Mice and Lyme Disease

Already, it has been a bad year for ticks–deer ticks. Sorry beasts.

Not only do they eat the wildflowers and shrubbery around the house and any of the garden they can get to, but they harbor disease and share it with humans.

But wait a minute: it turns out that the deer might not be the main culprit for things spreading things like Hanta Virus and Lyme Disease.

That distinction goes to the rodents named after them. Deer mice, in many places, are the primary carriers of these diseases.

And when mouse populations go up, so do deer ticks, which do little harm to the mice. Rodents spread the disease organisms easily in crowded habitats where they are more likely to encounter each other.

Then, there are factors that encourage increased mouse populations: a decrease in predators (coyotes and fox, bobcat and certain hawks and owls); a decrease in the severity of winters; an abundance of natural foods for mice; and an increase in hiding places around human habitations.

That being said, look out for a really bad year in places (like SWVA) where Lyme disease already is common. Why? Partly because last autumn was a heavy MAST year–meaning that the oaks produced a heavy crop of acorns.  The mice have eaten well, and this typically results in larger and more frequent clutches of babies.

Out west, where climate-related disease has wiped out the Aspen trees, they are also seeing more deer mice, and increased risk of Lyme, Hanta, and other human pathogens.

Not surprisingly, tick-borne pathogens are increasingly present in transfusion blood supplies. Ever heard of Babesia? Probably not, because it did not used to be at all common. It’s been called “America’s malaria.” As the climate shifts warmer winters northward, you’ll likely hear more about this in years to come.

So what we learned the first day in Ecology back ages ago is true: You CAN’T do just one thing. Every perturbation in nature will have repercussions–often ones that we would not have imagined. In the case of deer ticks and mice, we know what to expect. And here’s the (sort of) good news:

It is possible (over a limited range) to recruit deer mice to help kill ticks. These Tick Tubes contain cotton (primo nesting material) that are treated with permethrin–the same compound found in the (too toxic for my dogs) spot-on tick drops. By the way, the Preventix collar we are using instead seems to be working well for Gandy.