August 10, 2010 Pet Safety

Mosquito Borne Illness and Pets

A cartoon of a dog and a mosquito

Mosquito Borne Illness and Pets

Last week the news out of Florida reported fatal human infections with a virus typically found in horses, and pet owners were worried. Many asked the question, can my dog or cat contract these diseases too? The viruses causing horse sleeping sickness are common infections in horses, but infection of humans with the sleeping sickness viruses is rare. In the United States there are less than 10-20 human cases reported per year. Horses are commonly vaccinated to protect them against sleeping sickness.

Multiple viruses can cause horse sleeping sickness, but the viruses are related and all found in the Togaviruidae family. These viruses are sometimes called aborviruses —short for arthropod borne viruses since mosquito’s transmission is common to all. The virus implicated in the Florida patients was Eastern equine encephalitis. Western equine encephalitis and Venezuelan equine encephalitis are the other two horse sleeping sickness viruses.

Pet owners should be mildly concerned about the risk of infection with mosquito borne illnesses in their cats and dogs. Although equine sleeping sickness is a zoonotic disease, cats may be infected with the virus, but infection does not make them sick. Dogs too are resistant to Eastern and Western equine encephalitis infection but may show depression, fever and aggressive behavior if infected with Venezuelan encephalitis. Fortunately, this virus is exotic to the United States.

Two other mosquito borne viral diseases are in the news. Dengue fever is making resurgence in the Florida, but it does not affect dogs and cats. West Nile virus does infect dogs and cats. Dogs do not develop clinical signs and cats may show non-specific signs of illness, such as slight fever and reduced activity.

The most important mosquito borne illness of both dogs and cats is heartworm disease. An assessment of your pet’s need for heartworm preventative should be a part of every annual veterinary visit for both dogs and cats.

When people and animals get the same infections, the disease is called zoonotic. In the case of these mosquito-transmitted infections, your animals do not give the infection to you. You and your animal share the same environment and thus have the same exposure to the infected mosquitoes.

Creating a mosquito-free environment is the key to preventing these zoonotic mosquito borne illnesses and will protect your pets as well as your family. Window screens avert mosquitoes from entering your home. Preventing accumulation of standing water in your yard deprives the mosquitoes of the opportunity to reproduce. If you live in a West Nile virus endemic area and your cat is allowed outdoor access to hunt, it may become infected if it eats prey infected with the virus. Finally, talk to your veterinarian about mosquito repellant for your pets. Human insect repellants are not recommended for pets because of the likelihood of ingestion of the insecticide when the pet grooms its haircoat.


The Animal Medical Center
For 100 years, The Animal Medical Center has been a national leader in animal health care, known for its expertise, innovation and success in providing routine, specialty and emergency medical care for companion animals. Thanks in part to the enduring generosity of donors, The AMC is also known for its outstanding teaching, research and compassionate community funds. Please help us to continue these efforts. Send your contribution to: The Animal Medical Center, 510 East 62nd Street, New York, NY 10065. For more information, visit To make an appointment, please call 212.838.7053.

Tags: animal, animal hospital, animal medical center, animals, ann hohenhaus, arthropod, canine, cat, dog, dogs, encephalitis, feline, health, mosquito, new york vet, pet emergency, pet health, pet insurance, pet owner, pets, repellant, sleeping sickness, vet, veterinarian, veterinary care, virus, west nile, zoonotic,

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