Antiparasitics against ectoparasites in small animals– important pharmaceutical substances or underestimated environmental hazards?

Application of chemical compounds for the control and prevention of arthropod infestations is standard in small animal veterinary medicine. However, concerns about potential negative effects of such substances in the environment, including their circulation in water, soil or plants, and consequent impacts, including infertility or death of sensitive non-target organisms, such as bird, fish, and insects, in particular pollinators, are increasing. Factors that determine the risk of environmental harm from different chemicals are not only their release, but also their retention, bioavailability, degradation, accumulation in different environmental compartments, bioaccumulation in different organisms or their organs, and the effects of excipients commonly used in drug formulations vs. not medical or veterinary use of chemicals. Here we briefly review the substance classes of insecticides, acaricides, or repellents used in veterinary medicine, their effects and possible side effects, and their fate in the environment, including reports of undesirable environmental impacts. In addition to existing literature, the possibilities of preventing, reducing and containing the unwanted release of such chemicals from animal treatments and the pivotal role of experts in veterinary parasitology are discussed. Knowledge gaps concerning the properties of chemicals used for the control of ectoparasites in veterinary medicine that must be addressed in future research are emphasized.