Don't expect more mosquitoes

Monday, May 05
Mosquito season is arriving after a disastrous winter for bats, a natural predator to the disease-carrying pests, but officials say they don't expect the reduction in bat population to create a noticeable increase in mosquitoes.

"We will have just as many (mosquitoes) as we always have," said Tom French, assistant director of the endangered species program at the Massachusetts Division of Fisheries and Wildlife. "I guarantee that it will not be a noticeable difference."

The Department of Public Health has already begun its annual mosquito surveillance, looking for bugs carrying West Nile virus and eastern equine encephalitis, or EEE. Until next winter, the state will be testing mosquito pools and dead birds for signs of disease.

Last year, six people in the state tested positive for West Nile virus, the DPH said. Of the 223 birds it tested, 43 were positive for West Nile virus, as were 65 mosquito pools. There were no positive tests for EEE.

Donna Rheaume, spokeswoman for the Department of Public Health, said the agency is stressing prevention, encouraging people to wear bug repellent that contains the active ingredient DEET, to cover up if outside during dawn and dusk hours, and to eliminate any standing pools of water such as those found in bird baths, pool covers and old tires. "We had six cases of West Nile last year and no cases of EEE," she said. "EEE is the more serious of the two, which can result in fatalities, which is why it is so important for people to take precautions."

There is no treatment for EEE, which can cause encephalitis, a swelling of the brain. EEE is usually found around freshwater, hardwood swamps, according to the DPH, and is spread when mosquitoes bite infected birds and then bite healthy mammals, particularly horses and llamas. The DPH reports that there have been 13 cases of EEE since 2004, with six fatalities.

West Nile virus can cause symptoms ranging from a mild fever to swelling of the brain, but 80 percent of people infected will see no signs of the disease, the DPH said; fewer than 1 percent will develop severe illness, including meningitis or encephalitis. West Nile virus is deadlier in birds, especially crows, blue jays and robins.

Mosquito-eating bats in Massachusetts have been affected by a mysterious condition that has been killing little brown bats that spend the winter in caves and mines.

Bats that would normally be safely snug in their cold-weather homes have instead been exhausting their supply of body fat and leaving their dens in search of food. They eventually die of cold and starvation.

Researchers have so far been baffled in their efforts to find a cause. Many of the dead bats are found with a white fungus on their face, but French, of the Division of Fisheries and Wildlife, said that appears to be a symptom and not a cause.

The condition is behaving like a disease, perhaps a virus, French said. It appears to have started in New York and moved outward, infecting some caves and not others. But researchers so far have found no detectable pathogen in the dead bats, nor have they found any unusual signs of pollution or contamination.

"Right now, we just don't know why, but they are starving to death in midwinter, when they should have enough fat to take them all the way through to spring," French said.

But other species of bats so far appear unaffected, including migratory bats and those that typically live only in barns and houses, so there should still be plenty bats to munch on mosquitoes, French said.


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