Protecting Your Livestock from West Nile Virus (WNV)

The West Nile virus (WNV) was first detected in the Western Hemisphere in 1999 and has since rapidly spread across the North American continent into all 48 continental states seven Canadian provinces and throughout Mexico. In addition WNV activity has been detected in Puerto Rico the Dominican Republic Jamaica Guadeloupe and El Salvador.

Mosquitoes acquire the West Nile virus (WNV) from birds and pass it on to other birds and animals. While humans and horses may be infected by the virus there is no documentation that infected horses can spread the virus to uninfected horses or other animals. Migrating birds appear to play a role in spreading the disease.

West Nile virus (WNV) has impacted thousands of horses since 1999 with some regions reporting over 30% of the horse cases dying or euthanized due to poor prognosis. There are currently two vaccines approved by the U.S. Department of Agriculture (USDA) for use in horses.

Because the virus is transmitted by mosquitoes it has the potential to affect livestock and poultry. In 2003 more than 5 181 equines in 48 States were diagnosed with cases of West Nile equine encephalitis.

Clinical signs of WNV infection in horses include ataxia (stumbling or poor coordination) depression or apprehension weakness of limbs partial paralysis muscle twitching or death. Fever is not often observed.

How You Can Protect Your Animals

You can decrease the chances of your animals being exposed to WNV by decreasing their exposure to adult mosquitoes. 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 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 water that collects on your property; mosquitoes can breed in any puddle that lasts more than 4 days. Thoroughly clean livestock–watering troughs on a monthly basis. Local mosquito–control authorities can help in assessing the mosquito–breeding risks associated with your property.

Currently there is no treatment for WNV; however there are currently two licensed WNV vaccines available to aid in the prevention of the disease in horses. In November 2002 VS granted a full license to Fort Dodge Animal Health of Fort Dodge IA for the manufacture of a killed WNV vaccine. A full license was also granted to Merial Inc. in December 2003 for the manufacture of a live vectored recombinant vaccine. Use of these vaccines is now no longer restricted to licensed veterinarians.

Simple steps to protect your horses:

1. House horses indoors during peak periods of mosquito activity particularly at dusk and dawn.
2. Aviod using lights inside stables during the evening and at night as lights attract mosquitos.
3. Place incandescent bulbs around the perimeter of the stable to attract mosquitos away from the horses.
4. Remove all birds including chickens that are in or close to the stable.
5. Check your property periodically for dead birds such as crows. Any dead birds should be reported to the local health deparment. Use rubber gloves to handle the birds or use an implement such as a shovel.
6. Eliminate standing water. Shallow standing water water in used tires manure storage pits and drainage areas with stagnant water are ideal mosquito breeding places.
7. Topical preparations containing mosquito repellents are available for horses. Read the product label before use and follow label directions.
8. Use fans on horses while in the stable to help deter mosquitoes.
9. Fog the stable premises with pesticide in the evening to reduce mosquitoes. Read directions carefully before using.