birds, psittacines, passerines, etc.

Pathogenic significance:

I-M. gallisepticum (MG): Disease called chronic respiratory disease (CRD) in

chickens and infectious sinusitis in turkeys. The disease is complicated with E.

coli, Pasteurella multocida, Haemophilus gallinarum and IB virus

Lesions:1-The body weight of birds is light.

2-Catarrhal sinusitis, tracheitis, bronchitis and airsacculitis (associated

with cheesy exudate).

3-Fibrinous pericarditis, perihepatitis and pneumonia

4-Some strains of MG can cause neurological signs in turkeys due to

vasculitis in the brain.

II-M. synoviae (MS): in chickens, turkeys, geese, quail, ducks, etc.

Subclinical infection of respiratory disease, sinusitis, tracheitis, airsacculitis,

conjunctivitis. It can cause severe synovitis and ulceration in joint (swollen joints

Some strains of MS can also cause neurological signs in turkeys and rarely

chickens due to vasculitis in the brain or disseminated vasculitis are seen in

synovium, eye, kidney, skeletal muscle, heart, lungs, etc. in turkeys

Mycoplasmosis: M. synoviae arthritis

Mycoplasmosis: M. gallisepticum airsacculitis.

III-M. meleagridis: affects turkeys.

Airsacculitis in day-old poults, decreased hatchability, swelling of

hock joint, bowing of tarsometatarsus, deformation of cervical

vertebrae (wry neck).

6-Mycobacteriosis:It is chronic progressive disease of a variety of species of birds with

unthriftiness, loss of weight, diarrhea, etc.

M. avium - wide host spectrum, poultry, pigeons, raptors, ratites, wild

birds, passerines, etc.

Lesions:Gross:

1-The birds are emaciated

2-Pale yellow or gray nodules in liver, spleen, intestine, bone

marrow, lung and heart.

micro:

The nodules consist of caseous necrosis surrounded by

macrophages, epithelioid cells, lymphocytes and multinucleated

giant cells. Fibrosis and acid fast bacilli are found.

TB: Yellowish caseous nodules in the liver, spleen and intestine

Tuberculous nodule in the liver consists of central aggregation

of macrophages, epithelioid cells, giant cells and lymphocytes

Tuberculous nodule in the liver consists of central aggregation

of macrophages, epithelioid cells, giant cells and lymphocytes

Tuberculous nodule in the liver consists of central aggregation

of macrophages, epithelioid cells, giant cells and lymphocytes

7-Spirochetosis It is a septicemic disease of turkeys and chickens of all ages and

characterized by depression, cyanosis, diarrhea, paralysis and deaths

(100%).

Etiology: Borrelia gallinarum.

Lesions:1-Presence of mites on the skin (intermediate host).

2-The spleen is enlarged and mottled (has uniform whitish foci with

ecchymotic hemorrhages).

3-The liver is enlarged and shows small necrotic or hemorrhagic foci.

4-The kidneys and heart are enlarged and pale.

5-Catarrhal enteritis.

6-The spirochetes are stained black by Levaditi’s stain.

Remark:

B. anserine causes, septicemia in poultry and canaries.

Serpulina hyodysenteriae associated with typhlitis in rheas and poultry

Serpulina piloscholi in ceca of pheasants, disease.

8-Clostridial diseasesI-C. perfringens (type A most common): necrotic enteritis in chicken, turkey

Lesions: the small intestine is markedly thickened due to extensive velvet-like

necrosis of the mucosa. The lesions become dry in the lower small intestine.

II-C. colinum: ulcerative enteritis in chickens, quail (quail disease), ratites,

Lesions: The mucosa of small intestine, ceca and upper large intestine show

small round superficial ulcers with hemorrhagic borders. They were coalesced

together and penetrate to the serosal causing peritonitis.

III-C. difficile: entero / typhlocolitis in ostrich.

Remark: Liver may have necrotic foci with the above clostridial diseases.

IV-C. septicum: gangrenous dermatitis in chickens (C. perfringens and

Staph. can also cause).

Lesions: The affected skin is dark red in color and moist. The underlying

muscles are edematous with gas bubbles. The internal organs are congested.

