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Department of Pathology,
Faculty of Veterinary Medicine,
Zagazig University, Egypt.
Pathology of Veterinary DiseasesBY
Mohamed Hamed [email protected]
+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