Saturday, September 09, 2006

An Overview of Avian Pathology

H. L. Shivaprasad
California Veterinary Diagnostic Laboratory System, Fresno Branch
University of California, Davis
2789 South Orange Avenue
Fresno, CA 93725
Tele: 559-498-7740
Fax: 559-485-8097
E-mail: hprasad@cvdls.ucdavis.edu

Avian Inflammation
Reaction is rapid in birds, 36 hours
Leakage of fibrin and fibrinogen common in early exudate
Intense granulomatous reaction (12 hours)
Coagulum of eosinophilic debris, degranulating heterophils, macrophages and giant cells
Macrophages, heterophils and thrombocytes are active phagocytes
Pus is caseous but liquefaction can occur
Birds respond with granulomatous inflammation to many insults
Acute inflammatory reaction in birds involve edema, congestion and vascular changes mediated by basophils and mast cells
1-3 hours: basophils, heterophils and monocytes
2-6 hours: basophils degranulate and die
6-12 hours: lymphocytes, monocytes, macrophages
12-36 hours: lymphocytes, macrophages, giant cells
Acute reaction peak by 12 hours (when giant cells appear)
36-72 hours: regeneration and repair
Fibroblasts, secondary lymphoid follicles, plasma cells
Chronic reaction with caseation, macrophages, giant cells, granuloma formation
Cells involved in inflammation
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
Eosinophils: have spherical granules
Function is not known, delayed type IV hypersensitivity?
Associated with eosinophilic enteritis in turkeys due to ascarids
Basophils: contain histamine, involved in acute inflammation
Thrombocytes: small round to oval cells with clear cytoplasm and small round nucleus (looks like small lymphocyte), phagocytic
Monocytes: precursors to cells of MPS, phagocytic, can fuse to form multinucleated giant cells
Make monokines; IL-1, IL-2, TNF, G-CSF, gamma intf.
Lymphocytes: various morphologies involved in subacute inflammation including plasma cells
Avian Bacterial Diseases
Disease caused by E. coli, Salmonella, Chlamydophila, Clostridia, Mycobacteria, Mycoplasma, Bordetella, Haemophilus, Pasteurella, Erysipelas, Yersinia pseudotuberculosis, Riemerella anatipestifer, Ornithobacterium rhinotracheale, Staphylococcus, Streptococcus, Pseudomonas and other miscellaneous bacteria
Colibacillosis
Disease of great economic significance in poultry
Any one of the syndromes in poultry caused by E. coli
Colisepticemia, air sac disease (CRD), peritonitis, coligranuloma, salpingitis, omphalitis/yolk sac infection, cellulitis, osteomyelitis/synovitis, swollen head syndrome and panophthalmitis
Enteritis with AAEC, eae gene present
Ceca most commonly involved
Common in turkeys, others; chickens, pigeons, quail, partridges, pheasants, ducks, ostriches, etc.
Septicemia and enteritis in psittacines and other birds?
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, etc.
10-20 species: S. typhimurium, S. enteritidis, S. heidelberg, S. anatum, S derby, S. bredeney, etc.
Arizonosis in turkey poults, S. arizonae
Also in chicks, ducklings, psittacines, passerines, etc.
Lesions
Pullorum/Typhoid
In chicks: Septicemic lesions of omphalitis, hepatitis, peritonitis, necrotic typhlitis, pericarditis, splenitis, pneumonia, synovitis, nephritis, opthalmitis, etc.
Pale yellow nodules in myocardium (histiocytes), intestine and gizzard in chronic cases
In adults: oophoritis, salpingitis, peritonitis, orchitis
Paratyphoid
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
Important in egg-associated food poisoning
Arizonosis, in turkey poults
Septicemic lesions, meningitis, ophthalmitis
Chlamydiosis
Naturally occurring contagious systemic disease of various species of birds
Chlamydophila psittaci, six serotypes (A, B, C, D, E and F)
Diagnosed in 139 avian species, 15 orders and 30 families
Psittacines, 25% of the reported host species, others; pigeons, passerines, wild and feral birds, rheas, turkeys, pheasants, etc.
Chickens relatively resistant
Clinical signs: vary greatly, species and age of bird, and strain of Chlamydia
Respiratory signs, oculonasal discharge, diarrhea often greenish colored, swelling above eye (turkeys), conjunctivitis (pigeons), etc.
Lesions: airsacculitis, pericarditis, pneumonia, hepatitis, splenitis, enteritis, conjunctivitis, nasal adenitis (turkeys), synovitis, encephalitis, nephritis, etc.
Chlamydia-taxonomy (Int. J Syst. Bact. April 1999)
Order: Chlamydiales
Family: Chlamydiaceae
Genus: Chlamydophila
Species: C. psittaci
C. pneumoniae
C. pecorum
C. felis
C. caviae
C. abortus
Genus: Chlamydia
Speices: C. trachomatis
C. suis
C. muridarum
Chlamydophila psittaci
Obligate nonmotile, coccoid intracellular bacteria
Depends on host cells for ATP metabolites
Multiply within membrane-bound inclusions, in the cytoplasm of host cells
Have a non-synchronous multimorphic developmental cycle:
Spore-like, non-vegetative elementary body (EB), uniformly spherical particle of 300nm diameter
Ingestion by host cell, fusion of bacterial endosome with host lysosomes?
EB undergoes conversion to metabolically active reticulate body (RB), 800-1200nm
RB replicate by binary fission, within a membrane bound vacuole, the chlamydial inclusion
Intermediate bodies (IB) can also be seen
Mature to infectious EB’s which infect other cells by lysis of host cells or by extrusion of chlamydial inclusion
Clostridial diseases
C. perfringens (type A most common) - necrotic enteritis in poultry, ratites, psittacines, etc.
C. colinum - ulcerative enteritis in poultry, especially in quail (quail disease), toucans, ratites, etc.
C. difficile - entero/typhlocolitis in ratites (ostrich)
Liver may have foci of necrosis and inflammation with the above clostridial diseases
C. septicum - gangrenous dermatitis in poultry, especially chickens (C. perfringens can also cause)
C. botulinum - limberneck in poultry
Mycobacteriosis
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, psittacines , passerines, etc.
M. genavense - psittacines, passerines?
M. tuberculosis - psittacines, others?
M. bovis - psittacine, others?
Lesions
Poultry, pigeons, raptors, ratites; grossly pale yellow or grey nodules in liver, spleen, intestine, bone marrow, lung, heart, etc.
micro: caseous necrosis surrounded by multinucleated giant cells and fibrosis
Psittacines, passerines, touracos; grossly pale mottling or diffuse enlargement of liver, spleen, intestine, lung, heart, eyelid, skin, etc.
micro: diffuse or focal infiltration of foamy macrophages with myriads of acid fast bacilli in the cytoplasm, necrosis is unusual
Mycoplasmosis
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?
M. gallisepticum (MG) – Disease called chronic respiratory disease (CRD) in chickens and infectious sinusitis in turkeys. Other birds susceptible include, quail, pheasants, partridges, peafowl, finches, etc.
Egg transmitted also
Respiratory disease with swollen infraorbital sinus, tracheitis, airsacculitis, conjunctivitis, etc.
Primarily of lymphocytic inflammation
MG can cause decreased egg production in layers
Some strains of MG can cause neurological signs in turkeys due to vasculitis in the brain
M. synoviae (MS) - in chickens, turkeys, geese, quail, partridge, ducks, etc.
Egg transmitted also
Subclinical infection of respiratory disease, sinusitis, tracheitis, air sacculitis, conjunctivitis
It can cause severe synovitis, ulceration
Lymphocytic inflammation, proliferation of synovial cells
Some strains of MS can cause neurological signs in turkeys, (chickens?) due to vasculitis in the brain
Disseminated vasculitis in synovium, eye, kidney, skeletal muscle, heart, lung, etc., can be seen in turkeys
M. melagridis - affects turkeys
Egg transmitted also
Airsacculitis in day-old poults
Decreased hatchability, swelling of hock joint, bowing of tarsometatorsus (TS-65 syndrome), deformation of cervical vertebrae (wry neck)
M. iowae - affects turkeys
Egg transmitted also
Causes decreased hatchability and embryo mortality
Turkey Coryza (Bordetellosis)
Caused by Bordetella avium
Upper respiratory tract infection primarily of young turkey poults; swollen sinus, collapsed trachea, watery eyes
Tracheitis: deciliation, squamous metaplasia, and lymphoplasmacytic inflammation
Decrease of GAGS (?) in the cartilage, effect of toxin ?
