Texas is in the middle of a serious outbreak of West Nile Virus (WNV). The mayor of Dallas, the hardest hit locale, has gone so far as to declare a state of emergency and begin aerial spraying for mosquitoes. According to an August 20 update on the situation, the Texas Department of State Health Services has "confirmed 586 human cases of West Nile illness in Texas this year, including 21 deaths."

West Nile is not limited to Texas or to people. Here in Colorado, five equine cases have been reported to the State Veterinarian’s office thus far in 2012. More are surely to come. According to State Vet’s press release:

The incidence of the disease varies from year to year and depends on a number of factors, including mosquito numbers. The West Nile virus can be carried by infected birds and then spread locally by mosquitoes that bite those birds. The mosquitoes can then pass the virus to humans and animals.

Infected horses may display symptoms including head tilt, muscle tremors, stumbling, lack of coordination, weakness of the limbs, or partial paralysis. If horses exhibit clinical signs consistent with WNV, it is very important for horse owners to contact their veterinarian in order to confirm the diagnosis through laboratory testing. Horse owners should consult their private practicing veterinarian to determine an appropriate prevention strategy for their horses.

Vaccines have proven to be a very effective prevention tool … Of the five horses that have been WNV-positive, we have not been able to confirm that any of the horses have been vaccinated for WNV.

In addition to vaccinations, horse owners also need to reduce the mosquito populations and their possible breeding areas. Recommendations include removing stagnant water sources, keeping animals inside during the bugs’ feeding times, which are typically early in the morning and evening, and using mosquito repellents.

Dogs and cats can also be infected with West Nile virus via mosquito bites, but they rarely become sick from the exposure. Most individuals have such mild, minor, and short-lived symptoms (e.g., fever and lethargy, if they have any clinical signs associated with infection at all) that their owners are never even aware that infection has occurred. Dogs and cats that have been diagnosed with West Nile virus infection do not pose a health risk to people.

If you are concerned about West Nile and want to reduce your own and your pets’ potential exposure to the virus, limit outdoor activity during the dusk to dawn hours, remove standing water from your property, and keep windows and doors shut or make sure that screens are in good repair. Mosquito repellants can be helpful too, but do not apply human products to pets or canine products on cats. Used incorrectly, they can be more dangerous than the disease you are trying to prevent!

Repellants made specifically for both dogs and cats are available and can help keep mosquitoes and the diseases they transmit at bay.

Dr. Jennifer Coates

Image: Screen Door Bella by .:[ Melissa ]:. / via Flickr