V-C. botulinum (Toxins): limberneck in poultry (toxins prevent the release of acetylcholine).

The affected birds show uncoordinated legs, and then wings and neck followed

by flaccid paralysis. The toxins don’t affect on the CNS.

VI-Clostridium piliformis (Tyzzer’s disease) - hepatic necrosis in

psittacines.

Ulcerative enteritis: Roughly circular ulcers in the mucosa.

Ulcerative enteritis: Roughly circular ulcers in the mucosa.

Cl. Perfringens : Necrotic enteritis.

Cl. Perfringens : Necrotic enteritis with coagulative

necrosis in the mucosa.

Cl. Perfringens : Necrotic enteritis with coagulative

necrosis in the mucosa.

Gangrenous dermatitis: Cl septicum with large area of gangrene

in the wing.

Avian Viral diseases1-Avian Paramyxoviruses

Newcastle Disease ND): It is acute viral disease of chickens, turkeys, pigeons, doves, pheasants and

psittacines.

Etiology: avian paramyxovirus-1, isolates vary greatly in pathogenicity to

chickens

Lentogenic: mild or inapparent (asymptomatic) infection in chickens

Mesogenic: cause disease and mortality in young chickens

Velogenic (viscerotropic and neurotropic): lethal for all ages chickens

Clinical signs

-Vary with strain, respiratory, digestive, ocular, neurological, sudden death

-In mature chickens, egg production and quality problems (mesogenic strain)

Lesions

In chickens: The disease has 3 forms:1-Respiratory Form: it characterized by

-Catarrhal tracheitis, pneumonia and conjunctivitis.

-Petechial hemorrhages on the heart and abdominal fat.

2-Intestinal Form: it characterized by

-Focal hemorrhagic or necrotic enteritis (similar to coccidiosis).

-Petechial hemorrhages on the mucosa of proventriculus and gizzard.

-The cecal tonsils are hemorrhagic or necrotic.

3-Nervous form (encephalitis): it characterized by

-Neuronal degeneration, gliosis and perivascular lymphocytic cuffing.

In velogenic: hemorrhages in conjunctiva, trachea, oral cavity,

esophagus, proventriculus and ceca due to disseminated vasculitis

beside lymphoid and mucosal necrosis (intestine). Inclusion bodies are

rare.

In recent cases:

Eosinophilic intranuclear and intracytoplasmic inclusion bodies in

conjunctiva, esophagus, lungs, brain, and adrenal ganglia of a

pheasant and in the brain of a chicken with a lentogenic type NDV.

-Eosinophilic intranuclear inclusions in hepatocytes in doves

associated with lentogenic type of NDV.

-In pigeons: enteritis, pancreatitis, nephritis, and encephalitis,

respiratory system rarely involved.

Newcastle Disease: Hemorrhages on proventriculus and GIT.

Newcastle Disease: Hemorrhages on proventriculus and GIT.

Newcastle Disease: Hemorrhagic enteritis.

Newcastle: Perivascular lymphocytic cuffing in brain.

2-Infectious laryngotracheitis (ILT)It is acute viral respiratory disease of primarily chickens and

pheasants.

Etiology: herpesvirus

Clinical Signs: ILT virus has 2 forms:

A-Epizootic acute form: it characterized by

1-Eye and nasal discharge.

2- Moist rales, gasping and coughing.

3-Expectoration of bloody exudate or mucus tinged with blood.

4-Drop of egg production reach to 40%

5-Mortality is 10- 20%.

B-Enzootic mild form: it characterized by

1-Unthriftiness.

2-Drop in egg production.

3-Watery eye and nasal discharge.

4-Swollen of orbital sinuses.

5-Mortality rate is 5%.

Lesions: 1-Hemorrhagic laryngotracheitis with presence of

bloody plugs in the tracheal lumina

2-Conjunctivitis and sinusitis are seen.

3-The peak and oral cavity are stained with blood.

Micro:1-Hemorrhage and/or fibrinous exudate in the trachea.

2-Syncytia formation and intranuclear inclusion bodies

in the epithelial lining of larynx and trachea during the

first 3 days of the disease.

ILT: Blood clot in the tracheal lumen (bloody plugs).

ILT: Syncytial formation and intranuclear inclusion

bodies in the epithelial lining of trachea.

