Last spring, we posted about a report of alveolar echinococcosis (AE) in a child in Quebec from 2018.  This very serious parasitic infection is caused by the intermediate stage of the fox tapeworm, Echinococcus multilocularis (EM), which despite its common name is often also found in coyotes (including right here in southern Ontario), and it can infect dogs as well.  Canids typically become infected by eating small mammals like rodents that carry the intermediate form of the parasite in their organs, and then the infected canids pass the tapeworm eggs in their feces, which then infect more small mammals when they’re ingested.  The big problem is people can also become infected by accidentally ingesting these tapeworm eggs and go on to develop AE. In most cases of AE, parasitic cysts start to develop in the liver, and the cysts grow and spread like a malignant tumour.  The cysts can also appear in other parts of the body, but in any case it often takes years for a person to start showing any signs of illness.  By the time AE is diagnosed, treatment can be very difficult, and it may be impossible to remove the cysts.  Occasionally dogs can also develop the AE form of infection.

Now a new report has been released about an unusual case of AE in a child from northern Manitoba (Joyce at al. 2020).  There are several noteworthy points about this case:

  • The patient was only 12 years old. Cases of AE in children are uncommonly reported – only 4 of 559 patients in a European registry from 1982-2000 were children. Although children are generally more likely to have fecal-oral exposure due to poorer hand hygiene, because of the long incubation period for AE (5-15 years) people exposed as children might not be diagnosed until they are adults.
  • The patient did not have any parasitic cysts in the liver. In the same European registry, only 13 of 559 patients lacked liver involvement. The authors speculate that this could be due to the fact that the patient also had a large portosystemic shunt (an aberrant vein that allows blood coming from the intestine to bypass the liver).  However, the patient did have lesions in the kidney, lungs and brain, all of which were presumed to be parasitic cysts once the diagnosis was made.  It’s an important reminder that what usually happens doesn’t always happen.
  • The boy had a history of latent tuberculosis which was treated 10 years earlier, so initially the masses seen on CT and MRI were thought to be due to tuberculosis, until more tests were completed. You can see how this would be a challenging diagnosis to make.
  • The authors also report that two years later the child does not have any clinical signs of disease from the cysts, and/but regular imaging shows that the lesions have not changed for better or worse.

The paper also provided a very brief summary of recent epidemiological findings regarding EM in Ontario and western Canada.

Since January 1, 2018, EM infection in animals in Ontario is reportable to public health.  In 2019 there were three cases of fecal shedding of EM in dogs reported in Ontario, in Niagara, Durham and Kawartha Lakes regions (though one dog was recently imported and was likely infected before coming to Ontario).  No cases of AE in people in Ontario were reported in 2019.  Nonetheless, this is definitely a parasite for veterinarians and dog owners to keep on the radar.  Dogs that hunt and may consume small mammals, or that have a lot of contact with coyote feces, may be at increased risk of exposure.  The best way for people to avoid infection is (dare I say it again) don’t eat poop (in other words, wash your hands and practice good hygiene around food and drink), and try to reduce the risk of infection in dogs in the household.

More information about Echinococcus multilocularis can be found on the Worms & Germs Resources – Pets page, or check out the EM infographic from the Ontario Animal Health Network.