Multiple-drug resistance in canine hookworm an emerging problem
The canine hookworm, Ancylostoma caninum is the most prevalent intestinal nematode parasite of dogs in the USA. Hookworms are typically well controlled by treatment with all commonly used anthelmintics approved for this use in dogs. However, in the past few years, cases of recurrent/persistent canine hookworm infections appear to have dramatically increased, suggesting that anthelmintic resistance may have evolved in this parasite. These cases are highly overrepresented by greyhounds, but multiple other breeds are also represented. In this study, the researchers aimed at characterizing these suspected resistant isolates to determine the incidence of true anthelmintic resistance in A. caninum.
The researchers demonstrated the presence of multiple drug resistance to benzimidazoles, macrocyclic lactones and pyrantel in canine hookworm. Coincident with this report, other researchers recently reported resistance to benzimidazoles and macrocyclic lactones in A. caninum recovered from a greyhound dog.
The origins of these resistant hookworms remain to be determined; however, evidence suggests that they originated from racing greyhound farms. Ancylostoma caninum is the most prevalent parasitic nematode in racing greyhounds and this is attributed to the near-constant exposure of these dogs to infective third-stage larvae in the sand/dirt exercise run/pens. Racing greyhounds are also treated extremely frequently with multiple different anthelmintics throughout their lives. The intervals between these treatments often are less than the pre-patent period for hookworms. Consequently, any worms surviving treatment will have a large reproductive advantage and will rapidly increase in frequency. This combination of factors is known to place heavy selection pressure for drug resistance and is very similar to the epidemiological factors that have led to high levels of multiple-drug resistance in nematodes of sheep and goats, worldwide.
Multiple drug resistance in A. caninum is an emerging problem in dogs. Evidence suggests that the problem originated in the greyhound racing industry and has since begun to spread through the pet population.
Original publication is open access and can be read at this link.
Reference: Jimenez Castro, P.D., Howell, S.B., Schaefer, J.J. et al. Multiple drug resistance in the canine hookworm Ancylostoma caninum: an emerging threat?. Parasites Vectors 12, 576 (2019). https://doi.org/10.1186/s13071-019-3828-6