Saturday, February 27, 2010
You have a much greater chance of getting sick from a tick bite today than you did 30 years ago. But a new tool might allow researchers to better understand why more ticks are making people sick.
“If you’re a health inspector and a bunch of people get food poisoning, the first thing you’d want to know is where they ate last. If you’re a disease ecologist and a bunch of ticks have a pathogen, the first thing you’d want to know is where the ticks ate last,” said Brian Allan, a post-doctoral researcher at the Tyson Research Station in St. Louis.
Allan led a team of researchers in developing a novel technology that probes the genetic contents of ticks’ gut. The tool can determine which wildlife species provided the tick’s last meal and which pathogens came along with that meal.
In the first study to use the new technology, Allan and his colleagues focused on several rapidly emerging diseases transmitted by the lone star tick. These include two pathogens responsible for a potentially fatal bacterial infection known as ehrlichiosis [ur-lick-ee-oh-sis]. In Missouri, over 200 cases of ehrlichiosis were documented last year.
Allan et al.'s study showed that about 80 percent of pathogen-positive ticks had fed on white-tailed deer. They also found that squirrels and rabbits were capable of infecting ticks at a higher rate than deer. However, since the lone star tick feeds on squirrels and rabbits less frequently, they account for a smaller percentage of infection.
Allan and his colleagues hope that the technique will shed light on theoretical questions in the field of ecology. They are especially interested in testing whether biodiversity is good for your health, a hypothesis known as “the dilution effect.”
Allan, B. F., L. S. Goessling, G. A. Storch, and R. E. Thach. 2010. Blood meal analysis to identify reservoir hosts for Amblyomma americanum ticks. Emerging Infectious Diseases 16: 433-440. DOI: 10.3201/eid1603.090911