CDC Study Shows that Pesticide Use Does Not Reduce Lyme Disease

A new study by the Centers for Disease Control and Prevention indicates that spraying pesticides to kill ticks on your property does not reduce the rate of Lyme disease – meaning that people who apply pesticides to their yards are not just risking ecological damage but are wasting their money too.

The study was conducted in Connecticut, Maryland and New York. Here’s an excerpt from a story in USA Today:

“The yards of 2,500 participants … were sprayed in spring 2011 and 2012 with either bifenthrin — which kills tick larvae, nymphs and adults for as many as 41 weeks — or a placebo.

“Participants were asked to detail tick bites and encounters through four monthly Web-based surveys. Those whose yards received the pesticide and those who got the placebo had virtually the same rates of ticks found crawling around on them, ticks found biting them and incidences of tick-borne disease. …”

Until now, the CDC (and the Connecticut Agricultural Experiment Station) recommended applying pesticides once a year, in spring, to control ticks, under the belief that killing ticks meant reducing the risk of tick-borne diseases. USA Today reported:

“Ben Beard, chief of the CDC’s Bacterial Diseases Branch, Division of Vector-Borne Diseases, said in a statement that the study accomplished what it set out to do: determine the public-health benefit of a single, springtime application of a tick-killing agent.

” ‘Before this study, there were no data to show how effective yard treatments with pesticide are in preventing Lyme and other tick-borne diseases,’ Beard said. ‘Results of this study showed us that a single pesticide application did effectively reduce the number of deer ticks in yards but did not decrease the number of ticks people found on (residents’) bodies or the number of tick-borne illnesses.’ “

One of the leading institutions for research on black-legged ticks is the Cary Institute of Ecosystem Studies, in Millbrook, N.Y. USA Today quoted Rick Ostfeld, a disease ecologist at the institute:

“Testing whether spraying reduces the risk of tick-borne disease is critical because people spend lots of money spraying their yards. These sprays can be toxic to wildlife, pets and people, and people expect a strong health benefit from doing so. The study’s finding … is very important in evaluating what works and what doesn’t. This was money well spent, in my opinion.”

Connecticut Audubon Society supports a general reduction in pesticide use, because of the effects those poisons can have on wildlife, although we have noted that for tick control people should follow the CDC’s recommendations. It’s not clear whether those recommendations will now change. — Tom Andersen, director of communications and community outreach.