West Nile Virus - Animals Infected West Nile Virus - Animals Infected

Birds

Q. Do birds infected with West Nile virus die or become ill?

A. In the 1999 New York area epidemic, there was a large die-off of American crows. West Nile virus has been identified in more than 70 species of birds found dead in the United States. Most of these birds were identified through reporting of dead birds by the public.

Q. How can I report a sighting of dead bird(s) in my area?

A. State and local health departments may start collecting reports of dead birds at different times in the year. Some will wait until the weather becomes warming before initiating their surveillance program. For information on your specific area, please contact your state or local health department at www.cdc.gov/ncidod/dvbid/westnile/city_states.htm.

Dogs and Cats

Q. Can West Nile virus cause illness in dogs or cats?

A. There is a published report of West Nile virus isolated from a dog in southern Africa (Botswana) in 1982. West Nile virus has been isolated from several dead cats in 1999 and 2000. A serosurvey of dogs and cats in the epidemic area showed a low infection rate.

Q. Can infected dogs or cats be carriers (i.e., reservoirs) for West Nile virus and transmit the virus to humans?

A. West Nile virus is transmitted by infectious mosquitoes. There is no documented evidence of person-to-person, animal-to-animal, or animal-to-person transmission of West Nile virus. Veterinarians should take normal infection control precautions when caring for an animal suspected to have this or any viral infection.

Q. How do dogs or cats become infected with West Nile virus?

A. The same way humans become infected-by the bite of infectious mosquitoes. The virus is located in the mosquito's salivary glands. During blood feeding, the virus is injected into the animal. The virus then multiplies and may cause illness. Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. It is possible that dogs and cats could become infected by eating dead infected animals such as birds, but this is unproven.

Q. Can a dog or cat infected with West Nile virus infect other dogs or cats?

A. No. There is no documented evidence that West Nile virus is transmitted from animal to animal.

Q. How long can a dog or cat be infected with West Nile virus?

A. The answer is not known at this time.

Q. Should a dog or cat infected with West Nile virus be destroyed? What is the treatment for an animal infected with West Nile virus?

A. No. There is no reason to destroy an animal just because it has been infected with West Nile virus. Full recovery from the infection is likely. Treatment would be supportive and consistent with standard veterinary practices for animals infected with a viral agent.

Horses

Q. Has West Nile virus caused severe illness or death in horses?

A. Yes, while data suggest that most horses infected with West Nile virus recover, results of investigations indicate that West Nile virus has caused deaths in horses in the United States.

Q. How do the horses become infected with West Nile virus?

A. The same way humans become infected-by the bite of infectious mosquitoes. The virus is located in the mosquito's salivary glands. When  mosquitoes bite or "feed" on the horse, the virus is injected into its blood system. The virus then multiplies and may cause illness. The mosquitoes become infected when they feed on infected birds or other animals.

Q. How does the virus cause severe illness or death in horses?

A. Following transmission by an infected mosquito, West Nile virus multiplies in the horse's blood system, crosses the blood brain barrier, and infects the brain. The virus interferes with normal central nervous system functioning and causes inflammation of the brain.

Q. Can I get infected with West Nile virus by caring for an infected horse?

A. West Nile virus is transmitted by infectious mosquitoes. There is no documented evidence of person-to-person or animal-to-person transmission of West Nile virus. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have this or any viral infection.

Q. Can a horse infected with West Nile virus infect horses in neighboring stalls?

A. No. There is no documented evidence that West Nile virus is transmitted between horses. However, horses with suspected West Nile virus should be isolated from mosquito bites, if at all possible.

Q. My horse is vaccinated against eastern equine encephalitis (EEE), western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE). Will these vaccines protect my horse against West Nile virus infection?

A. No. EEE, WEE, and VEE belong to another family of viruses for which there is no cross-protection.

Q. Can I vaccinate my horse against West Nile virus infection?

A. A West Nile virus vaccine for horses was recently approved, but its effectiveness is unknown.

Q. How long will a horse infected with West Nile virus be infectious?

A. We do not know if an infected horse can be infectious (i.e., cause mosquitoes feeding on it to become infected). However, previously published data suggest that the virus is detectable in the blood for only a few days.

Q. What is the treatment for a horse infected with West Nile virus? Should it be destroyed?

A. There is no reason to destroy a horse just because it has been infected with West Nile virus. Data suggest that most horses recover from the infection. Treatment would be supportive and consistent with standard veterinary practices for animals infected with a viral agent.

Q. Where can I get more information on horses and West Nile virus?

A. Visit the USDA Web site Animal and Plant Health Inspection Service (APHIS).
Courtesy of the Centers for Disease Control and Prevention.

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