When Spraying Fails Our Neighbors

The Centers for Disease Control and Prevention announced in July a total of more than 4,684 people in Puerto Rico had tested positive for the Zika virus.

Because of the severity of Zika virus, Dr. Angela Harris, program officer (Gates Global Health Fellows Track) for Neglected Tropical Diseases at The Bill & Melinda Gates Foundation, was deployed to Puerto Rico on Feb. 20, 15 days after the country declared a state of emergency due to the Zika virus.

Because numerous control methods are required in such a situation, this spring tests were performed on a variety of adulticides to determine if Aedes aegypti, mosquitoes that typically carry the Zika virus, were resistant to them. Ultimately, the Aedes aegypti was found to be resistant to most.

As the tests were being conducted, Harris said she was deployed by the Gates Foundation to provide support for the CDC. The team had to come up with more creative ways for people to be protected from the Zika virus.

“It was kind of all hands on deck,” she said. “Tragically the local Aedes aegypti is very resistant to public health pesticides. It’s a pretty grim picture from an insecticidal standpoint.”

In May, the Gates Foundation donated $1.5 million to Puerto Rico’s cause — half of the money went to the CDC Foundation, a charity in support of the CDC, and half to the Pan American Health Organization. Harris said the money is, in part, going for Zika virus education efforts.

The more shocking part of Harris’ visit was observing the Puerto Rican peoples’ lack of understanding of mosquito biology and what mosquito larvae look like, she said. “People seeing standing water in their yards that have breeding sites didn’t seem to know what larvae looked like, so it got me wondering where you stand when you tell people, ‘Clean out your buckets, clean out your water’ and that kind of thing,” Harris said. “A lot more education is needed there.”

CONTROL TECHNIQUES. The work required for effective control of Aedes aegypti is labor-intensive. Harris said there is a lot of surveillance that comes with the job, such as clearing out breeding sites, disposing of trash, turning objects over, getting rid of standing water that collects inside old tires and inspecting plant boxes, to name a few.

Because of permethrin-resistance issues, and because most Aedes aegypti populations breed in small containers, the use of larvacides and adulticides is the primary pesticide treatment being deployed by CDC. (Supplementing CDC’s use of larvacides and adulticides is targeted fogging and ground spraying by CDC.) The larvacides and adulticides being used are Altosid Pro-G, Altosid Briquets, Fourstar Bti CRG, Fourstar Bti Briquets 150 day and Fourstar Bti 45 days (of control).

As part of control efforts in Puerto Rico, ADAPCO representatives are distributing these products and working with CDC officials to educate public health officials on the control of Aedes aegypti mosquitoes, including habitat modification, ongoing surveillance, how to educate residents, and the use of larvacides and adulticides.

There are stark contrasts between conditions in Puerto Rico and at-risk ares in the United States, primarily the southern U.S., Harris said. “I think the main difference is the scale and the density of the population, as well as the environment, which is more conducive to mosquito breeding.”

HISTORICAL EXPERIENCE. Harris previously worked on mosquito control and research in the Cayman Islands for nine years before coming to Puerto Rico. In Grand Cayman, she had a staff of 25 for 50,000 people. In comparison, Puerto Rico has 70 times more people — about 3.5 million. “Of course it’s very challenging, but it’s not impossible,” she said.

In 2005, the Gates Foundation funded a project in Australia for vector control. The project consisted of breeding mosquitoes that are less able to transmit viruses. The project has created mosquitoes that cannot transmit diseases such as dengue and the West Nile virus as well as Zika. The project has expanded to South and Central American countries, such as Brazil and Columbia, where anyone is able to breed these mosquitoes in their backyard.

Though the project has been launched in several countries — Brazil, Columbia and Vietnam to name a few — Harris said she doesn’t see it coming to Puerto Rico anytime soon.

“I’m sure the Foundation would be keen to have their projects in Puerto Rico, but the moment needs to be right,” Harris said. “It needs to have funds on the ground and the blessing of the Puerto Rico Department of Health, as well as to meet all regulatory requirements. I would predict this won’t be a fast process.”

The Zika virus is still hard for the general public to fully understand, let alone those who are directly affected like the people of Puerto Rico, Harris said. “It’s difficult because I think a lot of people have other things to worry about. If I’m not a pregnant woman, I’m concerned about the financial situation of the island — I’m worried about my job. We really have to jump to the forefront of everyone’s mind,” she said.

The author is an editorial intern with PCT.