3-Infectious BronchitisEtiology: coronavirus, many serotypes, and great antigenic

variation among strains of virus.

Lesions: It is characterized by

-Catarrhal tracheitis and rarely with a mucus or caseous

plug found near the bronchi.

-Conjunctivitis, bronchitis, and severe airsacculitis (thick

and opaque)

-Interstitial nephritis with nephropathogenic IB viruses

“Infectious nephritis-nephrosis syndrome or Infectious

uremia”. Dehydrated carcass and dark red discoloration of

the muscles. The kidneys of affected birds are pale, mottled

and the ureters are distended with urates (gout).

-In the layer: hypoplastic or cystic oviduct resulting in

“false layer”. Flaccid ovarian follicles and yolk are present

in the peritoneal cavity (internal layer).

IB: tracheitis with lymphocytic infiltration and hypertrophy of

the mucous glands.

IB (nephrogenic strain): The kidneys are swollen and pale.

IB (nephrogenic strain): The kidneys showed interstitial

lymphocytic aggregations.

4-Avian Influenza (Fowl Plague)Avian influenza is a viral disease (known as fowl plague) affecting the

respiratory, digestive and/or nervous system of many species of birds.

Etiology: type A influenza virus of family Orthomyxoviridae

-Numerous subtypes based on surface antigens, hemagglutinin (H)

and neuraminidase (N).

-Viruses of H5 (H5N2) and H7 (H7N1) subtypes are considered

pathogenic, H1N1 (swine flu) in turkeys.

-H4N8, H4N6, H3N8 in exotic birds.

-H5N1 in chickens and humans, Hong Kong, 1997 and 2002.

Clinical signs:The clinical signs vary greatly and depend on many factors including

the age and species of poultry affected, husbandry practices, and the

inherent pathogenicity of the influenza virus strain.

The Clinical signs may include:

A-Mild form (Mildly Pathogenic).

B- Systemic form (Highly Pathogenic).

Mild form (Mildly Pathogenic):i-Decline egg production and soft-shelled eggs ii-Mild respiratory disorder

iii-Sneezing- coughing iv- Low mortality.

Systemic form (Highly Pathogenic):i-Chronic respiratory infection (blood-tinged discharge from nostrils).

ii-Pin-point hemorrhages on the feet and shanks.

iii-Drowsiness, incoordination, swelling of heads.

iv-Sinuses filled with cheese (like plugs). v-High mortality.

Lesions: depending on pathogenicity of the virus, age of the bird, type of poultry.

Mild Form:-Catarrhal tracheitis, sinusitis, airsacculitis, conjunctivitis, pneumonia.

Systemic Form: (Hemorrhagic or septicemic lesions).

- Cyanosis (purplish-blue coloring) and swelling of wattles and comb.

-Hemorrhages in skin of face, comb, wattles, trachea, intestine, proventriculus & gizzard

-The hemorrhages include the muscle along the breastbone as well as in the heart and

abdominal fat

-Clear straw-colored fluid in the subcutaneous tissues.Blood vessels are usually engorged

-Young broilers may show signs of severe dehydration with other lesions less pronounced

or absent entirely.

Micro: interstitial pneumonia and nephritis, encephalitis, conjunctivitis,

myocarditis, pancreatitis, myositis, lymphoid necrosis, vasculitis and thrombosis.

Avian Influenza: Edematous cyanotic comb and wattle.

Avian Influenza: Petechial

Hemorrhages on the skin of legs.

-Avian Influenza: On the heart and fat.

Avian Influenza: Petechial Hemorrhages on

the fat around gizzard.

Avian Influenza: Petechial Hemorrhages on the

proventricular glands.

5-Avian PoxIt is slow spreading viral disease of chickens, turkeys, quail, pigeons, canaries, .

Etiology: poxvirus of genus Avipoxvirus, many strains: Fowl pox, turkey

pox, pigeon pox, canary pox

Clinical Signs: cutaneous, respiratory, digestive, ocular. It causes septicemic

form in canaries with 70 - 90% mortality.

