Avian Pathology review image disease

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Gross Morbid Pathology of 
Selected Avian Diseases
C. L. Davis Symposium
St. Paul, MN
July 10, 2013
Rob Porter, D.V.M., Ph.D.
Minnesota Veterinary Diagnostic Lab
UM College of Veterinary Medicine
Dept. Vet Population Medicine
St. Paul, MN
porte349@umn.edu
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AVIAN PATHOLOGY
• Emphasis on poultry
• Broiler, layer, turkey, duck, pheasant
• Pet birds
• “Not all avian pathology is enlarged liver 
and spleens and fibrin-covered air 
sacs…only about 40% is!”
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 John Barnes, North Carolina State University
 John King, Cornell University
 Purdue University, ADDL
 Univ. of Wisc., Dept. of Pathobiological Science
THANK YOU
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Aviary System
Enriched Cage
Enriched Cage
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Pheasant Pens
Partridges Bobwhite Quail
23 weeks
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Outline
• Systemic, Lymphohematopoietic, 
Musculoskeletal, Respiratory, Integumentary, 
Nervous, Cardiovascular, Digestive, Urogenital, 
Neoplasia
• Virus Taxonomy (8th report): Fauquet et al. 
(eds.) Elsevier Press, 2005.
ictvonline.org/virusTaxonomy.asp
• CD Poultry Diseases
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Normal pelvic nerve plexus
Marek’s disease
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Normal eye
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Day 4 Day 35
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Normal vertebral 
column
Spondylolisthesis
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145 146
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Broiler chicken
Turkey
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169 170Normal turkey wing
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Courtesy of Dr. Joel Cline
Auburn University
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Target 
lesions
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Thank you!
 1 
Gross Morbid Pathology of Selected Avian Species 
 
 
July 10, 2008 
 
 
 
1. Rob Porter, D.V.M., Ph.D., Diplomate American College of Veterinary Pathologists, 
Diplomate American College of Poultry Veterinarians. Minnesota Veterinary Diagnostic 
Laboratory and University of Minnesota College of Veterinary Medicine, Department of 
Veterinary Population Medicine, 1333 Gortner Avenue, St. Paul, MN 55108 
Tel: (612) 624-7400 Fax: (612) 624-8707 porte349@umn.edu 
 
2. Intro Slide: “Not all avian pathology is enlarged liver and spleens and fibrin-covered air 
sacs…only about 40% is!” 
 
3. Acknowledgements for contribution of photographs. 
John Barnes, North Carolina State University 
John King, Cornell University 
University of Wisconsin, Department of Pathobiological Sciences 
 
4. Poultry Industry 
Broiler: Progeny of broiler breeders, indoor confinement/litter bedding, marketed at 5-7 
weeks of age; feed efficiency <2.0. 
 
Turkey: progeny of turkey breeders; poult = young turkey; indoor confinement or range 
rearing, hens marketed at 15 weeks and toms at 18-24 weeks (30-45 pounds) 
 
Layer (usu. white leghorn): Mostly cage layers; pullet = immature laying hen; lay for 
approximately 40 weeks, then molted at 60+ weeks of age, used for second cycle for another 
30 weeks. Hen produces 250+ eggs in a lifetime (2 years). 
 
Duck: White Pekin duck; raised on litter or plastic grating; feed efficiency <2.0, processed 
at 38 days of age (6.5 lbs). 
 
5. Newer variations of layer housing: A. Cageless aviary system- hens access multiple levels, 
perches and litter floor, B. Enriched battery cages- hold larger number (40-100) of hens and 
provide perches, scratch pad and hiding places. 
 
6. Game bird production: Pheasants, partridges, grouse and quail. Pheasants and partridges 
raised indoors (litter) 8 weeks then placed in flight pens on soil. Ready to market after 20-23 
weeks. 
 
7. Oultine: systemic, Lymphohematopoietic, Musculoskeletal, Respiratory, Integumentary, 
Nervous, Cardiovascular, Digestive, Urogenital, Neoplasia. 
 
Virus Taxonomy, Classification and Nomenclature of Viruses. 
ictvonline.org/virusTaxonomy.asp 
 2 
__________________________________________________________________________ 
SYSTEMIC DISEASES 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
 
 
 
8. Head, chicken Cyanosis/ edema wattle and comb Highly pathogenic avian influenza 
(HPAI) 
9. Ventral neck, chicken Edema HPAI 
10. Legs, chicken Mf cutaneous hemorrhage HPAI 
11. Proventriculus, chicken Mf hemorrhagic proventriculitis HPAI 
12. Peritoneum, chicken Mf peritoneal hemorrhage HPAI 
13. Trachea, chicken Hemorrhagic tracheitis HPAI 
 
Family Orthomyxoviridae, Genus Influenzavirus A, Species Influenza A virus: 
negative stranded ssRNA virus 
 
AI viruses have total of 15 HA and 9 NA. Pathogenicity determined by chick inoculation or by 
amino acid sequence at HA cleavage site. Most HPAI has been H5 or H7. Italy H5N2 and 
H7N1. Hong Kong H5N1 = “bird flu” with potential to directly infect humans. Virus replicates 
in endothelium, myofibers, renal tubules, pancreatic acinar cells. Lesions of coagulative necrosis 
and vascular thrombosis/ischemia. 
 
DDX: END, ILT, IBV, END, bacterial sepsis 
 
14. Eggs, turkey Shell thinning, wrinkling and depigmentation Low path AI 
 
DDX: NDV, avian metapneumovirus 
_____________________________________________________________________________ 
15. Yolk sac/heart, chick Fibrinous pericarditis/yolk sacculitis Escherichia coli 
16. Heart, chicken Fibrinous pericarditis E. coli 
17. Liver, chick Fibrinous perihepatitis E. coli 
18. Peritoneum, chicken Fibrinous peritonitis, “egg yolk” E coli 
19. Oviduct, hen Fibrinous salpingitis/peritonitisE. coli 
20. Liver, intestine, hen MF granulomatous (coligranuloma) E. coli 
 
Most common poultry serotypes are O1, O2, O35, O78, and many are untypeable. 
 
DDX, pericarditis: E coli, Chlamydophila, MG, P. multocida 
DDX, granulomas: Mycobacteriosis, LL, Leukosis/sarcoma complex 
DDX, egg yolk peritonitis: P. multocida, HPAI, Salmonella 
_____________________________________________________________________________ 
21. Head, chicken Facial edema Exotic Newcastle Disease 
22. Proventriculus, chicken Annular mucosal hemorrhage END 
23. Ovary, hen Mf hemorrhagic oophoritis END 
24. Intestine, chicken Necrohemorrhagic enterotyphlitis/tonsillar necrosis END 
25. Esophagus, rooster Mf necrohemorrhagic esophagitis/pharyngitis END 
 3 
26. Trachea, chicken Hemorrhagic tracheitis END 
 
Family Paramyxoviridae, Subfam Paramyxovirinae, Genus Avulavirus, 
Species Newcastle disease virus, negative stranded ssRNA virus 
 
Exotic (Velogenic) Newcastle disease (END); also lentogenic (mild) and mesogenic (moderate) 
pathogenicity. Usu. lentogens in U.S. END usually introduced by birds that are more resistant 
to disease. 
 
DDX, tracheitis: HPAI, ILT, IBV 
DDX, enteritis: HPAI, erysipelas, DVE, acute FC 
DDX, esophagitis: Trichomoniasis, HPAI, DVE 
_____________________________________________________________________________ 
27. Head, turkey Cutaneous infarction Erysipelas rhusiopathiae 
28. Liver, spleen, turkey MF necrotizing hepatitis/splenitis E. rhusiopathiae 
29. Duodenum, turkey Acute hemorrhagic enteritis E. rhusiopathiae 
 
Causes swine erysipelas and erysipeloid of humans. All gallinaceous birds, usually turkeys. 
Lesions of sepsis with bacterial emboli, thrombosis, necrosis and hemorrhage (closely resembles 
colibacillosis of broiler chickens). 
Hemorrhagic hepatitis/myocarditis, Necrohemorrhagic splenitis 
 
DDX: P. multocida, Salmonella, E. coli, HPAI and END. 
______________________________________________________________________________ 
30. Oviduct, turkey Fibrinoheterophilic salpingitis Pasteurella multocida 
31. Wattle, rooster BB Fibrinoheterophilic cellulitis P. multocida 
32. Lung, turkey Necr. fibrinohet. pleuropneumonia P. multocida 
33. Spleen air sac, turkey Fibrinous airsacculitis and necr. splenitis P. multocida 
34. Heart, turkey Fibrinoheterophilic pericarditis P. multocida 
 
“Fowl cholera,” Sepsis of both domestic and wild birds- usually older birds, e.g., turkeys >10 
weeks.. Sixteen serotypes- 1, 3 and 4 are most common isolates. Enters through pharynx of bird. 
Lesions of bacterial embolism, thrombosis, necrosis and disseminated intravascular coagulation. 
 
