The authors gratefully acknowledge Lenaig Halos and Frederic Beugnet, Veterinary Parasitologists, for the scientific editing of the manuscript. “
“Tick control is an important concern for public health officials, pet owners, and veterinarians

(Dantas-Torres et al., 2012 and Otranto and Wall, 2008). Indeed, tick infestations can be a nuisance, and heavy tick infestation can lead to anemia, particularly in young or small dogs. Dermacentor variabilis, generally known as ‘American dog tick’, is one of the most common tick species affecting dogs in the USA ( Dryden and Payne, Apoptosis inhibitor 2004 and Goldberg et al., 2002). D. variabilis is widely distributed across the central and eastern United States, and also occurs along the Pacific coast, and it is an important vector of several infectious agents, including those that cause Rocky Mountain spotted fever, tularemia, and ehrlichiosis in both dogs and humans ( Chomel, 2011, Dantas-Torres et al., 2012, Dryden and Payne, 2004 and Steiert learn more and Gilfoy, 2002). D. variabilis is also commonly implicated as a cause of tick paralysis ( Vedanarayanan et al., 2004). Currently, tick control for dogs is only available in formulations

that are topically applied (Sprays, powders, shampoos, spot ons) or in collars ( Beugnet and Franc, 2012). Afoxolaner is a novel insecticide–acaracide that is administered orally in a chewable formulation (Nexgard®, Merial). Afoxolaner is a member of the science isoxazoline class and works by inhibiting insect GABA and Glutamate-gated chloride channels ( Shoop et al., 2014), thereby leading to prolonged hyper-excitation and death of both insects and

acarines. This paper describes two studies that were performed to demonstrate the efficacy of afoxolaner against D. variabilis ticks. Two similar studies were conducted to demonstrate the efficacy of afoxolaner against D. variabilis. Both studies were performed in the USA and were designed in accordance with standard methods for evaluating the efficacy of parasiticides for the treatment, prevention and control of tick infestations ( Marchiondo et al., 2013). The studies were approved by the Merial Institutional Animal Care and Use Committee. Dogs were managed consitent with the US Animal Welfare Regulations ( USDA, 2008). The studies involved 32 purpose bred beagles (16 per study) which were individually identified by unique ear tattoos. Study 1 included 6 male and 10 female dogs aged 6–8 months and weighing 5.7–9.1 kg. Study 2 included 10 male and 6 female dogs aged 7–10 months and weighing 5.9–9.6 kg (Table 1). Studies followed a controlled, randomized design. Dogs were in good health and had not been treated with ectoparasiticides for at least 3 months prior to treatment. Tick infestations and subsequent counts were performed prior to treatment, and confirmed that dogs were capable of maintaining adequate infestations. Dogs were housed individually.