With each issue, Trib+Health brings you an interview with experts on issues related to health care. Here is this week's subject:
David Herrin is a professor at the University of Texas at Austin College of Natural Sciences. He is part of a team working to develop a method of mosquito control involving algae.
Editor's note: This interview has been edited for length and clarity.
Trib+Health: Could you speak generally about what your recent research has been on Zika?
David Herrin: Ours is about mosquito control. We’re looking at controlling the mosquitoes that transmit the virus but also mosquitoes that transmit West Nile, which in the U.S. are different ones. We’re looking at controlling both.
Mosquito control attracted me because it’s unique in that it controls multiple diseases at one time and there’s not many things that do that. Usually drugs and vaccines are very specific in stopping a certain disease, but mosquito control ends up stopping a number of them.
Also, mosquitoes are just pests. Even if they’re not transmitting diseases, many people can get bad reactions from them, which then turn into other kinds of infections.
For all mosquitoes, the larvae stays developed in water, and then turn into adults, which then fly. Only the females seek a blood meal. The water is really kind of their Achilles heel, because once they turn into adults and can fly they’re really hard to stop. When you think about the space they occupy, an adult mosquito could occupy almost infinite amounts of space, whereas the water that larvae grow in is very confined. For example, it can’t be moving water, it has to be water that’s very still.
Mosquito larvae eat algae, bacteria. We worked with a particular type of algae for many years doing molecular biology and genetics. We came upon the idea of getting strains genetically that would kill mosquito larvae. The technology has sort of been developing. These algae are really non-toxic — they really don’t kill anything, in fact they’re a perfectly good food source — so we have to alter them to make them toxic specifically to mosquitoes.
Fortunately, there is a naturally occurring bacteria that is specifically toxic to mosquitoes and certain kinds of flies. The strain that specifically kills mosquito larvae was found in Israel in the late 1970s. It’s used for mosquito control. The problem with the bacteria, though, is that it’s very finicky. It doesn’t grow in most habitats, like it doesn’t like sunlight. It actually grows inside of dead insect carcasses. If you put out the bacteria, basically, it won’t survive in most places. You can put out the toxin that it makes as a protein complex, and that’s what’s really used for mosquito control now.
Since it’s a protein, that means there’s genes that code for it. When the sequence of those genes were determined, we looked at those. So we can get our algae to make proteins that are pretty much exactly the same as the bacteria ones. That’s basically what we’re doing.
We kind of have the first generation. If you have the right combination of proteins there, the mosquitoes can’t develop resistance to this protein toxin like they can to chemical toxins. They have developed resistance to all the chemical pesticides that have been used against them, which is why they have to keep switching around to different ones.
But we have to get a combination of proteins there in order to keep them from getting resistance, so that’s sort of where we’re at now. We’ve got more engineering work to do.
We have a little money from the National Institutes of Health to do this, which is quickly running out, so we’re looking for more funds now to keep it going. We have a patent that was just issued this past month also on the technology on this approach, but we don’t really have commercially viable strains yet, at least not ones that I think would be viable for some years to come.
Trib+Health: Could you speak a bit to what the challenges that scientists and researchers are facing in trying to research this virus and ways to combat the mosquito population in real time, as there are outbreaks around Latin America? What kind of time pressure is there?
Herrin: The U.S. Agency for International Development just issued a call for two kinds of proposals — one, if you had anything that could work right now, the desperation one, and then the second one was if you have something that might prevent future outbreaks. We fall into the second category. We don’t have anything that works right now.
Particularly for something to go onto a market that a lot of people are going to use, there’s so much testing and regulation that goes into it, anything takes a while. I think they’re having some luck with a vaccine against a couple of the viruses that Aedes aegypti transmits, but it’s still going to be probably years before you have a vaccine that you can use safely and give to a large number of people. Same thing with the new chemical pesticides.
Right now, in this outbreak, what I would be concerned about in Central Texas is that we have no mosquito control districts. Mosquito control districts are basically professionals who help control mosquitoes. Only part of Texas is covered by mosquito control districts. Most of Central Texas doesn’t have a mosquito control district.