DDX: Ornithobacterium, E. coli, Staph.aureus, Chlamydophila 
_____________________________________________________________________________ 
35. Spleen, air sac, duckling Fibrinous airsacculitis/necr. splenitis Riemerella anatipestifer 
36. Brain, duckling Purulent meningoencephalitis R. anatipestifer 
37. Heart, liver, duckling Fibrinous pericarditis/perihepatitis R. anatipestifer 
38. Oviduct, duckling Fibrinoheterophilic salpingitis R. anatipestifer 
 
“New duck disease.” Closely related to Ornithobacterium rhinotracheale. Lesions of septicemia 
closely resemble colibacillosis of broiler chickens. 
 
DDX: E. coli (best), chlamydiosis, P. multocida 
_____________________________________________________________________________ 
39. Liver, poult Mf necrotizing hepatitis Salmonella pullorum 
40. Heart, broilers Mf granulomatous myocarditis Salmonella pullorum 
41. Heart, spleen, chick Mf necrohemorrhagic splenitis Salmonella pullorum 
 4 
42. Cecum, poult (closed/open) Fibrinonecrotic typhlitis Salmonella pullorum 
 
New designation of “Salmonella enterica subspecies enterica serovar Gallinarum-Pullorum” 
represents combination of S. pullorum and S. gallinarum. S.gallinarum causes ovarian 
degeneration and sepsis in adult birds in contrast to S. pullorum. Nonmotile Salmonella: 
possess few flagella. 
 
DDX: E. coli, Mycoplasma synoviae, viral arthritis-reovirus, paratyphoid salmonellae 
_____________________________________________________________________________ 
43. Eye, poult Hypopyon Salmonella arizona 
44. Brain, poult Purulent meningoencephalitis Salmonella arizona 
45. Air sac, poult Fibrinous airsacculitis Salmonella arizona 
46. Cecum, poult Necrohemorrhagic typhlitis Paratyphoid Sal. 
47. Liver, pigeon Mf necrotizing hepatitis Paratyphoid Sal. 
 
Salmonella arizona; biochemically distinct from paratyphoid Salmonella but cause similar 
clinical disease and lesions. Paratyphoid salmonellae refers to the motile serotypes 
(approximately 2400), and does not include S. pullorum and S. gallinarum. 
 
DDX: paratyphoid Salmonella, E. coli, pullorum-typhoid 
_____________________________________________________________________________ 
48. Head, hen Fibrinoheterophilic cellulitis Staphylococcus aureus 
49. Tibiotarsus, hen Necrotizing fibrinohet osteomyelitis Staph aureus 
50. Leg, turkey Fibrinoheterophilic arthritis Staph aureus 
51. Foot, duck Granulom. Plantar pododermatitis Staph aureus 
52. Liver, hen Mf to coalesc. necrotizing hepatitis Staph aureus 
 
S. aureus requires skin penetration. Coagulase positive strains are the most pathogenic. 
 
DDX: other systemic bacteria, esp. P. multocida and E. coli 
 
_____________________________________________________________________________ 
LYMPHOHEMATOPOIETIC 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
53. Wing, chick Necrohemorrhagic dermatitis Necrotic dermatitis 
54. Bursa of Fabricius, broiler Cloacal bursal atrophy Chicken infectious anemia 
55. Thymus, chick Thymic atrophy Chicken infectious anemia 
56. Femur, chick Bone marrow aplasia Chicken infectious anemia 
 
Family Circoviridae, Genus Gyrovirus, Species Chicken anemia virus, ssDNA virus 
 
Chicken infectious anemia virus: circovirus replicates in hematopoietic cells and T lymphocytes 
 anemia and immunosuppression. Circovirus immunosupression promotes Staphylococcus 
aureus/Clostridium infection in skin. Had been referred to as “blue wing disease,” but is actually 
necrotic dermatitis. DDX: exudative diathesis 
 
DDX: IBDV, trichothecene mycotoxins 
 5 
____________________________________________________________________________ 
57. Cloacal bursa, broiler Necrohemorrhagic cloacal bursitis Infectious bursal disease 
58. Leg, broiler Intramuscular hemorrhage Infectious bursal disease 
 
Family Birnaviridae, Genus Avibirnavirus, Species Infectious bursal disease virus; 
dsRNA virus 
 
Replicates in bursa of Fabricius lymphocytes of young chickens, followed by spread to other 
lymphoid sites  cytolysis and immunosuppression. Classic serotype 1, variant serotype 1 and 
serotype 2 viruses. 
 
DDX: ionophore toxicosis, chicken infectious anemia, trichothecene mycotoxins, exudative 
diathesis (vitamin E deficiency) 
_____________________________________________________________________________ 
59. Liver, bursa, WL hen Hepatic/bursal lymphoma Lymphoid leukosis 
60. Liver, WL hen Mf hepatic lymphoma Lymphoid leukosis 
61. Liver, WL hen Diffuse hepatic lymphoma Lymphoid leukosis 
 
Family Retroviridae, Subfamily Orthoretrovirinae, Genus Alpharetrovirus, 
Species Avian leukosis virus; RNA Reverse Transcribing virus  DNA proviral insert 
into host cell genome 
 
Retrovirus of leukosis/sarcoma complex. Chicken genome contains endogenous viral loci (ev). 
Exogenous virus subgroup A transmittedvertically and horizontally. Exogenous virus induces 
neoplastic transformation of B lymphocytes. Subgroups A-D avian leukosis viruses can produce 
lymphoid leukosis. ALV Subgroup J produces myelocytomatosis. 
_____________________________________________________________________________ 
62. Lung, spleen, pheasant Splenomegaly/pulmonary edema Marble spleen disease 
 
Family Adenoviridae, Genus Siadenovirus, Species Turkey adenovirus A (Marble spleen 
disease virus), ds DNA virus 
 
Type II adenovirus (old terminology) related to hemorrhagic enteritis virus of turkeys; pheasants 
3 – 12 months, IgM-positive B cells and macrophages are primary viral targets. Death from 
pulmonary edema/hemorrhage or secondary infection. 
 
DDX: Salmonella, erysipelas 
_____________________________________________________________________________ 
63. Body, pullet Marek’s disease “range” paralysis Marek’s disease 
64. Pelvic nerves, broiler Neural lymphoma Marek’s disease 
65. Liver, spleen Hepatic/splenic lymphoma Marek’s disease 
66. Pectoral muscle, broiler Muscular lymphoma Marek’s disease 
67. Kidney, pullet Renal lymphoma Marek’s disease 
68. Eye, broiler “grey eye” Ocular/iridial lymphoma Marek’s disease 
69. Body, processed broiler Cutaneous lymphoma Marek’s disease 
 
Family Herpesviridae, Subfamily Alphaherpesvirnae, Genus Mardivirus, 
Species Gallid herpesvirus 2 (Marek’s Disease virus type 1) 
 
 6 
MD serotype 1 (oncogenic) strain. Productive infection (viral replication) in feather follicle 
epithelium and transmitted in dander. Neoplastic transforming infection and latent infection in T 
lymphocytes. Lesions observed as early as 4 weeks. 
 
DDX: Mycobacteriosis, coligranuloma, lymphoid leukosis in older birds (visceral lesions) 
 
_____________________________________________________________________________ 
70. Subcutis, Macaw Mf subcutaneous hemorrhage Avian polyomavirus 
71. Heart, liver, Macaw Anemia, epicardial hemorrhage, hepatomegaly Avian polyomavirus 
 
 
Family Polyomaviridae, Genus Polyomavirus, Species Budgerigar fledgling disease 
polyomavirus (Avian polyomavirus), dsDNA virus 
 
Originally identified as budgerigar fledgling disease/French molt. Papovaviridae contains 
papillomavirus and polyomavirus families. I have diagnosed in Macaw, Electus parrot, 
Budgerigar, Lovebird and Conure. Intranuclear inclusion bodies in spleen, kidney mesangial 
cells and liver Kupffer cells. 
 
 
_____________________________________________________________________________ 
MUSCULOSKELETAL SYSTEM 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
72. Femur/ tibiortarsus, normal broiler Rapid growth long bones Normal 
73. Leg, young pheasant Angular limb deformity Metabolic/traction 
_____________________________________________________________________________ 
74. Foot, parakeet Articular gout 
75. Leg, rooster Articular gout 
 
Mostly males, occurs with or without visceral/renal gout; high protein in diet promotes 
hyperuricemia, possible genetic predisposition; occurs with or without renal disease or renal 
gout. Not as common as visceral gout. 
_____________________________________________________________________________ 
76. Body, turkey Nonambulatory poult Ionophore toxicosis 
77. Leg, turkey Muscular necrosis/degeneration Ionophore toxicosis: 
 
Polyether ionophores: Promote movement of mono and divalent cations across cell membrane. 
Toxicosis causes cellular loss of K+ and gain of Ca+2 into mitochrondria  cell death. 
Myocytolysis with proliferation of satellite and myocyte nuclei (inset photo). 
 
