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San Antonio Prepares For Zika. Is It Enough?

Aaron Schrank
Texas Public Radio
Texas A&M San Antonio undergraduate student Alejandra Moya uses tweezers to identify the species of mosquitos caught in a sticky trap.

Some infectious disease experts believe the Zika virus has already infected the Texas mosquito population –it just hasn’t been detected.

In this report for our series, “Preparing for Zika in Texas” we look at what health officials in San Antonio say they’re doing to prevent an outbreak and how they would respond if we have one. 

In a neatly landscaped front yard in North San Antonio biology students from Texas A&M University-San Antonio record the types of mosquitoes snared by their sticky traps.

Undergraduate Alejandra Moya; biology Professor Dr. Megan Wise de Valdez; and graduate student Estephanie Moya are part of Texas A&M-San Antonio's mosquito surveillance team.
Credit Aaron Schrank / Texas Public Radio

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Most of the mosquitoes they’re finding are Culex quinquefasciatus, the species that can carry West Nile.

They’re also identifying Aedes aegypti, a daytime biter that can transmit a whole host of diseases, including Zika, the rapidly spreading virus that can result in pregnant women delivering babies with small, deformed brains.

This is the third year Professor Megan Wise de Valdez and her students have set mosquito traps around San Antonio. 

“Where we are right now is one house out of our 120 we have around the city where we have placed traps for weekly mosquito collections,” she explains.

Professor Valdez says different types of traps attract mosquitoes in different proportions.  Last summer 44 percent of the mosquitos captured were Aedes aegypti. With the type of trap being used this year, it’s about 16 percent.  Either way, she says, the mosquitoes that spread Zika are in South Texas, and she’s sharing the data she collects with area health officials.

“Houston and Dallas and Austin, they all have publicly-funded mosquito districts, surveillance and control. San Antonio does not,” says Wise de Valdez. “Our role was to be part of the city’s preparation, if you will, for Zika becoming locally transmitted.”  

Concerns About Adequate Surveillance

So far, Texas has no recorded cases of Zika being transmitted by local mosquitoes.  All of the known cases have originated outside of the state.

But Dr. Peter Hotez believes the monitoring in many communities for mosquitoes and infected patients is incomplete.  Hotez is Dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston.

“The big concern is that Zika transmission may have started but we’re not picking it up, we’re not detecting it.”  

Dr. Hotez believes the best way to find locally transmitted cases and prevent an outbreak is through the active surveillance of medical providers. And he says communities aren’t doing it.

“Right now we’re not going into clinics, emergency rooms, community health centers identifying people with fever and rash and then testing them to see if they have Zika virus either in their blood and urine, and that’s how you know if transmission of Zika virus has started. 

How San Antonio is Responding

Credit Shelley Kofler / Texas Public Radio
Texas Public Radio
Rick Riojas from San Antonio Metro Health checks for mosquito larvae in standing water at a city park.

Dr. Anil Mangla with San Antonio’s Metro Health Department believes that approach is premature.

“To start something like this now when we don’t have an endemic or local case is just redundant for us.  I think that’s going to be a big of waste of money,” Dr. Mangla said.

Dr. Mangla is the assistant director who oversees communicable diseases. He says San Antonio would initiate active surveillance after a locally transmitted case is found. Health officials would target the neighborhoods of those infected.

“We would go to surrounding houses.   And have anyone who is entering a clinic-- do you have fever in the past 10 days? Did you have a rash?  Did you have muscle pain?  If so, let’s get tested."   

Mangla says health and environmental experts from the city, county, military, universities, and other groups began meeting monthly in February to share information about Zika.

He says area clinics and medical providers file patient reports through a shared computer system that should help identify those infected with Zika.

He says Metro Health’s other primary effort is aimed at wiping out mosquitoes.

One Licensed Tech For Metro Health’s Mosquito Control

Recent rains have left a pool of stagnant water in San Antonio’s Lady Bird Johnson Park.  Rick Riojas, the city health departments’ only licensed vector control technician pulls a red canister with a spray pump from a truck and sprays a thin film of larvacidal oil on the water.  

Stephen Barscewski is Riojas’ supervisor.

“What it does is calm the tension on the water.  It suffocates the larvae in the water.”

Barscewski says other employees with Metro Health and various city departments assist in mosquito control, but they aren’t licensed like Riojas and can’t use all of the equipment and pesticides.  They are often used to place larvicidal bricks known as dunks in standing water on public properties. The bacteria in the dunks kills developing mosquitoes.   

When it comes to private property Metro Health relies heavily on a media campaign that urges residents take personal responsibility around their homes.

“Just dumping the water is the best thing a homeowner can do,” says Barscewski.  “If they have a lot of vegetation in their yards they can use general-use pesticides to fog their back yards.”  He said some organic sprays are also available.

Are We Doing Enough?

Across the state and South Texas it seems as though public health officials are holding their breaths.  Hoping their media campaigns and some public mosquito control efforts will be enough until mosquito season winds down this fall.  

Dr. Hotez from the Baylor College of Medicine is worried.

“What I’m more worried about are the outlying counties that don’t have the well-oiled machine for doing Aedes aegypti control. You know there are some counties where there’s no mosquito control capability.”

Dr. Hotez says we won’t really know if Texas beat Zika this year for another  9 to 10 months.  That’s when babies conceived during this last phase of mosquito season will be born, hopefully without the brain deformities that can be caused by Zika.