B. avium can be a significant pathogen in young broiler chickens, ratites, passerines and psittacines (lock jaw?)
Infectious Coryza
Disease primarily of young chickens caused by Haemophilus paragallinarum
Pheasants and guinea fowl are also susceptible
Upper respiratory tract infection; swollen sinus (sinusitis/rhinits), facial edema, conjunctivitis
Occasionally tracheitis, bronchitis and airsacculitis
Fowl Cholera
Also called avian cholera, pasteurellosis
Septicemic disease of birds with high mortality and morbidity
Etiology: P. multocida
Most common in turkeys, chickens, wild waterfowl
Other birds such as geese, quail, pheasants, raptors, psittacines, passerines, zoo birds, etc., are susceptible
Lesions
Acute: petechiae on viscera, consolidated lungs (common in turkeys), enlarged liver with foci of necrosis, pericarditis, airsacculitis, cellulitis, endocarditis, etc.
Mucoid enteritis in waterfowl
Peritonitis and oophoritis in breeders
Chronic: swollen wattles, synovitis, otitis, osteomyelitis of cranial bones, sinusitis, conjunctivitis, etc.
Esophageal abscesses in raptors
Erysipelas
Acute septicemic disease of primarily turkeys
Etiology: Erysipelothrix rhusiopathiae
Chickens, emus, pheasants, ducks, grebes, geese, chukars, raptors, psittacines, zoo birds, etc.
Lesions
Acute cases: hemorrhages over epicardium, abdominal fat, skin, muscle, congested and enlarged spleen, foci of hepatic necrosis
Chronic cases: vegetative endocarditis and arthritis
Pseudotuberculosis
Chronic contagious disease of psittacines, canaries, finches, poultry, raptors, wild birds, etc.
Yersinia pseudotuberculosis
Birds often found dead, loss of weight, digestive and respiratory signs can be seen
Lesions
Pale yellow nodules of caseous granulomas in liver, spleen, intestine, lung, airsacs, bone, muscle, etc.
Lesions can be confused with mycobacteriosis or coligranuloma
Riemerella anatipestifer
Previously classified as Pasteurella anatipestifer
Disease called new duck disease, goose influenza
Disease of young domestic ducks, geese and turkeys
Respiratory signs, ocular discharge, diarrhea, neurological signs, as much as 10% mortality
Fibrinosuppurative airsacculitis, pericarditis, perihepatitis, meningitis, uveitis, etc.
Skin and joints may be involved
Ornithobacterium rhinotracheale
Recently described Gram negative bacillus associated with respiratory disease in poultry, primarily turkeys and broiler chickens
It has been isolated from layer-type chickens, pheasants, partridges, pigeons, psittacines, etc.
Consolidated lungs (similar to fowl cholera), tracheitis, airsacculitis, sinusitis, peritonitis, hepatic necrosis, etc.
Staphylococcosis
Systemic infection of birds caused by S. aureus
Less commonly by S. epidermidis and S. hyicus
S. aureus most common in turkeys and broiler chickens, but has been isolated from a variety of bird species
Lesions: omphalitis, synovitis, arthritis, osteomyelitis, green liver, gangrenous dermatitis, cellulitis, endocarditis, abscesses (bumblefoot), etc.
Streptococcosis
Systemic infection of a variety of birds caused by species of genus Streptococcus
S. zooepidemicus, septicemia in chickens, turkeys, pigeons, wild birds, etc.
Valvular endocarditis with secondary infarcts in heart, liver, spleen, etc.
Others: osteomyelitis, arthritis, tenosynovitis, salpingitis
S. bovis, septicemia in turkeys, pigeons, etc.
S. faecium, septicemia in ducklings and goslings
Enterococcus hirae, encephalomalacia with vascular thrombosis and meningitis in broiler chicks
Miscellaneous bacteria
Pseudomonas aeruginosa, Klebsiella pneumoniae - can cause localized or systemic infection in poultry and other birds
Bacillus anthracis - been reported in ostriches as a cause of septicemia
Listeria monocytogenes - can cause septicemia and encephalitis in chickens
Campylobacter jejuni - been associated with enteritis and hepatic necrosis in ostriches
Lawsonia intracellulare - associated with enteritis in ratites
Megabacteria ? - associated with proventriculitis in psittacines, ostriches, etc.
Eubacterium tortuosum - granulomas in liver and spleen, broiler chickens and turkeys
Clostridium piliformis (Tyzzer’s disease) - hepatic necrosis in psittacines
Spirochetosis:
Borrelia anserina, septicemia in poultry and canaries
Serpulina hyodysenteriae associated with typhlitis in rheas, in poultry?
Serpulina piloscholi in ceca of pheasants, disease?
Avian Fungal diseases
Aspergillosis
One of the most common fungal diseases of poultry, water fowl, psittacines, passerines, ratites, raptors, zoo birds (penguins), etc.
Aspergillus fumigatus and A. flavus most common
Others: A. niger, A. terreus, A. glaucus, etc.
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 grey or blue material (conidiophores-fruity bodies) on air sacs, pleura, etc.
Fibrinosuppurative or granulomatous pneumonia, airsacculitis, syringitis, sinusitis, encephalitis, ophthalmitis, vasculitis (aortic rupture), hepatitis, osteomyelitis, pericarditis, etc.
Candidiasis
Common mycosis of the upper digestive tract
Also called thrush, crop mycosis, moniliasis
Young birds most susceptible
Candida albicans most common etiology
Poultry, psittacines, passerines, ratites, raptors, pigeons, water fowl, etc.
Oral cavity, esophagus and crop involved with white proliferative plaques
Proventriculus, gizzard, intestine less often involved
Systemic and ocular candidiasis have been described
Zygomycosis
In ostriches, psittacines, water fowl, canaries involving proventriculus and gizzard and air sacs in a pigeon
Mucor sp, Absidia sp. and Rhizopus sp. isolated
necrotizing lesions with granulomatous reaction
Favus (avian ringworm)
Due to Microsporum gallinae, dermatophyte of chickens with white powdery material on head, face and eyelids
Acanthosis, hyperkeratosis and dermatitis
Dactylariosis
Due to D. gallopava in turkeys and quail
Fibrinosuppurative encephalitis and ophthalmitis
Crpytococcosis
Due to C. neoformans in psittacines, pigeons, pheasant and experimental infection in chickens
Sinusitis, encephalitis, hepatitis, pneumonia, etc.
Rhinosporidiosis
Due to R. seeberi in swans
Granulomatous conjunctivitis
Others fungal diseases
Histoplasmosis - due to H. encapsulatum
Granulomatous iridocyclitis in experimental infection of chickens
Penicillium
Penicillium griseofulvum, systemic infection in a toucanet
P. cyclopium, beak infection in a macaw
Trichosporon
Trichosporon beigelii, granulomatous pneumonia, myocarditis, hepatitis in a macaw
Curvularia
Curvularia geniculata, mycetoma in a parrot
Scedosporium
Scedosporium prolificans isolated from feet of an ostrich with severe hyperkeratosis
Geotrichum and Paecilomyces
Geotrichum candidum and Paecilomyces variota have been isolated with disease
Avian Viral diseases
Diseases caused by herpesvirus, retrovirus, coronavirus, paramyxovirus, orthomyxovirus, picornavirus, poxvirus, birnavirus, parvovirus, adenovirus, reovirus, enterovirus, circovirus, papovavirus, arbovirus, bunyavirus and other miscellaneous viruses
Marek’s Disease
One of the most common and well studied diseases of young chickens
Quail and turkeys are also susceptible
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
Lesions
Gross: bursal and thymic atrophy, swollen peripheral nerves, enlarged organs with pale white tumors in liver, spleen, kidney, lung, proventriculus, intestine, heart, gonads, thymus, irregular/gray iris, prominent feather follicles, etc.
