Earlier this month, the Fairfax County Health Department confirmed a dead crow found in Reston tested positive for West Nile virus, signaling it is once again time to break out the DEET and long sleeves.
But it is not just humans that are at risk of the virus. The virus, transmitted by the bite of an infected mosquito, can spread to humans, horses, birds and other mammals. However, animals such as dogs and cats seem to escape serious harm from the disease.
"West Nile doesn't seem to affect dogs and cats," said Jorge Arias, Fairfax County environmental health entomologist. "Dogs are frequently infected, but do not show signs of the disease."
THE LEVEL of protection from West Nile virus for animals varies from mosquito repellent for dogs and cats to vaccines for horses.
According to the Centers for Disease Control (CDC) Web site, West Nile virus can be found in at least 138 species of wild, exotic and captive varieties of birds including cockatiels, cockatoos and domestic chickens. The Web site adds that most birds, with the exception of crows and jays, will survive the infection.
Arias said that so far there is no evidence West Nile virus can be spread from an infected bird to a human.
Conversely, 40 percent of horses infected with the virus die from the disease. Arias said there were three horse deaths attributed to West Nile virus in Fairfax County last year.
"The year before last it was only birds. Last year it was horses," Arias said of the animal infections. "But horses can be vaccinated, it came out late last year."
So far, no horses have tested positive in Virginia this year, said Michelle Stoll, public relations coordinator for the Virginia Department of Health's Office of Epidemiology.
The CDC Web site cautions that horses that have been vaccinated for eastern equine encephalitis, western equine encephalitis and Venezuelan equine encephalitis are not protected against West Nile virus, which has its own vaccine.
AS FOR DOGS and cats, the virus does not seem to pose as much of a threat as it does for humans and horses. Stoll said that in 1999 there was one report of a feral kitten in New Jersey becoming infected and dying; and that there has been one confirmed death, in 1982 in Africa, of a dog attributed to West Nile virus. Stoll said that in the case of the dog, it had already been sick before contracting the virus.
"If the pet is not sick enough to go to the vet, we may never know about it," Stoll said.
Arias said that typically, dogs are infected with the virus, however, they rarely show signs of the disease.
In addition, other native mammals can also become infected such as bats, chipmunks, squirrels and domestic rabbits.
"There is no evidence of person-to-person or animal-to-person infections," Arias said.
Dr. Mark Johnson, one of the founders of the Pender Veterinary Centre in Fairfax, said medications for dogs and cats such as Advantix repel mosquitoes to some degree. And while using insect repellent containing DEET is recommended for adults and children, it can be toxic to animals.
The best way to protect household pets is to follow the many of the same precautions recommended for humans: avoid going outside during the mosquitoes' peak activity periods of dawn and dusk; eliminate standing water from the yard; and screen animal housing. Consult a local veterinarian before using any sort of insect repellent on a household animal.
For more information concerning West Nile virus, visit the county health department's Web site at http://www.fairfaxcounty.gov/service/hd/westnile/.