DDX: Infectious bursal disease, chicken infectious anemia, Vit E/Se deficiency, injection site 
myopathy 
_____________________________________________________________________________ 
78. Hock joint/footpad, poult Tenosynovitis/arthritis(right) Mycoplasma synoviae (MS) 
79. Wing, poult Tenosynovitis Mycoplasma synoviae 
Exudate clear to serofibrinous 
 
 7 
“Infectious tenosynovitis.” Chicken, turkey and guinea fowl. Usu. colonizes subclinical upper 
respiratory tract, but can invade synovial membranes to cause tenosynovitis and sternal bursitis. 
Vertical and horizontal transmission. Lameness is primary sign with occasional airsacculitis. 
Pure MS infection is usually clear to serofibrinous fluid, not suppurative, but can be altered by 
secondary bacteria. 
 
DDX: Staph. aureus, viral arthritis, salmonellae 
_____________________________________________________________________________ 
80. Pectoral muscle, broiler Deep pectoral m. infarction Deep pectoral myopathy 
 
 “Green muscle disease, deep pectoral myopathy,” turkeys (esp. breeder hens during artificial 
insemination) and meat-type chickens with vigorous exercise  swelling of supracoracoideus 
muscle within fascial sheath  ischemic necrosis of muscle. Usually found at processing. 
 
DDX: ionophore toxicosis, injection site myopathy 
_____________________________________________________________________________ 
81. Skull, crested polish chicken Open fontanelle, skull Common in crested 
polish breed 
82. Skull, crested polish chicken Open fontanelle, melanosis 
_____________________________________________________________________________ 
83. Vert. column, turkey Fibrinoheterophilic/caseous osteomyelitis Staph., P. multocida 
and E. coli 
_____________________________________________________________________________ 
84. Leg, rooster Osteopetrosis/periosteal hyperostosis Leukosis/sarcoma virus 
85. Leg, rooster Osteopetrosis ALV 
 
Retrovirus: many of the avian leukosis viruses causing lymphoid leukosis can also induce 
osteopetrosis. Infected osteoblasts proliferate and produce periosteal and some endosteal bone. 
Lesions begin in tibiotarsus and tarsometatarsus, but can spread to other long bones, pelvis and 
ribs. 
_____________________________________________________________________________ 
86. Pectoral muscle, layer Granulomatous myositis/cellulitis Killed vaccine injection 
_____________________________________________________________________________ 
87. Body, Chicken Gastroc. Tendon rupture, bilateral Viral arthritis 
88. Leg, chicken Gastroc. Tendon rupture with hemorrhage Viral arthritis 
89. Leg, chicken Gastroc. Tendon rupture with hemorrhage Viral arthritis 
90. Leg, tom turkey Gastroc. Tendon rupture with hemorrhage Turkey Reo 
 
Family Reoviridae, Genus Orthoreovirus, Species Avian orthoreovirus, dsRNA virus 
 
Chicken reovirus is transmitted both vertically and horizontally. Cause tenosynovitis + rupture 
and hemorrhage of gastrocnemius tendon (tendon tensile strength pullet > broiler). Often 
associated with heterophilic infiltrates in the myocardium. Turkey reoviral arthritis recently 
observed and characterized. Turkey virus is distinct from chicken reo and does not infect 
chickens. 
 
DDX tenosynovitis: Staph.aureus, Mycoplasma synoviae, trauma 
_____________________________________________________________________________ 
91. Leg, white leghorn hen Acute femoral fracture Osteoporosis 
 8 
92. Keelbone, WL hen Osteoporosis, keelbone deformation Osteoporosis 
93. Ribs, chick Medial deviation ribs, rickets Rickets 
94. Ribs, chick Deformed ribs/beaded costocondral jxn Rickets 
95. Head, chick Pliable beak, rickets Rickets 
96. Leg, chick Pliable tarsometatarsus, Rickets Rickets
 Rickets 
 
Laying hen mobilizes 2% of skeletal calcium into egg shell each day. Deficiencies or imbalance 
of calcium, phosphorus and vitamin D3 (cholecalciferol)can promote osteoclastic resorption of 
bone without sufficient osteoblast activity. 
_____________________________________________________________________________ 
97. Body, broiler Spondylolisthesis Spondylolisthesis 
98. Vertebral column, broiler Dorsal deviation T4, S/C compression 
 
Spondylolisthesis=“kinky back” of 3-6 week broilers. Deviation of T4 vertebral body and 
deformation of T5 resulting in spinal cord compression (histo photo). Conformation defect 
(genetic trait) complicated by rapid growth rate of broiler. 
____________________________________________________________________________ 
99. Vertebral column, broiler Normal (L) and spondylosis/osteomyelitis Enterococcus 
100. Vertebral column, broiler Necrotizing, fibrinohet osteomyelitis T6 Enterococcus 
Most of these lesions in broilers associated with Enterococcus cecorum- affect mostly vertebral 
body T6. 
 
DDX: Staph aureus, E. coli 
____________________________________________________________________________ 
101. Tibia, broiler Tibial dyschondroplasia 
102. Tibia, turkey Osteochondrosis/ Tibial dyschondroplasia 
 
Core of avascular cartilage in proximal tibiotarsus (metaphysis) or tarsometatarsus + bowing of 
bone and lameness. Failure of blood vessels to invade zone of cartilage hypertrophy in growth 
plate. Promoted by genetic line of broiler #1 and marginal deficiency of calcium or a Ca/P 
imbalance. Experimentally induced by Fusarium roseum toxin. 
 
_____________________________________________________________________________ 
103. Leg, turkey Curvature of tibiotarsus Mycoplasma meleagridis 
 
Turkey syndrome 65 chondrodystrophy: inadequate linear bone growth at physis while 
appositional growth remains normal; associated with MM infection (impaired vascular invasion) 
and genetic predisposition (autosomal recessive inheritance). 
 
DDX: tibial dyschondroplasia, rickets; Chickens, turkeys, ratites: lateral rotation of 90-180 
degrees is multifactorial; rapid growth rate with early nutritional deficiency (Ca, P, Vit D3, 
protein) complicated by poor traction. 
 
 
 
 
 
 
 9 
_____________________________________________________________________________ 
RESPIRATORY SYSTEM 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
104. Body, chick Chick-respiratory distress Tracheal obstruction 
105. Trachea, chick Focal granulomatous bronchitis Aspergillus fumigatus/flavus 
106. Lung, poult Mf granulomatous pneumonia/airsacculitis Aspergillosis 
107. Lung, chicken Granulomatous airsacculitis Aspergillosis 
_____________________________________________________________________________ 
108. Spleen, air sac, parrot Necrotizing splenitis Chlamydophila psittaci 
 
Genus Chlamydophila includes C. psittaci, C. abortus, C. felis, C. caviae, C. pneumoniae and C. 
pecorum. Obligate intracellular parasite. Systemic inflammation characterized by necrosis and 
fibrinous exudates, hepatosplenomegaly. 
 
Turkeys, pigeons, ducks and psittacine birds. Eight serovars (A-H): A = psittacine, B/E = 
pigeons, B/D = turkey. Obligate intracellular parasite. 
 
DDX: P. multocida, Erysipelothrix, Pacheco’s disease, Staphylococcus, Salmonella 
_________________________________________________________________________ 
109. Oral cavity, poult Catarrhal rhinitis/blepharitis Cryptosporidium baileyi 
 
Cryptosporidium baileyi: chicken, turkey, duck- respiratory epithelium, bursa of Fabricius, 
cloaca; C. meleagridis- turkey and quail small intestine. Host specific and do not infect 
mammals. 
 
DDX: Bordetella avium 
_____________________________________________________________________________ 
110. Body, pullet Respiratory distress Infectious laryngotracheitis 
111. Trachea, pullet Fibrinohemorrhagic tracheitis ILT 
112. Trachea, WL hen Fibrinonecrotic tracheitis with occlusion ILT 
113. Trachea, WL hen Fibrinonecrotic tracheitis with glottis occlusion ILT 
 
Family Herpesviridae, Subfamily Alphaherpesvirnae, Genus Iltovirus, Species Gallid 
herpesvirus 1, (infectious laryngotracheitis virus), dsDNA virus 
 
Propagated on chorioallantoic membrane of embryonated eggs. Cytolytic for respiratory 
epithelium of nasal sinus, conjunctiva, air sacs and trachea. No evidence of viremia. Trigeminal 
ganglion is site of viral latency. 
 
