Five Premises Under VS Quarantine in Wyoming

The USDA has reported the detection of vesicular stomatitis (VS) in nine horses on five premises in eastern Wyoming. Vesicular stomatitis, which normally moves up from the Southwest along waterways, has not appeared elsewhere in the country this year. This has lead researchers to believe VS might have overwintered in Wyoming, and they're trying to figure out how. Vesicular stomatitis is a viral disease that primarily affects horses, cattle, and swine, but it can also affect sheep and goats. The disease causes blister-like lesions in the mouth and on the dental pad, tongue, lips, nostrils, hooves, prepuce, and teats of livestock. When the blisters break, they can leave raw, painful areas that can precipitate lameness and reluctance to eat. Animals with VS should be isolated from other livestock to ensure that troughs and feed buckets are not shared. Affected farms are encouraged to increase their insect control measures because biting flies such as Culicoides midges might be responsible for carrying the disease. The two affected counties--Converse and Natrona--border one another, and the affected premises (one in Converse and four in Natrona) are situated near waterways. Donal O'Toole, MVB, MRCVS, PhD, Dipl. ECVP, FRCPath, director of the Wyoming State Veterinary Laboratory and head of the Department of Veterinary Sciences at the University of Wyoming in Laramie, said VS typically moves up out of the southwestern United States and appears in other states before springing up in Wyoming. This year there was no warning. "The virus isolate from the first horse to come up positive in Natrona this year has been compared by the USDA to isolates from from Wyoming and Montana last year," said O'Toole. "Although I don't know the specific details, I understand it is a close match. The inference is that vesicular stomatitis virus somehow managed to overwinter in Wyoming in 2005-06. "This is an interesting situation since in the past we've always assumed this disease comes out of Central America or Mexico and moves north in big jumps we don't understand," he added. "The similarity of the current isolate suggests that some years the virus can hang around in the U.S. and pop up the following year."....

Crows eyed in war against West Nile virus

Where there are communal crow roosts, look for the West Nile virus, say scientists at the University of California, Davis. Corvids, including American crows, yellow-billed magpies, western scrub-jays and other members of the Corvidae family, serve as the primary reservoirs or incubators for the mosquito-borne virus, according to research entomologist William Reisen of the Center for Vectorborne Diseases at UC Davis. "Corvid surveillance is crucial to stopping the transmission of the virus," he says. September is a crucial month in the war against the virus, which usually peaks in late August and September and ends in October. "Communal crow roosts help drive the West Nile virus into the Culex (mosquito) populations -- that's why it's so important for people to find and report dead birds," says Mr. Reisen, a professor with the Department of Pathology, Microbiology and Immunology at the UC Davis School of Veterinary Medicine. "Crows are good hosts for mosquitoes. There's an amazing amount of virus in the bloodstream of infected crows, sometimes as much as 10 billion virus particles in one millimeter of blood. They're like a big sack of virus." "We're investigating how the distribution of host-seeking mosquitoes and infected corvids intersect in time and space to effectively amplify the West Nile virus in an urban California landscape," he says. "We're studying how landscape features, mosquito abundance patterns and corvid roosts affect the distribution and abundance of West Nile virus in Davis." Infected crows usually die very quickly, says Mr. Reisen, who's seen crows in Southern California literally "fall out of the sky" during a WNV epidemic....