Mosquito numbers, virus activity down but picking up

Tobie Blanchard, Kramer, Wayne L.  |  1/4/2011 1:08:24 AM

News Release Distributed 08/18/10

Wayne Kramer’s phone hasn’t been ringing incessantly yet this year. The LSU AgCenter mosquito expert said that’s one unscientific indication the state’s mosquito population is down.

“Mosquitoes really are under the radar this year,” Kramer said. “You hear from people when mosquito populations are high.”

Both mosquito numbers and virus activity associated with mosquitoes have been significantly lower than normal, according to Kramer. Reports he is receiving from mosquito abatement district directors indicate the state’s mosquito population is 50 to 60 percent of what we would normally see this time of the year.

But Kramer said this doesn’t mean there hasn’t been any activity. Nine cases of West Nile virus have been confirmed in humans so far in 2010 in Louisiana.

“Right now we’re sort of in the peak of the mosquito season when we talk about those species that are important for West Nile virus,” he said.

Kramer credits the unusually cold winter in combination with a dry late spring and early summer for keeping mosquito numbers low.

“This really inhibited the start of the mosquito season, and it seems like it’s taken the over-wintering population significantly longer than normal to get started this year than in a normal year,” he said.

Statewide testing of mosquitoes has shown an increase in virus activity in the past month, which Kramer says is normal in late summer.

In Florida, mosquito-borne virus activity has raised concerns. Locally acquired cases of dengue virus, common in many tropical areas of the world, have been confirmed in the Key West area.

“We haven’t had cases of dengue transmitted in the continental United States in 50 to 60 years.” Kramer said.

West Nile virus was introduced into the United States about 10 years ago, Kramer said, and now it is an established virus. He said the same thing could happen with dengue virus.

While locally acquired cases haven’t been confirmed, Louisiana should be on alert.

“The concern in Louisiana is that we have mosquitoes that are very competent, capable vectors of dengue virus,” he said.

One mosquito common in Louisiana that can transmit dengue virus is the Asian tiger mosquito.

“This mosquito is closely associated with people,” Kramer said. “It’s more active during the daytime, quite aggressive and really abundant locally here.”

Symptoms of dengue are similar to West Nile virus and include fever, aches and chills. According to the Centers for Disease Control and Prevention, more than 100 million people world-wide are infected with dengue virus each year.

Tobie Blanchard
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