The recent discovery of three dead crows in New York and New Jersey is additional evidence of what health officials knew to be true: the mosquito-borne West Nile encephalitis virus has endured the winter.
Now the virus is apparently being spread again.
What remains to be seen is whether there will be a repeat outbreak of West Nile fever in humans and the mass bird die-off witnessed this past year in the Northeast when the West Nile virus was diagnosed for the first time in the Western Hemisphere.
On June 9, the New York State Health Department announced that a pair of crows found in Rockland County, New York, was infected with the virus. That same day, the New Jersey Department of Health and Senior Services reported that a crow found in Bergen County, New Jersey, had also tested positive for the West Nile virus.
No human cases of West Nile encephalitis have been reported in either state this year.
In April, the JAVMA reported that wintering Culex pipiens mosquitoes in New York City were carrying the live virus. Additionally, scientists at the University of Connecticut announced that a red-tailed hawk from Westchester County, New York, had succumbed to the virus (see JAVMA, April 15, 2000, page 1199).
The virus was confirmed by the New York State Health Department in the pair of crows on the basis of positive results of polymerase chain reaction, immunofluorescent antibody, and viral culture tests. In New Jersey, one of the 120 crows tested by the Department of Health and Senior Services Public Health and Environmental Laboratory using PCR was positive for the virus. The national Centers for Disease Control and Prevention confirmed the laboratory's finding.
Detection of infected mosquitoes and birds may indicate that the multistate surveillance and prevention program, put in place following last year's outbreak, is working.
"The New Jersey test shows that the surveillance system we have established to monitor West Nile virus is working as planned," said Health and Senior Services Commissioner Christine Grant.
The program is a cooperative effort by federal, state, and local health and wildlife departments to test for the West Nile virus, while also attempting to curb mosquito activity and educate the public how to guard against infection.