Veterinary Medicine Offers Potential as New Tool to Reduce Lyme Disease

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Blacklegged ticks (Ixodes scapularis) acquire the pathogen that causes Lyme disease from mice and other small mammals. A new study shows that a drug for protecting pets from ticks could be deployed in rodent baits to interrupt the host-to-vector transmission cycle. (Photo by James L. Occi/Armed Forces Pest Management Board via Flickr, CC BY-NC-ND 2.0)

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Blacklegged ticks (Ixodes scapularis) acquire the pathogen that causes Lyme disease from mice and other small mammals. A new study shows that a drug for protecting pets from ticks could be deployed in rodent baits to interrupt the host-to-vector transmission cycle. (Photo by James L. Occi/Armed Forces Pest Management Board via Flickr, CC BY-NC-ND 2.0)

By John P. Roche, Ph.D.

Lyme disease causes a significant public health burden, leading to an estimated 476,000 cases per year in the U.S. The disease is caused by a bacterium, Borrelia burgdorferi, which is spread in eastern and central North America by blacklegged ticks (Ixodes scapularis). The primary hosts of the bacterium in this region are the white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus).Lyme disease is an expanding problem, and thus control strategies are critical to reduce its growing medical and economic costs.

To explore a potential new control strategy, researchers at the University of Montreal and the Public Health Agency of Canada examined the following question: If Peromyscus mice are dosed with fluralaner, a medication for tick and flea control on dogs, will the number of ticks on the mice be reduced? Their study was published in August in the Journal of Medical Entomology.

Reducing Lyme disease risk involves a variety of interconnecting goals, including reducing the density of ticks in the environment, reducing the number of ticks in the environment that are infected with the Lyme disease bacterium, reducing human exposure and risk of transmission of Borrelia, and preventing human infection using vaccines or antibiotics. This study focused on the first two of these goals by testing whether fluralaner reduces the density of ticks in the environment and the number of infected ticks in the environment when used on small mammals.

Fluralaner offers several advantages as a compound to kill ticks (an acaricide). It is safe for humans and pets, and, after a dog receives a dose, fluralaner kills ticks quickly and continues to kill them for weeks. This makes it highly effective for eliminating ticks that land on an individual animal.

The study, led by Jérôme Pelletier, DVM, a Ph.D. candidate in epidemiology at the University of Montreal, was conducted in the wild in the Estrie region of southern Quebec, Canada. Pelletier and colleagues set up two manipulated treatment zones and one unmanipulated control zone, and each of these zones contained several 75-meter-by-75-meter experimental plots.

In the treatment-zone plots, baits loaded with fluralaner mixed with peanut butter were deployed for six weeks for three summers in July and August. In Treatment Zone 1, the density of baits deployed in 2017 and 2018 was 4.4 baits per 1,000 square meters. In Treatment Zone 2, the density of baits deployed in 2017 and 2018 was 2.1 baits per 1,000 square meters. Animals were also sampled in 2016, but the sample size was too small that year to be statistically usable.

For sampling, the team captured small mammals in each zone two times each summer. Investigators sedated each animal; removed and recorded the number of tick adults, larvae, and nymphs on it; and then released it back into the wild.

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