OAHN Companion Animal Project: Haplotyping of Echinoccus multicularis in domestic, captive and wildlife species in Ontario (in progress)

Project Lead: Dr. Andrew Peregrine

Collaborators:  

Project Proposal

Echinococcus multilocularis (EM) is a small, zoonotic tapeworm that is typically maintained in a wildlife cycle. Wild canids (e.g., coyotes and foxes) are the typical definitive hosts and harbour the adult stage of the parasite in their small intestine. Ingestion of the eggs, shed by definitive hosts, by small mammals can result in alveolar echinococcosis (AE), caused by the formation of budding parasitic cysts in the liver and other organs.  Ingestion of these infected intermediate hosts by a canid (or rarely felid) leads to completion of the life cycle.  Humans can also be affected by AE after ingestion of parasite eggs, and non-human primates are similarly susceptible.  Interestingly, domestic dogs can be both definitive and intermediate hosts.  Alveolar echinococcosis typically has a slow, insidious onset, and is often difficult to treat by the time a diagnosis is made, and is commonly fatal if left untreated.

Prior to 2012, Ontario was thought to be free of this parasite. Since then, cases of AE have been reported in dogs, captive primates, and wildlife.  A study from 2015-2017 partially funded by OAHN demonstrated that this parasite is now commonly present in wild canids throughout southern Ontario, with an overall sample prevalence of 23% (Kotwa et al. EID 2019).  Since then, with the increasing availability of diagnostic testing in Ontario (both tissue PCR for AE and fecal PCR to detect intestinal infection), EM fecal shedding has been identified in at least 13 dogs and one cat, and AE in at least 9 dogs, 5 chipmunks, a muskrat and 4 non-human primates in Ontario.  At least 4 cases of AE have been detected in people since the disease became reportable to public health in 2018, at least one of which was likely domestically acquired (Zewude et al. JAMMIDC 2024).

EM occurs through much of the northern regions of Europe, Asia and North America.  Different genetic variants (haplotypes) have been described from each of these regions, though they are not necessarily entirely distinct. Importation of EM via transboundary movement of dogs from different regions outside and within North America is a risk.  In recent years, European-like haplotypes have been detected in Western Canada (Alberta, British Columbia, and Saskatchewan) in wild and domestic hosts, alongside a surge in human cases, particularly in Alberta (Houston et al. Am J Trop Med Hyg 2021). Molecular characterization of the parasite in a number of the human cases has been consistent with a European-like haplotype, different from those previously found in sporadic cases in Canada. It has been suggested that the European-like strains could be more pathogenic and/or virulent than the North American strains for people, based on the historically low incidence of human cases of AE in the US and Canada prior to the 2010s (Polish et al 2021; Polish et al 2022).  As this pathogen is still emerging in Ontario, and haplotyping has not previously been consistently performed in this region, the distribution and epidemiology of different strains remains unclear, but could provide valuable information regarding transmission between different wildlife,  domestic animal (dog/cat) and human populations, and the occurrence of AE versus intestinal infection in definitive hosts (dog/cat).

The project was discussed with and is supported by the OAHN companion animal team.  Other funding for a pilot project of this kind is not readily available, and the project does not qualify for SCAP funding as it is companion animal focused.  Industry funding was not explored, as haplotyping is not a test that is commercially available through any diagnostic lab at this time, and as an exploratory study it is better suited to being an OAHN pilot project.