Microscopic: lymphoid necrosis and depletion in bursa, and thymus, neuritis, encephalomyelitis, pleomorphic lymphocytic lymphoma in various organs
Intranuclear inclusion bodies in feather epithelium
Arteriosclerosis can be produced with MD virus
Leukosis/Sarcoma Group
Genus, ALV- related viruses of family Retrovirus
Six subgroups; A, B, C and D (exogenous viruses), E (endogenous) & J (recombinant)
A, B and J are common in the field, C and D are rare
Various oncogenes been identified (see table 1)
They can produce a variety of neoplasms in chickens
Influenced by strain of virus, virus dose, route of inoculation, age of host, genotype and sex of host
Neoplasms: sarcoma’s (fibro, osteochondro, myxo, histio, lympho, hemangio), meningioma, mesothelioma, erythroblastosis, myeloblastosis, nephroblastoma, granulosa cell tumor, hepatocellular carcinoma, glioma, (osteopetrosis), etc.
Lymphoid Leukosis
Disease of semimature and mature chickens
Etiology: retrovirus of leukosis/sarcoma group
Exogenous viruses, subgroups A,B, C and D
Transmission
Horizontal, transient viremia, immunity, LL rare
Egg transmission, chronic viremia, immune tolerance, LL common
B cell lymphoma in various organs, bursa of Fabricius, liver, spleen, kidney, gonads, etc.
Osteopetrosis
thickening of long bones
Effect of virus on osteoblasts
Myelocytomatosis
Neoplastic disease primarily of broiler breeders and broilers
Etiology: retrovirus, subgroup J (leukosis/sarcoma group)
Lesions: liver, spleen, kidney, sternum, etc., with nodules made up immature granulocytes
Hemangiosarcoma, histiocytoma, myxoma, carcinomas in liver, fibrosarcoma, lymphoma, ganglioneuroma, renal tumors, etc., have also been associated with subgroup J virus
Reticuloendotheliosis
Includes runting syndrome, chronic lymphoma and acute reticulum cell sarcoma
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, 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, kidney, heart, gonads, etc.
Infectious laryngotracheitis
Acute viral respiratory disease of primarily chickens
Pheasants and peafowl are also susceptible
Etiology: herpesvirus
Lesions: oculonasal discharge, trachea with hemorrhage and/or fibrinous exudate
Conjunctivitis, tracheitis and sinusitis, syncytia formation and intranuclear inclusion bodies
Infectious Bronchitis
Highly contagious viral respiratory disease of young chickens
Drop in egg production and egg quality in layers
Etiology: coronavirus, many serotypes, and great antigenic variation among strains of virus
Lesions: catarrhal tracheitis, conjunctivitis, bronchitis, and airsacculitis
Fibrinosuppurative inflammation in cases complicated with E. coli
Interstitial nephritis with nephrotropic strains
Avian Paramyxoviruses
Newcastle Disease
Acute viral disease of chickens, turkeys, pigeons, doves, pheasants, ratites, psittacines, cormorants, etc.
236 species of birds comprising 27 orders
Etiology: avian paramyxovirus - 1, isolates vary greatly in pathogenicity to chickens
Lentogenic: mild or inapparent infection in chickens
Mesogenic: cause disease and mortatlity in young chickens
Velogenic (viscerotropic and neurotropic): lethal infection of chickens of all ages
Clinical signs
Vary with strain, respiratory, digestive, ocular, neurological, sudden death
In mature chickens, egg production and quality problems (mesogenic strain)
Lesions
In pigeons: enteritis, pancreatitis, nephritis, encephalitis, respiratory system rarely involved
In chickens; tracheitis, pneumonia, enteritis, conjunctivitis, encephalitis, myocarditis, lymphoid necrosis
Velogenic; hemorrhages in conjunctiva, trachea, oral cavity, esophagus, proventriculus, ceca, rectum
Disseminated vasculitis, lymphoid necrosis and depletion, mucosal necrosis and ulceration
Inclusions are rare
In a recent case, discrete eosinophilic intranuclear and intracytoplasmic inclusions in conjunctiva, esophagus, lung, brain, 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
Other Avian Paramyxoviruses
PMV - 2 (Yucaipa):
Respiratory disease in young turkeys and drop in egg production in layers, chickens are susceptible
PMV - 3, two strains, turkey and psittacine
Turkey; egg production drop in turkeys
Psittacine; neurological and digestive problems in psittacines and passerines
Encephalitis with intranuclear and intracytoplasmic inclusion bodies in neurons and glial cells
Myocarditis, pancreatitis with intranuclear inclusions
PMV -5 (Kunitachi):
Enteritis and mortality in budgerigars and lorikeets
Avian Influenza
Acute viral disease of poultry; turkeys and chickens and psittacines, passerines, ratites, etc.
It has been isolated from many species of birds
Waterfowl may serve as reservoir
Etiology: type A influenza virus of family Orthomyxoviridae
Numerous subtypes based on surface antigens, hemagglutinin (13) and neuraminidase (9)
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
Clinical signs: vary greatly, respiratory, digestive, ocular, neurological, sudden death, etc.
Drop in egg production in layers
Lesions: vary greatly in pathogenicity
Mildly pathogenic: catarrhal tracheitis, sinusitis, airsacculitis, conjunctivitis, pneumonia, etc.
Highly pathogenic: hemorrhagic lesions in skin of face, comb & shanks and GI tract, interstitial pneumonia & nephritis, encephalitis, conjunctivitis, myocarditis, adrenalitis, pancreatitis, myositis, lymphoid necrosis, vasculitis and thrombosis, etc.
Avian Encephalomyelitis
Viral disease of young (1-3 weeks) chickens, turkeys, pheasants and coturnix quail
Neurological signs (epidemic tremor)
Drop in egg production in layers
Egg transmitted
Etiology: enterovirus (family Picornaviridae)
Lesions: neuronal swelling, chromatolysis, lymphocytic perivascular cuffing, lymphocytic foci in muscular layer of proventriculus and gizzard, pancreatitis
A few survivors can develop cataract
Avian Pox
Slow spreading viral disease of chickens, turkeys, quail, pigeons, canaries, raptors, psittacines, ostrich, peacock, waterfowl, etc.
60 species of wild birds
Etiology: poxvirus of genus Avipoxvirus, many strains
Fowl pox, turkey pox, pigeon pox, canary pox, quail, mynah, psittacine, junco, sparrow, starling, etc.
Signs: cutaneous, respiratory, digestive, ocular
Septicemic form in canaries, 70 - 90% mortality
Lesions
Gross:
Dry pox or cutaneous form: proliferative skin lesions on face, eyelids, beak, feet, legs, vent, etc.
Wet pox or diphtheritic form: yellow raised plaques in sinus, trachea, oral cavity esophagus/crop, conjunctiva, etc.
Micro:
Proliferation of epithelial cells, ballooning degeneration with eosinophilic intracytoplasmic inclusion bodies (pathognomonic)
Desquamative pneumonia in canaries
Some avipoxviruses are oncogenic, wart-like growth
Infectious Bursal disease
Acute viral disease of young chickens (1-6 weeks) and secondary immunosuppression
Turkeys and ducks, subclinical infection
Etiology: birnavirus
Lesions: enlarged and edematous bursa of Fabricius some times with hemorrhages and atrophy in later stages, hemorrhages in skeletal muscle, thymic atrophy with virulent IBD
Lymphoid necrosis and depletion
Secondary infections with inclusion body hepatitis, gangrenous dermatitis, bursal cryptosporidiosis, etc.
