Viral Encephalitic Disease (not done)

What genus are EEE, WEE, and VEE?

Alphavirus

What genus is WNV?

Flaviviridae

What family are EEE, WEE, VEE, and WNV?

Togaviridae

Where is WEE located?

Not in US

Where is EEE located?

Coastal atlantic, SE US, MI, and TX

Where is VEE located?

Central and south america

How are EEE and WEE maintained?

Cycling between birds and mosquitoes

What is an overwintering host for EEE?

Snakes

What are the amplifying hosts of EEE and WEE?

Birds

What are the dead end hosts of EEE and WEE?

Horses

How is VEE maintained?

Mosquitoes and small odents

What are the amplifying hosts of VEE?

Horses

When do EEE and WEE pop up?

Epizootic for 1-3 months in the summer and fall (favors mosquitoes)

What are the C/S of the viruses?

Inapparent infection with low-grade viremia and fever

Generalized febrile illness with anorexia, depression, tachycardia, and diarrhea

Clinical encephalomyelitis (classic form)

What horses are most susceptible to viral encephalitis?

Young

What virus is more severe and rapidly progressive CS?

EEE

What is the localization of the viruses?

Initially cerebral and progresses caudally to brainstem and spinal cord (EEE)

What are the cerebral signs of viral encephalomyelitis?

Obtunded mentation

Head pressing

Hyperesthesia

Compulsive walking

Blindness/lack of menace

What are the brainstem signs of the viruses?

Abnormal PLR, head tilt, nystagmus, facial and tongue paralysis

What are the spinal signs of the viruses?

Ataxia and paresis

What is on CSF of EEE?

High protein and cell count

Neutrophilic pleocytosis

What is on CSF of WEE?

High cell count

Lymphocytic pleocytosis

What blood work changes can you see?

Leukocytosis

Hyperfibrinogenemia

How do you diagnose the viruses?

Serology with hemagglutination-inhibition or plaque reduction neutralizing titer (need a 4 fold rise between acute and convalescent)

IgM capture (MAC) ELISA to DIVA

What is a human health hazard of the viruses?

CNS tissue

How do you diagnose the viruses on necropsy?

Virus isolation, IHC, or PCR of brain tissue

Meningoencephalomyelitis multifocal to diffuse

What infiltration is present with EEE?

Neutrophilic

What infiltration is present with WEE?

Lymphocytic

How do you treat the viruses?

Cerebral inflammation

Cerebral edema

Supportive care

What supportive care should you provide for the viruses?

IV fluids, nutritional support

Prophylactic antibiotics

Control hyperthermia

Slinging

Limb bandages

Sedation as needed

How do you control cerebral inflammation?

Steroids AND NSAIDs (never do in small animals)

What usually causes mortality from the viruses?

Laceration, head trauma, fracture, contaminated joints

What is the prognosis of EEE?

Highest mortality of 75-95% with 2/3 of survivors having residual CNS signs

Treatment is ineffective with EEE

What is the prognosis of WEE?

19-50% mortality with most recoveries being very good

What is the mortality of VEE?

19-83% mortality with slow improvement if they survive

how do you prevent EEE and WEE?

AAEP core vaccines before onset of mosquito season annual or biannual depending on mosquito activity

Mosquito control

Quarantine VEE infected horses

How do we control Venezuelan encephalitis?

No disease in over 20 ears but there is a MLV vaccine that can be conditionally released

What is the public health significance for the viruses?

Zoonotic and humans can die or can be subclinical, febrile, or neurologic

Horses are amplifying hosts for VEE

What species can also get EEE?

New world camelids, emus, pigs

What species can get VEE?

Pigs, domestic rabbits, goats, dogs, sheep

What type of virus is WNV?

Positive ssRNA

How is WNV transmitted?

Classic vector with birds amplifying and mosquitoes transmitting with humans and horses ad dead end hosts

What is the incidence of WNV?

Coincides with vector availability

Seasonal in temperate regions

Year round in subtropical or tropical areas

What are the C/S of WNV?

Fever, anorexia, depression with sudden onset and progression of neurologic signs

Muscle fasciculations

Changes in personality

Gait abnormalities: lameness, ataxia, weakness

CN abnormalities for short periods

What is on clin path with WNV?

Mild lymphopenia

Elevated muscle enzymes

What is on CSF of WNV?

Increased mononuclear cell population

Elevated protein

Xanthochromic (yellow)

How do you diagnose WNV?

IgM capture ELISA (DIVA)

Plaque reduction neutralization test

What in the brain does WNV attack?

Grey matter

How do you confirm WNV postportem?

PCR

IHC of CNS tissues

Polioencephalomyelitis

CNS TISSUE IS HUMAN HEALTH HAZARD