March 19, 2012
Fewer Acorns And Mice Leave Humans Vulnerable To Lyme Disease
Scientists are predicting an unusually large surge of Lyme disease this summer in the northeastern U.S, thanks to a low acorn crop of all things. Dr. Richard S. Ostfeld, a disease ecologist at the Cary Institute of Ecosystem Studies in Millbrook, NY, says that the mild winter has nothing to do with this expected surge.
This prediction comes after 20 years of research and observations of acorn levels, mice population and lyme disease conducted by Dr. Ostfeld, Cary Institute forest ecologist Dr. Charles D. Canham, and their team.
Their team has found that acorn crop levels vary from year-to-year, ranging from very high amounts to very low amounts. The fall of 2011 saw a very low acorn crop. As these crop yields fluctuate, so too does the population of white-footed mice. The mice are the preferred hosts for black-legged ticks and are very effective at transmitting the bacterium that causes Lyme disease, Borrelia burgdorferi.
Reporting his findings, Ostfeld said “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,”
“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.”
This season´s low yielding acorn crops follow a previously prosperous year in 2010, with the highest levels reported at the Millbrook research site. The white-legged mouse population followed suit, peaking this past summer. Fall 2011´s low acorn crops are setting up prime conditions for high numbers of people infected with Lyme disease.
Black-legged ticks (also known as the deer tick or bear tick) take three “blood meals” during their lifecycle-as larvae, nymphs, and adults, This means the blood meal taken by larvae in early 2011 will soon be looking for their next meal as nymphs. The ticks lie in wait on low-lying vegetation for their next meal to brush against the vegetation as they walk by. This could be an animal, such as a deer or mouse, or a human. With lower mouse populations, Ostfeld predicts that there will be more ticks waiting on vegetation for a meal. Previous research has shown that the last time the conditions were present in 2006 and 2007, the population nymphal black-legged ticks was at a 20-year high.
Due to these conditions, Ostfeld and his team warn that this May-July nymph season will be very dangerous. As such, they suggest that people exercise great care and caution when venturing outside. While the white-legged mice can contract Lyme disease with little effect, humans are quite susceptible to the disease. Some symptoms of the disease in humans are Chronic fatigue, joint pain, and even neurological problems.
While the adult ticks can carry the disease, Ostfeld warns that nymphal ticks pose more of a threat to humans, as they feed during the warmer spring-summer months, when more humans are enjoying outdoor activities.