New study considers Lyme disease, pesticides

Hopping ticks and Lyme disease are the focus of a new collaborative study led in Connecticut by the Yale Emerging Infections Program, a joint effort between the Connecticut state public health department and the Centers for Disease Control and Prevention.

Funded by the Centers for Disease Control and Prevention, the study is attempting to determine whether a more sparse approach to common pesticide spraying techniques, which involve several annual sprays of insecticide across large areas, can reduce the prevalence of Lyme disease and other tickborne diseases in Connecticut, New York, and Maryland.

While it is known that the proposed pesticide technique, a single strategically-placed springtime spray of bifenthrin, can effectively reduce tick populations, there have been no studies that identified whether this reduction would trigger a similar change in the occurrence of Lyme disease and other tickborne diseases, Julie Ray, the Connecticut program coordinator, said.

“There has been a steady increase in Lyme disease cases in the past few decades,” Brian Fallon, director of the Lyme and Tick-Borne Diseases Research Center at Columbia, said, adding that the rise in cases is a “failure” of the public health system.

According to a Connecticut State Department of Public Health study, there were 4,156 cases of Lyme disease in Connecticut in 2009, with 460 in New Haven County alone.

If her study proves that the incidence of Lyme disease will diminish even with the more conservative approach to pesticide administration, Ray said she hopes it will encourage people to ask their pesticide companies to spray less bifenthrin than they normally would. Most pesticide companies currently spray the chemical throughout people’s properties several times a year, she said.

Ray added that while the spraying of bifenthrin as a pesticide is not harmful to humans, the chemical is toxic to aquatic invertebrates, who come into contact with the spray through water runoff. The researchers are taking extra precautions to avoid this contamination, including not enrolling households with water on the property within 100 feet of where the pesticide will be sprayed.

But two scholars interviewed questioned the need to use the insecticide in the first place.

School of Forestry and Environmental Sciences professor John Wargo GRD ’84 said bifenthrin, which is part of a family of insecticides that typically affect insects’ nervous systems, might have long-term consequences for humans.

“I’m always a skeptic of spraying persistent chemicals, especially where children might be playing,” Wargo said. “It’s really important not to trade Lyme disease with another health threat.”

Jay Feldman, executive director of the nonprofit Beyond Pesticides, said pests like ticks are better managed by personal efforts like applying insect repellent and tucking pants into socks when walking through areas that could contain ticks. He added that another way of dealing with pests is to alter their habitats or breeding areas.

But Ray said people are often unlikely to actively pursue the personal efforts Feldman mentions.

Connecticut State Entomologist Kirby Stafford, who has studied ticks and the spread of Lyme disease extensively, said that landscape management could fight, but not eliminate, the presence of ticks. Still, he said that while pesticides are more effective in controlling tick populations, other alternatives should be considered.

The Yale study is being conducted in 1500 households across three states, Ray said. Half the study’s participants will have parts of their lawns sprayed with bifenthrin, while the other half will receive a harmless water spray, in order to test the assumption that people most often contract Lyme disease and other tick-borne illnesses from their own backyards rather than from elsewhere. The study’s method of control will allow for strong comparisons to be drawn from the two groups of households, she said.

The study will begin administering the pesticide in May, and expects to publish its results in April 2012.

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