Chicken Infectious Anemia
Viral disease of young chickens characterized by aplastic anemia and immunosuppression
Chicks 1-3 weeks of age most susceptible
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: pale bone marrow, severe thymic atrophy, atrophy of bursa, hemorrhages in skeletal muscles
Lymphoid necrosis and depletion, bone marrow hypoplasia
Gangrenous dermatitis, colibacillosis, aspergillosis, viral infection, etc.
Eosinophilic (red) intranuclear inclusions in mononuclear cells of thymus, spleen, bone marrow, bursa, lung, etc. in some cases
True nature of these inclusions not known
Duck Viral Enteritis
Acute viral disease of primarily adult ducks, geese and swans characterized by high mortality
Etiology: herpesvirus
Lesions: hemorrhages on heart, liver, gizzard, fibrinonecrotic lesions in esophagus, rectum, cloaca, bursa, annular band of hemorrhage and necrosis in intestine, ceca, and thymic atrophy
Necrosis, inflammation and intranuclear inclusions in liver, intestine, thymus, gland of Harder, conjunctiva, etc.
Esophagitis and bursal necrosis with intranuclear and intracytoplasmic inclusions in mucosal cells
Duck virus hepatitis
Peracute viral infection of ducklings (< 5 weeks) characterized by high mortality
Etiology:
DVH - 1, enterovirus
DVH - 2, astrovirus
DVH - 3, enterovirus (unrelated to DVH1)
Lesions: petechiae or ecchymotic hemorrhages and necrosis in liver, minimal inflammation
Parvovirus Infection
Goose parvovirus (Derzsy’ disease): highly contagious disease of young geese and Muscovy ducks
Serofibrinous pericarditis and perihepatitis
Myocarditis with intranuclear inclusions
Muscovy duck parvovirus
Serologically related to goose parvovirus
Causes locomotor problems with high mortality in 1-3 weeks-old ducks, loss of weight , pale leg muscles, serofibrinous pericarditis and perihepatitis
Myositis, myocarditis, encephalomyelitis, neuritis, etc.
Ascites, round hearts in ducks recovered infection
Avian Adenoviruses
Three groups:
Group I - quail bronchitis, inclusion body hepatitis and hydropericardium syndrome in chickens, also disease in turkeys, pigeons, psittacines, raptors, etc.
Group II - hemorrhagic enteritis virus of turkeys (HEV), marble spleen disease of pheasants (MSD) and splenomegaly of chickens
Group III - egg drop syndrome of chickens
Quail bronchitis
High mortality in young bobwhite quail associated with bronchopneumonia, tracheitis, hepatitis, pancreatitis, bursal necrosis, intranuclear inclusions
Inclusion body hepatitis of chickens, also in turkeys, guinea fowl, pigeons, psittacines, etc.
In chickens usually secondary to immunosuppression caused by IBDV, CIAV
Liver enlarged and mottled red/pale, foci of necrosis, inflammation and intranuclear inclusion bodies, also pancreatitis
Similar lesions seen in turkey poults, guinea fowl, pigeons
Hepatitis, enteritis, bronchitis, pancreatitis, nephritis, encephalitis, etc., associated with intranuclear inclusions in psittacines
Hemorrhagic enteritis virus (HEV) of turkeys and Marble spleen disease (MSD) of pheasants
Caused by group II adenovirus
Guinea fowl, psittacines, (partridge) susceptible
Young turkeys (4-12 weeks) and pheasants (3-8 months)
With HEV, intestinal hemorrhage and enlarged mottled white spleen and immunosuppression
Intranuclear inclusions in mononuclear cells of spleen and intestine, renal epithelial cells in HEV
In pheasants mottled white enlarged spleen, MPS cell hyperplasia, intranuclear inclusions
Poult Enteritis
Disease of young turkeys, multiple etiologies
Viruses include coronavirus (blue comb disease), enterovirus, rotavirus, astrovirus, etc.
Diarrhea, loss of weight, mortality 1 - 55%, small intestine and ceca distended with watery or frothy contents, caseous exudate in bursa, thymic atrophy
Increased cellularity of lamina propria, necrosis of cells in lamina propria, villus atrophy, lymphoid necrosis in thymus and bursa (virus?)
Herpesviruses
Psittacine Herpesvirus
Probably diverse group of viruses which infect a variety of psittacines
Three diseases are known
Pacheco’s disease
Acute viral disease of a variety of psittacines (common in 1980’s in US)
Lesions:
enlarged liver occasionally with petechiae, enlarged spleen, fluid filled intestine, diptheretic membrane in oral cavity, esophagus, etc.
liver necrosis with or without inflammation, enteritis, stomatitis, esophagitis, pancreatitis, conjunctivitis, splenic and bursal necrosis, nephritis with intranuclear inclusion bodies
syncytia formation with inclusions in liver
Amazon tracheitis, disease characterized by tracheitis, bronchitis, rhinitis, laryngitis with syncytia formation and intranuclear inclusions
Virus has some cross reactivity with ILT virus of chickens
Budgerigar herpesvirus, rare disease associated with decreased hatchability and "feather duster" plumage
Other herpesviruses
Pigeon herpesvirus
Common in young squabs characterized by hepatitis, pancreatitis, esophagitis associated with intranuclear inclusions
Conjunctivitis, enteritis, myocarditis, encephalitis, laryngitis, splenitis, etc. can also be seen
Raptors and budgies susceptible
Finch herpesvirus (cytomegalovirus)
Disease of primarily Gouldian finches characterized by high mortality, conjunctivitis, tracheitis, bronchitis, associated with cytomegalic cells and inclusions
Others herpes viruses of owls, falcons, eagles, cranes, etc.
Hepatitis associated with inclusion bodies
Psittacine Beak and Feather Disease
Viral disease of many species of psittacines characterized by chronic feather and beak dystrophy
Acute immunosuppression and sudden death in young birds due to secondary bacterial septicemia and fungal infections
Etiology: circovirus
Clinical signs: dystrophic feathers first noticed of the powder down, progress to contour feathers, followed by primary, secondary tail and crest feathers, almost symmetrical
Lesions
Gross: abnormal and loss of feathers, sloughing of claws, beak necrosis, necrosis of oral mucosa, liver, bursa, thymus, etc.
Microscopic: pterylitis and pulpitis associated with botryoid inclusions in macrophages, also in bursa, bone marrow, thymus, beak, claws, liver, pancreas, thyroid, testes, etc.
Intranuclear inclusions in feather epithelium, intestine, esophagus, hepatocytes
Papovavirus
Two genera are known to cause disease in psittacines and passerines
Papillomavirus
Polyomavirus
Papillomavirus
It has been associated with cutaneous papillomas in wild finches (Fringilla) and an African Grey Parrot
No virus has been associated with papillomas of cloaca, conjunctiva, tongue, larynx, oral cavity, crop/esophagus, etc., in psittacines
Polyomavirus
Causes Budgerigar fledgling disease (BFD)
One of the most common diseases of psittacines (disease of 90’s?) and passerines
Antibodies to BFDV been detected in chickens, but chickens are resistant to infection
Etiology: polyomavirus, different strains such as psittacine, passerine, etc., may exist
Variety of psittacines, finches and canaries are susceptible
Young psittacines are highly susceptible with very high mortality (30 - 100%), also adults
Feather dystrophy in budgerigars, acute death, digestive, neurological, respiratory, etc.
Lesions
Gross: variation among psittacines and also passerines
In most of psittacines feather dystrophy, hemorrhages in skin, subcutis, skeletal muscle, heart, intestine, liver enlarged and mottled red or with white foci, splenomegaly, pale kidneys, ascites, lung congestion, pale carcass, etc.
In passerines, liver enlarged and mottled white, serosal or subserosal hemorrhage of intestine, pale myocardium, etc.
Microscopic: hemorrhages in various organs, necrosis in spleen, bursa, thymus and bone marrow, midzonal or random necrosis in liver, myocarditis, enteritis, nephritis, membranous glomerulopathy, pancreatitis, conjunctivitis, encephalomyelitis, ganglionitis (spinal), etc.