Lesions:

Gross:

Dry pox or cutaneous form: It starts as small whitish foci that develop into

wart-like nodules. The nodules eventually are sloughed and scab formation

precedes final healing. Lesions are most commonly seen on the featherless parts

of the body (face, eyelids, beak, feet, legs, vent, etc.).

Wet pox or diphtheritic form: It is associated with yellow raised plaques on

the mucous membrane of the oral cavity and the upper respiratory tract,

particularly the larynx, trachea sinus, esophagus/crop, conjunctiva, etc.

Micro: -Proliferation or hyperplasia of epithelial cells (papules), ballooning

degeneration with eosinophilic intracytoplasmic inclusion bodies (Bollinger’s

bodies or Borrel elementary body) in the epithelium of the epidermis, feather

follicles, larynx, trachea -Pneumonia in canaries.

Avian Pox: Grayish warts on comb, face.

Avian Pox: Grayish warts on comb, face and wattle.

Avian Pox: whitish plaques on the oral mucosa.

Avian Pox: ICIB (Bollinger’s bodies).

6-Infectious Bursal disease (Gumboro Disease):It is acute viral disease of young chickens (1-6 weeks) and secondary

immunosuppression. Turkeys and ducks are subclinically infected.

Etiology: Birnavirus

Clinical Signs: Depression, ruffling feather, loss of appetite, tremors the

whole body, incoordination, vent picking and watery yellowish-white

diarrhea. The course of the disease is 5-9 days with high morbidity 10-

30% and low mortality (1-20%). The peak of mortality is reached on the

3rd day after symptoms have appeared then gradually declined to zero

during the next 5 days (i.e. at 8-9th day).

Lesions: -Enlarged and edematous bursa of Fabricius sometimes with hemorrhages

and atrophy in later stages with caseated material.

-Hemorrhages in skeletal muscles of the thigh and breast.

-Petechial hemorrhages at the junction between proventriculus and gizzard.

-The kidneys are enlarged, pale and the ureters filled with urates.

-Thymic atrophy with virulent IBD

-Lymphoid necrosis and depletion in spleen, bursa, cecal tonsil and thymus.

Gumboro disease: Edema and enlargement of the bursa.

Gumboro disease: Edema and enlargement of the bursa

with hemorrhages.

Gumboro disease: Depletion and necrosis of lymphocytes

with cystic formation in the lymphoid follicles.

Gumboro disease: Depletion and necrosis of lymphocytes

with cystic formation in the lymphoid follicles.

Gumboro disease: Depletion and necrosis of lymphocytes

with cystic formation in the lymphoid follicles.

Gumboro disease: Hemorrhages among muscles of thigh.

Gumboro disease: Hemorrhages at the junction

of proventriculus and gizzard.

7-Avian EncephalomyelitisIt is viral disease of young (1-3 weeks) chickens, turkeys,

pheasants and quail. It is characterized by:

-Paralysis and tremors of the head and neck (epidemic tremor)

-Drop in egg production in layers

-Egg transmitted

Etiology: enterovirus (family Picornaviridae).

Lesions: Neuronal swelling, chromatolysis, lymphocytic perivascular

cuffing, gliosis. Lymphocytic aggregations among muscle

fibers of proventriculus and gizzard. Pancreatitis with

immature lymphocyte infiltrations.

-A few survivors can develop cataract.

Avian encephalomyelitis: Incoordination, ataxia and tremors.

Avian encephalomyelitis: Neuronal degeneration

with central chromatolysis.

Avian encephalomyelitis: Lymphocytic infiltration

in the muscularis of proventriculus

8-Marek’s Disease:It is one of the most common and well-studied diseases of young chickens.

Etiology: Cell-associated herpesvirus.

Pathogenesis: virus replicates in feather follicle-epithelium, infection

through respiratory route, viremia, infection of B cells, cytolysis,

infection of activated T cells, cytolysis, immunosuppression, infection of

other organs like nerves (paralysis & blindness), latency, transformation

of T cells (CD4), lymphoma. The disease includes 4 syndromes:

1-Neural Syndrome 2-Ocular Syndrome(Gray eye disease)

3-Cutaneous Syndrome 4-Acute Marek’s Syndrome

Lesions:

Gross:

i-Bursal and thymic atrophy.

ii-Swollen , thickened and beaded peripheral nerves.

iii-Enlarged organs with pale white tumors in liver, spleen,

kidneys, lungs, proventriculus,

iv-intestine, heart, gonads and thymus.

v-Irregular/grayish-white iris.

vi-Prominent feather follicles and skin ulceration.

