Fort Worth

Tarrant County wary of West Nile, Zika as mosquito season begins

Culex quinquefasciatus mosquito is a vector for the West Nile Virus.
Culex quinquefasciatus mosquito is a vector for the West Nile Virus. Purdue University

The headlines have screamed concerns about Zika virus coming to the United States, but another, better-known nemesis cannot be ignored.

The number of Culex mosquitoes, the vector for West Nile virus, has been climbing across Tarrant County over the last month.

So far this year, mosquitoes have tested positive for West Nile in at least six sites, including one each in Arlington, Crowley, Lake Worth, Pantego, River Oaks and Westover Hills. There have been no West Nile human cases this year in Tarrant County and only one in the state, in El Paso.

But the summer of 2012 serves as a reminder of how bad West Nile can become.

That year, there were 1,868 confirmed human cases statewide. Tarrant County saw 280 cases in 2012 and 11 deaths.

Last year, Tarrant recorded 30 human cases and one death. Across Texas, there were 275 confirmed human cases of West Nile and 16 deaths.

“I think I’m more concerned about West Nile than Zika,” said Mike Merchant, an urban entomologist with the Texas A&M AgriLife Extension Service. “An early start to West Nile is always a bad thing, but a lot of it will depend on how hot of a summer it will be. If it gets really hot and really dry, those are the worst conditions.”

Since Jan.1, 20.35 inches of rain has fallen at Dallas/Fort Worth Airport, which is 2.31 inches above normal. But it’s far less than the 31.63 inches that fell through the same time last year.

Other areas have seen far more rainfall and flooding over the last several weeks.

The rural Parker County neighborhood of Horseshoe Bend was hit hard by flooding in recent weeks and is now overwhelmed with mosquitoes.

“We here in Horseshoe Bend are fighting those mosquitoes that are by the millions,” Bart Salter wrote via email.

Salter and other residents have been asking Parker County for help, but county spokesman Joel Kertok said it doesn’t have the funds or resources to attack mosquitoes in unincorporated areas.

“It's not just Horseshoe Bend,” Kertok said. “It's all over. Of course it is going to be bad down by the river with all of the flooding and standing pools of water. We advise all of our residents to take the common-sense approach to mosquito protection.”

‘Standing water breeds mosquitoes’

Tarrant County Public Health Director Vinny Taneja said the recent rainfall has provided the perfect environment for mosquitoes to multiply.

“The season has started and, of course, we have had a lot of rain,” Taneja said. “There has been plenty of water, and warm standing water breeds mosquitoes.”

Did you know a soda can filled with water is big enough to be a breeding ground for 20 mosquitoes. Kelly Hanes of the Tarrant County Public Health office provides important tips to keep the mosquitoes away this summer.

The best weapon against soaring mosquito populations begins at home, where residents should be getting rid of standing water everywhere.

If we can reduce the amount of mosquito breeding sites, that is our best weapon along with personal protection.

Tarrant County Public Health Director Vinny Taneja

“If we can reduce the amount of mosquito-breeding sites, that is our best weapon, along with personal protection,” Taneja said. “The Culex mosquito loves dirty, standing water — so does the Aedes mosquito that is the vector for Zika.”

That means not only dumping standing water in buckets or trash cans but also checking gutters and metal fence posts and looking for things like children’s toys in the yard.

Joon Lee, an assistant professor of environmental and occupational health sciences, oversees the sampling and testing programs at the University of North Texas Health Science Center in Fort Worth. He said it is “quite unusually early” to already have six positive West Nile traps countywide.

West Nile spreads when Culex mosquitoes bite infected birds and then bite humans. There have been more Culex mosquitoes this year in traps than at the the same time last year, Lee said.

“The data indicates that higher levels of West Nile virus amplification and transmission in avian hosts have been occurring … ,” Lee wrote in an email.

The Fort Worth City Council voted Tuesday to spend $220,000 to pay the UNT Health Science Center to enhance its efforts to trap and test mosquitoes.

Zika fears remain

While West Nile is a familiar foe, there is also concern about the Zika virus.

In Tarrant County, there have been five imported Zika cases this year and none locally transmitted. The most recent case was announced Friday: a traveler who had been to St. Lucia in the Caribbean. The previous Tarrant County imported cases were from individuals who had traveled to El Salvador, Puerto Rico (two cases) and St. Martin.

Tarrant County Public Health issues Zika home care kits, which include insect repellent and mosquito dunks, to anyone identified as a possible case.

Last month, the World Health Organization said “canceling or changing the location of the 2016 Olympics will not significantly alter the international spread of Zika virus” since it is just one of 60 countries where it has been found.

There have been 148,905 suspected cases of Zika virus disease reported in Brazil, including three deaths this year, according to the Pan American Health Organization.

Zika has caused alarm for its link to microcephaly, a birth defect in which a baby’s head and brain are smaller than normal. The World Health Organization has urged women to delay pregnancy if traveling in areas affected by Zika.

Between October and June, 7,830 suspected cases of microcephaly were reported in Brazil.

Zika can be carried by both Aedes aegypti and Aedes albopictus mosquitoes. These are daytime biters; the Culex mosquito bites at night, making it important to use insect repellent around the clock.

Aedes moquitoes can also carry chikungunya and dengue fever.

“The fact that there haven’t been widespread chik or recent dengue outbreaks in the U.S. gives us some hope,” said Merchant, the A&M AgriLife entomologist. “Most Texans don’t sleep with the windows open. A very high percentage of us are not outdoors at night or sitting on the porch during the day. Lifestyle is very important.”

Yet much remains unknown about Zika.

“I think if it’s going to get settled here in the U.S., it’s going to happen in the next two months,” Merchant said.

Staff writer Sandra Baker contributed to this report.

Bill Hanna: 817-390-7698, @fwhanna

The biting season

Preventing mosquito bites

  • Wear long-sleeved shirts and long pants, especially at dawn and dusk.
  • Regularly drain all standing water. Mosquitoes can breed in as little as a tablespoon of water.
  • Use an approved insect repellent (containing DEET, picaridin, IR3535 or oil of lemon eucalyptus).

Keep mosquitoes from breeding

Residents are encouraged to maintain their property to reduce mosquito-breeding sites, especially after the recent rains.

  • Routinely dump standing water.
  • Overturn all small containers.
  • Dispose of any trash or debris that can contain small amounts of water.

Watch for symptoms


High fever, headaches, rash, and muscle aches and severe joint pain in the arms, back and legs.

Zika virus

High fever, rash, joint pain, conjunctivitis (red eyes), muscle pain and headache.

West Nile virus

Neuroinvasive disease: Neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness and paralysis. This form can be deadly.

Headache, fever, muscle and joint aches, nausea and fatigue.

More information