DDX: fowl pox, infectious bronchitis, END, HPAI 
_____________________________________________________________________________ 
114. Air sac, chick Serous airsacculitis Infectious bronchitis 
115. Kidney, broiler Urolithiasis/hydroureter IB, nephrotropic strain 
 
Family Coronaviridae, Genus Coronavirus, Species Infectious bronchitis virus (Group 3 
species), Positive sense ssRNA virus 
 
 10 
Coronavirus of chickens that causes respiratory signs, decreased egg production and wrinkled 
egg shells in layers. Nephrotropic strains can cause urolithiasis and visceral gout. 
 
DDX for airsacculitis: NDV, MG 
_____________________________________________________________________________ 
116. Head, WL hen Marked caseous sinusitis/conjunctivitis Avibacterium paragallinarum 
 
“Infectious coryza,” Chickens are the natural hosts of A. paragallinarum. Usually begins as 
catarrhal infection with facial edema later complicated by other bacteria  fibrinous to caseous 
inflammation. 
 
DDX: P.multocida, E. coli, Staph. aureus, vitamin A deficiency, pox. 
_____________________________________________________________________________ 
117. Head, turkey Serous/catarrhal infraorbital sinusitis Avian pneumovirus 
 
Family Paramyxoviridae, Genus Metapneumovirus, Species Avian Metapneumovirus, 
negative sense ssRNA virus 
 
Can also cause malformation of oviduct with misshapen eggs/poor shell quality. Associated with 
“swollen head syndrome” in chickens- fibrinpurulent exudates in subcutis of head, neck and 
wattles. 
 
DDX: Mycoplasma gallisepticum, respiratory cryptosporidiosis (C. baileyi). 
_____________________________________________________________________________ 
118. Head, turkey Infraorbital sinusitis Mycoplasma gallisepticum 
119. Head, turkey Serous/catarrhal infraorbital sinusitis MG 
120. Air sac, poult Mild acute serofibrinous airsacculitis MG 
121. Lung, liver, chicken Fibrinous pericarditis and perihepatitis MG/E. coli 
 
“Chronic respiratory disease of chickens” and “infectious sinusitis of turkeys” Can cause 
decreased egg production in adults. MG occurs naturally in galliformes, especially chicken and 
turkey, but also isolated from gamebirds. Transmitted both vertically and horizontally. Infected 
birds remain carriers. Mycoplasma is extracellular parasite that causes degeneration of epithelial 
cells. 
 
DDX: Cryptosporidiosis, avian metapneumovirus 
_____________________________________________________________________________ 
122. Air sac, poult Mild, acute serofibrinous airsacculitis Mycoplasma meleagridis 
 
Specific pathogen of turkeys in which primary lesion is airsacculitis of 1-4-week-old poults. 
Referred to as veneral disease of Tom turkeys. 
 
DDX: Mycoplasma synoviae, gallisepticum or iowae, Newcastle disease. 
_____________________________________________________________________________ 
123. Air sac; poult Serous airsacculitis Newcastle disease (lentogen). 
124. Infraorbital sinus poults Caseous infraorbital sinusitis NDV plus bacteria 
 
DDX: acute MG, MM, ORT, pneumovirus, Bordetella avium complicated by E. coli 
 
 11 
_____________________________________________________________________________ 
125. Lung, heart, turkey Necrofibrinohet.pericarditis/pleuropneumonia Ornithobacterium 
rhinotracheale 
 
Affects turkeys, chickens and many other galliformes. Airsacculitis and unilateral pneumonia in 
chickens; pneumonia/hepatosplenomegaly in turkeys. Fibrinopurulent arthritis and osteomyelitis 
in older turkeys and chickens. 
 
DDX: P. multocida #1 and E. coli. 
_____________________________________________________________________________ 
126. Lung, pheasant Acute, diffuse hemorrhagic pneumonia Avian paramyxovirus-3 
 
Family Paramyxoviridae, Genus Avulavirus, Species Avian Paramyxovirus 3, 
negative sense ssRNA virus 
 
Avian paramyxovirus-3; AMPV-1, 2, 3, 6 and 7 are known to cause disease in poultry. APMV-2 
and 3 cause mild respiratory signs and decreased egg production in turkey breeders. APMV-3 is 
subclinical or causes neurologic signs in psittacine birds. NDV is an APMV-1. 
 
DDX: Any bacterial sepsis 
_____________________________________________________________________________ 
127. Trachea, bobwhite quail Fibrinonecrotic tracheitis Quail bronchitis 
 
Family Adenoviridae, Genus Aviadenovirus, Species Quail bronchitis virus, dsDNA virus 
 
Type 1 adenovirus causes high mortality in young bobwhite quail. Also causes multifocal 
necrotizing hepatitis, splenitis and pancreatitis. 
 
DDX: Aspergillosis, Salmonella, E. coli 
_____________________________________________________________________________ 
128. Trachea, chicken Tracheal nematodiasis Syngamus trachea 
129. Trachea, peahen Mf granulomatous tracheitis with nematodes Syngamus trachea 
 
Direct or indirect (earthworms) life cycle. Affects most galliformes. Form granulomas at site of 
attachment to tracheal mucosa. 
 
DDX, tracheal nodules: granulomatous nodules can resemble Marek’s disease lymphoma, ALV-
induced myelocytoma or aspergillosis. 
_____________________________________________________________________________ 
130. Air sac, chicken Air sac acariasis Cytodites nudus 
 
Cytodites nudus = air sac mite of galliformes; lives in bronchi, lungs, air sac, and bone cavities 
Sternostoma tracheacolum = tracheal mite of passerines-finches, canaries 
_____________________________________________________________________________ 
131. Body, poult Serous blepharitis, submand. edema Bordetella avium (acute) 
132. Trachea, turkey Tracheitis w/chrondrolysis/ luminal collapse B. avium 
 
“Turkey coryza,” 2 to 6-week-old poults (and occasionally broilers) causing blepharitis and 
submandibular edema. Usually concomitant infections that create conjunctival exudate. 
 12 
Colonizes apices of respiratory epithelium and produces cytotoxin that causes chondrolysis of 
tracheal rings. 
 
DDX: Respiratory cryptosporidiosis, mycoplasmosis, chlamydiosis, NDV can mimic or 
complicate infection. 
 
 
_____________________________________________________________________________ 
INTEGUMENTARY SYSTEM 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
133. Head, Mollucan Cockatoo Feather alopecia and dystrophy Beak and Feather Dis 
134. Body, Mollucan Cockatoo Feather alopecia Beak and Feather Dis 
 
Family: Circoviridae, Genus: Circovirus, Species: Beak and feather disease virus 
Circovirus causing feather dystrophy and immunosuppression. Necrosis, fracture, bending or 
hemorrhage, or dystrophic feathers that emerge from follicle and cease growing after each 
successive molt. Flank contour feathers in most feather tracts  primary and secondary 
feathers of wings, tail and crest. Occasionally see progressive distortion of beak. Death caused 
by secondary infections. 
_____________________________________________________________________________ 
135. Beak, chicken Normal beak amputation Beak normal 
136. Beak, chicken Exuberant granulation tissue Beak inadequate trim 
_____________________________________________________________________________ 
137. Body, turkey Chronic,, hemorrhagic sternal bursitis “Breast blister “ 
138. Body, turkey Sternal bursitis 
 
Most common in heavy tom turkeys: Conformation and pressure effects; no cutaneous pterylae 
over sternal bursa  friction of bursa against litter bursal edema and hemorrhage  fibrosis 
and occasional rupture. 
 
139. Sternal keel, processed turkey Multifocal ulcerative dermatitis “Breast button” 
 
Contact dermatitis; contact/friction of sternal skin (keel) with coarse, moist, contaminated litter. 
Breast buttons and breast blisters do not necessarily occur together. 
_____________________________________________________________________________ 
140. Foot, chicken Chronic, granulomatous plantar pododermatitis Staph. aureus 
 
Usually. moist environment or constant pressure on foot. 
_____________________________________________________________________________ 
141. Body, layer Necrohemorrhagic dermatitis/alopecia Cannibalism 
142. Cloaca, layer Multifocal ulcerative cloacitis Prolapse/cannibalism 
_____________________________________________________________________________ 
143. Body, processed broiler Fibrinoheterophilic cellulitis E. coli cellulitis 
 
Referred to as “inflammatory process” at processing plant. Usu. caseous to fibrinous exudate in 
subcutis of abomen or flank initiated by skin trauma. Usu. found at processing to cause carcass 
 13 
downgrade. Management problem- incidence increased by poor feather coverage, crowding, 
coarse, most litter, aggressive strains of birds. 
______________________________________________________________________________ 
144. Body, pullet chick Hemorrhagic omphalitis Bacterial infection of navel often 
progresses to yolk sac infection. 
 