Microscopic: i-Pleomorphic lymphocytic lymphoma in various organs (different

population of plasma cells, small lymphocytes and lymphoblasts).

ii-Intranuclear inclusion bodies in feather epithelium.

iii-Arteriosclerosis can be produced with MD virus.

NB: The Marek’s disease has 3 types (A, B and C). In type A show

primitive and activated reticular cells, lymphoblasts and

lymphocytes; Type B show intraneuretic edema and Schwann cell

proliferation, small lymphocytes and plasma cells; and type C

show lymphocytes and plasma cells. Types A and B induce

demyelination of the nerves and paralysis.

9-Leukosis/Sarcoma Group:Genus: ALV- related viruses of family Retrovirus.

Six subgroups: A, B, C&D (exogenous viruses), E (endogenous) & J

(recombinant) -A, B and J are common in the field, C and D are rare.

Neoplasms: sarcoma’s (fibro, osteochondro, myxo, histio, lympho,

hemangio), meningioma, mesothelioma, erythroblastosis, myeloblastosis,

nephroblastoma, granulosa cell tumor, hepatocellular carcinoma, glioma,

(osteopetrosis), etc.

A-Lymphoid LeukosisIt is the disease of semimmature and mature chickens (after 4

months). It is characterized by a gradual onset and persistent low

mortality. The neoplastic changes start in bursa and metastasize to

the organs, particularly the liver, spleen and kidneys.

Etiology: retrovirus of leukosis/sarcoma group. Exogenous viruses,

subgroups A, B, C and D.

Lesions:-Focal or diffuse white or gray neoplastic lesions are seen in

the bursa, liver, spleen and kidneys

-Microscopically, uniform population of B lymphocytes (large

lymphocytes and lymphoblasts) are focally or diffusely seen in

the affected organs.

B-Myeloid Leukosis: It is neoplastic disease primarily of broiler and originates from the

granulocytic series in bone marrow.

Etiology: retrovirus, subgroup J (leukosis/sarcoma group).

Lesions:i-Large numbers of immature granulocytes (myelocytes and

myeloblasts) in the bone marrow,

peripheral blood (500,000/mm3 ), splenic red pulps and liver (in

blood vessels and sinuses).

ii-The yellow bone marrow becomes grayish-red.

iii-The liver, spleen and kidneys are enlarged and brownish red.

C-Erythroblastosis: It is very rare in chickens (more 1 year) and affecting the

erythropoietic tissue.

Lesions:i-Accumulation of large numbers of immature erythrocytes in the

blood and bone marrow.

ii-The fatty (yellow) bone marrow is replaced by red one.

iii-The liver, spleen and kidneys are diffusely enlarged (5 times)

and reddish in color.

iv-The hepatic and splenic sinusoids are dilated with immature

RBCs. (invade the white pulps).

v-The hepatic cords are atrophied or necrotic.

D-Osteopetrosis: Thickening of long bones, particularly the legs with

narrowing or occlusion of the marrow cavity (anemia). The virus effects

on the osteoblasts (proliferation).

E-Reticuloendotheliosis

It includes runting syndrome, chronic lymphoma and acute reticulum

cell sarcoma. It is primarily in chickens and turkeys

Etiology: retrovirus of REV group, distinctly different from

leukosis/sarcoma group.

Lesions :In Runting Syndrome: thymic and bursal atrophy, neuritis,

abnormal feathering and lymphoma (similar to Marek’s disease).

In Chronic Lymphoma: bursal and visceral lymphoma (similar to

Lymphoid Leukosis).

In Acute Reticulum Cell Sarcoma: enlarged liver, spleen, kidneys,

heart, gonads, pancreas, etc. as a result of focal or diffuse

reticulum cells and lymphocytes.

