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Midwest Pet Owners Concerned About West Nile Virus

Pet Column for the week of September 23, 2002

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Services - Public Health

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Jennifer Stone
Information Specialist

On September 17, the Veterinary Diagnostic Laboratory at the University of Illinois College of Veterinary Medicine in Urbana announced for the first time that a U.S. dog had died as a result of West Nile infection. Since then pet owners have been clamoring for more information about the disease, and some people have even taken measures to protect their pets that instead have resulted in accidental poisoning.

Despite pet owners' concerns, the risk West Nile virus poses to companion animals is very small. Dr. Christine Merle, an Extension veterinarian at the College of Veterinary Medicine, explains, "While it is possible for cats and dogs to be infected with this disease, infection rates in areas where the disease is prevalent are low. In addition, the virus does not usually cause severe illness in pets."

The animals that are truly at risk for severe clinical signs of the disease are those who are very young, very old, or have a compromised immune system. Signs of this disease can include incoordination, depression, decreased appetite, difficulty walking, tremors, abnormal head posture, circling, and convulsions.

"In a healthy animal many of these more extreme signs may not manifest," says Dr. Merle. "For the majority of companion animals, the signs caused by the West Nile virus are mild."

West Nile virus is spread through the bite of infectious mosquitoes. There is also a concern that the disease could be spread to household pets by eating dead, infected animals such as birds. "This method of transmission has not been proven," says Dr. Merle, "but it may be a good idea to keep your pet away from any animals that may have died as a result of the virus."

Ways that you can protect your pet include keeping your pet indoors during peak mosquito hours (dawn, dusk, and early evening) and removing standing water from your property. There are also a few mosquito repellents on the market that are made for pets.

Big problems occur when people try to use products designed for humans on their pets. "Mosquito repellants that are for human use and not approved for animals should never be used on pets," says Dr. Merle. "People could actually do their pet much more harm than good by using these products inappropriately."

DEET (N,N-diethyl-m-toluamide, N,N-diethyl-3-methylbenzamide ), for example, is a human mosquito repellent which may result in serious adverse effects when used on dogs and cats. Citrus oil extracts and other repellent oils should also be avoided because of extreme sensitivity of some animals to these products.

Aside from limiting exposure to mosquitoes, there is no other prevention available for household pets. There is no vaccine for cats and dogs, and there is no treatment for the virus other than supportive care. There is also no evidence that the virus can be spread from animal to animal or from animal to person.

Dr. Merle says, "The best thing that you can do to help your pet is to stay informed about the disease. The College of Veterinary Medicine has a Web page with information on West Nile virus at"

If you have other concerns about West Nile virus, please contact your local veterinarian.