Innovative Puerto Ricans Trying To Fight The Zika Virus … Without Using Chemicals
CAGUAS — On this hard-hit tropical island, even the dead are getting pulled into the fight against Zika.
On a recent weekday, Roberto Barrera led a team of disease investigators into a graveyard in Caguas, a town about 20 miles south of San Juan. He shoved aside the heavy cement lid of an unused crypt and peered into the darkness. Instead of a coffin, he found about 4 feet of rancid water: a perfect breeding ground for the mosquitoes that carry the Zika virus.
“That’s not good,” he said, as he re-sealed the tomb.
In hot and humid Puerto Rico, the mosquitoes carrying Zika have found the perfect breeding ground. There have been 37,889 confirmed cases on the island, both homegrown and imported, according to Puerto Rico’s Health Department. Florida, by contrast, has 1,329 confirmed cases of Zika despite having six times the population — and only 262 two of them were locally acquired infections.
And unlike the mainland, Puerto Rico rejected the widespread use of insecticides like naled to fight the menace, fearing their toll on people and the environment.
And that’s where Barrera’s team is stepping in. For the last several weeks, the Centers for Disease Control and Prevention has been working with the local government to turn this mid-sized city into a mosquito graveyard deadly enough to kill the spread of the Zika virus.
In the process, they’re making Caguas a test case for chemical-free Zika reduction.
At the heart of the effort are thousands of black 5-gallon buckets that have been modified to lure mosquitoes to their death. In the coming weeks, the CDC and Puerto Rican health authorities will be placing about 90,000 of these traps — called autocidal gravid ovitraps, or AGO traps — to cover 80 percent of the city’s center.
Whether the system is effective should become clear in the spring when wetter and warmer weather boosts the mosquito population.
Unlike other hard-hit areas, such as Brazil and Colombia, Zika has spread over the entirety of this 3,500-square-mile island and all of its 3.5 million residents are vulnerable, said Steve Waterman, the chief of the CDC’s dengue branch, who is overseeing Zika efforts here.
But it’s unclear if enough people have already been exposed to it — becoming immune to reinfection — that they’ll provide a human buffer once the mosquito-season resumes.
“The question is: Is there enough immunity — what we call herd immunity — for the transmission to really, really slow down?” he asked.
Scientists don’t know the answer to that yet. That’s why authorities are rushing to turn Caguas into an anti-insect fortress.
On a recent weekday, a small army of blue-clad workers were laying hundreds of AGO traps between the tombstones at Caguas’ cemetery. In the process, they were looking for pools of water often found in graveside flower vases or empty crypts, like the one Barrera examined, where mosquitoes might breed.
Getting the entire community — including the dead — to participate is critical, said Barrera, head of the CDC’s entomology and ecology activities and one of the trap’s inventors. The project aims to put three AGO traps in 30,000 homes. But a single noncompliant household can become a disease vector that ruins the efforts of an entire neighborhood, he said.
The system relies on creating a “constellation” of “sink holes” that will crash the mosquito population, he explained.
The buckets are a study in simplicity. Each one holds a few inches of water and fermenting hay that lures the Aedes aegypti in through a fist-sized opening at the top.
A screen prevents the mosquito from reaching the water, and the insects get caught in sticky, non-toxic resin inside the opening. The traps cost about $11 each, and although they’ve been used to monitor mosquito populations in the past, they’re just now being considered eradication tools.