About 7 percent of the ticks contained both Lyme disease and babesiosis. The team crunched some probability numbers for this kind of co-infection occurring by chance alone vs. the data they observed and found the likelihood of co-infection was greater than expected.
Ticks typically get their pathogens from infected wildlife. Lead author of the study, and assistant professor of biology at Sarah Lawrence College, Michelle Hersh, singled out two such critters. "Mice and chipmunks are critical reservoirs for these two pathogens, so ticks that have fed on these animals are much more likely to be co-infected," she said.
Just as spooky as the double-pathogen delivery was the team's finding that the chance of a triple infection -- Lyme, babesiosis and anaplasmosis (which causes anaplasmosis in humans) -- was twice as likely as expected.
The moral of the story? Expect the unexpected, if you get a tick bite.
"People in tick-infested parts of the United States such as the Northeast, Mid-Atlantic, and Upper Midwest, are vulnerable to being exposed to two or three diseases from a single tick bite," said the paper's co-author Felicia Keesing, a biology professor at Bard College and an Adjunct Scientist at the Cary Institute. "Health care providers and the public need to be particularly alert to the possibility of multiple infections."