Possums And Ticks
An Unexpected Plus
Serving as inadvertent innkeepers for opossums may turn out to be good for your health. Scientists at the Cary Institute of Ecosystem Studies in Millbrook, New York, have learned that opossums act like little vacuum cleaners when it comes to ticks, including those that can spread debilitating Lyme disease to humans and other animals.
In lab experiments, scientist Richard Ostfeld and his colleagues studied six species of wildlife—three kinds of rodents, two types of ground-nesting birds and opossums—applying precisely 100 ticks to each animal’s neck, then studying tick feeding, survival and Lyme transmission. According to Ostfeld, opossums prove to be “a very poor reservoir” for Lyme and several other diseases, meaning that ticks feeding on the animals were unlikely to get infected or, by extension, go on to infect other hosts after dropping off the initial host.
Beyond this, the researchers found that, on average, about 50 percent of the 100 ticks on white-footed mice in the experiment fed to repletion then dropped off alive, but only 3.5 percent of ticks on opossums survived to drop off. Why? It turns out that the fastidious opossums were killing their ticks in the process of grooming—scratching, licking and chewing away at ticks in their fur. Examination of opossum feces confirmed that some of the ticks had been eaten.
This is significant because during late summer, when ticks are most abundant, the average opossum may be walking around with roughly 200 ticks on its body, according to the researchers. Based on their study results, they calculate that a single opossum might kill an astonishing 4,000 ticks in a week, a number that “really got our attention,” says Ostfeld. By “hoovering up and killing” so many ticks, he says, opossums are “not only protecting themselves, they’re protecting us because we know that human risk is a function of the abundance of infected ticks out in the environment.”
So, for all their homely quirks, opossums vacuum up garden pests and thousands of nasty ticks and also may hold the secrets to antivenom in humans—a good deal all around. Now do you still think they’re ugly?