West Nile Virus.
Quick Links:
* What is West Nile Virus?
* Symptoms
* Prevention
* Treatment
* Horses do not have to be euthanized
* Quarantine is not necessary
* Horse Mortality
* Dogs and Cats
* Spread of the Disease
* West Nile Virus in Humans
* The Bottom Line
What is West Nile Virus?
West Nile is a mosquito-borne virus that was first detected in the United States in 1999. The virus, which causes encephalitis, or inflammation of the brain, has been found in Africa, western Asia, the Middle East, the Mediterranean region of Europe, and recently is spreading across the United States. Mosquitoes acquire the West Nile virus from birds and pass it on to other birds, animals, and people. While humans and horses may be infected by the virus, there is no documentation that infected horses or humans can spread the virus to uninfected horses or other animals. Migrating birds may play a role in spreading the disease.
Symptoms:
Clinical signs of the virus in horses included listlessness, stumbling and incoordination, weakness of limbs, depression or apprehension, muscle twitching, partial paralysis, or death. A fever was not usually observed (these symptoms may also indicate other diseases: i.e., rabies, etc).
Prevention:
Preventing animals exposure to mosquitoes is essential. The best way to do this is by removing any potential sources of water in which mosquitoes can breed. Dispose of any water-holding containers, including discarded tires. Drill holes in the bottom of containers that are left outside. Clean clogged roof gutters on an annual basis. Turn over plastic wading pools or wheelbarrows when not in use, and do not allow water to stagnate in birdbaths. Aerate ornamental pools or stock them with fish. Clean and chlorinate swimming pools that are not in use and be aware that mosquitoes can breed in the water that collects on swimming pool covers. Use landscaping to eliminate standing water that collects on your property; mosquitoes can breed in any puddle that lasts more than 4 days. Thoroughly clean livestock-watering troughs regularly. Local mosquito-control authorities may help in assessing the mosquito breeding risks associated with your property.
Birds can also be protected by limiting their exposure to mosquitoes. In areas reporting large numbers of bird deaths, investigations are conducted and samples collected to determine the cause of the deaths. People finding dead birds should notify local health officials.
Treatment:
No treatment is currently available for West Nile virus; however, USDA issued a conditional license to Fort Dodge laboratories, Inc. of Fort Dodge, IA, a division of American Home Products, Inc., for a vaccine intended to aid in the prevention of the disease in horses. The product is restricted to use by a veterinarian in those States where use of the product has been approved by the State regulatory authorities.
Horses do not have to be euthanized:
Because horses are incidental hosts, it is highly unlikely that mosquitoes feeding on an infected horse could ingest enough of the virus to transmit it to other animals. Horses are humanely euthanized only when the viral infection is so severe they will not be able to recover.
Quarantine is not necessary:
Since infected horses do not appear to be carriers for the disease, it is unlikely a quarantine would be necessary.
Horse Mortality:
In 1999 and 2000, a total of 85 horses had clinical signs of a West Nile virus infection. Of those, 32, or 38 percent, died or were euthanized, and the others recovered. This does not rule out the possibility that other horses may have been infected with the virus. It is likely that many horses recover from infection without clinical illness.
Dogs and Cats:
It is unlikely that dogs and cats will show signs of clinical illness, although any mammal or bird could potentially be exposed to the virus through mosquito bites. A survey of blood samples from dogs and cats in the New York City epidemic area showed a low infection rate.
Spread of the Disease:
(see map)
West Nile Virus in Humans:
The virus has claimed 18 lives from its inception in New York in 1999 through year end 2001. The CDC has found it in 27 states and expects it to spread throughout the country. Recently it was reported that 2 men in Texas were thought to have been infected. Neither are in danger.
The Bottom Line:
If you suspect you or your animals may be infected, seek medical/veterinarian treatment immediately.
