Two types of Arboviruse

Encephalidites

• Eastern/Western/Venezuelan Encephalomyelitis (Sleeping Sickness)

• West Nile Virus

• Bite of infected mosquito
• Reservoir host-birds
• Horse is a dead end host
• Human is a dead end host
• Prepatent period 3-5 days

• Fever
• Depression/stupor
• Impaired vision
• Convulsions
• Incoordination
• Circling
• Head pressing
• Death

Supportive care

• NSAIDs
• Antibiotics
• Fluid replacement
• Physical support/protection

Prognosis: Guarded to poor

Older animals more severely affected

Vaccination

• every 3-4 months during mosquito seasons

Mosquito Control

• Aerosol transmission
• Virus is species specific

What are factors affecting susceptibility to Equine Influenza Virus?

• Age usually young (2-3 years old)
• Population density (high density causes more stress)
• Stress ( racetracks, training/show stables)

• Fever
• Depression
• Loss of appetite
• Nasal discharge
• Cough
• Muscle soreness/stiffness

Supportive care

• NSAIDs
• Antibiotics
• Rest

Symptoms resolve in 4-7 days although a dry cough may persist

• Failure to treat
• Continued Stress/training during dz can cause cardiomyopathy and pleuropneumonia

• Vaccinate young horses prior to departure for training center/racetrack
• At risk population,booster vaccination every 60-90 day

Direct-aerosol

Flu-like symptoms

• Fever
• Depression
• loss of appetite
• Cough
• Nasal discharge
• Lymph node enlargement

• Weakness
• Ataxia
• Paralysis (Can last up to 30 days. Horses can completely recover with supportive care.)

• Late term abortion (last trimester)

Birth of term foals

• Weak
• Fail to thrive
• Death within several days to weeks

Supportive care

• NSAIDs
• Antibiotics
• Intensive nursing care for recumbent horses
• Complications of protracted recumbency (Decubital ulcers, Pneumonia, colic)

Vaccination

• Pregnant mares at 5^th, 7^th, 9^th months of gestation
• At risk populations every 60-90 days

• Aerosol (virus praticles rapidly diluted in open-air environment)
• Carrier state in accessory sex glands of the stallion
• Endemic in Standardbreds

Variable

• Limb edema
• Urticaria(hives)
• Fever
• Loss of appetite
• Abortion
• Respiratory symptoms

Supportive care

• NSAIDs
• Antibiotics
• +/- Antihistamines
• Rest

• Virus isolation
• Serology
• Ongoing outbreak and consistent symptoms

• Vaccination
• Isolation of affected horses and consistent symptoms

Mechanical vectors-blood transfer

• Virus viable in horsefly for 15-30 minutes
• Proximity of horses required for disease transmission

Pre-patent period 1-3 weeks is average but may be up to 3 months

• Anemia
• Weight loss
• Unthriftiness
• Recurrent fever

NO CURE

• Reportable Disease
• Infected animals are managed by State Department of Agriculture at approved facility
• Culling of infected animals

• Coggins Test (required for interstate movement of horses)

Bite of infected animal

Wildlife sources of infection

• Fox
• Skunk
• Raccoon

Dumb/Paralytic form (most common EQ form)

• Weakness/incoordination
• Tail paralysis/urine dribbling/scald on hind legs
• Colic

Aggressive Form

• Photophobia
• Belligerence
• Grinding of teeth/obsessive chewing
• Seizures

Ante-mortem

1. Fluorescent Antibody Test

• Full thickness skin biopsy
• Cheek epithelial cells

Post mortem

• Submit brain and spinal cord to laboratory

Vaccination

• Rabvac-3 (Ft.Dodge) -only FDA approved rabies vaccine for horses

Avoid Exposure

• Wire mesh fencing preventing wildlife access