Mosquito control crews battle outbreak of pests
Galveston County’s mosquito control crew is seeing an increase in the blood-sucking insects since the heavy rains and high tides created by Tropical Storm Bill in June.
On its website recently, the county posted that mosquito control staff were observing a mixture of species, including the large freshwater Psorphora mosquito, a determined biter. The website, www.gavlestoncountytx.gov, noted that the increase in Psorophora and other freshwater mosquitoes is normal after a significant rainfall.
The Psorophora, one of the largest mosquitoes in the United States, often lay eggs in the humid soil and grassy overgrowth of lowlying areas.
The county’s crew is spraying by airplane and truck until the current outbreak is under control, according to the website notice.
“The bottom line is that there are a lot of mosquitoes out there,
and we are trapping,” said Mustapha Debboun, director of Harris County’s Mosquito Control Division, which operates under the county’s Public Health and Environmental Services department and services that county, which includes parts of the Bay Area and Friendswood.
Now that the rains have stopped, mosquitoes are finding pockets of water and laying eggs in them, he said. The high humidity and current temperatures above 90 degrees are conducive for mosquito proliferation. It takes four to five days for an adult mosquito to be produced from an egg, Debboun said.
“The good thing is that we don’t have a lot of West Nile virus cases (where pools of mosquitoes tested positive), although we do have some.”
As of June 25, 12 mosquito pools in the county had tested positive for the virus. Mosquitoes pick up the virus while feeding on infected birds. West Nile can be transmitted to humans when certain species of mosquito feed on them for blood, which has proteins mosquitoes need for their eggs. In humans, the virus can produce severe neurologic illness in a small portion of the population.
One in five people infected will develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea or rash, according to the U.S. Centers for Disease Control and Prevention. Most people with the symptoms recover completely; however, fatigue and weakness can last for weeks or months. Most people who become infected with the virus, however, do not develop symptoms.
Based on last year’s mosquito population carrying the virus, Debboun said there could be more positive pool tests in the region this summer but stated that it is hard to predict.
Harris County monitors mosquito populations in 268 areas. Last summer, 1,286 pools of mosquitoes tested positive with West Nile virus in Harris County. The summer before that, only 147 pools in the county tested positive for the disease.
Last week, the county had not sprayed the Friendswood area because no positive tests of West Nile came from mosquitoes there. At least one person in Harris County was reported to have contracted the disease this year.
“Even if you have a lot of mosquitoes, they might not be getting enough virus from birds or birds might not be as viremic,” Debboun said. “There are a lot of ecological things that happen. That is why we can’t predict one year from the other.”
Debboun said area residents should be aware of other mosquito-spread illnesses this summer, including dengue fever and the chikungunya virus.
Dengue is a mosquitoborne tropical disease. Symptoms include fever, headache, muscle and joint pain, and a skin rash, according to the CDC. Several species of mosquito spread the virus, and it can be life-threatening to some people.
People infected with the chikungunya virus, according to the CDC, can have a sudden onset of fever that can last two to seven days. Other symptoms can include joint pain that can last weeks or months and sometimes years. Two species of mosquitoes, the Asian tiger mosquito and the yellow fever mosquito, pass the virus to humans. The mosquitoes can pick up the virus from monkeys, birds, cattle and rodents.
Both viruses are in the United States, Debboun said. Although dengue has been around for a while, he said the chikungunya virus came ashore in Florida from the Caribbean last summer. Florida reported 11 cases of chikungunya virus last year.
“That means chikungunya has entered the United States,” Debboun said. “We have it. It is only a matter of somebody coming from Florida traveling to Harris County or Houston with the virus in his or her body and one of the local vectors (mosquito species susceptible to the virus) gets a blood meal from that person and picks up the virus and gives it to another person, and then a local transmission starts.”
Debboun said Harris County’s mosquito control division will continue to monitor mosquitoes and set out traps. The division will intensify surveillance of dengue and chikungunya with additional traps.
“As far as the West Nile virus, we’ll continue, as we have been for the last few years, to monitor for that,” he said.
Mosquito control crews monitor traps and collect specimens daily for testing in a virology lab. In addition to West Nile, dengue and chikungunya, the county tests for St. Louis encephalitis and Eastern equine encephalitis.
Debboun said area residents can help reduce mosquito populations and the risk of contracting the virus by removing containers that hold water from their yards. Containers could include old tires, plant pots, plastic children’s swimming pools, birdbaths and other items that can collect rain water and stagnate.
He also said residents should use mosquito repellent when outdoors, especially during dawn and dusk.
“They can also wear long-sleeve shirts and pants and use netting to sit under and obviously use screens on open windows,” Debboun said. “Do not expose yourself completely. Don’t wear tight clothing because (a mosquito’s needle-like) hypopharynx can go right through the shirt or pant and go right through to get a blood meal.”
Visit the web pages of the county mosquito control divisions at www. galvestoncountytx.gov and www.hcphes.org to keep track of spray schedules and potential mosquito outbreaks.
To request mosquito control services, call Galveston Mosquito Control at 800-842-5622. Friendswood residents in Harris County may call 713440-4800.