Is more Lyme disease on the way?
The answer is yes, according to a leading expert on the spread of Lyme.
The Northeastern U.S. should prepare for a surge in Lyme disease risk this spring.
We can blame fluctuations in acorns and mouse populations, reports Dr. Richard S. Ostfeld, a disease ecologist at the Cary Institute of Ecosystem Studies in Millbrook, NY.
Boom-and-bust acorn crops and a decline in mice leave humans vulnerable to infected ticks.
What do acorns have to do with illness?
Acorn crops vary from year-to-year, with boom-and-bust cycles influencing the winter survival and breeding success of white-footed mice.
These small mammals pack a one-two punch: they are preferred hosts for black-legged ticks and they are very effective at transmitting Borrelia burgdorferi, the bacterium that causes Lyme disease.
“We had a boom in acorns, followed by a boom in mice. And now, on the heels of one of the smallest acorn crops we’ve ever seen, the mouse population is crashing,” Ostfeld explains. Adding, “This spring, there will be a lot of Borrelia burgdorferi-infected black-legged ticks in our forests looking for a blood meal. And instead of finding a white-footed mouse, they are going to find other mammals—like us.”
Black-legged ticks take three bloodmeals—as larvae, as nymphs, and as adults. Larval ticks that fed on 2011’s booming mouse population will soon be in need of a nymphal meal. These tiny ticks—as small as poppy seeds—are very effective at transmitting Lyme to people. The last time Ostfeld’s research site experienced a heavy acorn crop (2006) followed by a sparse acorn crop (2007), nymphal black-legged ticks reached a 20-year high.
The May-July nymph season will be dangerous, and Ostfeld urges people to be aware when outdoors. Lyme disease is debilitating to humans. Left undiagnosed, it can cause chronic fatigue, joint pain, and neurological problems. It is the most prevalent vector-borne illness in the U.S., with the majority of cases occurring in the Northeast.
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Ostfeld says that mild winter weather can change tick behavior. Adult ticks, which are slightly larger than a sesame seed, are normally dormant in winter but can seek a host whenever temperatures rise several degrees above freezing. The warm winter of 2011-2012 induced earlier than normal activity. While adult ticks can transmit Lyme, they are responsible for a small fraction of tick-borne disease, with spring-summer nymphs posing more of a human health threat.
Learn More: Lyme disease – Risk of Lyme Disease Expands
References and Further Reading:
Ostfeld, R. S. 2011. Lyme disease: The ecology of a complex system. Oxford University Press
Keesing, F., J. Brunner, S. Duerr, M. Killilea, K. LoGiudice, K. Schmidt, H. Vuong and R. S. Ostfeld. 2009. Hosts as ecological traps for the vector of Lyme disease. Proceedings of the Royal Society B, Biological Sciences 276:3911-3916.
Schauber, E. M., R. S. Ostfeld, and A. S. Evans, Jr. 2005. What is the best predictor of annual Lyme disease incidence: Weather, mice, or acorns? Ecol. Appl. 15:575-586