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Mississippi labs increase efforts to address West Nile
MISSISSIPPI STATE -- Less than two years after test results identified the first West Nile virus case in the state, two Mississippi laboratories are working hard to identify hot spots needing increased control efforts by the state Health Department.
Dr. Lanny Pace is head of the pathobiology and population medicine department at Mississippi State University's College of Veterinary Medicine and is the executive director of the Mississippi Veterinary Research and Diagnostic Laboratory System. That system includes the State Diagnostic Lab in Jackson and a lab at MSU's veterinary college.
"In 2000, we did not have any cases of West Nile virus. We had our first cases last year in birds and horses, and most of those were in one part of the state (near Tupelo)," Pace said. "The veterinary diagnostic lab handles requests for West Nile tests in birds and horses while the Mississippi Department of Health handles testing of mosquitoes and humans. This year, we started getting positive cases from mosquito pools, horses, birds and humans at the same time. Since then, we have been busy helping the health department track cases across the entire state."
Dr. Sally Slavinski, veterinary epidemiologist with the state Health Department, said in 2001, only 108 human samples were tested. This year, more than 1,500 samples have been tested and more than 163 have tested positive for West Nile. In 2001, she said Mississippi tested 127 birds and three were positive for the virus.
This year, the Veterinary Diagnostic Lab in Jackson has screened about 2,000 birds and out of 600 tested, more than 300 were positive. Seventy-nine of Mississippi's counties have had a confirmed case of West Nile.
Pace said by knowing were the majority of the cases are located, the health department can concentrate its "Fight the Bite" efforts in those areas. This year's first cases were all confirmed the week ending July 19.
"We receive a lot more dead birds than we are able to test. Even though more than 110 bird species are susceptible to West Nile, we only test bluejays and crows to track the virus for the health department," Pace said. "If the carcasses are in good condition, we only test a couple per day from counties known to have a prevalence of West Nile. That way we can tell where the problems are heating up and where they are cooling down."
Pace said the lab personnel as a team are working overtime to test as many samples as possible, and two new employees have been added to the staff. They may process as many as 130 to 140 on some days or as few as 25 birds on other days. The numbers will decline as fall arrives. In addition, the diagnostic lab at MSU's College of Veterinary Medicine has been involved in setting up an immunohistochemical test for West Nile. This test can detect the virus in tissue from dead birds or horses.
"Even without the threat of West Nile virus, we'd be busy with routine sampling and testing for other forms of encephalitis, but the additional testing of birds has really increased our workload," Pace said. "We've learned how to run different tests to improve our methods and are still working on others."
With encouragement from the Centers for Disease Control and Prevention in Fort Collins, Colo., Pace said one researcher is studying the results using a different test kit on other bird species. The agencies hope the results could help determine an even better diagnostic technique.