DDX: Salmonella, E. coli, Pseudomonas, Enterococcus, Staph aureus 
_____________________________________________________________________________ 
145. Feet, pullet chicks Cutaneous dehydration Dehydration/water deprivation 
 
DDX: Frostbite, contact dermatitis with disinfectant (quat, cresol, phenol) 
_____________________________________________________________________________ 
146. Cloaca, layer Cloaca normal 
147. Cloaca, layer Cloaca after egg lay 
148. Cloaca, layer Necrohemorrhagic cloacitis with prolapse 
 
Cloacal prolapse complicated by trauma/cannibalism. DDX: HPAI, END 
_____________________________________________________________________________ 
149. Head, chick Serous blepharitis with edema Conjunctivitis vaccine rxn 
 
DDX: field challenge with respiratory virus- ILT, IBV, NDV, ammonia toxicosis 
_____________________________________________________________________________ 
150. Head, chick Granulomatous/hemorrhagic cellulitis Contaminated MD vaccine 
151. Head, poult Necrotizing cervical myositis Contaminated NDVvaccine 
_____________________________________________________________________________ 
152. Head, turkey Serous blepharitis Cryptosporidium baileyi 
 
DDX: avian metapneumovirus, NDV, acute Bordetella infection. 
_____________________________________________________________________________ 
153. Foot, turkey poult/hen Digit amputation turkey Normal microwave process 
154. Beak, poult Normal (L) and locally extensive thermal necrosis (R) Microwave 
_____________________________________________________________________________ 
155. Feet, broiler (L) and turkey (R) MF necro. plantar pododermatitis Contact dermatitis 
_____________________________________________________________________________ 
156. Body, cockatiel nestling Emphysema Secondary to primary respiratory disease 
_____________________________________________________________________________ 
157. Wing, Broiler chickHemorrhagic dermatitis Vitamin E deficiency 
 
Exudative diathesis = vitamin E and selenium-responsive dermal hemorrhage; oxidative damage 
to endothelial cells extravasation of blood and edema fluid through capillaries 
 
DDX: necrotic dermatitis 
_____________________________________________________________________________ 
158. Head, WL hen Chronic blepharitis with cleft formation Eyelid notch syndrome 
 
Probably primary eyelid trauma or bacterial infection with ulceration of lid and cleft formation. 
_____________________________________________________________________________ 
159. Head, chicken Proliferative dermatitis (dermatophytosis) Favus 
 
 14 
Microsporum gallinae; chicken, turkey, duck, quail, canary 
_____________________________________________________________________________ 
160. Vent, chicken Cutaneous acariasis Ornithonyssus sylviarum 
 Inset- higher mag. of mites 
161. Vent feathers Cutaneous acariasis Ornithonyssus sylviarum 
 Covered with mites, mite excreta (no eggs/nits at base of shaft) 
 
Ornithonyssus sylviarum = northern fowl mite; entire life cycle spent on chicken 
Dermanyssus gallinae = red chicken mite; feed on chickens at night and reside in litter, nests, 
crevices during the day 
_____________________________________________________________________________ 
162. Head, pullet/hen Proliferative blepharitis and dermatitis Fowl pox 
163. Uropygial gland, poult Proliferative dermatitis/adenitis of uropygial gland Fowl pox 
 
Family Poxviridae, Subfamily Chordopoxvirinae, Genus Avipoxvirus, Species Fowl pox 
virus, dsDNA virus 
 
Avian poxviruses are antigenically and immunologically distinguishable from one another: fowl, 
turkey, pigeon, canary, junco, mynah, psittacine, quail, sparrow, crow, peacock, penguin, alala, 
apapane, condor, starling. Mechanical transmission through injured skin; can be spread by 
mites and mosquitoes to skin, conjunctiva and mouth. 
 
DDX: Pecking trauma/cannibalism, squamous cell carcinoma, bacterial/fungal conjunctivitis 
_____________________________________________________________________________ 
164. Head, budgerigar Proliferative dermatitis Knemidocoptes pilae 
165. Feet, chicken Proliferative pododermatitis Knemidocoptes mutans 
 
Scaley-leg mite, inhabits nonfeathered sites- beak, legs. DDX: Vitamin B6, Zn deficiency, biotin 
deficiency 
 
166. Body, chicken Cutaneous pediculosis Various chewing lice- Order Mallophaga 
Note egs/nits near base of feather shaft 
Chicken: Cuclogaster (head louse), Goniocotes (fluff louse), Menacanthus (body louse) 
Turkey: Menacanthus, Chelopistes, Oxylipeurus 
Duck and goose: Anaticola, Trinoton 
Pigeon: Columbicola, Campanulotes 
_____________________________________________________________________________ 
167. Body, broiler Fibrinous sternal bursitis Staph. aureus, Mycoplasma synoviae 
_____________________________________________________________________________ 
168. Body, broiler Necrohemorrhagic dermatitis Necrotic dermatitis 
169. Body, processed broiler Locally extensive necrohemorrhagic dermatitis 
 
Usu. sudden death in 4-8-week-old broilers, but also turkeys. Caused by Clostridium 
perfringens type A, Clostridium septicum and Staphylococcus aureus, often complicated by 
immunosuppression from infectious bursal disease, chicken infectious anemia, 
reticuloendotheliosis virus. Associated with edema, hemorrhage and gas-production in subcutis 
of breast, wings, flank. 
 
DDX: Cutaneous aspergillosis, candidiasis, E. coli cellulitis (inflammatory process). 
 15 
_____________________________________________________________________________ 
170. Wing, tom turkey Normal wing 
171. Wing,thigh tom turkey Hemorrhagic cellulitis with emphysema Turk clostr cellulitis 
172. Body, tom turkey (3) Hemorrhagic cellulitis with emphysema Turk clostr cellulitis 
Turkey clostridial dermatitis/cellulitis- associated with subcutaneous overgrowth of Clostridium 
septicum and Clostridium perfringens. Assoc. with wet litter and large body size. 
_____________________________________________________________________________ 
173. Body, chicken Xanthomatosis Idiopathic 
 
Yellow, subcutaneous nodules (granulomatous inflammation of fat) in galliformes and psittacine 
birds. Sometimes associated with obesity and lipomas. Classic poultry lesion described in 
1950’s. 
 
_____________________________________________________________________________ 
NERVOUS SYSTEM 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
174. Eye, chicken Ulcerative keratitis Ammonia toxicosis 
175. Eyes, chicken Ulcerative keratitis Ammonia toxicosis 
 
Wet litter conditions/poor air movement  aerosolized NH3 above 25ppm impairs ciliary 
apparatus of trachea/sinus and direct toxic effect on corneal epithelium (simple diffusion). 
_____________________________________________________________________________ 
176. Body, chicks Ataxia Avian encephalomyelitis 
177. Proventriculus, chick Mf lymphocytic proventriculitis AE 
178. Eye, chicken Cataract AE 
 
Family Picornaviridae, Genus Hepatovirus, Species Avian encephalomyelitis(-like) virus, 
Positive sense ssRNA virus 
 
Infects chicken, turkey, quail, pheasant; enterotropic virus with both horizontal and vertical 
transmission. Sudden decrease in egg production in adults. Fine head tremors in young birds. 
 
DDX, proventricular lesion: Marek’s disease, vitamin E deficiency 
DDX, cataracts: congenital cataracts, nutritional deficiency, induced by artificial light, old age. 
_____________________________________________________________________________ 
179. Body, mallard duck Flaccid paralysis Clostridium botulinum type C toxin 
 
Prevents release of acetylcholine from neuronal presynaptic vesicles  “limberneck.” = flaccid 
paralysis of wings, neck, legs and eyelids. Wide variety of birds affected. 
 
DDX: organophosphate, lead toxicosis 
_____________________________________________________________________________ 
180. Eye, poult Hypopyon Ochroconis gallopava 
181. Brain, poult Necrotizing/granulomatous encephalitis O. gallopava 
 
Formerly Dactylaria. Contaminant in hard wood shavings; translucent to grey lesions in 
tissue compared to Aspergillus. Dematiaceous fungus with hyphae observed in H&E. 
 16 
Neurologic disease is most common clinical sign in chicks and poults. Lesions in eye, brain, 
lung and air sac. 
 
DDX: Aspergillus, coliforms, Salmonella (hypopyon), Vitamin E deficiency (brain lesion) 
_____________________________________________________________________________ 
182. Eye, chick Fibrinous panophthalmitis E. coli (puncture) 
 
DDX: Aspergillus, Staph. aureus 
_____________________________________________________________________________ 
183. Brain, Black australorp Melanosis Increased melanin accumulation in 
variety of tissues is a breed trait. 
_____________________________________________________________________________ 
184. Body, pigeon Ataxia Avian paramyxovirus-1 
 
Family Paramyxoviridae, Genus Avulavirus, Species Avian Paramyxovirus-1, negative 
sense ssRNA virus. APMV-1 virtually identical to Newcastle disease virus; primarily 
nonsuppurative encephalitis in pigeons. There are no diagnostic gross lesions. 
 
