ST. PAUL (AP) -- Tests confirm that five horses in Minnesota have been infected with the mosquito-borne West Nile virus, an illness that was first detected in Minnesota a week ago.
The fifth horse tested positive on Wednesday, said Mike Schommer, spokesman for the Minnesota Department of Agriculture
At least 11 more horses in the state have developed symptoms of West Nile, which include sleepiness and loss of coordination.
Of the five horses positively diagnosed with the virus, none had been vaccinated. Two of those infected horses have been destroyed, but the other three appeared to be recovering, Schommer said.
Jeff Bender, a professor of veterinary public health at the University of Minnesota College of Veterinary Medicine, said the virus appears to be spreading more rapidly than expected among horses in Minnesota, which is estimated at 800,000 statewide.
"This is a little bit of an uncomfortable sign that we've seen so many cases in such a short amount of time," said Bender, who added that the peak risk for mosquito-borne infections is in August and September.
About two-thirds of infected horses recover. The virus also affects birds and is especially deadly to crows and blue jays. Health officials say the risk to humans is low.
The latest diagnosis involved a horse from Grant County. Other counties where horses have been diagnosed with the virus are Clay, Hennepin, Roseau and Beltrami.
There are cases suspected but not yet confirmed by the National Veterinary Services Laboratories in Laq qui Parle, Traverse, Becker, Murray, Stearns and Carver counties.
In Murray County, a donkey tested positive in an initial screening this week. A horse in the same county is showing symptoms but has not yet been tested, Schommer said.
Bender said wet weather has contributed to a bumper crop of mosquitoes, helping spread the virus throughout the state. Minnesota also lies in the path of bird migration routes. West Nile is often carried into new areas by birds that are bitten by infected mosquitoes.
"I would expect to see evidence of disease or infection throughout the state," Bender said.
Earlier this week, West Nile claimed its first confirmed U.S. victim this year, a woman in her 70s who died in Baton Rouge, a state health department spokesman said.
The woman, who was not identified, died Monday. Before the woman's death, the Centers for Disease Control and Prevention had confirmed 185 cases, including 18 deaths, since the first Americans were diagnosed in 1999. The virus was first detected in New York City and has been found in 34 states and the District of Columbia.
On the Net:
Minnesota Department of Health page on West Nile virus: http://www.health.state.mn.us/divs/dpc/ades/wnv/wnv.htm
Centers for Disease Control West Nile virus page: http://www.cdc.gov/ncidod/dvbid/westnile
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