New York’s health department has and Aedes mosquito eradiction program and is investing in new technologies to halt the rapid spread of dengue fever in the densely populated city.
If you haven’t spent a summer in New York you may not know how tropical its climate can be. Months of sultry heat and cloudbursts make mosquito outbreaks common. Mosquitos and mosquito-borne diseases have been part of New York life for centuries but the recent establishment of Aedes Aegypti has raised new problems. Health department trucks have been spraying pesticide in the streets and flyers on street corners urge people to stay indoors.
New York Health Department has been using a mosquito “adulticide” this year: pesticides which kill flying insects rather than their larvae. It’s usually done as a last resort when other methods have failed but this year, New York has been spraying aggressively to eliminate Aedes albopictus, a carrier of the Zika virus, and switching to a new insecticide that specifically targets Aedes.
Like Delhi, Singapore and Miami, New York is struggling to contain Dengue outbreaks caused by Aedes aegypti, the primary carrier for a host of viruses like chikungunya and Zika. Delhi’s chikungunya outbreak resulted in more than a thousand new cases reported last week. In New York, Aedes cousing, Aedes albopictus (aka Asian tiger mosquito) has not infected anyone yet but the health department is treating the mosquito like a disease carrier. NYHD announced a three-year, $21 million Zika prevention campaign and much of that is being spent on mosquito control. At a recent event, NYHD health commissioner Dr. Mary Bassett said, “We’re just trying to kill the Aedes mosquito.”
Aedes albopictus is known to carry more than 20 viruses and was responsible for a global chikungunya epidemic ten years ago. A native of Southeast Asia, it has spread far and wide and is on the list of 100 most invasive species on the planet. The Asian tiger was first discovered in the USA in a mosquito trap in a Memphis cemetery in 1983. Since then it’s spread to 40 states and today can be found as far north as Maine. Investigators suspect it arrived in the US in used auto tires from Japan or Taiwan.
Many New Yorkers have felt its bite at a backyard barbeque. “The entire metropolitan area is infested,” says Dr. Laura Harrington, Chair of the Department of Entomology at Cornell University. She and her students are mapping Aedes albopictus spread in the Hudson valley and have been picking up dead mosquitos from back yards across Westchester County. Long, hot summers and unpredictable weather have contributed to the growth of the mosquito in the New York area, Harrington says.
NYHD is aware that mosquito-borne diseases can spread rapidly in densely populated urban areas (Aedes is an urban, indoor mosquito) and is experimenting with the novel the BG-Sentinel trap, which has proven useful in capturing Aedes and tracking mosquitoes in their natural habitat like back yards, cemeteries and public parks. A collapsible, fabric container the size of an ice bucket, it releases ammonia, lactic acid and a chemical cocktail that mimic the scent of human skin. The New Yorker says the traps “smell like a hot subway car during rush hour.” The traps’ contents, a heap of dead mosquitoes, are sent to a public health lab where they are tested for the presence of Zika virus.
NYHD made a user-friendly mosquito map based on tracking data with orange dots marking Aedes hotspots and blue dots for the Culex mosquito (West Nile virus carrier). The department is sharing this information with the public for the first time this year. The northern Queens neighbourhood of College Point, which was “ground zero” for the West Nile epidemic of 1999, has the highest mosquito counts because local wetlands and marshes are an ideal breeding ground for Culex but now there are signs that the Asian tiger presence is growing. “I’ve picked lots of Aedes in College Point,” says Dr. James Cervino, a Queens-based marine biologist who’s been examining neighborhood mosquitoes in as part of his research on climate change. Queens, he says has a number of “blighted areas” with thriving mosquito populations and the interactive map hotspots are just the tip of the iceberg.
Forested and swampy areas in Queens, Brooklyn, the Bronx and Staten Island are the focus of mosquito control efforts early in the season. Ponds and lakes are treated with larvicide dropped by helicopter.
Because Aedes albopictus hides in tree holes and stumps, sprayed insecticides which kill adult mosquitoes are less effective in there . The new pesticides this year may help overcome this. Duet (the commercial name for the pesticide) has an added an ingredient, which acts as an irritant to draw mosquitoes out of their hard-to-reach spots and forces them to fly around. Once airborne, the mosquito comes in contact with an ultra-low volume spray of a synthetic pyrethroid called sumithrin, which kills them on contact. Duet was tested at the Center for Vector Biology at Rutgers University and found to be almost 100% effective on a sample of Asian Tiger mosquitoes from New Jersey.
New York has the largest outbreak of Zika cases in the US: 599 people have the disease, tough all contracted the virus overseas. Mayor Bill de Blasio pointed out that the city is home to a large Caribbean and Latin American community: “Right now, the central challenge is people who bring it back”. Pregnant women are urged not to travel to these regions as the virus can cause severe birth defects including microcephaly. In some Bronx immigrant neighborhoods the virus is already a concern. “We have quite a few cases of pregnant women from the Dominican Republic with Zika.” said Dr. Tammy R. Gruenberg, an obstetrician at the Women’s Health Pavilion at Morris Heights Health Center. Doctors there have been handing out prevention kits to pregnant women planning trips to a Zika-affected countries. The kit contains insect repellent spray, condoms and two donut-shaped “dunks” that kill mosquito larvae in standing water.
With temperatures dropping, the threat of locally transmitted Zika in New York is dropping but the Asian tiger mosquito is still a concern. To truly defeat Aedes, Laura Harrington feels big cities cannot just rely on larvicides and pesticides: “We’ve been spraying for decades. We need new ways to target mosquitoes, safer insecticides and rapid development of vaccines.”