State presses hunt for deadly West Nile virus

Methods range from genetics to chickens

July 13, 2000|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Sharon Taylor is a Maryland public health lab technician whose job it is to pluck the brains from dead crows.

Her work isn't pretty, but it's a vital part of the state's defensive mobilization against the deadly West Nile virus that killed seven people in New York City last year.

The birds' brains are harvested daily in the basement of a Baltimore state office building. Later they're ground up and tested for infection by the West Nile virus.

Nearby, state health department workers are also grinding batches of mosquitoes for testing, and processing the blood drawn from Maryland's flock of early-warning "sentinel" chickens.

The virus has already been detected this year in the New York area. So far, however, after testing nearly 120 bird brains, and more than 1,000 batches of mosquitoes gathered since May 19, the Department of Health and Mental Hygiene lab has found no new sign of the virus in Maryland.

The virus has surfaced here only once, in a single crow found dead near the harbor last year. But the surveillance is expected to continue indefinitely, as long as the virus keeps showing up on the East Coast, said lab director Robert A. Myers.

"It appears the virus over-wintered, so it seems it's here to stay," he said.

The state virology lab took over testing in May after acquiring the equipment and training to conduct West Nile genetic tests developed by the Centers for Disease Control and Prevention in Atlanta. Until then, the work had been done by the National Wildlife Health Center in Madison, Wis.

The work will soon move to a new laboratory, one constructed with heightened bio-safety standards. It was built this year at 201 W. Preston St. with help from a $199,000 federal bio-terrorism grant.

The West Nile virus was first described in Uganda in the 1930s. It has since spread through much of Africa, western Asia, the Middle East and temperate parts of Europe.

There are no reliable estimates of how many people are infected each year. Fatality rates range from 3 percent to 15 percent, and are highest among the elderly, according to the CDC.

The virus first appeared in the Western Hemisphere last year, in and around New York City. The infection is carried by mosquitoes, and transmitted by their bite to humans, birds and horses.

Before cold autumn weather stilled the mosquitoes and the epidemic, seven people had died from West Nile encephalitis, and at least 62 more had been hospitalized.

The victims' ages ranged from 16 to 87. Their symptoms included fever, headache, skin rash, swollen lymph glands, stiff neck and disorientation. The infection can lead to brain swelling, coma and death. There is no vaccine.

The virus has resurfaced this year in 16 crows found dead in Suffolk, Rockland and Westchester counties in New York, and in Bergen County, N.J. But so far no new human infections have been reported. In the Old World, most cases surface in the late summer and fall.

The Maryland birds tested daily at the lab in Baltimore are brought in by the state Department of Natural Resources, which operates a statewide toll-free, dead-bird hotline (888-584-3110).

Callers are carefully questioned, and only a fraction of the birds are collected for testing. The lab wants mostly crows, and only the freshest, least traumatized of them.

In a 15-minute operation in her lab, Taylor deftly peels back the feathers and skin covering the crow's skull, and snips open the cranium with surgical scissors. It's a little like opening a hard-boiled egg.

"It's not for everybody," Taylor, 40, said of her job, her voice muffled by a surgical mask and plastic face-shield. "But I love it. To me, it's a dream job."

In a series of steps, the virus' genetic sequence - if it's present - is extracted and reproduced until there is enough to be detected and identified by genetic probes.

The state Department of Agriculture, meanwhile, gathers a steady stream of mosquitoes to test. They arrive 40 mosquitoes to a vial. The bugs are sorted by species and geography, ground up by ball bearings in a "vortex" machine, and tested like the brain tissue for the West Nile virus.

"It's like searching for needles in a haystack," Myers said. New York officials last year tested 22,000 vials of mosquitoes to turn up the 11 that proved positive for the virus.

"We've only tested 1,000," he said. "It's a real drain on resources to do mosquito testing. It really takes time."

The state virology lab is also running daily tests on blood from a platoon of 56 "sentinel" chickens posted in mosquito-infested parts of the state.

The chickens are cooped at 14 sites, mostly on state property. If any are bitten by infected mosquitoes, they don't die, but they do develop West Nile-specific antibodies.

Department of Agriculture workers draw blood from the chickens in a two-week cycle. If the lab finds West Nile antibodies, they will know that infected mosquitoes are in the area.

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