June 25, 2012 Gray squirrels have been implicated as a major reservoir for the bacteria that cause Lyme and other diseases, a new study reports. Blood from ticks was traced back to the squirrels using new DNA techniques, confirming a previously hypothesized role for these small mammals in the spread of tick-borne pathogens.
A Lyme disease-related condition, Southern Tick-Associated Rash Illness, or STARI, is common in the southeastern United States, along with ehrlichiosis, another disease spread by ticks. In these cases, the tick responsible is the lone star tick, not the deer tick, which is normally associated with Lyme disease. Identifying the animals that act as tick hosts is essential for understanding, and potentially restricting, transmission, but previous research had not been able to identify the small mammal species involved.
Researchers at Washington University in St. Louis applied two different DNA tests to their ground-up tick samples: one to check which bacteria they carried, and the other to detect the origin of the ticks’ bloodmeals. They probed the tick blood for a number of species and came up with a match for the gray squirrel. These squirrels may act as a significant reservoir for Borrelia lonestari, the bacteria that cause STARI.
While white-tailed deer are still the largest source of blood for ticks, squirrels, merely by being so numerous, are also an important host species, and are equally efficacious in infecting ticks with disease-causing bacteria. Moreover, squirrels are widespread in both urban and rural settings, though the researchers found that 25% of squirrels in a wooded suburb were infected, compared with just 5% in a more urban area. These results appeared in the May issue of the Journal of Medical Entomology.
Source: jsonline.com by Amanda Alvarez