As official warnings about the Zika virus escalate, Baylor University mosquito researchers say they are bracing for the possibility of mosquito-borne cases in Central Texas this year.
“I think we will see it this summer,” said Richard Duhrkopf, a Baylor biologist who serves as regional director for the American Mosquito Control Association. He said Texans should be thinking now about how to fight the spread by draining mosquito breeding grounds.
“If anyone is going to see the Zika virus circulated, it’s Florida, Louisiana, Texas and probably California,” Duhrkopf said.
By Wednesday afternoon, state health officials were reporting 10 cases of Zika virus, spread among Harris, Bexar and Dallas counties. News reports Wednesday indicated that two additional cases had been discovered in the San Antonio area and one in Dallas. The state of Texas is expected to have its own lab set up by next week to test for Zika.
So far, no cases have been reported in McLennan or surrounding counties, but Duhrkopf and his colleagues will be working with local health officials starting in April to monitor the mosquito population.
The primary vector of the disease is the Aedes mosquito, but so far no cases of mosquitoes transmitting the virus within the U.S. have been documented. Most cases have involved people who have traveled to foreign countries, including those in Latin America, where the disease has spread rapidly.
The Zika virus has been known for decades, but until last year it was known for causing relatively minor symptoms, such as fever, rash, joint pain and red eyes. Eighty percent of those affected do not show symptoms.
But in the past year, evidence has tied Zika in pregnant women with a debilitating birth defect called microcephaly. No vaccine has yet been developed for Zika.
“The complications have caused people to sit up and take notice,” Duhrkopf said.
He said he hopes a healthy fear of the virus will lead to more research and mosquito control projects.
“It helps us realize the potential of these things and helps us mobilize resources,” Duhrkopf said.
The U.S. Centers for Disease Control is warning pregnant women who travel to Mexico, Central and South America, the Caribbean and the Pacific Islands to take extra precautions to avoid mosquitoes and to be tested for the virus when they return.
In addition, men who travel to affected areas should use condoms when having sex with women, because the disease can be transmitted through sex, according to the CDC.
Kelly Craine, spokeswoman for the Waco-McLennan County Public Health District, said pregnant women considering taking a prenatal “babymoon” to a tropical country should weigh the risks.
Even if they stay here, they should take special heed of the usual advice for avoiding mosquito bites, Craine said.
That advice includes wearing long-sleeved shirts and pants outside, using DEET-based insect repellent, using permethrin-treated clothing and gear and using window screens.
“The things your mother taught you still apply,” Craine said.
Health authorities also stress the importance of destroying mosquito habitat. Duhrkopf said Aedes mosquitoes can breed in a cupful of water, and homeowners can make a huge difference by draining every drop of standing water.
Aedes mosquitoes tend to live their lives on the block where they were born, so neighborhood and community efforts to drain water can be effective, he said.
“They do not travel far,” Duhrkopf said. “Most of the time, if you’re getting bitten by mosquitoes, it’s almost certainly coming from your backyard.”
Duhrkopf and his biologist colleague Cheolo Sim raise and study mosquitoes in a warm, humid vault in an on-campus laboratory. They and their students have worked for years to sample mosquitoes around McLennan County, helping local health officials monitor the mosquito that carries West Nile virus.
That mosquito, known as Culex, thrives in underground storm sewers in the height of summer and mostly comes out in the evening.
But the Aedes mosquito that carries the Zika virus is more common and often bites during the day, Duhrkopf said. And the patterns of contagion are quite different, he said.
“To some extent, West Nile virus is something we know how to deal with,” Duhrkopf said. “This is different enough from West Nile virus that we’re going to have a learning curve.”
Whereas the Culex mosquito transmits West Nile virus to humans from migrating bird populations, Aedes mosquitoes appear to spread Zika from person to person. But scientists don’t yet know whether Zika will spread as fast in the U.S. as it has in parts of Latin America, such as Brazil.
“Given the way in which it seems to spread through South America, it seems to be quite contagious,” Duhrkopf said. “That may be because of conditions unique to South America, where there are large cities with very dense populations.”
In Central Texas, the dominant Aedes mosquito is A. albopictus, or the Asian tiger mosquito, notable for the white stripes on its body. Sim said the tiger mosquito arrived in the 1980s in a shipment of old tires from Asia and has now become widespread.
Sim said one key to the success of this invasive species appears to be its ability to go into “diapause,” or hibernation, during the winter. Now they are found as far north as Washington, D.C.
“In the last 30 to 40 years, they’ve spread that fast and expanded their habitat,” Sim said.