West Nile Virus and Animals
Can West Nile Virus cause severe illness or death in horses?
Yes, West Nile Virus can cause illness and even death in horses. However, the majority of horses infected with the disease recover.
How do horses become infected with West Nile Virus?
West Nile Virus is transmitted to horses by the bite of an infected mosquito. The mosquito gets infected with the virus after feeding on a bird or other horse infected with the West Nile Virus. Not all mosquitoes transmit WNV.
Can I get infected with West Nile Virus by caring for an infected horse?
No. There is no evidence of person-to-person or animal-to-person transmission of West Nile virus. If your horse becomes infected with West Nile Virus, normal infection control precautions should be followed.
Can a horse infected with West Nile virus infect neighboring horses?
There is no documented evidence that West Nile virus is transmitted between horses. Horses suspected to have been infected with West Nile Virus should be isolated from mosquito bites, if at all possible to avoid further mosquito contamination.
Can I vaccinate my horse against West Nile Virus?
A West Nile Virus vaccine for horses was recently approved, but its effectiveness is unknown.
Should a horse infected with the West Nile Virus be destroyed?
Data suggest that most horses recover from the infection, therefore there is no reason to destroy a horse infected with West Nile Virus.
Where can I get more information about West Nile Virus and Horses?
You can obtain more information on West Nile Virus and horse by visiting the Animal and Plant Health Inspection Service website at www.aphis.usda.gov.
Dogs and Cats
Can West Nile Virus cause illness in dogs or cats?
Yes, West Nile Virus can cause illness in dogs or cats. Most dogs or cats infected with West Nile Virus do not show signs of illness and most will recover from the infection. Experimentally infected dogs showed no symptoms after being infected with WNV, and some infected cats exhibited mild, nonspecific symptoms during the first week after infection.
How do cats and dogs become infected with West Nile Virus?
Dogs and cats become infected with West Nile Virus when they an infected mosquito bites them. There is also evidence that cats can become infected with the virus after eating experimentally infected mice.
Can I, or other pets, become infected with West Nile Virus by coming in contact with a dog or cat that has been infected with the virus?
No, West Nile Virus is transmitted by the bite of an infected mosquito. There is no documented evidence of dog or cat-to-person, or animal-to-animal transmission of West Nile Virus.
Can an infected dog or cat become a carrier of the disease?
The evidence suggests that dogs do not develop enough virus in their bloodstream to infect more mosquitoes.
Cats develop slightly higher levels of virus in their bloodstream, but it is unclear if this would be enough to infect mosquitoes. It is very unlikely that cats would be important in furthering the spread of the virus.
Can I become infected with WNV if a dog with the virus bites me?
Preliminary studies have not been able to detect virus in the saliva of infected dogs. This suggests that dog bites pose a low risk, if any, of transmission of WNV from dogs to other animals or people.
Is there a vaccine for cats or dogs?
Should a dog or cat infected with West Nile virus be destroyed?
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.
Can I use insect repellent on my pets?
DEET-based repellents, which are recommended for humans, are not approved for veterinary use (largely because animals tend to ingest them when licking.) Talk with your veterinarian for advice about the appropriate product for use on your pet.
Does WNV infect other animals?
WNV infections have been documented in sheep, cattle and pigs in Africa and Eurasia. Most infections were without clinical signs and animals developed antibodies to the virus. However, in laboratory studies sheep infected with WNV exhibited fever, abortion and encephalitis.
What about domestic birds?
Birds usually do not show any clinical signs when infected with WNV. Chickens can be infected with WNV and not become sick. However, natural disease due to the virus has been reported in domestic geese, ducks, pigeons and chickens.
Birds are not currently suspected of transmitting WNV to humans. Regardless, gloves should be worn if handling any dead bird or animal.
What should I do if I see a dead bird?
Certain birds, especially crows, ravens, jays and hawks, are highly vulnerable to West Nile virus. Dead birds are usually the first indication of virus transmission in a particular area. If you find a dead bird the California Department of Health Services requests that you call 1-877-WNV-BIRD to report it.(Dead squirrels can also be reported to that line.) If the bird is a candidate for testing, they will arrange for a District technician to pick it up.
Where can I get more information about West Nile Virus?
Fact sheets on West Nile Virus and pesticides used during adult mosquito control can be obtained from Contra Costa Health Services by calling 925-313-6740.
Content provided by the Public Health Division of Contra Costa Health Services.