West Nile season is underway in Tarrant County

Posted Thursday, Jun. 19, 2014  comments  Print Reprints
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Outside a far north Fort Worth station, Hunter Taylor is on the hunt for mosquitoes.

Inside a mosquito trap that he set out the night before, Taylor is looking for female Culex mosquitoes that can transmit the West Nile virus to humans. One type of mosquito, known as Culex quinquefasciatus, is also commonly known as the “southern house mosquito.”

Taylor, 24, is one of five University of North Texas Health Science Center graduate students who are helping to collect samples across Fort Worth that serve as an early warning system for the West Nile virus.

It’s part of network that’s been set up across Tarrant County in case West Nile starts multiplying like it did two years ago when North Texas suddenly found itself in the midst of an epidemic.

So far this year, none of the mosquitoes collected have tested positive for West Nile, and no human cases have been reported. But this is the time of year when officials start looking for mosquitoes to test positive.

“You never know what you’re going to find when you go out,” Taylor said. “Weather and wind can always play a factor.”

Back in the lab, the pickings are slim; windy conditions led to an unusually low number of mosquitoes being caught in the traps.

The hope remains that this year won’t be as bad as the summer of 2012, but no one really knows. Tarrant County can test samples from as many as 200 traps per day and works with all of the county’s 42 cities.

“Generally speaking, it’s very rare to see an epidemic in the same place in two or three consecutive years,” said Anita Kurian, associate director of Environmental Health for Tarrant County Public Health.

In 2012, Tarrant County had 280 confirmed cases and 11 deaths. Last year, there were far fewer in Tarrant County, with nine confirmed cases and two deaths.

On the lookout for new virus

While the focus remains on West Nile, officials are also warily watching for the next mosquito-borne virus.

This week, the Centers for Disease Research and Policy reported that the number of confirmed chikungunya cases in the Caribbean was surging past 170,000. The first cases of the virus have also been reported in the Central American country of El Salvador.

While no homegrown cases have been found in the United States, 57 travelers have brought the virus back to the U.S. from other parts of the world, authorities say.

Doctors have been advised to test patients who display the symptoms and have recently traveled to areas that have the virus.

Locally, Kurian said, officials realize that they will eventually need a separate sampling and testing program for chikungunya.

“It’s not a question of if it gets here, but when,” Kurian said.

Chikungunya is carried by Aedes mosquitoes, which are also prevalent in North Texas. The difference is these mosquitoes bite during the day while Culex mosquitoes tend to bite at night.

If chikungunya makes it to Texas, it may require a change in behavior among residents. Wearing insect repellent or long sleeves every time you go outdoors may become a necessity, Kurian said.

“Most of these infectious diseases are just a plane ride away,” Kurian said.

The symptoms reported with chikungunya are typically fever and joint pain. Headaches, muscle pain, joint swelling, or rash can also occur. Chikungunya outbreaks have been reported in many parts of the world, including Africa, Asia, and Europe. The first cases in the Caribbean were reported in late 2013, according to the Centers for Disease Control and Prevention.

“To prevent the bite is key”

For now, local officials are focused on West Nile and trying to find ways to reduce environments suitable for mosquito breeding.

Joon Lee, an assistant professor of Environmental & Occupational Health Sciences who oversees the sampling and testing program at the health science center, said he is also studying where mosquitoes breed.

“Whenever we have an epidemic, the weather pattern is kind of unique,” Lee said. “We tend to have big summer temperatures and normal or below normal precipitation.”

His initial research, which he says still needs more years of data to be conclusive, has shown that the number people infected can actually increase when the mosquito population is down.

Officials have recommended draining all areas of standing water in and around the home, including wading pools, pet dishes and birdbaths. But Lee said he hasn’t seen much standing water around most homes while collecting mosquitoes.

In searching for mosquito habitats, Lee has looked at storm drains as another possibility. When water is flowing, those wouldn’t be a problem. But Lee is studying what happens when droughts occur and little or no water flows through the drains.

In 2012, Texas led the nation in West Nile cases with 1,868, including 89 deaths.

But for some reason, the number of cases plunged in 2013. Dallas County had 16 cases and two deaths, and Tarrant County had nine confirmed cases and two deaths. Statewide, Texas had 172 cases and 13 deaths, according to the federal Centers for Disease Control and Prevention.

In 2013, other states had more cases. California had 368 cases and 15 deaths while Colorado had 318 cases but only seven deaths.

Fort Worth, which has a partnership with the health science center, has 62 sampling sites, including some city parks. Because there is no cure for West Nile, persuading residents to take precautions is crucial.

“To prevent the bite is key,” said Elmer DePaula, consumer health superintendent for the city of Fort Worth. “Education is important. In 2012, I think everybody got the message and, yes, there is some traction. The purpose of our partnership with UNT is to emphasize that.”

Bill Hanna, 817-390-7698 Twitter: @fwhanna

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