West Nile Virus WNV

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West Nile Virus (WNV)
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West Nile virus was first isolated in the West
Nile District of Uganda in 1937. Equine disease
was first noted in Egypt and France in the early
1960s. The appearance of WN virus in North
America in 1999, with encephalitis reported in
humans and horses, may be an important milestone
in the evolving history of this virus.
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West Nile virus (WNV) has emerged in recent years
in temperate regions of Europe and North America,
presenting a threat to public, equine, and animal
health. The most serious manifestation of WNV
infection is fatal encephalitis (inflammation of
the brain) in humans and horses, as well as
mortality in certain domestic and wild birds.
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Finding a dead crow could be the first sign of WNV
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Three State Agencies Involved in WNV Activities
in Illinois

• Illinois Department of Agriculture
• Equine surveillance
• Dead bird necropsy and testing
• Illinois Department of Natural Resources
• Field biologists
• Research
• Illinois Department of Public Health
• Management of surveillance data

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The Culex mosquito
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Although the vast majority of infections have
been identified in birds, WN virus has been shown
to infect horses, cats, bats, chipmunks, skunks,
squirrels, dogs and domestic rabbits.
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Symptoms of WNV in Horses

• Ataxia (failure of muscle coordination)

• Weakness of limbs

• Recumbency (lying down)

• Muscle fasciculation

• Death

• Fever has been detected in less than one-quarter
  of the confirmed cases

Incubation period for WNV is usually 5 to 15 days
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There is not specific treatment for WNV in
horses. Supportive veterinary care is recommended.
Many horses infected with WNV never develop the
illness. Of those that did during the 1999-2000
outbreak, 38 died or were euthanized.
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WNV in horses is often confused with

• Rabies

• Equine herpesvirus-1

• Equine protozoal myeloencephalitis (EPM)

• Eastern, western or Venezuelan equine
  encephalomyelitis (EEE, WEE, VEE)

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• How Can I Help Protect My Horses From WNV?
• Keep horses indoors during peak periods of
  mosquito activity (dusk and dawn)
• Avoid turning on lights inside the stable after
  dark, as mosquitoes are attracted to lights.
• Keep birds away from the stable area.
• Eliminate areas of standing water including
  plastic containers, old tires, bird baths,
  wheelbarrows and gutters.
• Use fans on the horses while in the stable to
  help deter mosquitoes.
• Drain puddles as mosquitoes can breed in any
  puddle that lasts for more than four days

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Protection against the virus is best achieved if
both doses of vaccine are received by the horse 4
- 6 weeks prior to the onset of mosquito season.
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Human Symptoms of West Nile Virus Most
infections are mild, and symptoms include fever,
headache, and body aches, occasionally with skin
rash and swollen lymph glands. More severe
infection may be marked by headache, high fever,
neck stiffness, stupor, disorientation, coma,
tremors, convulsions, muscle weakness, paralysis,
and, rarely, death. The incubation period in
humans is usually 3 to 15 days.
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