Criteria Marek’s Disease Lymphoid Leukosis

Susceptible Age

Prevalence

Clinical Signs

Gross lesionsPeripheral nerve enlargement

Bursa of Fabricius

Skin, eyes, muscles or proventriculus

Involvement

Microscopic LesionsCell Morphology

The Predominant Lymphocytes

Nerve infiltration

Cuffing in white matter of cerebellum

Liver

Bursa of Fabricius

Follicular patterns of lymphoid cells

infiltration in the skin

4-6 weeks or older

Usually above 5%

Frequently paralysis or paresis

Usually present

Diffuse enlargement or atrophy

May be present

Mixed population of

lymphoblasts, small, medium and

large lymphocytes, reticulum

cells and plasma cells .

(T cells).

Present

Present

Frequently Perivascular

Interfollicular tumor or atrophy

Present

Over 16 weeks old

Seldom above 5%

Absent

Absent

Nodular tumors

Usually absent

Uniform populations

of lymphoblasts

(B cells)

Absent

Absent

Focal or diffuse

Intrafollicular tumor

Absent

Marek’s Disease: Enlargement of sciatic nerve, gray eye, skin nodules

and liver nodules. Microscopically, mixed population of lymphoblasts,

lymphocytes, plasma cells and fibroblasts

Lymphoid Leukosis: Enlarged liver with multiple whitish nodules.

Lymphoid Leukosis: Uniform

population of lymphoblasts.

Lymphoid Leukosis: Osteopetrosis (increase

in the thickness of bone).

10-Chicken Infectious Anemia: It is viral disease of young chickens characterized by aplastic anemia

and immunosuppression. Chicks 1-3 weeks of age most susceptible

and vertically transmitted.

Etiology: circovirus

Hematology: Anemia, hematocrit less than 27% (N: 35%),

leukopenia, thrombocytopenia due to cytotoxic effect of virus on bone

marrow precursor cells.

Lesions: i-Pale bone marrow,

ii-Severe thymic atrophy,

iii-Atrophy of bursa, hemorrhages in skeletal muscles and

lymphoid necrosis and depletion (similar to IBD).

iv-Bone marrow hypoplasia.

v-Eosinophilic (red) intranuclear inclusions in mononuclear cells

of thymus, spleen, bone marrow, bursa, lung, etc. in some cases.

11-Duck Viral EnteritisIt is acute viral disease of primarily adult ducks, geese and swans

characterized by high mortality.

Etiology: herpesvirus

Lesions: -Hemorrhages on heart, liver and gizzard.

-Fibrinonecrotic lesions in esophagus, rectum, cloaca and bursa.

-Annular band of hemorrhage and necrosis in intestine and ceca.

-Thymic atrophy.

Micro: Necrosis, inflammation and intranuclear inclusions in liver,

intestine, thymus, gland of Harder (Harderian gland), conjunctiva

-Esophagitis and bursal necrosis with intranuclear and

intracytoplasmic inclusions in mucosal cells.

12-Duck virus hepatitisIt is peracute viral infection of ducklings (less 5 weeks) characterized by

-Sudden and rapid mortality (high).

-Spasmodic paddling in legs.

-Opisthotonus (down and back word head).

Etiology: DVH-1, enterovirus

DVH-2, astrovirus

DVH-3, enterovirus (unrelated to DVH-1)

Lesions: -The liver is enlarged, friable and mottled with hemorrhagic spots.

-The spleen is enlarged and mottled.

-The kidneys are enlarged and pale.

Micro:-Hemorrhages and necrosis in the hepatic cells.

-Proliferation of bile ducts with minimal inflammation.

-Intracytoplasmic (Shehata bodies) and intranuclear inclusion

bodies in the liver cells.

Fungal Diseases1-Aspergillosis

It is one of the most common fungal diseases of poultry, waterfowl,

psittacines, passerines, ratites, raptors, zoo birds (penguins), etc.

Etiology: Aspergillus fumigatus and A. flavus most common

Clinical Signs: Respiratory signs (brooder pneumonia in poultry),

unthrifty, diarrhea, neurological signs, ocular involvement, etc.

Lesions:

-Pale yellow nodules in lungs, air sac, syrinx, sinus, liver, brain,

cloudy cornea, etc.

-White plaques with fuzzy green or gray or blue material

(conidiophores-fruity bodies) on air sacs (fructification).

