Parasite transmission from wildlife feces or prey to adventuresome pets is a known risk. Some parasites, such as the tapeworm, also pose risk to human health if accidentally ingested. But recent study out of the University of Saskatchewan’s veterinary microbiology team has suggested that these risks may be increasing – both as new strains of the tapeworm are seen emerging in North America, and as increased urban sprawl brings us in closer contact with wildlife like coyotes.
Humans and dogs are not the usual host of the tapeworm. Coyotes and foxes harbour the adult parasite, the eggs of which are shed in their feces. Rodents will ingest these eggs and act as an intermediate host. In the rodents, the eggs become larvae. These eventually grow into a cyst and kill the rodent. If a coyote or fox happens to eat an infected rodent, the larvae can then develop into adults, thus closing the cycle.
Where do dogs and people fit in? Dogs can also ingest carrion and become hosts for theadult tapeworm. People, however, cannot act as a primary host. One type of tapeworm – Echinococcis multiocularis – will instead migrate through the body and form tumour-like cysts in the brain, liver, or lung. This not a common occurrence in North America; there have only ever been two cases reported. The majority are seen in China, with emerging trends in Europe.
So what’s the big deal if only two human cases have been reported ever in North America? As the team from the University of Saskatchewan suggests, it is a matter of monitoring trends. This summer, a strain of Echinococcis multiocularis thought to be isolated to Europe was discovered in a dog from British Columbia. Wildlife health ecologists surveying the tapeworm load of coyotes in the Calgary area suggest about 25% of that population carry the parasite, the ‘North American’ strain. Finally, we know that as our cities expand, dog and human interactions with wildlife is ever-increasing. What this amounts to is a situation where parasitic strains are expanding their territory from continent to continent and into the suburbs.
How does this affect you? At this point in time, risk of parasite transmission to people is still extremely low. However with the consequences of that potential transmission being so costly from a health perspective, it pays to engage in preventative behaviours. Even simple hand washing after ‘stooping and scooping’ or cleaning the litter box goes a long way. Regular pet fecal exams and parasitic prevention are the second line of defense. Finally, asking us questions about your level of risk can help us tailor a prevention plan for your family situation.