DDX: head trauma, lead toxicosis, vitamin E deficiency. 
_____________________________________________________________________________ 
185. Body, broiler Ataxia Vitamin E deficiency 
186. Brain, Turkey Encephalomalacia and hemorrhage Vitamin E deficiency 
 
Brain lesions are not responsiveto selenium supplementation, unlike muscle and skin lesions. 
 
DDX: aspergillosis, ochraconosis, avian encephalomyelitis (body position) 
 
 
_____________________________________________________________________________ 
CARDIOVASCULAR SYSTEM 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
187. Heart, parrot Aortic atherosclerosis 
 
Most often observed in aged blue-front Amazon, African grey parrots and macaws. 
Accumulation of lipid/macrophages/fibrous connective tissue in media of aorta  subclinical or 
decreased blood supply to brain and pectoral muscle  death 
_____________________________________________________________________________ 
188. Head, turkey Hematochezia Aortic rupture 
189. Abdominal cavity, turkey Hemoperitoneum Aortic rupture 
190. Abdominal cavity, turkey Aortic rupture 12-16 weeks, M>F, rupture near 
 cranial mesenteric (celiac) artery 
 
191. Peritoneum, turkey Perirenal hemorrhage Males, 8-14 weeks, probably 
 a variant of aortic rupture of turkeys 
 
DDX: trauma, cannibalism, anticoagulant rodenticides 
 
 17 
_____________________________________________________________________________ 
192. Body, broiler Ascites 
193. Peritoneum, broiler Ascites 
194. Peritoneum, broiler Ascites 
195. Heart, broiler Right ventricular dilatation 
196. Heart, broiler Left atrioventricular endocardiosis 
 
Ascites syndrome of broilers and ducklings: right-sided congestive heart failure promoted by 
rapid growth rate hypoxemia  polycythemia, increased blood viscosity, decreased 
erythrocyte deformability  pulmonary hypertension, increased cardiac workload  right-sided 
cardiac failure and ascites. 
 
DDX: Cardiomyopathy, salt toxicosis, liver disease 
_____________________________________________________________________________ 
197. Heart, broiler Vegetative valvular endocarditis, RV E. coli 
 
DDX: Erysipelothrix, Enterococcus, Salmonella, Staphylococcus aureus 
_____________________________________________________________________________ 
198. Heart, Macaw Anemia, Mf myocardial hemorrhage Avian polyomavirus 
199. Heart, parrot Hydropericardium Avian polyomavirus 
 
DDX, hydropericardium: salt toxicosis, avian viral serositis; EEE, West Nile virus 
_____________________________________________________________________________ 
200. Heart, poult Cardiomegaly Dilated cardiomyopathy 
201. Heart, turkey Left and right ventricular dilatation Dilated cardiomyopathy 
 
Dilated cardiomyopathy (Round heart disease), poults 2-3 weeks old, cause unknown, but 
possible genetic predisposition complicated by hypoxia in incubator with pathogenesis similar to 
ascites syndrome of broilers. 
 
DDX: salt/sodium toxicosis if ascites present 
 
 
_____________________________________________________________________________ 
DIGESTIVE SYSTEM 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
202. Intestine, chicken Intestinal ascariasis 
 
Ascaridia galli (chicken, turkey); A. dissimilis (turkey); A. columbae (pigeon) 
_____________________________________________________________________________ 
203. Crop, pullet Beak trim injury 
204. Crop, pullet Choanal and ingluvial hemorrhage Beak trim injury- hemorrhage 
_____________________________________________________________________________ 
205. Crop, turkey poult Proliferative ingluvitis Candida albicans 
206. Oral cavity, chicken Proliferative stomatitis Candida albicans 
 
 18 
Candida albicans = crop mycosis; ubiquitous yeast colonizes mucosal surfaces when normal 
bacterial microflora is altered by or antibiotics or other diseases. 
 
DDX: capilliariasis, poxvirus, trichomoniasis 
____________________________________________________________________________ 
207. Crop, Bobwhite quail Prolif ingluvitis with intralesion nematodes Capillariasis 
 
Capillaria contorta (direct), C. annulata (earthworm intermediate host). Eggs shed in feces and 
larvae develop in 10-15 days, consumed by bird or earthworm. Larvae hatch and burrow into 
wall of crop and upper esophagus. Mature after additional 15-25 days. 
 
Capillaria obsignata (direct life cycle) resides in small intestine of birds and can cause decreased 
egg production in layer and broiler breeders. 
 
DDX: candidiasis, vitamin A deficiency, trichomoniasis 
_____________________________________________________________________________ 
208. Yolk sac, chick Chick normal yolk sac 
209. Yolk sac, chick Hemorrhagic yolk sacculitis 
210. Peritoneum, chick Fibrinous peritonitis 
 
Coliforms, Salmonella, Enterococcus. Peritonitis often secondary to yolk sac infection and 
rupture 
_____________________________________________________________________________ 
211. Liver, chick Gall bladder distension Inanition, 
212. Gizzard, poult Foreign body- litter impaction Litter impaction 
 
Gall bladder enlarges with inanition (“starve out”). Litter consumption indicative of discomfort 
of digestive tract (e.g., viral enteritis) or poor adaptation to brooder. 
_____________________________________________________________________________ 
213. Duodenum, broiler Mf necrotizing enteritis Eimeria acervulina: schizogony and 
 gametogony in prox. small intestine 
214. Jejunum, broiler Mf necrotizing enteritis E necatrix: schizogony in intestine 
and gametogony in cecum 
215. Cecum, chicken Necrohemorrhagic typhlitis E. tenella: schizogony and 
gametogony in cecum 
216. Cecum, chicken Fibrinonecr. Typhlitis E. tenella 
 
217. Ileum, broiler Necrotizing enteritis Eimeria brunetti: schizogony in 
 prox. small intestine and 
 gametogony in distal small intestine 
 
218. Cecum, turkey Catarrhal typhlitis/coccidiosis Eimeria adenoeides 
 
Turkey: Eimeria adenoeides-cecum, E. dispersa-small intestine, E. gallopavonis- ileum and 
colon; E. meleagrimitis- duodenum/jejunum 
 
DDX for E. tenella is Salmonella 
_____________________________________________________________________________ 
219. Cecum, pheasant Fibrinonecrotic typhlitis Eimeria cholchici 
 19 
 
Coccidia in pheasants are Eimeria colchici (cecal cores); E. duodenalis and E. phasiani. 
 
DDX: Salmonella 
____________________________________________________________________________ 
220. Intestine, duck Necrohemorrhagic enteritis Duck viral enteritis (DVE) 
221. Esophagus, duck Fibrinonecrotic esophagitis Duck viral enteritis 
 
Family Herpesviridae, Subfamily Alphaherpesvirus, Species Anatid herpesvirus 1 (duck 
plague herpesvirus), dsDNA virus 
 
DVE =“Duck plague.” Susceptibility limited to family anatidae-ducks, geese and swans. 
Transmitted by secretions/direct contact with rapid, high mortality. Probable carrier state in wild 
ducks. Lesions of vasculitis and necrosis: petechial hemorrhage and multifocal necrosis of 
heart, liver, pancreas, kidney. Intestines and gizzard filled with blood. Necrohemorrhagic to 
fibrinonecrotic membranes in esophagus 
 
DDX: END, P. multocida, necrotic enteritis 
_____________________________________________________________________________ 
222. Liver, WL hen (2 views) Hepatic lipidosis/hemorrhage Fatty liver disease 
 
Most common in caged layers due to high calorie rations and minimal exercise. Also occurs in 
turkey breeder hens early in egg production. 
 
223. Liver, cockatiel Hepatic lipidosis Fat diet, e.g. sunflower/safflower 
 
Fatty liver DDX: bacterial sepsis, Pacheco’sdisease, chlamydiosis 
_____________________________________________________________________________ 
224. Gizzard, duckling Ventricular (gizzard) myodegeneration Vitamin E deficiency 
 
Vitamin E is natural antioxidant in alcoholic form. Selenium (co-factor for glutathione 
peroxidase) supplementation can reduce lesions in duck, turkey and chicken. Breast muscle 
similarly affected. Muscle lesions of Vit E deficiency are partially selenium responsive. 
 
