Viral Encephalomyelitis Flashcards
Family
All alphaviruses in Togaviridae
Structure
Enveloped, positive-sense ssRNA
Vector-borne Disease agents
Mosquitos:
EEE: Culiseta melanura
WEE: Culex tarsalis
VEE: Ochlerotatus taeniorhynchus and Culex spp.
Reservoir species
Birds and rodents
can infect some mammals- equine highly susceptible, can be severe in humans
Transmission Cycle
EEE: prefer birds but sometimes rodents/ mammals
VEE&WEE: prefers rodents/mammals but sometimes birds
Pathogenesis
enters dermal tissue-> dendritic and Langerhans-> viral replication occurs-> attacks CNS-> causes significant inflammation
Incubation
4-10 days
VEE SPECIAL TRANSMISSION
if high enough viremia can secrete in bodily fluids in equine
potentially can infect humans but very rare
Clinical Signs Birds
most wild birds are asymptomatic
depression, tremors, leg paralysis
Clinical signs Emus/ostriches
hemorrhagic enteritis, vomiting
Clinical signs Equine
impaired vision, aimless wandering, head pressing, circling, difficulty swallowing, convulsions, paralysis, sudden death
Pathologic Lesions
petechial to ecchymotic serosal hemorrhages in intestines: unclotted or partially digested blood in intestinal lumen
congestion and petechiation in liver, splenomegaly, myocardial hemorrhage, foamy fluid in trachea, pale streaks in pelvic limb muscles
Pathologic Lesions in Horses
focal locations of necrosis with neutrophil infiltration and hemorrhage in brain
Diagnosis
Preliminary clinical diagnosis
ELISA for IgM antibodies, Neutralization assays, PCR on blood or tissue
VEE and WEE uses CSF for ELISA and PCR as well
Management
Equine vaccination for all 3, mosquito management (prevent still-standing water, pesticide control), prevention of horses in passerine heavy areas
