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Laura C. Harrington, professor and chair of the Department of Entomology, offers tips to avoid contracting Lyme disease.

Why are Lyme disease-carrying deer tick populations growing in central New York?

“The reason for increasing tick populations and concomitant infections is likely complex,” said Laura C. Harrington, professor and chair of the Department of Entomology at Cornell. “Recent trends with less extreme sustained cold temperatures in the winter may lead to greater overwintering survival of ticks. Higher populations or infection rates in key Lyme bacteria reservoirs, such as the white-footed mouse, also may be responsible. Even factors such as increased awareness and vigilance by physicians and veterinarians may play a role.”

Harrington said in all of New York state in 2010 and 2011, there were 2,385 and 3,118 reported cases of Lyme disease, respectively, compared with the annual state average of 4,560 cases. But in some regions, such as central and northwestern New York state, Lyme disease cases are increasing.

“Populations of Ixodes scapularis – commonly known as the ‘black-legged tick’ or ‘deer tick’ – appear to be increasing in central New York,” Harrington said. “Increases in laboratory-confirmed Lyme disease cases in both humans and dogs also have been noted in our region.”

In 2011, the most recent year for which data are available, there were 145 cases of Lyme disease in Tompkins County residents, compared with only eight in 2007. But by 2012, there were 338 confirmed cases in Tompkins County dogs.

“Ticks are hard to avoid, especially for those who are active outdoors and want to enjoy the summer weather,” Harrington said. She offers these tips to avoid contracting Lyme disease:

• Know what to look for. Nymphal ticks, which are about the size of a poppy seed or a freckle, are considered the most dangerous because they have already fed once in their larval stage and may already be infectious.
• Make a habit of checking for ticks daily if you are active outdoors. Ticks don’t start transmitting Lyme disease until after they have been attached to human skin for at least 24 hours.
• Properly remove ticks. Carefully place the tips of a pair of tweezers as close to the base of the skin where the tick is attached with its mouthparts as possible (not the body), and gently pull it out. If the body is squeezed, there is a risk of infecting yourself by pushing Lyme bacteria into the skin. Not all ticks are infected. Save the tick on a piece of tape or in a vial and consult your physician, who may recommend having the tick tested for Lyme bacteria.
• Use repellent. DEET and picaridin are highly effective repellents against ticks and other biting pests.