September 6 & 7, 2007
Try and picture this--15 volunteers sitting in a room waiting for a hoard of tiny bloodsuckers to crawl onto their bodies.
They didn't really itch, no one was particularly grossed out, and everyone seemed to maintain a sense of humor as Dr. Thomas Mather, director of the Center for Vector Borne Disease, and his staff conducted a 2-day test to see how effective repellent - treated clothing is in combating disease-carrying deer ticks.
The experiment was conducted, said Mather, because previous studies on permethrin clothing repellents were conducted many years ago by the military using subjects who wore long pants and sleeves.
"The problem is that people don't wear long pants in the summer" Mather said, "and there have been no studies involving repellent-treated summer-wear like shorts and tee shirts." Mather noted that it is in the warmer months when most people encounter disease-carrying ticks.
Word was put out recruiting volunteers willing to spend two afternoons letting ticks crawl on their bodies in the name of science. Of course, monetary compensation sweetened the offer and Mather says his staff received more than 100 replies.
Fifteen brave students and staff were chosen. The study plan called for dividing the volunteers in groups of five-five would wear commercially treated clothing provided by Buzz Off Insect Shield, five would have clothing treated using an at-home treatment kit (Sawyer Clothing Only repellent), and five would wear untreated clothing. On the second day, each team would wear different clothing.
Atrium 1 in the Union was set up with 15 chairs, each placed in the middle of a large piece of white cloth taped to the floor. The white cloth made it easier to spot any ticks that dropped off the volunteers essential for accounting for all ticks at the end of the day.
Mather welcomed the group and assured them that the ticks being used were all raised in his lab and were certified pathogen-free. Then Center staff members started applying the ticks, which were loaded onto three cotton discs. Each disc contained 10 hungry nymphal deer ticks. The discs were taped on the volunteers for 10 minutes-one on a shoe, one on the knee of the opposite leg, and one on the upper arm.
For two and a half hours, the ticks were allowed to crawl on the volunteers' bodies. Some fell off on the white sheets very quickly. Newspaper photographers hovered around the volunteers and several were interviewed by crews from three local TV stations. Volunteers watched a movie to help pass the time.
Mather's team worked to keep accurate records of the number and condition of the ticks.
"Generally speaking, we were a bit surprised by the number of ticks that attached to people with the treated clothing," Mather explained, "but it was pretty clear when we removed them, that most of the attached ticks from treated subjects were already dead," said Mather.
"In contrast", he continued, "the ticks on the volunteers with un-treated clothing were mostly alive when we pulled them off".
One interesting preliminary observation made, was that the treated shoes (sneakers were supplied for the study) seemed quite effective in killing ticks. Treated shoes had not been used in the previous military tests.
Mather said results might have been more conclusive if the ticks could have been left on the volunteers all day as they went about their normal routines, so that those dead ticks would have been brushed off, but it would have been difficult to get that procedure past the Institutional Review Board that approves such studies.
The experiment was designed to find out how effective treated summer clothing can be in deterring tick bites, said Mather and while the preliminary data looks promising, a complete analysis of the data is necessary before any conclusions can be drawn.