ZOONOTIC & VECTOR-BORNE DISEASE RESEARCH: Host-Targeted Insecticidal Baits
In public health, traditional rodent control has involved the use of rodenticides to eliminate vertebrate pests. However, exclusively eliminating the rodent, while ignoring their ectoparasites, can cause parasitizing disease vectors such as ticks and fleas to leave the deceased host and search for alternative blood meals, potentially spreading disease pathogens to wildlife, pets, or humans. In addition, traditional methods of vector control such as broadcast spraying can be costly and pose risk to non-target vertebrates and invertebrates such as pollinators. A potential solution is the use of baits containing insecticides or acaricides to control fleas and ticks blood feeding on rodents.
In 1999, Genesis scientists began screening a variety of insecticidal compounds, incorporated into rodent baits, for control of parasitizing fleas and ticks. Many of the compounds screened were absorbed into the blood of treated rats and mice at levels sufficient to control fleas and ticks. This research, as well as many additional experiments in the lab and field resulted in development of multiple products for elimination of host vectors. These products discriminately target hosts critical to vector life cycles, resulting in a reduction in the amount of insecticide being applied in the field which subsequently reduces risk to non-target organisms. Additionally, Genesis research has led to the development of baits containing both rodenticides and insecticides/acaricides to concurrently control the rodent and its fleas or ticks. Rodents and disease vectors pose a variety of problems, and the integration of these innovative control tools could serve an important role in improving public health.
Plague has killed millions of people throughout history, resulting in elimination of a sizable proportion Europe’s population in the 14th Century. While not as much of a human concern in present day, human plague is still considered an “emerging disease” and plague incidence still occurs in many parts of the world, including Madagascar, Kazakhstan, Mongolia, and even the western U.S. Plague is transmitted by fleas, and disease outbreaks present a significant threat to native wildlife, including the endangered black-footed ferret. Genesis has developed and evaluated systemic insecticide baits for control of flea species commonly associated with plague, including those parasitizing California ground squirrels and black-tailed prairie dogs. These baits are taken up orally by the target host and kill parasitizing fleas as they blood feed. This Genesis strategy has been proven successful in studies conducted in the lab and field, is now being utilized by state and federal agencies in black-footed ferret restoration efforts.
Lyme disease is the most prevalent vector-born disease in United States, with the CDC estimating more than 500,000 new cases per year, most cases which occur in the Northeast and upper Midwest. While often not fatal, Lyme disease is difficult to diagnose, expensive to treat, and the symptoms of post-treatment Lyme disease syndrome, such as pain, fatigue, and difficulty thinking can last for years. Small rodents, primarily the white-footed mouse, act as a reservoir host for the Lyme disease spirochete which is transmitted by the blacklegged tick during blood feeding. Additionally, white-tailed deer serve as an important blood meal source and reproductive host for multiple medically important tick species, including blacklegged ticks and lone star ticks. Genesis research has led to the development of oral acaricide-based control techniques targeting small rodents and white-tailed deer to control parasitizing ticks. Laboratory and field-based research has demonstrated the substantial promise for these host-targeted approaches to reduce tick abundance in the field, reduce pathogen prevalence, and reduce the risk of infected tick bites in humans.