Bluish karyomegalic inclusions in various tissues; epidermis, feather follicle epithelium, esophagus, kidney, macro/lympho of spleen, bursa, thymus, bone marrow, liver, etc., hepatocytes, myocytes, endothelial cells, glial cells, Purkinje cells, etc.
Proventricular Dilation Syndrome (PDD)
A common chronic disease of psittacines
Characterized by dilation of proventriculus, anorexia, regurgitation, passing of undigested seeds in feces, diarrhea, neurological signs, loss of weight, etc.
Etiology: not known, presumed to be a virus
Lesions
Gross: dilated thin proventriculus in 70% of cases, distended duodenum, etc.
Microscopic: lymphoplasmacytic ganglioneuritis of splanchnic nerves of crop/esophagus, proventriculus, gizzard, intestine, adrenalitis, myocarditis, neuritis, encephalomyelitis, choroiditis, etc. (see table 2)
Miscellaneous Viral Diseases
Turkey viral hepatitis
Disease of young turkeys
Etiology: picornavirus
Liver and pancreas with foci of necrosis and inflammation
Viral arthritis
Disease primarily of young chickens and turkeys
Etiology: reovirus
Joints enlarged with fluid, proliferative synovitis
Turkey Rhino Tracheitis (TRT) of turkeys, Swollen Head Syndrome (SHS) of chickens
Highly contagious respiratory diseases
Etiology: pneumovirus (Paramyxoviridae)
Lesions: swollen sinuses, sinusitis, tracheitis, rhinitis, conjunctivitis
Avian nephritis
Highly contagious disease of chickens
Etiology: picornavirus
Nephritis and secondary visceral urate deposition
Arboviruses
Eastern Equine Encephalomyelitis virus
Causes neurological signs and encephalitis in pheasants, partridges, finches and turkeys
In young turkeys and chickens, myocarditis, lymphoid necrosis in bursa and thymus
Hemorrhagic enteritis and splenic necrosis in emu’s
Western Equine Encephalomyelitis virus
Encephalitis, myocarditis, hemorrhagic leiomyositis of intestine associated with vasculitis in emu
Encephalitis in pigeon and neuro signs in turkeys
Highland J virus:
Encephalitis and myocarditis in partridges and young turkeys
Associated with precipitous drop in egg production in turkeys
Hepadna virus in ducks (hepatitis B virus):
Common but no significant clinical disease or lesions
Bunya virus (Turlock-like):
Associated with encephalomyocarditis in an ostrich chick
Avian Parasitic diseases
Protozoa: coccidia, histomonas, cryptosporidia, sarcocystis, toxoplasma, atoxoplasma, amoeba, microsporidia, trichomonas, leucocytozoon, malaria, haemoproteus, giardia, cochlosoma, spironucleus (Hexamita), balantidium, trypanosomes, hemoporozoa, etc.
Nematodes: Ascarids, Capillaria, Syngamus, Tetrameres, Heterakis, Baylisascaris, etc.
Cestodes: Raillietina, Davainea, Hymenolepis, etc.
Trematodes: Prosthogonimus, Schistosomes, etc.
Arthropods: mites, fleas, lice, etc.
Protozoa
Coccidiosis
Common disease of many species of birds caused by species of genera primarily Eimeria and Isospora and are quite host specific
Chickens: disease of universal importance
Eimeria tenella (ceca), E. acervulina (upper small int.), E. maxima and E. necatrix (mid small intestine)
Hemorrhagic, mucoid, necrotic, proliferative enteritis
Numerous coccidia in different stages of development
Turkeys: common, less severe than in chickens
E. adenoides (ceca), E. meleagrimitis (mid small intestine)
Mucoid, hemorrhagic, necrotic enteritis
Geese: E. truncata occurs in kidney
Nephritis and urate deposits
E. anseris causes enteritis
Ducks: renal coccidia due to E. boschadis, etc.
Quail, partridges, and pheasants: various species of Eimeria causes enteritis
In quail coccidiosis is commonly associated with ulcerative enteritis caused by Cl. colinum
Pigeons: E. labbeana causes enteritis
Psittacines:
Species of Eimeria, E. dunsingi and Isospora can cause enteritis in budgerigars, lories, parakeets, parrots, etc.
Passerines:
Finches: Isospora lacazei has been associated with enteritis
Cranes:
E. gruis and E. reichenowi causes granulomatous enteritis, hepatitis, splenitis, pneumonia, myocarditis, etc. in whooping and sandhill cranes
Histomoniasis
Also called black head, a common protozoal disease of turkeys and partridges
Also in chickens, peafowl, quail, pheasants, rhea, etc.
Etiology: Histomonas meleagridis
Cecal worm, Heterakis gallinarum and earth worms act as accessory hosts
Lesions: saucer shaped depressions or white foci in liver and fibrinonecrotic mucosa and thickened wall of ceca
Granulomatous hepatitis and typhlitis associated with spherical protozoa, 8 - 21 um in diameter
Cryptosporidiosis
Common protozoa of various species of birds
Chickens, turkeys, quail, ratites, ducks, pheasants, peafowl, psittacines, passerines, etc.
C. baileyi, C. meleagridis and probably others
Infect various body systems
Cloaca, bursa of Fabricius and trachea most common
Nasal cavity, sinus, bronchus, air sac, conjunctiva
Proventriculus, intestine, ducts of pancreas, salivary and esophageal glands and bile duct
Ureter, collecting tubules of kidney
Inflammation and hyperplasia of epithelium
Sarcocystosis
Systemic protozoal disease of psittacines caused by S. falcatula
Opossum is the definitive host, cowbirds and grackles are intermediate hosts
Old World psittacines highly susceptible
Young new world psittacines, canaries, finches, pigeons are susceptible, gallinaceous birds and anseriformes are resistant
Sarcocystis with encephalitis has been described in a golden eagle, capercailles and chickens
S. riley causes sarcocystosis in skeletal muscle of ducks, innocuous incidental finding
Lesions
Pulmonary edema, congestion, liver may be enlarged and mottled white, splenomegaly
Lymphoplasmacytic interstitial pneumonia, edema and schizonts in capillaries
Myocarditis, hepatitis, splenitis, nephritis, encephalomyelitis, neuritis, myositis, uveitis, etc., associated with schizonts
Mature cysts in the heart and skeletal muscle
Generally no reaction to cysts in muscles
Toxoplasmosis
Sporadic disease of various species of birds
It has been described in passerines (canaries), chickens, psittacines, pigeons, ducks, penguin, Japanese quail, chukar partridges, etc.
Turkeys, pheasants, Bob White quail, owls resistant
Etiology: T. gondii
Lesions: encephalomyelitis, ophthalmitis, pneumonia, myocarditis, hepatitis, splenitis, neuritis, myositis, enteritis, adrenalitis, etc. associated with zoites and cysts
Optic nerve; may be enlarged and yellow with necrotizing and granulomatous neuritis in chickens
Atoxoplasmosis
Common coccidian infection of canaries and finches, (previously called Lankesterella)
Also in mynah’s, sparrows, grosbeaks
Etiology: A. serini (Isospora serini), A. adiei
Lesions
Liver enlarged with white foci, splenomegaly
Enteritis, hepatitis, myocarditis with arteritis, splenitis, myositis, etc.
Schizonts in cytoplasm of macrophages
Lankesterella-like coccidia associated with pneumonia in a Northern Cardinal
Microsporidiosis
It can be a significant disease of psittacines
It has been reported in a variety of lovebirds, budgerigars, parrots, cockatiels, etc.
Also reported in ostrich
Encephalitozoon hellum, others?
Lesions: granulomatous nephritis, necrosis and inflammation in liver, enteritis, pneumonia, etc. associated with Gram positive organisms
Trichomoniasis
A common infection of pigeons and raptors
Also in canaries, finches, doves, psittacines, ducks, poultry, wild birds, etc.
