Comparing common tick treatments vs lone star ticks

A lone star tick (Amblyomma americanum).

ondreicka/Adobe Stock

Kathryn E. Reif, PhD, MSPH, an associate professor in the Auburn University College of Veterinary Medicine’s Department of Pathobiology, presented her session, “Tick Tidbits: Novel insights & protection updates on these tiny troublemakers,” at the Fetch dvm360 Conference in Atlantic City, New Jersey, from October 14-16, 2024. In her session, Reif shared a comprehensive background of ticks and the threats they pose, before presenting a study comparing speed to kill the lone star tick (Ambylomma americanum) between 3 common monthly-use isoxazoline-containing parasiticide acaricides/treatment products.¹

“[The lone star tick] is an extremely aggressive tick species that will happily bite anything with a pulse at any life stage,” Reif said in her presentation.¹ “You may be a mouse, a deer, a dog, a person, even a lizard. If you are alive and have blood, consider yourself fair game for this tick species… this tick is also notable because it is one of the most challenging species for tick-control products to work against, or to kill. So, if you can kill a lone star tick rapidly, you should feel really, really good about that tick-control product.”

Similar to other ticks, lone star ticks are arachnids with 8 legs, no heads or eyes, and a Haller’s organ, which they use in place of antennae to observe their surroundings and detect physical and chemical cues of potential hosts. There are 3 life stages for ticks, progressing from larvae, to nymph, to adults. Ticks usually feed 3 times in their lives, 1 time per life stage, and they live 2 to 3 years. They typically live in open spaces of forest, brush, or grassland habitats, and although they prefer warmer, humid weather, lone star ticks can be found questing for hosts even on sub-40°F days.¹

Comparing speed to kill

“So, our question was, ‘how quickly is the lone star tick killed on dogs treated with either [lotilaner], [sarolaner], or [afloxolaner]? And we rationalized the need for this study because the faster we kill these ticks, the less likely they are going to be to transmit any pathogens that they’re potentially carrying,” Reif said, introducing her study.¹ “We specifically chose the lone star tick because it’s one of the most challenging tick species to kill… we also wanted to see, not only is this [treatment] working fast on dosing, but is it working fast at the end of the month, right before it gets re-dosed.”

The study examined the speed of kill provided by 3 monthly-use isoxazoline-containing products, the generics of which are lotilaner, sarolaner, and afoxolaner.^1,2 The team of researchers, led by Reif, looked at 4 groups of 8 healthy and randomized beagles (32 total; 16 males, 16 females) that were treated with either lotilaner, sarolaner, afoxolaner, or part of a control group left untreated. Controlled infestations of 50 pathogen-free, adult, lone star ticks were initially conducted 7 days prior to the dogs’ treatment in order to determine each dog’s susceptibility to tick attachment. Infestations were conducted again 2 days before their treatment, in addition to 21- and 28-days post-treatment.²

The intention of the recurring controlled infestations was to measure the efficacy of the treatments against both existing and new infestations. Ticks were counted and removed 5 days before treatment, 72 hours post-treatment, and 72 hours following each subsequent infestation. In situ ticks from the infestation 2 days before treatment were counted, without removal, 4-, 8-, 12-, 24-, and 48-hours post-treatments. The same timepoints for tick counting were used following the infestations on days 21 and 48.^1,2

On the day of treatment, lotilaner was the only acaricide to significantly reduce the count of lone star ticks by the 12-hour checkpoint. According to the study, the efficacy of lotilaner and afoxolaner at 24 hours post-treatment were 95.3% and 97.6%, respectively, both significantly higher than sarolaner, which was 74%. On day 21, at the 12-hour post infestation checkpoint, lotilaner efficacy was 59.6%, which was significantly higher than sarolaner, at 0.0%, and afoxolaner, at 6.3%. Later in that same day, at the 24-hour post infestation checkpoint on day 21, lotilaner’s efficacy was 97.4%, compared to 13.6% for sarolaner, and 14.9% for afoxolaner.^1,2

The results of the study demonstrated that the speed to kill for lotilaner did not decline over the course of the study period, whereas sarolaner and afoxolaner both declined significantly. “Time to ≥ 90% efficacy following new infestations consistently occurred 24-48 hours earlier for lotilaner compared with sarolaner or afoxolaner,” the authors of the study wrote.²

“So, from this study, we can conclude that [lotilaner] has a rapid, and I would argue as importantly, a sustained, rapid speed of tick kill throughout the product’s full treatment period,” Reif concluded.¹ “Why do we care about tick speed of kill, and why do we want it to happen throughout the product’s dosing lifespan? It’s all about reducing the risk of pathogen transmission.”

Despite these findings, Reif reiterated that the best, most effective tick product is one that a client will use properly, and that starts with their veterinarian’s encouragement. She also advises that no tick product is 100% effective and offers a reminder that the label should be considered before any recommendations are made. She recommends regular tick checks, both on pets and humans. Upon the discovery of a tick, they should be promptly removed. It’s best to grab them close to the skin with tweezers, pulling back with steady, even pressure. The bite site should then be sanitized.

References

1. Reif K. Tick Tidbits: Novel insights & protection updates on these tiny troublemakers. Presented at: Fetch dvm360 Conference; October 14-16, 2024; Atlantic City, NJ.
2. Reif KE, Kollasch TM, Neilson JC, et al. Comparative speed of kill provided by lotilaner (Credelio), sarolaner (Simparica Trio), and afoxolaner (NexGuard) to control Amblyomma americanum infestations on dogs. Parasit Vectors. 2024;17(313). https://doi.org/10.1186/s13071-024-06363-w.