Back to the study. The Connecticut group chose a location where they could track a small, contained deer herd: a peninsula jutting out into Long Island Sound, where the terrain around a decommissioned power plant reverts to a wild state. They deployed a feeder that regularly dispersed a small amount of corn — enough to stun the animals, but not make them fat — and dosed the bait with moxidectin, a second-generation ivermectin that comes in a veterinary formula. Then, with the help of the non-profit conservation organization White buffalountil 2021 and 2022, they periodically drugged and captured deer, tagged them, took blood samples, and counted the ticks on their bodies.
They focused on the lone star tick, Amblyoma americanumthose ehrlichiosis, borreliosis, Bourbon and Heartland viruses and the meat allergy known as alpha-gal syndrome. That tick prefers to feed on white-tailed deer, while the type that spreads Lyme disease also preys on rodents. (For both species, humans are opportunistic targets. Ticks don’t have good eyesight, but they detect exhaled carbon dioxide – so if we dart past them as they perch on vegetation, they sense us and attack.)
In this first round of research, the researchers found that the number of ticks crawling on an individual deer didn’t change with blood levels of the drug — which makes sense, because the ticks wouldn’t know before biting whether a deer was dosed or not. However, the amount of clinging, blood-engorged ticks decreased as the level of the drug rose in a deer’s blood. “As serum levels rise, ticks don’t have to consume as much before they become paralyzed and fall off,” says Williams. “You wouldn’t see ticks engorged and feeding on animals with higher serum levels, because it would affect them much more quickly.”
The work has piqued the interest of the Centers for Disease Control and Prevention, whose division of vector-borne diseases gave the group a five-year grant. “The prep work looked good in the proof-of-concept phase,” said Lars Eisen, a research entomologist in the Department of Vector-Borne Diseases. “This is additional funding for a larger-scale field trial in Connecticut, in an inland environment, and on an island in Maine.”
The project contains complexities. a Attempt from the 90’s to feed the original formulation of ivermectin to deer that got stuck on the many roles deer play in the landscape. They’re not just free-living wildlife, and not just suburban offenders, charming or invasive, depending on whether they’re posing or chewing on your yard. They are also the preferred target of sport hunters, who spend money billions of dollars per year for access to them. Ivermectin had a legal restriction, called a withdrawal period, that prohibited consuming meat from a treated animal within 48 days. For hunters, that made the proposal a nonstarter.
That led to the best current method of tick control for deer, a device developed by the U.S. Department of Agriculture and called a “4-poster” for its loose resemblance to that style of bed. A four-poster bed contains a tub of treated corn, two integrated troughs that the corn falls into, and – this is the poster area – two upright paint rollers, saturated with tick-killing chemicals, on either side of both troughs. To get to the corn, the deer have to put their heads between the rollers. That paints their cheeks and ears with the chemicals, which eventually coat the rest of their bodies — a messy field version of the tick-killing solutions dog and cat owners spray on their pets’ necks.