Etiology: T. gallinae
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, episcleritis
Leucocytozoonosis
Disease of anseriformes, turkeys, raptors, wild birds and columbiformes
Black flies (Simuliidae) are vectors
Etiology: L. simondi in anseriformes, L. smithi in turkeys, L. marchouxi in columbiformes, L. toddi in falconiformes, L ziemanni in owls
Infect both white and red blood cells
Lesions
Disseminated characteristic megaloschizonts in endothelial cells of liver, spleen, heart, brain, eye with hepatitis, myocarditis, encephalitis, etc.
L. caulleryi, which causes severe disease in young chickens in south and eastern Asia, is classified as Akiba caulleryi
Vectors are biting midges of genus Culicoides
Lesions are similar to ducks
Leucocytozoon-like infection has been described in budgerigars, parakeets and a buzzard
Myositis, myocarditis and hemorrhages in skin, pericardium, pancreas, hepatosplenomegaly, etc.
Avian Malaria
Hemoprotozoal infection of canaries, penguins and raptors caused by species of Plasmodium
Ducks, pigeons, chickens, grouse, pheasants, sparrows, blackbirds, robin, etc. are susceptible
Three species of Culicoides are vectors
Etiology: P. relictum, P. elongatum, P. circumflexum, etc.
Infect red blood cells and cells of MPS
Lesions: anemia, interstitial pneumonia, hepatitis, splenitis, encephalitis, etc.
Brown-black pigment (malaria pigment) in RBC, MPS Cells
Hemoproteus
Hemoprotozoa of some significance primarily in columbiformes
Common in raptors, water fowl, passerines, etc.
Also seen in psittacines
Etiology: H. columbae in pigeons and doves
Biting flies of hippoboscids and Culicoides are vectors
Infects red blood cells and endothelial cells
Lesions: anemia, hepatitis, splenitis, myositis, pneumonia, etc.
Schizonts and megaloschizonts can be seen
Giardia, Spironucleus (Hexamita)
Giardia psittaci cause of enteric disease in budgerigars
Others: cockatiels, love birds, parrots, conures, many wild birds, herons , egrets, sparrows, etc.
H. meleagridis an enteric protozoa of turkeys
Others: pheasants, quail, partridge, ostrich, pea fowl, etc.
Lesions
Emaciation, fluid filled intestine, catarrhal enteritis
Other enteric protozoa
Cochlosoma anatis, a flagellate enteric protozoon of small intestine is associated with catarrhal enteritis in turkeys
Entamoeba gallinarum common in large intestine of turkeys, significance?
Others: Chilomastix gallinarum in turkeys, Balantidium spp. in ostriches, Wenyonella philiplevinei in ducks, Blastocystis sp. in pheasants, etc.
Miscellaneous protozoa
Hemosporozoa of undetermined taxonomy
Disseminated myositis associated with cysts and high mortality in BW quail in California
Also hepatitis, splenitis, myocarditis, nephritis, etc. associated with cysts, encephalomyelitis
Large protozoan cysts of undetermined spp. associated with hepatitis, splenitis, pneumonia in canaries, conures, love birds, oropendola, etc.
Amoeba of undetermined spp. associated with meningoencephalitis in a cockatiel
Others: trypanosomes, aegyptianella, etc.
Nematodes
Ascariasis
Common intestinal parasitism of many birds
Chickens, turkeys, pigeons, partridges, raptors, psittacines (Australian parakeets), passerines, etc.
Etiology: Ascaridia galli (chicken), A. dissimilis (turkey), A. columbae, A. hermaphrodita, species of Porrocaecum and Contracaecum, etc.
Lesions: loss of weight, intussusception, mild enteritis if in large numbers
Eosinophilic enteritis in turkeys
Granulomas in livers due to larval migration
Bile duct hyperplasia and pericholangitis associated with larvae in bile ducts in parakeets
Capillariasis
Significant disease primarily of upper digestive tract in many species of birds
Quail, pheasants, partridges, guinea fowl, turkeys, pigeons, chickens, raptors, ducks, pscittacines, etc.
Etiology: C. contorta, C. annulata, etc.
Lesions: hyperplastic mucosa, fibrinonecrotic esophagitis, ingluvitis, etc.
C. obsignata, C. caudinflata may cause enteritis in galliformes and columbiformes
Cerebrospinal nematodiasis
Common condition in a variety of birds
Chickens, emus, ostriches, psittacines, raptors, quail, partridges, wild birds, etc.
Etiology: Baylisascaris procyonis (raccoon) and occasionally B. columnaris (skunk)
Lesions: non-suppurative encephalomyelitis
Larvae of Chandlerella quiscali, a filarid nematode of grackle has been associated with encephalitis in emu
Syngamus
Common tracheal worm (gape worm) of pheasants
Others: turkeys, geese, quail, peafowl, chickens
Etiology: Syngamus trachea
Lesions: granulomatous tracheitis and occasionally bronchitis
Cyathostoma bronchialis can cause bronchitis and pneumonia in geese
Also been associated with tracheitis in emus
Nematodes of Proventriculus and Gizzard
Dispharynx nasuta, Cyrnea colini, Tetrameres americana, Cheilospirura hamulosa and species of Acuaria, Synhimantis, Habronemia, Amidostomum, Hadjelia, etc.
Occur in pigeons, chickens, quail, ducks, turkeys, pheasants, psittacines, passerines, etc.
Lesions: proventriculitis and ventriculitis
Geopetitia aspiculata (Habronemia) causes severe proventriculitis in passeriformes and others
Libyostrongylus douglassii causes severe proventriculitis in ostriches
Miscellaneous nematodes
Heterakhis isolonche: fibrous and granulomatous typhlitis in pheasants
Trichostrongylus tenuis: enteritis in young grouse and geese
Oxispirura mansoni: conjunctivitis in galliformes
Thelazia sp. have been associated with conjunctivitis in psittacines
Pelecitus calamiformis(filarid): tenosynovitis associated with adult nematodes in parrots
Microfilariae are common in psittacines, especially cockatoos, not pathogenic
Microfilariae associated with severe pneumonia in magpies
Paronchocerca ciconarum (filarid): myocardial degeneration with adult nematodes in a Marabou Stork
Cardiofilaria - heart worm in psittacines
Cestodes
Common intestinal tapeworms of many species of birds
Chickens, turkeys, ducks, geese, pigeons, psittacines, passerines, wild birds, etc.
Etiology and lesions:
Davainea proglottina (smallest); enteritis in chickens
Raillietina echinobothridia: granulomatous enteritis in chickens
Species of Raillietina, Hymenolepis, Amoebotaenia, etc. are common in psittacines and finches
Pathogenic in large numbers, obstruction, enteritis, etc.
Trematodes
Schistosomiasis: common in waterfowl
Dendritobilharzia sp.
Medial hypertrophy of vessels in the intestinal wall
Rarely hepatitis, encephalitis, nephritis, enteritis
Dicroceliidae: been associated with dilated bile ducts and severe cholangiohepatitis in cockatoos and an amazon parrot
Gigantobilharzia sp. associated with hemorrhagic ulcerative colitis and cloacitis in a nanday conure
Sphaeridiotrema globulus: causes severe ulcerative hemorrhagic enteritis in swans and cygnet and chickens (experimental)
Philophthalmus gralli: associated with conjunctivitis in ostriches
Collyriclum faba cause cysts in the skin of poultry, wild birds including robins
Prosthogonimus sp. oviduct fluke of poultry
Tanaisia bragai in collecting tubules of kidney in poultry, pigeons, etc.
Arthropods
Mites
Most common ectoparasites of a variety of species of birds
Chickens, canaries, finches, psittacines, pigeons, turkeys, pheasants, wild birds, etc.
Etiology (see table 3): species of Dermanyssus, Onithonyssus, Knemidocoptes, Sternostoma, etc.
Lesions
Anemia
Hyperkeratosis, acanthosis, epidermitis, dermatitis
Blockage, granulomatous tracheitis, airsacculitis, pneumonia
Cysts in skin, poor feather growth, loss of feathers, etc.
