Efficacy of Credelio Quattro™ (lotilaner, moxidectin, pyrantel, praziquantel) and Credelio™ (lotilaner) against longhorned tick, Haemaphysalis longicornis,-induced infestations on dogs.

Background: Haemaphysalis longicornis, the longhorned tick, is an invasive tick species that has been identified in increasing numbers and regions across the USA. This tick species is a competent vector for various pathogens to dogs, humans, and other species, with heavy infestations documented to lead to exsanguination. Therefore, determination of ectoparasiticides providing adequate treatment and control of H. longicornis is imperative to help reduce vector-borne disease transmission and protect against infestation in dogs.

Methods: Three laboratory studies were conducted to evaluate the efficacy of Credelio Quattro and Credelio for the treatment and control of H. longicornis. A total of 30 dogs per study were randomized to receive either placebo, Credelio Quattro, or Credelio on Day 0 according to a complete block design on the basis of pre-treatment live attached H. longicornis counts, infested on Day -7. To assess efficacy against preexisting infestations, enrolled dogs were infested with 50 unfed adult H. longicornis on Day -2 or -1 prior to treatment. Residual efficacy post-treatment was evaluated with subsequent infestations on Days 5, 12, 19, and 30. All ticks were collected and evaluated as live or dead and free or attached 48 h after treatment or infestation.

Results: Adequacy of infestation was achieved in at least two studies for every infestation time point evaluated. Both Credelio Quattro and Credelio provided 100% efficacy against H. longicornis from Day 2 through Day 32, with no live ticks observed on any dogs. A statistically significant number of dead ticks were recovered from both treated groups as compared with control on all assessment days. Post-treatment, treatment-related diarrhea was reported in six dogs receiving Credelio Quattro and one dog receiving Credelio on Day 0, with all dogs recovering on Day 1.

Conclusions: The laboratory studies described confirm the safety and effectiveness of a single dose of Credelio Quattro and Credelio, at the minimum effective dosage of 20 mg/kg lotilaner, 0.02 mg/kg moxidectin, 5 mg/kg praziquantel, 5 mg/kg pyrantel, and 20 mg/kg lotilaner, respectively, for the treatment and control of H. longicornis infestations in dogs for one month.