DDX: furazolidone toxicosis, lymphoma 
_____________________________________________________________________________ 
225. Liver, Mynah bird Hepatic hemochromatosis and pulmonary edema 
 
Excessive iron storage is disease of mynahs, toucans, birds of paradise. Hemochromatosis; 
enhanced intestinal iron absorption compared to other birds and mammals, with inability to 
down-regulate iron absorption when fed iron rich ration. Ascites often occurs from hepatic 
disease or heart failure. Hepatomegaly, golden brown with scattered dark foci (Kupffer cells 
packed with hemosiderin). 
_____________________________________________________________________________ 
226. Body, turkey Cloacal hemorrhage HE of turkeys 
227. Intestine, spleen, turkey Hemorrhagic enteritis/necrotizing splenitis HE of turkeys 
 
Family Adenoviridae, Genus Siadenovirus, Species Turkey adenovirus 3 (Turkey 
hemorrhagic enteritis virus), dsDNA virus 
 20 
 
Hemorrhagic enteritis of turkeys = subgroup II adenovirus infecting turkeys 4 weeks of age or 
older; causes immunosuppression of turkeys by cytopathic effects on IgM-positive B cells and 
macrophages. Serologically related to marble spleen disease virus of pheasants and avian 
adenovirus splenomegaly virus of broiler breeders. 
 
DDX: Cannibalism; END, HPAI 
_____________________________________________________________________________ 
228. Cecum, chicken (2 views) Cecal nematodiasis Heterakis gallinarum 
 
H. gallinarum infects variety of galliformes. Severe infections can form granulomas in cecal 
wall. Paratenic host (ova) for Histomonas meleagridis protozoa. 
_____________________________________________________________________________ 
229. Cecum, liver, turkey Mf necr. hepatitis/fibrinonecr. typhlitis Histomonas meleagridis 
Inset: cytology of cecum  amoebae of Histomonas 
 
DDX: Salmonella 
_____________________________________________________________________________ 
230. Oral cavity, WL hen Focal ulcerative stomatitis 
 
DDX: Idiopathic, trichothecene mycotoxin, disinfectant contact necrosis 
_____________________________________________________________________________ 
231. Esophagus, goose Focal esophageal dilatation/impaction Lead toxicosis 
232. Gizzard, vulture Erosive ventriculitis with bile staining Lead toxicosis 
 
Chickens and turkeys more resistant than waterfowl. Acid-fast intranuclear inclusions in renal 
tubule epithelium, basophilic stippling of erythrocytes and myonecrosis of heart. 
_____________________________________________________________________________ 
233. Body, chicken Pectoral muscle atrophy, emaciation Mycobacteriosis 
234. Viscera, chicken Mf granulomatous enteritis, hepatitis and splenitis Mycobacteriosis 
 
Mycobacterium avium subspecies avium, serovars 1, 2, 3. Observed most often in psittacine 
birds rather than galliformes, usually adult poultry. 
 
DDX: Coligranuloma; Marek’s disease, lymphoid leukosis, carcinomatosis 
_____________________________________________________________________________ 
235. Intestine, broiler Fibinonecrotic enteritis Necrotic enteritis 
236. Intestine, broiler Fibinonecrotic enteritis Necrotic enteritis 
 
Clostridium perfringens toxin types A and C. Overgrowth often preceded by coccidiosis or 
ascariasis, immunosuppression (IBD), wheat products in ration. 
 
DDX: coccidiosis, ulcerative enteritis (C. colinum) 
 
_____________________________________________________________________________ 
237. Peritoneum, parrot Splenomegaly and mesenteric edema Pacheco’s herpesvirus 
238. Liver, parrot Necrotizing hepatitis Pacheco’s herpesvirus 
 
 21 
Family Herpesviridae, Subfamily Alphaherpesvirinae, Unassigned Genus, Species Psittacid 
herpesvirus 1, (Parrot herpesvirus), dsDNA virus 
 
DDX: Chlamydiosis, polyomavirus; Salmonella 
_____________________________________________________________________________ 
239. Cloaca, parrot Cloacal papilloma Idiopathic 
 
No virus consistently isolated. Can be associated with hepatic or biliary carcinoma. 
____________________________________________________________________________ 
240. Proventriculus, Af. Grey Normal 
241. Proventriculus, Af. Grey Proventricular dilatation disease Bornavirus 
 
Myenteric ganglioneuritis, Macaw wasting disease. Diagnosis: lymphoplasmacytic 
inflammation of myenteric plexus of tunica muscularis of ventriculus and proventriculus, as well 
as small intestine and crop. Nonsuppurative encephalitis present in some instances. Bornavirus 
infection or exposure identified in recent reports 
 
DDX: Gastric foreign body or other obstruction 
_____________________________________________________________________________ 
242. Body, poult Marked abdominal distension Viral enteritis 
243. Intestine, cecum, poult Catarrhal enterotyphlitis Viral enteritis 
 
“Poult enteritis/mortality syndrome (PEMS)” Multifactorial transmissible disease 1-3 week-old 
poults with diarrhea, growth depression or death. Complex of enteric viruses (astrovirus, 
reovirus, rotavirus, coronavirus), Cryptosporidium meleagridis and bacteria (enteropathogenic E. 
coli). 
_____________________________________________________________________________ 
244. Body, poult/tom (2 views) Crop dilatation/Pendulous crop 
 
Cause uncertain in turkey and chicken; genetic predisposition, often rapid water consumption in 
hot weather, other dietary influences such as high fat or starch in ration 
 
DDX: Impaction, foreign body 
_____________________________________________________________________________ 
 
245. Oral cavity, WL hen Fibrinonecrotic stomatitis Quaternary ammonium 
 
Quaternary ammonium disinfectants: direct toxic insult to mucosa 
 
DDX: pox, vitamin A deficiency, trichothecene mycotoxins 
 
_____________________________________________________________________________ 
246. Abdomen, poult (2 views) Ascites Sodium toxicosis 
247. Abdomen, subcutis, poult (2 views) Ascites, anasarca Sodium toxicosis 
 
Greater than 2% sodium in ration or 4g/kg body weight  visceral hemorrhages and ascites 
 
DDX: dilated cardiomyopathy 
_____________________________________________________________________________ 
 22 
 
248. Cecum, rhea Fibrinonecrotic typhlitis Intestinal spirochetosis 
 
Brachyspira hyodysenteriae: Four pathotypes; inhabit the cecum, ileum and rectum or rheas. 
Spirochetes not identified in ostrich and emu. Necrotizing typhlitis with high mortality in 
rheas. 
 
Brachyspira intermedia: chickens- typhlitis and diarrhea, no mortality; Brachyspira alvinipulli: 
chickens-typhlitis, reduced growth rate and reduced egg production; Brachyspira pilosicoli: 
chickens- diarrhea and decreased egg production. 
_____________________________________________________________________________ 
249. Intestine, chicken Intestinal cestodiasis 
 
Chicken: Genus: Raillietina, Davainea, Amoebotania, Choanotaenia and Hymenolepsis; 
Turkey: Raillietina, Metroliasthes; Ducks/geese: Hymenolepsis, Fimbrairia 
_____________________________________________________________________________ 
250. Proventriculus, pigeon Proventricular parasitism Tetrameres americanaT. americana, a proventricular nematode, has grasshopper/cockroach intermediate host. Adult 
female embeds in proventricular glands. Often subclinical, but can lead to emaciation and 
anemia. 
T. crami- wild and domestic ducks 
T. fissispina- wild and domestic ducks 
 
 
 
_____________________________________________________________________________ 
 
251. Macaw chick Fibrinous cellulitis Trauma: crop tube injury 
 
DDX: esophageal thermal burn, injection granuloma 
_____________________________________________________________________________ 
252. Oral cavity, dove Fibrinonecrotic stomatitis Trichomonas gallinae 
253. Esophagus, pigeon Fibrinonecrotic esophagitis Trichomonas gallinae 
 
Pigeons (canker), falcons (frounce), flagellated protozoan that colonizes upper digestive tract 
mucosa to form multifocal to coalescing, punctate fibronecrotic lesions. Lesions can extend to 
crop/proventriculus and flagellates can occasionally invade liver (multifocal necrosis). 
 
DDX: vitamin A deficiency, candidiasis, poxvirus 
_____________________________________________________________________________ 
254. Oral cavity, broiler Mf ulcerative stomatitis and glossitis Trichothecene 
mycotoxicosis 
 
Fusarium mold toxins: T-2, diacetoxyscirpenol (DAS) and deoxynivalenol (DON, vomitoxin), 
and nivalenol. Promote feed refusal and necrosis of oral mucosa and skin in contact with mold 
toxins, rapid necrosis/depletion of lymphoid and hematopoietic tissues. 
 
DDX: quaternary ammonium exposure, wet pox, trichomoniasis. 
 23 
_____________________________________________________________________________ 
255. Liver, duodenum, poult Mf necrotizing hepatitis and pancreatitis Turkey viral hepatitis 
(TVH) 
 
Virus causing TVH has not yet been identified, suspect picornavirus. Affects only turkeys; 
under 6 weeks; usu. sudden death with causing multifocal hepatic and pancreatic necrosis. 
_____________________________________________________________________________ 
256. Int, Liver, Bobwhite quail Mf fibrinonecr enteritis, necr. hepatitis Ulcerative enteritis 
 
UE = “Quail disease.” Clostridium colinum: acute infection resulting in sudden death; quail 
most susceptible, but also turkey, chicken, pheasant, grouse, partridge, pigeon. Bird ingests 
feces, litter, water or feed contaminated with spores multifocal fibrinonecrotic enteritis + 
peritonitis and pale, necrotic foci in liver. Splenomegaly and hemorrhage also observed. 
 