-Micro:

-Thin branched and septated hyphae are seen on the caseated nodules

-Granulomatous reaction of macrophages and giant cells are

predominant.

-Vasculitis (aortic rupture), which explicate the pathogenesis of the

disease (invasion the wall of blood vessels with the hyphae).

Aspergillosis: Miliary nodules in the lungs.

Aspergillosis: Thin basophilic septated branching hyphae.

2-Candidiasis: called thrush, crop mycosis, sore crop and moniliasis.

It is common mycosis of the upper digestive tract of young birds.

Etiology: Candida albicans

Lesions:-The crop is usually empty or contains slimy mucus.

-The mucosa of the crop is thickened and shows areas or raised

patches of ulceration, which tend to flake off leaving a raw parboiled

appearance.

-Ulcers may be found in the oral cavity, esophagus Proventriculus,

gizzard and intestine.

-Systemic and ocular candidiasis has been described.

Micro: non-branched pseudohyphae and blastocysts are seen in the lesions

with granulomatous reaction.

3-ZygomycosisIn ostriches, psittacines, water fowl, canaries involving proventriculus

and gizzard and air sacs in a pigeon

Etiology: Mucor sp, Absidia sp. and Rhizopus sp. isolated

Lesions: necrotizing lesions with granulomatous reaction

Thrush (Moniliasis): Ulcerated mucosa with empty crop

4-Favus (avian ringworm):It is a chronic dermatomycosis, characterized by development of

grayish-white crusts mainly on the comb and wattle of chickens, turkeys

and duck.

Etiology: Microsporum or Trichophyton gallinae

Lesions:

-Grayish-white circinate spots (ring) on comb and wattles. These spots

increase in size and join together to form dirty grayish-wrinkled crusts.

-In advanced cases, the lesions extend to the neck and body causing the

feather fall out in patches.

Micro:

Acanthosis, hyperkeratosis and dermatitis beside the fungi and

microspores are seen.

5-Crpytococcosis:Etiology: C. neoformans in psittacines, pigeons, pheasant and

experimental infection in chickens

Lesions: Sinusitis, encephalitis, hepatitis, pneumonia, etc.

Histoplasmosis - due to H. encapsulatum

Granulomatous iridocyclitis in experimental infection of chickens

Parasitic Diseases

Protozoal Diseases1-Coccidiosis

It is common protozoal disease of many species of birds caused by species of

genera primarily Eimeria and Isospora and is quite host specific.

Etiology: Eimeria tenella (ceca), E. acervulina (upper small int.), E. maxima

and E. necatrix (mid small intestine) in chickens.

Lesions:

-Hemorrhagic enteritis with white to yellow foci or petechial hemorrhages on the

serosal.

-Micro: Numerous coccidia in different stages of development are seen in the

epithelial lining.

Remark:

A-Turkeys: common, less severe than in chickens. E. adenoides (ceca), E.

meleagrimitis (mid small intestine).

-Hemorrhagic or necrotic enteritis.

B-Geese: E. truncata occurs in kidneys. Nephritis and urate deposits

E. anseris causes enteritis

C-Ducks: renal coccidia due to E. boschadis.

Coccidiosis: Hemorrhagic enteritis, cecitis.

Coccidiosis: Hemorrhagic enteritis, cecitis.

Coccidiosis: Developmental stages of Eimeria in the enterocytes.

2-Histomoniasis (Blackhead disease or infectious

typhlohepatitis)It is a common protozoal disease of turkeys, chickens, peafowl, quail.

Etiology: Histomonas meleagridis

Cecal worm, Heterakis gallinarum and earthworms act as accessory hosts.

Lesions: -The lesions are restricted to the ceca and liver.

-The ceca are enlarged; show ulceration and necrosis

(fibrinonecrotic) in the mucosa.

-The liver shows yellow necrotic areas surrounding a darker

hemorrhagic depressed center (saucer shaped depressions).

-The skin of affected birds is bluish-black in color, particularly on

the head (blackhead).

-Micro:

The lesions are represented by caseous necrosis with spherical

trophozoites of H. meleagridis (8 - 21 um in diameter) and

surrounded by granulomatous reaction in liver and ceca.

Histomoniasis (Black head disease of turkey): Typhalo-hepatitis.

