Anthelmintic resistance (AR) has thus far only rarely been reported for intestinal helminths of dogs and cats, in contrast to parasites of livestock and horses. We highlight possible reasons for this striking and important discrepancy, including ecological, biological and genetic factors and/or intervention regimens of key intestinal helminths concerning both host groups. In view of the current knowledge related to the genetics, mechanisms and principles of AR development, we point at issues which in our view contribute to a comparatively lower risk of AR development in intestinal helminths of dogs and cats. Finally, we specify research needs and provide recommendations by which, based on the available information about AR in ruminant and equine helminths, the development of AR in dog and cat helminths may best be documented, prevented or at least postponed.