DDX: necrotic enteritis, coccidiosis, histomoniasis 
_____________________________________________________________________________ 
257. Esophagus, chicken Proliferative esophagitis (hyperkeratosis) Vitamin A deficiency 
 
Vitamin A maintains epithelial structure/function and mucus production . Deficiency: decreased 
egg production, ocular discharge with eyelid pasting, hyperkeratosis caused by squamous 
metaplasia of mucous glands; renal tubular degeneration results in visceral gout. Affects a wide 
variety of birds. 
 
DDX: candidiasis, wet pox, trichomoniasis, capillariasis 
 
 
_____________________________________________________________________________ 
UROGENITAL SYSTEM 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
258. Egg, chicken Egg membrane (air cell) mycosis, Aspergillosis Aspergillus fumigatus 
 
Common contaminant of ducts, vents of incubators. 
_____________________________________________________________________________ 
259. Body, pullet chick Ureteral/cloacal urate accumulation Dehydration 
260. Kidney, pullet chick Visceral gout Dehydration 
 
DDX: high calcium or vitamin D3 in ration, avian nephritis virus (astrovirus in Japan; affects 
only chicks). 
_____________________________________________________________________________ 
261. Eggs, WL chicken Soft shell and shell-less eggs Egg drop syndrome 
 
Family Adenoviridae, Genus Atadenovirus, Species Duck adenovirus A 
(Duck adenovirus 1 = egg drop syndrome virus) 
 
Subgroup III adenovirus (old terminology); not documented in U.S., but in Europe an Asia 
causes egg production losses in otherwise healthy laying hens. Histology: Lymphoplasmacytic 
inflammation of shell gland of oviduct. 
 24 
 
DDX: low calcium in ration, NDV, IBV, incomplete molt 
_____________________________________________________________________________ 
262. Oviduct, Bantam hen Egg-impacted oviduct Most common in small breeds 
_____________________________________________________________________________ 
263. Kidney, WL hen Renal/visceral gout Water deprivation 
264. Peritoneum, WL hen Visceral gout 
265. Liver, heart, WL hen Visceral gout 
266. Kidney, chicken Urolithiasis with hydroureter and contralateral renomegaly IBV 
 
DDX: Water deprivation, primary renal disease, nephrotropic IBV, high Ca or Vit D3 in ration, 
citrinin/ochratoxin/oosporein mycotoxins; vitamin A deficiency 
_____________________________________________________________________________ 
267. Egg, WL chicken Malformed/wrinkled egg shells Infectious bronchitis 
(coronavirus) 
 
DDX: Newcastle disease virus, abnormal calcium/phosphorus in ration 
_____________________________________________________________________________ 
268. Egg, WL chicken Thinning of thin albumen layer Infectious bronchitis 
 
DDX: Newcastle disease, nicarbazine (anticoccidial) 
_____________________________________________________________________________ 
269. Peritoneum, WL hen Internal oviposition Oviduct obstruction/tumor /infection 
 
Often idiopathic and may not affect long term productivity of hen unless extreme 
 
_____________________________________________________________________________ 
270. Oviduct, WL hen Cystic right oviduct Persistence of right Mullerian duct 
_____________________________________________________________________________ 
271. Oviduct, chicken Fibrinoheterophilic salpingitis E. coli #1 
 
DDX: P. multocida, Riemerella anatipestifer (duck) 
 
 
 
 
_____________________________________________________________________________ 
NEOPLASIA 
 
Tissue/bird Morphologic/Etiologic Diagnosis Etiology/Disease 
_____________________________________________________________________________ 
Chicken neoplasms associated with infection by the leukosis/sarcoma group of retroviruses: 
Lymphoid leukosis, erythroblastosis, myeloblastosis, myelocytomatosis, fibrosarcoma, 
myxosarcoma, histiocytic sarcoma, chondroma, osteosarcoma, nephroblastoma, renal carcinoma, 
ovarian carcinoma, hepatic carcinoma, pancreatic adenocarcinoma, hemangiosarcoma, 
mesothelioma, meningioma, glioma and benign counterparts. 
 
Family Retroviridae, Subfamily Orthoretrovirinae, Genus Alpharetrovirus, Species 
Avian leukosis virus; RNA Reverse Transcribing virus  DNA provirus 
 25 
 
Retrovirus of leukosis/sarcoma complex. Chicken genome contains endogenous viral loci (ev). 
Exogenous virus subgroup A transmitted vertically and horizontally. Exogenous virus induces 
neoplastic transformation of B lymphocytes. Subgroups A-D avian leukosis viruses can produce 
lymphoid leukosis. ALV Subgroup J produces myelocytomatosis. 
_____________________________________________________________________________ 
272. Pancreas, chicken Pancreatic adenocarcinoma 
_____________________________________________________________________________ 
273. Ovary, WL hen Ovarian adenocarcinoma 
_____________________________________________________________________________274. Peritoneum, WL hen Metastatic carcinoma (Carcinomatosis) 
_____________________________________________________________________________ 
275. Peritoneum, BB hen Metastatic carcinoma (Carcinomatosis) 
_____________________________________________________________________________ 
276. Kidney, rooster Embryonal nephroma 
_____________________________________________________________________________ 
277. Lung, chicken Hemangiosarcoma 
_____________________________________________________________________________ 
278. Peritoneum, rooster Mesothelioma 
_____________________________________________________________________________ 
279. Head, chicken Cranial myelocytoma ALV-J virus 
280. Liver, spine, chicken Hepatic/vertebral myelocytomas ALV-J virus 
281. Liver, chicken Mf hepatic myelocytomas ALV-J virus 
 
Myelocytoma (myelocytic myeloid leukosis) develops from periosteum on flat bones of skull, 
ribs, pelvis, trachea, sternum 
____________________________________________________________________________ 
282. Body, processed broiler Squamous cell carcinoma 
Usu. seen at processing and histologically resemble keratoacanthoma rather than carcinoma. 
Arise in feather follicle epithelium and can regress. 
_____________________________________________________________________________ 
283. Liver, turkey Mf hepatic lymphoma Reticuloendotheliosis 
 
Retrovirus structurally distinct from leukosis/sarcoma complex. Natural hosts are turkey, 
chicken, ducks, geese, pheasants, quail, peafowl. Both vertical and horizontal transmission. 
_____________________________________________________________________________ 
284. Wing, lovebird Cutaneous fibroma 
 
DDX: feather follicle cyst, poxvirus, squamous cell carcinoma 
_____________________________________________________________________________ 
285. Kidney, budgerigar Renal adenocarcinoma 
_____________________________________________________________________________ 
286. Beak, budgerigar Hemangiosarcoma 
_____________________________________________________________________________ 
287. Subcutis, cockatiel Lipoma, subcutis 
_____________________________________________________________________________ 
288. Liver, parrot Biliary carcinoma 
 
 
 26 
REFERENCES 
1. Diseases of Poultry. M. Saif (ed.) 12 edition; Blackwell Publishing, 2008 
2. Poultry Production (13
th
 Edition). R. Austic and C. Neshem, Lea & Febiger Publishers, 1990 
3. Avian Disease Manual (6
th
 Edition). C. Whiteman and A. Bickford (eds.), Kendall Hunt 
Publishing, 1990 
4. Isolation and Identification of Avian Pathogens, 5
th
 Edition. Swayne et al. (eds). American 
Association of Avian Pathologists, 2004. 
5. Commercial Chicken Meat and Egg Production, 5
th
 Edition. D. Bell and W.D. Weaver, Jr. 
(eds.), Kluwer Academic Publishers, 2002. 
6. Avian Histopathology, 2
nd
 Edition. C. Riddell (ed). American Association of Avian 
Pathologists, 1996. 
7. Pathology of Pet and Aviary Birds. R.E. Schmidt, et al. (eds.), Iowa State Press, 2003. 
8. Pigeon Health and Disease. D. C. Tudor. Iowa State University Press, 1991. 
9. Ratite Management, Medicine and Surgery. T.N. Tully and S.M. Shane (eds.). Krieger 
Publishing Company, 1996. 
10. Poultry Metabolic Disorders and Mycotoxins. S. Leeson, G. Diaz and J.D. Summers. 
University Books, 1998. 
11. Color Atlas of Avian Histopathology. C. Randall and R. L. Reece. Mosby-Wolfe Publishers, 
1996. 
 
	CL Davis Avian Porter 2013
	CL Davis Avian Path Porter 2013