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, etc.
Immunosuppression, myocardial, kidney degeneration, etc.
Model for hepatocarcinogenesis
Citrinin, Ochratoxins, Oosporein: renal tubular necrosis and visceral urate deposition
In addition vacuoles, bile duct hyperplasia, etc. in liver associated with citrinin and ochratoxins
Trichothecenes (T2, DAS): radiomimetic effect, oral, proventricular and gizzard erosions, lymphoid necrosis and depletion, hepatic necrosis, etc.
Fumonisins: hepatic necrosis, biliary hyperplasia, widening of growth plates, myodegeneration, etc.
Moniliformin: myocardial degeneration, hepatic necrosis
Fusarochromanone: tibial dyschondroplasia
Cyclopiozonic acid: skeletal muscle, heart, liver, GI degeneration
Zearalenone: mycotoxin with estrogen activity
Cystic oviduct with inflammation, cysts in vent, etc.
Ergotism: beak and toe necrosis
Heavy metals
Lead: one of the most commonly reported toxic compounds of waterfowl and companion birds
Lesions: hemorrhagic enteritis, myocardial degeneration, hyalinosis of cerebral vessels with hemorrhage, nephrosis, demyelination of nerves, etc.
Acid fast intranuclear inclusions in renal tubular epithelial cells
Zinc: common in companion birds, waterfowl
Lesions: gizzard erosion, pancreatic acinar necrosis, enteritis, nephrosis
Iron: seen in a variety of birds
Lesions: hepatic necrosis, hemolysis of RBC
Ionophore toxicity
Ionophores widely used as anticoccidials in poultry
Toxicity most common in turkeys and chickens
Also described in quail, guinea fowl, etc.
Monensin, Lasalocid, Salinomycin, Narasin
Various compounds interact and influence toxicity
Lesions: degeneration of skeletal muscles (pectoral muscles not affected) and occasionally heart
In addition demyelination and axonal degeneration of peripheral nerves and spinal cord have been associated with lasalocid toxicity
Selenium, salt, calcium
Selenium: pulmonary congestion and edema in an ostrich chick
Salt: causes right heart hypertrophy, dilation and ascites in turkey poults and broiler chicks and occasionally encephalomalacia
Water high in salinity causes conjunctivitis, cataracts and hyperemia of brain in wild adult waterfowl
Cystic testes in poultry?
Calcium: nephrosis in young poultry
Vitamins
Vitamin D: common in psittacines
Soft tissue mineralization, proventriculus, heart, air sacs, etc.
Vitamin A: conjunctivitis and rickets in chickens
Hepatic degeneration, Ito-cell hyperplasia?
Gases; PTFE, Ammonia, CO
Polytetrafluoroethylene (PTFE): Teflon coated pans when overheated release toxic gases
Seen in companion birds, also in free flying birds
Pulmonary congestion and edema
Carbon monoxide: pulmonary congestion and edema, bright red colored blood
Ammonia: conjunctivitis, corneal erosions and ulcers and sinusitis and tracheitis in poultry
Rodenticides
Diphacinone, Brodifoucum: blood in abdominal cavity, hemorrhage in liver
Zinc phosphide: hydropericardium, pulmonary edema, congestion and hemorrhage in liver, congestion in kidney
Antibiotics
Gentamicin, Amikacin - nephrosis
Sulfa drugs - disseminated hemorrhages, nephrosis
Tetracyclines - nephrosis
Furazolidone - round heart, hepatocellular vacuoles
Plants
Avocado and oleander: myocardial degeneration
Oak: nephrosis
Coffee senna: degeneration of muscles
Parsley: photosensitization, dermatitis
Others
Organo-phosphates - acute and delayed neurotoxicity
Acute, inhibition of acetyl cholinesterase, no lesions
Delayed, axonal degeneration in peripheral nerves and spinal cord, chicken is the (test) animal model
Nitrate, Nitrite: Brown mucus membranes, methemoglobinuria
Arsenilic acid, nitro-phenyl-arsenic acid: demyelination of peripheral nerves
Quaternary Ammonium: erosions and ulcers in upper GI tract
Domoic acid (marine neurotoxin):
In pelicans and cormorants
Hemorrhage and necrosis in skeletal muscles
Avian Metabolic diseases
Goiter
In male mature buff Cochin chickens (Dr. D. Webb, IL)
Severely enlarged cystic thyroid glands with follicles lined by flattened epithelial cells
Genetics suspected
Hemochromatosis
Abnormal accumulation of iron in tissues associated with tissue disturbance such as cirrhosis
Most common in mynahs, toucans, crows, starlings, ducks, fruit doves, horn bills, psittacines, etc.
Hepatic degeneration, fibrosis, myocardial degeneration, ascites, etc.
Genetics, nutrition, hemorrhagic syndromes, starvation, etc.
Diabetes mellitus
It has been described in psittacines, toco toucans and a red-tailed hawk
Glucagon is the major glucose - regulating hormone in granivorous birds
Carnivorous birds are similar to mammals
Lesions
Hyperplasia of islet cells
Enlarged islets with eosinophilic cytoplasm in toco toucans
Islet cell tumor
Amyloidosis
Accumulation of amorphous eosinophilic material in various tissues
Liver, spleen, intestine, adrenal, kidney, synovium, heart, pancreas, thyroid, skin, brain, lung, etc.
Commonly associated with chronic infections
Most common in ducks and finches
Also in other water fowl, game birds, turkeys, psittacines, ratites, canaries, flamingoes, touracos, pigeons, doves, etc.
Lesions
Gross: ascites (water belly) in commercial ducks, firm enlarged and waxy liver sometimes with nodules, enlarged mottled white spleen, pale or brownish kidneys, etc.
Microscopic: interstitial accumulation of amyloid in liver with hepatocellular atrophy in severe cases, kidney, adrenal, thyroid, pancreas, spleen, in the lamina propria of intestine and proventriculus, in subepithelium of synovium, bronchus, in myocardium, brain, skin, vessels, etc.
Severe hepatic capsular fibrosis and nodules made up of hyperplastic hepatocytes
Gout (visceral and articular)
Uric acid is the end product of protein and purine metabolism (uricotelic) in birds, where as in mammals’ urea is the end product (ureotelic)
Birds lack the enzyme carbamyl phosphate synthetase to dispose of ammonia and the enzyme uricase to decarboxylate uric acid to allantoin
Gout is a metabolic condition where abnormal accumulation of white chalky or white semifluid-like urates in soft tissues of various organs in the body
Gout occurs as two distinct syndromes, visceral and articular gout
These two syndromes differ in age of onset, frequency, sex predilection, gross and microscopic lesions, pathogenesis and causes
Great deal of confusion exists between the two syndromes because urate deposition takes place in joints in visceral gout also
Term "visceral gout" should be replaced with the term "visceral urate deposits"
See table 4 to help clarify differences between the two syndromes
Hepatic Lipidosis
Common in some psittacines, budgerigars, amazons, rose breasted cockatoos, shell parakeets, etc.
Diet, environment, toxicities, hormones, genetics (shell parakeets) influence lipidosis
Lesions: obesity, hepatic lipidosis, and lipidosis in liver and other organs in shell parakeets
Hemorrhagic fatty liver syndrome (chickens)
Condition of obese layer-type chickens
Fat in abdominal cavity, fatty livers, ruptured livers
Atherosclerosis
Very common in psittacines especially amazons
Others: ducks, geese, chickens, turkeys, ostriches, flamingoes, herons, vultures, falcons, pigeons, etc.
Etiology: diet, environment, genetics, virus, age, etc.
