CSU ext

West Nile Virus (WNV) is an insect born virus disease that is present throughout North America, affecting mainly humans, horses and birds, and occasionally llamas, sheep and dogs.


How is it transmitted?  WNV is generally maintained in the environment by cycling through mosquitoes and wild birds. When an infected mosquito feeds on a person, horse or other animal typical signs of WNV infection may develop. Horses and humans are “dead end” hosts and cannot spread WNV. 

WNV cycle
Photo courtesy of CDC
What are the signs in animals?  The virus causes meningioencephalitis (inflammation of the brain and spinal cord) that results in  fever, in coordination, muscle fasciculation’s, head pressing, hyper excitability, anorexia, lethargy, recumbency and death. Horse in sling
West Nile Virus infected horse in a sling
What are the symptoms in humans?  Some people may show no symptoms at all, others may have a mild symptoms including; fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back.  Others may have severe symptoms that include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent or fatal.

anti mosqito

Use mosquitoe spray and wear protective clothing, avoid being outside during dawn and dusk.

More information at Merck Vet Manual: