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9.6.2000 00:31
Officials say precautions should keep people safe
By FELICE J. FREYER
Journal Medical Writer
When health and environmental officials began preparing for the possible spread of West Nile virus to Rhode Island, no one knew whether the bug that killed seven New Yorkers last year would even get here.
But it did, and with the death of a horse in Wakefield last weekend, awareness of the mosquito-borne disease -- new to this continent -- has crossed a new threshold in Rhode Island. Now we know that West Nile is being carried by mosquitoes that bite mammals, and their other mammal target -- us -- could be next.
So far, there have been nine reported cases of West Nile virus in people in this country this year, all but one in New York City. None has died.
But for all we know, Rhode Islanders may have already been bitten by West Nile-infected mosquitoes. The reason we don't know is that most who are bitten don't fall ill and many who do get sick won't get sick enough to seek medical attention.
Furthermore, most who get sick won't die from it, although in the frail elderly and those with weakened immune systems West Nile can cause a fatal inflammation of the brain. The mortality rate is described as anywhere from 3 percent to 15 percent.
"This disease is now well established in the Northeast and it's here to stay," says Alan Gettman, the state's mosquito-abatement coordinator.
For the average Rhode Islander, says Helen Drew, the state Health Department's legislative liaison, "the message is the same: that personal protection should be important in reducing the risk for West Nile virus."
That means wearing insecticide containing DEET when you go out and donning long-sleeved shirts and long pants in the evening and early morning, when mosquitoes are most active.
Additionally, individuals can contribute to the effort by eliminating stagnant pools where mosquitoes breed. Change the water in your birdbath twice a week; remove old tires, garbage cans, buckets and such; clean out your rain gutters so water can flow through, and don't let puddles form in your pool cover.
"We are not surprised at all to see the disease show up in Rhode Island, particularly when we were charting its movement and spread within the state of Connecticut and the wild spread across the entire state of New York," Gettman said. "It popped up in the Boston area; then we knew it was only a matter of time before it popped up in Rhode Island. . . .
"So when a horse showed up with it, that was no surprise to us. We didn't expect it, we didn't not expect it." Twenty horses were infected on Long Island last year. Another horse was infected in New York this year, and one horse recently died in Massachusetts from the West Nile disease.
Is it only a matter of time before a person becomes infected?
" 'Only a matter of time' -- I don't like that phrase very much," Gettman said. "We're hoping people will heed the simple precautions. . . . That is by far the best way for risks to be reduced -- for people to take personal responsibility."
Although the individual's role in controlling West Nile remains critical, an extensive public health apparatus has also been in operation since the spring to watch for it and to keep it under control.
The effort, coordinated by the Health Department and the Department of Environmental Management, included spreading larvicide in catch basins to prevent baby mosquitoes from growing up, training municipal officials in the use of larvicide, and trapping and testing mosquitoes throughout the state.
The first sign that West Nile virus was among us came early last month, when a dead crow found in Warwick tested positive. Birds are the primary reservoir for West Nile; mosquitoes pick it up when they bite infected birds, and then spread it by biting other birds and other animals. Some birds are unaffected by the virus, but others are killed by it, and crows appear to be especially vulnerable.
A total of four crows in Rhode Island have been found dead from West Nile infection.
But so far, despite trapping mosquitoes at 30 to 40 sites once a week, the state has yet to find a single infected mosquito. That's because the traps catch dozens to hundreds of mosquitoes, while there are many millions of them buzzing around the state, Gettman says. The infected ones have so far escaped the traps.
"The disease is much more evident in the form of dead birds that get reported than it is in mosquitoes," Gettman says. "Realize that we have citizens all over Rhode Island looking around for dead birds."
Dead crows have been the sentinels for discovering West Nile in other states as well.
Gettman says the mosquito trapping is worth the trouble because eventually it will provide valuable information on which species of mosquitoes have been infected. Also, the state was already trapping mosquitoes as part of its annual effort to watch for Eastern equine encephalitis, a less common but deadlier mosquito-borne infection.
When a crow killed by West Nile is found, a two-mile radius around the spot is sprayed with pesticide to kill as many mosquitoes as possible. The bird that died was probably ill -- and being bitten by mosquitoes that would then spread the illness further -- for a number of days before its death. Because mosquitoes don't travel far, such targeted spraying is considered the best response.
The pesticide kills not just mosquitoes but any invertebrate exposed to a large enough dose, so environmental officials want to be judicious in its use.
Gettman notes that the continual, intermittent rains of this summer provided ideal conditions for breeding mosquitoes. Without the state's widespread distribution of larvicide, he says, there would probably be many more mosquitoes biting than there are.
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