Emergence of Canine Hookworm Treatment Resistance: Novel Detection of Ancylostoma Caninum Anthelmintic Resistance Markers by Fecal PCR in 11 Dogs from Canada

Objective: To describe dogs with detected Ancylostoma caninum anthelmintic treatment resistance markers in Canada.

Animals: 11 client-owned dogs with fecal quantitative PCR (qPCR) assay detected A caninum with benzimidazole (BZ) resistance genotypic markers.

Methods: Signalment, presenting concern, duration of clinical signs, fecal testing, treatment, and outcomes were obtained. Where available, follow-up data were collected via telephone or email with the primary veterinarian.

Results: Ancylostoma spp was detected from 184/32,205 dog fecal samples by reference laboratory qPCR surveillance, between May 15, 2022, and April 26, 2023. 11 of these 184 samples had A caninum with genetic BZ F167Y resistance marker detection. 4 dogs had not traveled outside Canada, 6 had been imported from the US, and the travel history was unclear in 1 dog. 7 of the dogs had gastro-intestinal signs (diarrhea or soft stool) on initial presentation. Clinical improvement was reported in 6 of these dogs (resolution of diarrhea and soft stool), with 1 dog lost to follow-up. All 11 dogs received anthelmintic treatment (varied drugs and duration).

Clinical Relevance: Identification of genetic markers of BZ resistance raises concerns about the potential animal and human impacts of resistant hookworms. 4 dogs lacked an origin from or travel history to the US, indicating true emergence and/or novel spread within Canada, not just importation from an area where resistance has been reported. Fecal surveillance was performed with a qPCR test incorporating treatment (BZ) resistance markers. There is a need to raise clinician awareness around treatment-resistant hookworm in dogs and the capability of fecal surveillance for genotypic and phenotypic resistance.