Marek’s disease virus (herpesvirus) can induce atherosclerosis in chickens
White Carneaux pigeon used as model
Lesions
Thickened walls or plaques in brachiocephalic, carotid, abdominal aorta, etc., coronary arteries rarely involved
Thickening of intima and media with lipid laden cells
Mucopolysaccharidosis type IIIB (emu)
Also called Sanfilippo B syndrome
First description in any animal
Deficiency of N-acetyl-a -D-glucosaminidase
Probably inherited as a autosomal recessive trait
Signs and lesions
Sudden death, neurological signs
Ruptured liver or subcutaneous hemorrhages
Accumulation of membrane bound substance in neurons of nervous tissue and visceral organs
Aortic aneurism/rupture
Most common in turkeys, also in ostriches and emus
Longitudinal slit cranial to kidneys or at the origin of aorta
Medial degeneration and loss of elastic fibers
Genetics, hypertension, low copper, vasa vasorum defect?
Coronary artery aneurysm (turkeys)
In male turkeys, 15 -16 weeks-old, 1.5-3.5% mortality
Hemopericardium, hemorrhage across base of heart, medial degeneration of coronary artery, rupture
Genetics, hypertension, low copper, increased body weights?
Round heart disease (turkeys)
Also called spontaneous cardiomyopathy
Common condition in young commercial turkeys
Dilated ventricles, chronic passive congestion of liver
Cause is not known, genetics?
Ascites syndrome (chickens)
Common condition in broiler chickens
Right heart hypertrophy, dilation, passive congestion of liver and ascites
Rapid growth coupled with insufficient pulmonary capillary capacity aggravates pulmonary hypertension leading to right heart failure
Tibial dyschondroplasia (TD)
Common condition in broiler chickens and turkeys and ducks
Abnormal masses of cartilage below the growth plate primarily in the proximal tibiotarsus but occurs also in the tarsometatarsus
Presence of prehypertrophic cartilage with no vascular channels
Etiology: multifactorial, nutrition, genetics, mycotoxin, etc.
Similar picture as TD can be seen grossly in the long bones of ratites but it is not TD nor is pathologic
It is normal embryonic cartilage which gets resorbed by 6-8 weeks of age
Deep pectoral myopathy
Seen in well muscled broilers and turkeys
Green discoloration of primarily supracoracoideus muscle due to ischemic necrosis
Perirenal hemorrhage
Seen in rapidly growing turkeys, 8-14 weeks of age
Hemorrhage over portion or entire kidney
Underlying vascular and cardiac problems?
Xanthomatosis
Common in psittacines and occasionally in chickens
Yellow subcutaneous swelling or nodules in the body cavity
Giant cells, lymphocytes, macrophages with cholesterol clefts
Auto immune thyroiditis (chicken)
Occurs spontaneously in obese strain of chicken
Used as model to study Hashimoto’s thyroiditis
Birds have long and silky feathers, large amount of abdominal fat
Thyroids become small gradually as the bird matures and atrophies
Lymphocytic infiltration with few macrophages and lymphoid nodules, loss of architecture, thyroid gland
Antibodies to thyroglobulin
Hyperlipidemia, low T3 and T4 and IgA deficiency
Diseases of Malnutrition
Xerophthalmia
In non-commercial poultry, psittacines, etc.
Etiology: vitamin A deficiency
Lesions: pustule-like nodules in upper GI tract, exudate in conjunctiva, nasal cavity, nephrosis, opaque dry cornea, hyperkeratosis of plantar surfaces
Microscopic: squamous metaplasia of epithelium, hyperkeratosis
Polyneuritis
Rarely seen in poultry
Etiology: vitamin B1 (thiamin) deficiency
Lesions: prominent peripheral nerves with edema and infiltration of mononuclear cells
Malacia of the brain in fish eating birds
Rickets/osteomalacia
Rickets in younger birds and osteomalacia in older birds
In poultry, ratites, psittacines, zoo birds, etc.
Etiology: deficiency or imbalance of calcium, phosphorus and vitamin D3
Lesions: soft and pliable beak, claws and keel, beading of ribs, enlarged epiphysis, fractures of long bones, enlarged parathyroid glands
Microscopic:
Calcium deficiency - lengthened proliferation of Prehypertrophic Zone and short Degenerating Hypertrophied Zone (DHZ)
Phosphorus deficiency/calcium excess: lengthened DHZ
Vitamin D3 deficiency - similar to calcium deficiency
Encephalomalacia
In young chickens, turkeys, pheasants, geese, ducks, etc.
Etiology: vitamin E deficiency
Lesions: soft and enlarged cerebellum, petechiae, hemorrhages especially in turkey poults
Microscopic: malacia, hemorrhage, vascular thrombosis, demyelination in brain
Occasionally spinal cord involved, poliomyelomalacia
Yellow fat disease in wild birds: herons, etc.
Fat is brownish yellow, steatitis
Muscular dystrophy/exudative diathesis
In chickens, quail, turkeys, ducks, etc.
Etiology: vitamin E/Selenium deficiency
Lesions
Subcutaneous green-tinged fluid
Pale streaks in skeletal muscles, gizzard
Degeneration of skeletal muscle, heart, gizzard, pancreatic acinar necrosis
Curled-toe paralysis
Seen in chicks, turkey poults, ducklings
Etiology: vitamin B2 (riboflavin deficiency)
Lesions: swelling of peripheral nerves, axon and myelin degeneration, Schwann cell proliferation, etc.
Perosis/slipped tendon (chicks, poults)
Etiology: manganese and choline deficiency
Lesions: deformity of hocks, enlargement of condyle, bowing of tarsometatarsus, slipping of gastrocnemius tendon
Deficiency of pantothenic acid, biotin, folic acid, niacin can cause similar lesions
In addition dermatitis can be seen in birds deficient in biotin and pantothenic acid and poor feathering and anemia in niacin deficiency
Goiter
Common in psittacines especially in budgerigars
Also seen in pheasants, geese, chickens, etc.
Etiology: Iodine deficiency
Lesions: enlarged thyroid glands, some times cystic
Microscopic: severe hyperplasia of follicle epithelium with papillary projections, pale or lack of colloid, hemorrhage and severe effacement of the gland in extreme cases
Neoplasia
Most common in chickens and psittacines especially budgerigars among birds
Birds in the order Passeriformes have the lowest incidence
In chickens most are caused by viruses such as retroviruses and herpesvirus (Marek’s Disease)
Etiology is not known in other species of birds
Incidence in budgerigars range from 16 to 24 %
Some of the common tumors in psittacines include renal tumors, fibrosarcoma, lymphoma, papilloma, tumors of gonads, gastric carcinoma, leiomyosarcoma, pituitary adenoma, etc.
References:
1. Avian histopathology, 1996, Ed. C. Riddell, 2nd ed, AAAP pub., Kennett Square, PA
2. Color atlas of Avian histopathology, 1996, C.J. Randall and R.L. Reece, Mosby-Wolfe
3. Diseases of poultry, 1997, Ed. B. W. Calnek, et al., Iowa State University Press, Ames, Iowa
4. Color atlas of Diseases and Disorders of the Domestic Fowl, 1991, C.J. Randall, Iowa State University Press, Ames, Iowa
5. Avian Medicine: Principles and application, 1994, Ed. B. W. Ritchie, G.J. Harrison and L.R.Harrison, Wingers publishing, Lakeworth, FL
6. Pathology of zoo animals, 1983, L. A. Griner, Zoological society of San Diego, CA
7. The comparative Pathology of zoo animals, 1980, Ed. R. J. Montali and G. Migaki, Smithsonian Institution Press, Washington, DC.
8. Field guide to wildlife diseases: General field procedures and diseases of migratory birds, 1987, Ed. M. Friend, US dept. Interior, Fish and Wildlife Service pub, Washington, DC.
9. Diseases of Cage and Aviary birds, 1996, W. J. Rosskopf and R.W. Woerpel, Williams and Wilkins, PA
10. Diseases of Wild waterfowl, 1981, G.A. Wobeser, Plenum Press, NY
Journals: Avian Pathology, Avian Diseases, Veterinary Pathology, J Comparitive Pathology, Veterinary Record, JAVMA, AJVR, JAMS, Poultry Sci., etc.

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