North Texas Daily

City officials hope to counter mosquito populations

City officials hope to counter mosquito populations

City officials hope to counter mosquito populations
April 29
01:14 2014

Obed Manuel // Senior Staff Writer 

The West Nile virus left its deadly mark on Texas in 2012, when a record 89 people died after contracting the virus, the most of any state in the country, according to the Texas Department of State Health Services.

In an effort to preemptively combat the threat of West Nile, the city of Denton has contracted biology professor James Kennedy’s students for the past 12 years to collect mosquitos for testing purposes.

This year, the students will look to provide quick results to the city by using a Rapid Analysis and Measurement Platform, a machine that measures the amount of West Nile present the mosquito samples from around the city.

Kenneth Banks, director of environmental services for the city of Denton, said most municipalities send their samples to the state – a process that can take seven to 10 days.

“Having the local capability to test for West Nile is a huge advantage. They can literally provide results to us within a day,” Banks said.

Testing at UNT 

Biology graduate student Bethany Hambrick said she has worked on the testing for two years now and is writing her thesis on the research.

The process begins by setting up 16 traps around the city.

When the traps are brought back to campus, Hambrick said, the mosquitoes are sorted by species and gender because only female mosquitoes carry the virus.

“We’re looking for three different species that are the main vectors of West Nile,” Hambrick said.

The three species in Denton that carry West Nile are the southern house mosquito, the Asian Tiger mosquito and culex tarsalis.

“Once you understand the differences, it’s easy to spot them even if they’re flying,” said Erin LaMere, a biology senior who works on the testing. “When you see one land, you think, ‘Oh, that’s a tarsalis.’”

The mosquitoes are placed in a refrigerator for at least an hour, where they eventually die. The samples are placed in small vials and are liquefied with a vortex mixer.

After being placed in a centrifuge to separate the liquid from solid mosquito parts, a dye is added to the extracted liquid.

The compound is then entered into the RAMP machine, which measures the amount of West Nile particles on a scale of 0-600.

Hambrick said that a measurement between 40 and 50 can be considered high, but classifying an outbreak varies at every level.

“If we get a positive result, we have to notify the city immediately, but they won’t issue a statement to the public because we also have to wait to see what the state finds,” Hambrick said.

The first tests were conducted April 28 and came back negative.

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Public awareness

Kenneth Banks said that even though it is very early in West Nile season, the city has placed an emphasis on source reduction, meaning that crews may be out draining stagnant water where mosquitoes can breed.

Banks also said it is important for the public to know its role in eliminating breeding grounds for mosquitoes.

“If folks can be diligent about looking around their property and making sure standing water is drained and dealt with, that’s a huge help to us,” Banks said. “At the end of the day, we can have the best program in the world, but it all does come down to the citizen taking precautions to not contract the disease.”

Kennedy, who oversees the testing at UNT, said that the species posing the biggest threat to the public is the southern house mosquito because it is a container-breeding mosquito. This means it is capable of breeding in small spaces like saucers under plant pots and empty cans.

“Mosquitoes are masters of breeding, so try to eliminate as many breeding spots as you can,” Kennedy said.

Banks said the public will likely start noticing many mosquitoes in the coming days and weeks, but they will likely be floodwater mosquitoes, which do not likely carry West Nile.

“The public sometimes doesn’t make the distinction that not every mosquito carries West Nile. They’re definitely a nuisance, but in terms of transmission, they’re not a big threat,” Banks said.

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The effects of 2012’s deadly season

Kennedy said that around the peak of West Nile season around August 2012, about 50 percent of the mosquitoes his students collected tested positive. It was alarmingly high, given that on a typical year, the average during peak season is less than 10 percent.

Kennedy said that the areas around Denton opted to do aerial spraying to kill off infected mosquito populations.

“Denton didn’t participate, which I think was the right move. We saw those high temperatures come and the West Nile dropped off,” Kennedy said. “We saw the same things were happening in the surrounding communities, but we didn’t have to spray everyone with the pesticide.”

Kennedy said he was surprised by the low West Nile season in 2013. Kennedy said his team did not collect pools of West Nile-infected mosquitoes until October.

In 2013, Texas recorded 172 human cases of West Nile and 13 deaths, according to the Texas Department of State Health Services.

Since 2012, Denton County has participated in a joint effort with Dallas, Collin and Tarrant counties to counter the virus.

According to the Centers for Disease Control and Prevention, 70 to 80 percent of people who contract he virus do not exhibit any symptoms.

One out of five people develop a debilitating fever that can cause headaches, body aches, joint pains, vomiting, diarrhea, or rashes, according to the CDC.

Juan Rodriguez, chief epidemiologist for Denton County, said that the county will continue the joint effort alongside those counties to educate the public on how to handle West Nile season.

“Ever since 2012, we’ve been getting together to discuss our practices, what we intend to do and our education efforts. We share information we can use, without each of us having to reinvent the wheel,” Rodriguez said.

Rodriguez said the number of reported West Nile cases might rise this year because a specific fever threshold will no longer be a factor. Anyone who exhibits symptoms West Nile symptoms will be classified as having contracted the virus.

“It’s a bit of a double-edged sword. We don’t want people to be scared, but we do want them to be concerned,” Rodriguez said.

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Top photo: Biology Master’s student Bethany Hambrick (left) and ecology senior Paul Hunninghaus (right) bring mosquito samples in traps into the lab on Monday morning. They are going to classify samples and test them to see if the mosquitos carry West Nile Virus. Photo by Zixian Chen / Senior Staff Photographer

Center photo: Biology Master’s student Bethany Hambrick uses a microscope to choose mosquitos to test for the West Nile Virus on Monday morning in the lab. Photo by Zixian Chen / Senior Staff Photographer

Bottom photo: Some live mosquito samples are put in jar and to be shipped to Austin lab. Photo by Zixian Chen / Senior Staff Photographer

Feature photo: A microscopic view of a male (bottom) and female (top) mosquitoes. Only female mosquitoes bite people and have the possibility to transmit the West Nile Virus to people. Photo by ZIxian Chen / Senior Staff Photographer

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