Is it time to re-evaluate anti-parasitic use in companion animals?

Anti-parasitics for companion dogs and cats are routinely used for prevention as well as treatment of parasites, and there has been a rapid evolution in the ease of use and choice available to prescribers and pet owners in this regard (Zajac, 1993; Epe, 2009; Becskei et al, 2020). While specific recommendations for preventive use vary from one geographical region to another (for example, depending on the occurrence of highly pathogenic parasites such as Dirofilaria immitis), veterinarians generally recommend at least some prophylactic use of anti-parasitics. Until relatively recently, the need for restraint in use of companion animal parasitics, in view of concerns over development of resistance in parasite populations and eco-toxicity, has not been widely discussed. This is in contrast to attitudes on use of anti-parasitics in farmed animals. However, there is now evidence to suggest that a renewed consideration of the strategic use of anti-parasitics in pets is warranted, in order to provide optimum protection against parasite-mediated pathogenic effects, while preventing both development of resistance and environmental damage.