Disruption to Balance of Ions in Salivary Glands of Ticks May Limit Pathogen Transmission

Tick are dangerous vectors that can transmit deadly diseases to humans and animals alike. As such, developing effective methods to prevent the spread of tick-borne diseases is of paramount concern.

A team of investigators from the Department of Entomology at Louisiana State University previously recognized that the salivary gland of a tick is critical to sustaining life and therefore may be a potential target tissue for acaricides.

The team hypothesized that the functioning of the tick’s salivary gland relies upon the epithelial transport of potassium ions and that the chemical modulation of inward rectifier potassium (Kir) conductance would have an effect on the biology of ticks. The findings of their research were presented at the American Chemical Society (ACS) Fall 2019 National Meeting & Exposition.

For the study, the research team fed ticks blood laced with 2 compounds documented to act on the Kir channels. According to the investigation, 2 of the molecules, VU0071063 and pinacidil, were effective and reduced saliva secretion by 95% or greater and reduced blood ingestion approximately 15-fold. Furthermore, ticks that fed on blood infused with either of these compounds died within 12 hours of ingestion. This is significant because transmission of pathogens through a tick bite takes a minimum of 12 hours.

The team also notes that ticks who were removed from the blood meal prior to death were lethargic and unable to walk, which may be attributable to an imbalance of potassium, sodium, and chloride ions. Typically, ticks return excess waters and ions back into the host when feeding but, in this situation, the ticks produced more ions despite less saliva production. The investigators hypothesize that an effect on the nervous system led to disruption of the biological function.

Although this research was conducted in artificial host feeding systems with blood meal, the next step is to evaluate this method when ticks feed on rodents.

According to the press release issued by ACS, the study team hopes that in the future these findings can be used to develop a spray, injection, or treatment to reduce the risk of tick bites in animals.

“These data strongly suggest Kir channels are critical for salivary gland function of ticks and are promising target sites for the development of novel acaricides,” the investigators wrote in the abstract.

The study, “Giving ticks 'dry mouth' through chemical modulation of inward rectifier potassium channels as a mechanism to prevent blood feeding,” was presented on August 26, 2019, at ACS Fall 2019 in San Diego, California.