L12/13: Reticuloendotheliosis + Encephalomyelitis (Romero)

Question 1

Reticuloendotheliosis virus is closely related to an endogenous retrovirus from echidna in Australia and New Guinea, and some sequences of the virus have been found in the genome of Gallid herpesvirus-2 and fowlpox virus

Answer 1

:)

Question 2

Outbreaks of REV originated from

Answer 2

Contamination of Fowlpox and Marek’s disease vaccines with replication competent REV
-worldwide

Question 3

CS of reticuloendotheliosis

Answer 3

• anemia
• runting (wt. loss)
• immunosuppression
• abnormal feathering
• paralysis due to nerve infiltration (rare)
• neoplasia: tumors of BOTH B and T cell origin

Question 4

Trans. Of reticuloendotheliosis

Answer 4

• Horizontal (shed in feces)
• Iatrogenic (contaminated vaccines)
• Vertical (rare)

Ab to REVs are widespread in layers, broilers, turkeys, ducks

Question 5

REVs

Answer 5

Chick syncytial virus
Duck infectious anemia virus
Spleen necrosis virus

Question 6

Pathology of reticuloendotheliosis

Answer 6

• atrophy of thymus and bursa of F
• enlarged peripheral nerves
• abn. Feather development
• proventriculitis
• enteritis
• anemia
• liver and spleen necrosis
• tumors anywhere (difficult to differentiate from LL and MD)

Question 7

Prevention of reticuloendotheliosis

Answer 7

• eradicate from genetic stocks (by testing layers and chicks)
• depopulate and disinfect when outbreaks occur
• NO vaccine available**

Question 8

Cause of avian encephalomyelitis/epidemic tremor

Answer 8

Hepatovirus in the picornaviridae family

-a hardy resistant virus

Question 9

Trans. Of avian encephalomyelitis/epidemic tremor

Answer 9

• fecal/oral
• fomites
• infection is perpetuated transovarially**

Hatched chicks shed virus and infect hatch mates

HORIZONTAL AND VERTICAL

Question 10

CS of avian encephalomyelitis/epidemic tremor

Answer 10

1-3 wk old baby chicks most affected: neuro signs including ataxia, incoordination, unable to stand, rapid tremors of head and neck

Adult birds usually asymptomatic except temporary drop in egg production in unvaccinated layers

Question 11

avian encephalomyelitis/epidemic tremor causes microscopic lesions located where?

Answer 11

Brain
Ventriculus
Proventriculus
Heart 
Pancreas

Question 12

Epi of avian encephalomyelitis/epidemic tremor

Answer 12

• acutely infected hens shed in eggs and feces up to 1 month
• virus can survive in feces 1 mo.
• chicks show signs from day 1 to 3 wks and shed virus in feces

Question 13

Gross pathology of avian encephalomyelitis/epidemic tremor

Answer 13

(Minimal):
-pale gizzard
+/- hydrocephalus

40% of recovered birds develop cataracts and bluish discoloration of the lens**

Question 14

Microscopic pathology of avian encephalomyelitis/epidemic tremor

Answer 14

• neuronal degeneration in brain stem
• purkinje cell degradation in cerebellum
• perivascular cuffing in CNS
• glial foci in molecular layer of cerebellum
• lymphoid foci in pancreas, ventriculus, proventriculus, heart, etc.

Question 15

Immunity to avian encephalomyelitis/epidemic tremor

Answer 15

• permanent immunity after field infection
• birds develop protective virus neutralizing Ab after recovery
• maternal Ab present in egg yolk render chicken embryos and newly hatched chicks resistant to virus*** which are the basis for testing embryonated eggs for passive immunity and protection from muscular dystrophy (test for flock immunity in layers)

Question 16

Dx of avian encephalomyelitis/epidemic tremor

Answer 16

• Hx, CS
• challenge of embryonated eggs from hatchery with AEV and resistance to muscular dystrophy
• histopath
• PCR
• virus isolation in eggs
• paired sera

Question 17

Vax for avian encephalomyelitis/epidemic tremor

Answer 17

• vax pullets at 8 wks. And then again 1 mo. Before onset of laying
• monitor for response to vax by embryo susceptibility assay or ELISA

(NOT zoonotic dz)