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Department of Pathology, Faculty of Veterinary Medicine, Zagazig University, Egypt.

Pathology of Poultry Diseases BY

Prof. Dr. Mohamed Hamed Mohamed mohamedelariny@yahoo.com +201224067373

2013


Avian Pathology Avian 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 suppurative inflammation 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 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 Diseases 1-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: affects layers. -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).


Moist inflamed navel (Omphalitis)


Yolk sac infection Caused by

E. coli, Salmonella,

Congested yolk sac


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: 1-Septicemic lesions of omphalitis with persistent yolk sac (contain creamy or caseated material. 2-Liver is enlarged, friable and with necrotic foci. 3-Catarrhal enteritis with white diarrhea. 4-Peritonitis, necrotic typhlitis, pericarditis, splenitis, pneumonia, synovitis, nephritis and opthalmitis.


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

In adults: 1-Oophoritis (hemorrhagic or atrophied), salpingitis, peritonitis (ascites), and orchitis 2-The liver is enlarged, bronzy color (hemosiderosis) and show necrotic foci (typhoid) 3-Enteritis (ulcerative duodenitis). 4-Grayish nodules in the lungs, liver, intestine heart, gizzard, spleen. 5-Inflamed and swollen joints. 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. NB: -S. enteritidis can cause septicemic lesions in chicks. In pigeons: brain, bone, and gonads often involved.

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.


Pedunculated ova Flaccid ova

Fowl typhoid (S. gallinarum)


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: 1-Petechial hemorrhages on viscera, serous and mucous membrane, fat and on the gizzard. 2-Hemorrhagic enteritis (duodenitis) 3-Enlarged liver with numerous necrotic foci ( corn meal liver). 4-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.


(CCRD) chronic complicated respiratory disease : E.coli and mycoplasma + bad managment


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 diseases I-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


-Ballooning of intestine - congested B.vs and liver


Ulcerative enteritis: Roughly circular ulcers in the mucosa.


Ulcerative enteritis: Roughly circular ulcers in the mucosa.


Thickening and Sloughing of intestinal mucosa Intestine is velvet like in appearance

Necrotic enteritis (Cl. perfringens )


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.


9-Staphylococcosis Staphylococcal Arthritis (Bumblefoot) It caused by Staphylococcus bacteria, mainly S. aureus and seen in chickens and turkeys worldwide. Morbidity is usually low and mortality 0-15% though affected birds. Infection is usually by the respiratory route with an incubation period of 2-3 days seen after artificial infection. Wounds, either accidental or induced by interventions such as beak trimming, and toe trimming may be a portal of entry with subsequent spread via the bloodstream to the typical sites of lesions. Damaged skin due to nutritional deficiencies (such as of biotin) may also be a point of entry.

Clinical Signs: Ruffled feathers, Lameness, Low mobility, Swollen above the hock and around the hocks and feet, Some sudden deaths from acute septicemia if very heavy challenge.

Lesions: 1-Tenosynovitis, most commonly in the plantar area of the foot or just above the hock joint. This may progress to abscess formation in these areas. 2-Infected joints may have clear exudate with fibrin clots.


Abscess formation in the plantar area of the foot


Avian Viral diseases 1-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 besides 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 Bronchitis Etiology: 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 iii-Sneezing- coughing

ii-Mild respiratory disorder 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 Pox It 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 1030% 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, S/C 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. -Liver shows peripheral areas of infarction.


Enlarged bursa of Fabricus

Kidney nephrosis

Gumboro disease


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.


Hemorrhages in skeletal muscles of the thigh and breast

Gumboro disease


Gumboro disease: Hemorrhages among muscles of thigh.


Gumboro disease: Hemorrhages at the junction of proventriculus and gizzard.


7-Avian Encephalomyelitis It 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 3-Cutaneous Syndrome

2-Ocular Syndrome(Gray eye disease) 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 Leukosis (Big liver): It 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 gray neoplastic lesions are seen in the bursa, liver, spleen and kidneys -Microscopically, uniform population of B lymphocytes (large lymphocytes and lymphoblasts) are focally 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 reticular cells and lymphocytes.


Criteria Susceptible Age Prevalence Clinical Signs

Gross lesions

Neural enlargement Bursa of Fabricius Skin, eyes, muscles or proventriculus Involvement

Microscopic Lesions Cell Morphology

Marek’s Disease 4-6 weeks or older Usually above 5% Frequently paralysis or paresis

Lymphoid Leukosis Over 16 weeks old Rarely above 5% Absent

Usually present Diffuse enlargement or atrophy

Absent Nodular tumors

May be present

Usually absent

Mixed population of lymphoblasts, small, medium and large lymphocytes, reticulum cells and plasma cells . The Predominant Lymphocytes (T cells). Neural involvement Present Cuffing in white matter of cerebellum Present Liver Frequently Perivascular (diffuse) Bursa of Fabricius Involved Spleen (Follicular patterns of lymphoid Interfollicular tumor or atrophy cells ) Infiltration in the skin Present

Uniform populations of lymphoblasts (B cells) Absent Absent Often Focal Not involved 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 Enteritis It 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 hepatitis It 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 Diseases 1-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 circular 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-Zygomycosis In 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)


1-Empty crop with slimy mucus. 2- Crop mucosa is : -Thickened, corrugated and with whitish circular areas or raised patches of ulceration -Pseudomembrane formation. 3- Ulcers found in oral cavity, esophagus Proventriculus, gizzard and intestine.

Thrush (Moniliasis)


Thrush (Moniliasis): Ulcerated mucosa with empty crop


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


Favus: Grayish-white circinate spots

Feather fall out in patches


Parasitic Diseases Protozoal Diseases 1-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: 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 ceci 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-Trichomoniasis It is a common infection of pigeons (squab) and raptors. Etiology: T. gallinae in pigeon. Tetratrichomonas anatis in ducks.

Lesions -Granulomatous stomatitis, pharyngitis, esophagitis, ingluvitis, and enteritis. -Hepatitis, pericarditis, airsacculitis, tracheitis, pneumonia, meningoencephalitis. -Sinusitis, rhinitis, .

Avian toxicosis Mycotoxins Generally 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 diseases 1-Vitamin A deficiency Vitamin 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 K Vitamin 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).



Pathology of Poultry Diseases