Avian Encephalomyelitis synonyms: Epidemic tremor, AE Dr. Latif Ahmad-PhD, Assistant Professor

Avian encephalomyelitis (AE) A viral dis. of young poultry characterized by Ataxia and Rapid tremors, esp. of head & neck; so it was often called “epidemic tremor.” AE occurs world-wide, resulting in: An asymptomatic egg prod. decline in commercial layers & breeders & Elevated mortality in vertically infected batches of chickens.

Etiology A picornavirus Previous studies suggested that AEV belongs to Enterovirus genus, but based on latter discovery that it has high levels of protein homologies with hepatitis A virus, it was tentatively placed in genus Hepatovirus

Host Range AE is a viral dis of young poultry (chickens, turkeys, Japanese quails, pheasants, pigeons). Turkeys are less suceptible to natural inf. and develop milder cl. dis. than chickens

Transmission Vertical transmission by transviral passage of virus from viremic hens (eggs) to their progeny. Lateral spread from birds which shed AE virus in feces results in direct & indirect inf. of susceptible flocks.

Clinical Signs Mortality occurs in chicks aged 3 - 20 days. Morbidity depends on transmission rate; usually < 5% under com. states, esp. if AE vaccination practiced. Depression progresses to prostration/lat. recumbency. Terminally, fine muscular tremors of head, neck & feet. May be lenticular opacity (cataracts) - recovered birds Inf. of susceptible breeder/com. egg flocks results in an asymptomatic decline in egg prod.

An incoordination & lat An incoordination & lat. recumbency in chicks may be due to AE, avitaminosis A, nut. encephalomalacia or arenavirus inf. (Spiking Mortality Syndrome). Detailed lab. exam. including histopathology is required to obtain an accurate Dx.

Pathology No gross lesions are observed. This is important in differentiating AE from encephalomalacia. Central chromatolysis of neurons in brain & spinal cord is histo-pathological lesion Clusters of lymphocytes in proventriculus muscle layer, gizzard muscle & pancreas.

Diagnosis Perivascular cuffing & neuronal deg. is revealed in brain & spinal cord histology. Lymphoid aggregated (proventriculus, panc. etc) Epidemic tremor virus can be isolated from brain tissue by inoculation of embryonated SPF eggs. Com. ELISA test kits can monitor antibody titer of flocks to determine susceptibility or following vaccination/challenge.

MCQs: Choose THE MOST CORRECT/THE ONLY CORRECT answer for the following questions: The addition of small amounts of anti- oxidants in the diet of chickens may prevent which of the following vit. E or Se def. dis. Muscular dystrophy Exudative diathesis Encephalomalacia Muscular dystrophy & exudative diathesis Exudative diathesis & encephalomalacia

2. For Dx of AE (avian encephalomyelitis), embryonated chicken eggs are inoculated (with brain susp. from affected chicks) via which of following route of inoculation? 3. Which of following live vaccines can be administered by wing-web stab method? AE vaccine AE & FC (Fowl cholera) vaccine AE and VA (viral arthritis) vaccines Yolk sac Allantoic cavity FC, VA & AE vaccines Amniotic cavity Chorio-allantoic memb

4. Central chromatolysis of neurons in brain & spinal cord is histo- pathological lesion of Dxic signif. which of following dis? 5. Clusters of lymphocytes in proventriculus musc. layer, gizzard muscle & panc. occur in chickens affected with which of following dis. MD AE Eastern eq. encephilitis AI ND Botulism IBD Viral arthritis

6. Which of following sp. is NOT resistant to natural inf 6. Which of following sp. is NOT resistant to natural inf. with AE virus? 7. Cataract was observed in some hens in a breeder flock of chickens. Inf. at early age with which of following infective agents should be considered as a possible cause? Quail Quail & pheasant Duck & geese vNDV Pigeon & quail AIV Pigeon & pheasant AEV MDV Salmonella

9. Mature chickens inf. lat. with AEV shed virus in 8. Mat. Abs. are very effective in protecting chicks &/or poults in protecting which of following dis. 9. Mature chickens inf. lat. with AEV shed virus in Eggs Feces Eggs & feces AE Egg & resp. secretions Chicken inf. anemia AE & IB Egg, feces & resp. secretions Chicken inf. Anemia & MD AE & chicken inf. Anemia

10. A flock of broiler breeder hens experienced 25% drop in egg prod 10. A flock of broiler breeder hens experienced 25% drop in egg prod. A virus that agglutinated chickens’ RBCs was isolated from the flock. The isolated virus could be any of following viruses EXCEPT 11. A live vaccine for which of following dis. should never be given to breeder hens within at least 4-wks before prod./during prod? Chicken inf. Anemia IBD & AE Chicken inf. anemia & IBD NDV AE & chicken inf. anemia AIV IBD, chicken inf. anemia & AE EDSV AEV

12. Quails are succumbed to natural inf 12. Quails are succumbed to natural inf. with which of following viruses? How many vaccinations against AE are adequate to protect breeder hens through-out their prod. life. IBV ILTV AEV 1 IBV & ILTV 2 ILTV & AEV 3 4

14. Biphasic mortality is a feature of vertical inf 14. Biphasic mortality is a feature of vertical inf. with which of following egg transmitted &/or hatchery transmitted dis.? 15. In chickens with neurologic signs due to nutritional encephalomalacia, characteristic gross lesions are most frequently found in what part of brain? Salmonellosis Aspergillosis Cerebrum AE Cerebellum Salmonellosis & aspergillosis Optic lobes Salmonellosis & AE Brain stem Medulla oblongata

16. Which of following lesions is characteristically found in chick embryos inoculated with brain suspension prepared from chicks inf. with field strain of AEV? 17. In chicks affected with avian encephalomyelitis, recommended specimens for virus isolation include brain as well as: Liver & spleen Petechial haem. brain Liver & duodenum Atrophy of sk. musc. Spleen & pancreas Diffuse S/C haem. Duodenum & panc. Opacity of eye Spleen & duodenum None of above

Nutritional foot-pad dermatitis 18. Which of following def. dis is commonly associated with rancidity of polyunsaturated fatty acids in diet? 19. Which of following viruses may induce a syndrome in broiler chicks characterized by partial/complete paralysis lasting 1- 2d? Rickets MDV Encephalomalacia AEV Curled toe paralysis NDV Nutritional foot-pad dermatitis AIV Eastern eq. encephilitis

20. There was sudden increase in mortality in a flock of 10-d old broiler chicks. Cl. Signs in affected birds include: apparent bindness, fine head tremors, ataxia & coma. Histopathological exam. from brain revealed no m/s lesions. The most likely condition is: AE Salmonellosis Mycotic encephilitis Vit. B1 def Spiking mortality synd.

21. Characteristic histopathologic lesion in cerebellum of chickens affected with nut. encephalomalacia include all of following EXCEPT: Focal areas of necrosis in cerebellar medullary rays Edeme, congestion of BVs & haem. Fibrin thrombi in capillaries Degen. of neurons Infiltration of heterophils

22. Many birds in flock of 2-wk old chickens exhibited cl 22. Many birds in flock of 2-wk old chickens exhibited cl. signs of leg weakness (paralysis). Birds were reluctant to move or walked on their hocks with aid of their wings. In some birds, toes were bent inwards & downwards. Postmortem exam. revealed thickening of sciatic nerves. Which of following condition would be first on your list of rule-outs? MD AE Riboflavin def. Thiamine def. Organic arsenic toxicity