Florida has a dengue problem. The solution may be more mosquitoes

In a major milestone, the World Health Organization endorsed widespread use of a vaccine aimed at stemming the effects of the parasitic disease malaria, particularly in sub-Saharan Africa. Miles O'Brien looks at efforts to tackle other diseases carried by mosquitoes in the Florida Keys, where scientists are testing a way to kill mosquitoes — with mosquitoes.

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  • Judy Woodruff:

    A milestone development today in the fight against malaria. The World Health Organization endorsed the widespread use of a vaccine aimed at stemming the effects of malaria, particularly in sub-Saharan Africa.

    An estimated 400,000 people, the majority of them children, die from the parasitic disease each year. The new vaccine, which requires four shots, reduced the number of cases by 30 percent. Malaria is transmitted by the anopheles mosquito, making it the most deadly animal on the planet.

    Miles O'Brien looks at efforts to tackle other diseases carried by a different breed of lethal mosquitoes. In most cases, there are no vaccines and precious few ways to control the mosquito population.

    His story begins in the Florida Keys, where scientists are testing a way to kill mosquitoes with mosquitoes.

  • Miles O’Brien:

    Bud Conlin won't set foot in his Key Largo garden without spraying on mosquito repellent. In June of 2020, he got sick with flu-like symptoms.

  • Bud Conlin, Florida Resident:

    You can't move. You are so sore. Your bones — everything aches, including your bones.

  • Miles O’Brien:

    Of course, he feared it was COVID, but it turns out he had dengue fever, a tropical viral illness so painful, it is commonly called the bone crusher.

  • Bud Conlin:

    Unfortunately, there's not a whole lot you can do about it. It is time-limited, and you can weather it out. It certainly made me confront my mortality.

    (LAUGHTER)

  • Miles O’Brien:

    He was among about 70 neighbors infected with dengue. The virus has been steadily spreading in the Florida Keys for the past 10 years, and now is starting to spike.

    The culprit is one of the most lethal animals on the planet, a mosquito called Aedes aegypti. Aside from dengue, it is a vector for Zika, chikungunya and yellow fever.

  • Andrea Leal, Florida Keys Mosquito Control District:

    So, as long as we have these mosquitoes in enough numbers for these transmission to occur, that's when we're going to continue seeing these outbreaks.

  • Miles O’Brien:

    Andrea Leal is executive director of the Florida Keys Mosquito Control District.

  • Andrea Leal:

    We're talking about a mosquito species that, here in the Keys, represents about 4 percent of our mosquito collection, so a very small percent of our population. And it's responsible for 100 percent of our mosquito-borne diseases.

  • Miles O’Brien:

    She and her team are fighting a multimillion-dollar, multifront war on these efficient disease spreaders.

    A fleet of helicopters routinely spreads a bacteria called Bti, which kills mosquito larvae, as well as liquid pesticides that target adults. And on the ground, 35 foot soldiers march door to door on patrol for standing water, where the mosquitoes hatch.

    This ceramics dealer in Key Largo is a frequent stop for Mosquito Control field inspector Ryan Rodriguez.

  • Ryan Rodriguez, Florida Keys Mosquito Control District:

    This is prime area for them. You got water, you got shade, and it's so damp and humid right now that this is like their good stuff. This is where they like to be.

  • Miles O’Brien:

    He adds Bti larvicide to standing water…

  • Ryan Rodriguez:

    I just drop one in there.

  • Miles O’Brien:

    … that is home to Aedes aegypti larvae.

  • Ryan Rodriguez:

    Standing water is potentially a breeding spot for aegypti, so no matter what it is. It can be in a bottle cap even. You just look in there.

  • Miles O’Brien:

    They estimate they have reduced the Aedes aegypti population by 50 percent, but that is not nearly enough.

  • Andrea Leal:

    If we can introduce another tool that is cost-effective and works very well, then that's something that we're really hoping that this trial will show.

  • Miles O’Brien:

    The trial. After a decade of tribulation, it is finally under way here.

    Rajeev Vaidyanathan, Director of U.S. Programs, Oxitec: This is our release box. This is where we have our eggs and some of the food.

  • Miles O’Brien:

    Entomologist Rajeev Vaidyanathan is director of U.S. programs for Oxitec, a company that produces genetically modified male mosquitoes with a gene lethal to females, which do all the biting.

  • Rajeev Vaidyanathan:

    The male mosquitoes mate with the female mosquitoes, and when those females lay eggs, all of their males will live, and their female progeny will die.

  • Miles O’Brien:

    Oxitec mosquitoes first flew in the field in Brazil and the Cayman Islands in 2010. The company claims dramatic reductions in the local mosquito population.

    In Brazil, public health officials are seeing reduced outbreaks of disease. Biochemist Nathan Rose heads regulatory affairs at Oxitec.

  • Nathan Rose, Oxitec:

    We have seen in Brazil a 90 percent reduction in disease in the areas where we released our mosquitoes, against approximately a 50 percent reduction in other parts of the city where other control measures were potentially being used.

  • Miles O’Brien:

    Researchers the world over are watching the high-stakes Oxitec field trials very closely.

  • Cate Hill, Purdue University:

    What are we looking at in the bucket today?

  • Miles O’Brien:

    Cate Hill is a professor of entomology at Purdue University.

    Climate change, population growth and travel patterns have put about half the world's population in harm's way of mosquito-borne diseases.

  • Cate Hill:

    Human vector contact is increasing. The chance or risk of acquiring an infectious bite from the mosquito is also increasing. And, unfortunately, we have a very limited set of tools to control mosquitoes and the diseases that they transmit.

  • Miles O’Brien:

    Oxitec's trial run here is modest. They are releasing their modified mosquitoes at six locations, mostly to track their flight patterns.

    A second gene is added to them that makes them fluorescent, so they can be spotted under a microscope. The team uses boxes that emit the odor of stinky feet, an Aedes aegypti favorite, as a way of running a real-time mosquito census.

    Michael Boehmler is a research biologist for the Florida Keys Mosquito Control District.

  • Michael Boehmler, Florida Keys Mosquito Control District:

    We try to get an idea of how much Aedes aegypti are breeding in a particular area.

  • Miles O’Brien:

    Look at those tiny little things.

  • Michael Boehmler:

    So, those are fresh born, maybe a day old.

  • Miles O’Brien:

    And a mama can produce how many in one set of eggs?

  • Michael Boehmler:

    One hundred to 300.

  • Miles O’Brien:

    Wow.

  • Michael Boehmler:

    For every female that we kill, we potentially can knock out 42,000.

  • Miles O’Brien:

    One female equates to 42,000 mosquitoes?

  • Michael Boehmler:

    It can, yes.

  • Miles O’Brien:

    Is that how you do it, how you do the math?

  • Michael Boehmler:

    Yes. Yes.

  • Miles O’Brien:

    Wow.

    That's the appeal of the Oxitec approach. And while a majority of people here support deploying GMOs for this purpose, the idea has its skeptics, even Bud Conlin.

  • Bud Conlin:

    It would be a great alternative to spraying. You know, so often when we mess with Mother Nature, there can be unintended consequences. But I guess I would say I lean in favor of that, other than — rather than spraying a lot of chemicals and having people getting dengue.

  • Miles O’Brien:

    If it goes well here, Oxitec will seek EPA approval for nationwide use, hoping its randy boys with the killer genes can stem this growing threat to human health.

    For the "PBS NewsHour," I'm Miles O'Brien in Marathon, Florida.

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