Tick Expert: RI Could See Slight Uptick In Infected Ticks This Summer

May 15, 2017

This summer, ticks may have a slightly higher chance of being infected with bacteria that causes Lyme disease, according to a Rhode Island tick expert.

Small ticks the size of poppy seeds, called nymphs, are active now and will be throughout the summer. Humans typically contract the bacteria that cause Lyme disease from nymphs. Before reaching the nymphal stage, tick larvae pick up the bacteria from rodents after latching onto them to feed. 

Tom Mather, director of URI's TickEncounter Resource Center, said signs of a possible increase come from high infection rates in adult ticks, which used to be nymphs. 

He and other researchers found more than 80 percent of adult ticks they tested were infected with bacteria that cause Lyme disease. 

Mather said it's important to know that the adult ticks carrying the bacteria will die off very soon because they're peak is in the fall. It's nymphal stage ticks that are active during the spring and summer. What determines if nymphs are infected with bacteria depends on what happened last year when they were larvae, Mather said. 

Rhode Island's rodent population has been strong the past few years because there has been more acorns for them to eat, Mather said. More rodents mean more hosts for larvae and more opportunities for them to be infected.

"So if there were a lot of larvae that fed on mice and chipmunks last summer, they might turn into a lot of infected nymphal ticks this year," Mather said.  

However, the size of the nymph population depends on how humid the days are. Ticks can only thrive during days with more than 80 percent humidity.

"If it stays below 80 percent for longer than eight hours, some of them start to die, and if it does it two days in a row, than more of them die, and if it does it three days in a row, more of them die,” Mather said. 

Mather said it's important to take precaution regardless of this summer's outlook because there are always infected ticks in Rhode Island. Precautions include spraying clothing and shoes with repellents containing Permethrin and tucking pant legs into socks.