Histomoniasis: Trophozoites of Histomonas mleagridis

In the hepatic tissue (PAS).

3-TrichomoniasisIt is a common infection of pigeons (squab) and raptors.

Etiology: T. gallinae in pigeon.

Tetratrichomonas anatis in ducks.

Tetratrichomonas gallinarum in mocking bird .

Lesions

-Granulomatous stomatitis, pharyngitis, esophagitis,

ingluvitis, and enteritis.

-Hepatitis, pericarditis, airsacculitis, tracheitis,

pneumonia, meningoencephalitis.

-Sinusitis, rhinitis, .

Avian toxicosisMycotoxinsGenerally ducklings, turkey poults and pheasants are more susceptible

Aflatoxins (B1, B2, G1and G2): B1 most toxic, liver has congestion,

necrosis, fatty change, karyomegaly, numerous mitotic figures, bile duct

hyperplasia, fibrosis, immunosuppression, myocardial, kidney

degeneration, etc.

Model for hepatocarcinogenesis.

Toxic Fat Syndrome:It affects the young chickens due to feeding on ration containing “Rancid

Fat”.

Lesions:1-Ascites with fibrinous clots.

2-Hydropericardium and Subcutaneous edema.

3-The crop filled with bloody content (stained the beak and head region

with blood).

4-The liver either

A-Large and mottled with pale and hemorrhagic areas early stage.

B- Shrinked, nodular and firm late stage.

5-Petechial hemorrhages on coronary fat.

Micro:1-Necrosis and hemorrhages in the liver.

2-Bile duct proliferation and fibrosis.

3-Myocardial degeneration.

4-Interstitial edema in the kidneys.

Nutritional diseases1-Vitamin A deficiencyVitamin A is essential in poultry diets for growth, vision and integrity of mucous

membrane.

Clinical Signs:Weakness, emaciation, ruffled feathers and decrease in egg production

beside Water discharge from nostrils and eye beside exophthalmia are seen.

Lesions:i-Small white pustules or caseated materials are found in mouth,

esophagus, larynx and nasal passage

ii-The pustules enlarged and raised above the surface and have

depression in the center

iii-Later on, it ulcerated and surrounded by inflammatory zone

Microscopically: (Nutritional roup)

i-Atrophy and deciliation of the respiratory columnar ciliated

epithelium is the first change. Later sloughing of the epithelium lining

occur, beside regenerating epithelium under the sloughed one.

ii-Stratified metaplasia of respiratory epithelium are noticed

iii-Metaplasia of the epithelium lining of the upper digestive glandular

duct, leading to blocking of the ducts of mucous membrane and

accumulation of secretion and debris.

Vitamin A deficiency: whitish nodules (nutritional roup).

2-Vitamin D:It is required for normal metabolism of calcium and phosphorus in

the function of skeleton, hard beaks, clause and strong egg shell.

Clinical Signs and Lesions:

i-Marked increased in thin and soft shell egg.

ii-Beak, claws and keel become soft.

iii-Sternum is bent easily and ribs lose rigidity and turn inward at

junction of the sternal and vertebral position.

iv-Enlarged parathyroid gland.

v-Rachitic rosary (Knobs) are found on the inner surface of ribs

and at costochondral junction.

3-Vitamin KVitamin K is required for synthesis of prothrombin

Lesions: Large hemorrhage appear on the breast, wing and legs

4-Riboflavin (Vitamin B2)Clinical Signs and Lesions:

-Diarrhea, inability to walk and walk on hocks when forced beside

drop wing, inward curled toe and atrophy of leg muscle

-Degenerative changes of myelin sheaths of peripheral nerve trunks

Rickets (Vitamin D def): Bending of the rib heads.

5-Thiamin (vitamin B1):Clinical Signs and Lesions:

-Polyneuritis, anorexia, loss of body weight, leg

weakness and unsteady gait

-Paralysis of muscle beginning with the flexors of

toes and extend upward affecting extensors muscle

of legs, wings and neck so the chicken sit on its

flexed legs and drawback the head (stargazing

position).

تـم بحمد اهللمحمد حامد محمد./ د.أ

أســـــــتاذ الباثولوجيا