Preference in Dogs of Two Oral Endectoparasiticide Formulations: NexGard Spectra ® (Afoxolaner and Milbemycin Oxime) and Credelio ® Plus (Lotilaner and Milbemycin Oxime)

Fleas and ticks are major ectoparasites of dogs globally. Their control is based on regular treatments with ectoparasiticides, which represent the most important part of veterinary drugs worth around 3 billion Euros per year. In many parts of the world, dogs are also at risk of infection by endoparasites like heartworm, eyeworm, and lungworm. In these areas, endectoparasiticide formulations are used to prevent the risk of ecto- and endoparasite infections. Since 2014, oral formulations of insecticidal-acaricidal drugs have been launched, followed by endectoparasiticide formulations. These oral formulations facilitate the treatment by the owners and are now the market leaders. Intense work has been done during their development to enhance their palatability through their consistence (hard to soft) and their flavors. Palatable oral formulations facilitate the dog-owner relationship and help ensuring compliance. The most recent palatable formulations include isoxazoline as the ecto-parasiticide molecule. They also include anthelmintics (milbemycin oxime or moxidectin + pyrantel) to provide control of parasitic nematodes. Being very similar in terms of spectrum of activity, any differences in palatability may be a key differentiating factor for the owners. The present study was conducted to verify if dogs exhibited a preference between two endectoparasiticide oral formulations, NexGard Spectra® (afoxolaner and milbemycin oxime) and Credelio® Plus (lotilaner and milbemycin oxime). For four consecutive days, 100 dogs were offered the choice between both products and consumption was recorded. If one product was more consumed than the other, it was defined as the preferred product. A total of 375 chewable tablets were consumed over the four days, with a significantly higher consumption (p 0.0001) for NexGard Spectra® (272 chews, 72.5%) compared to Credelio® Plus (103 chews, 27.5%). Seventy-six dogs showed a preference for a product amongst whom 68 preferred NexGard Spectra® (89.5%) and 8 preferred Credelio® Plus (10.5%), resulting in a preference ratio of 8.5 to 1 for NexGard Spectra® (p 0.0001).