Mila Bassil, New Science Communicator
Harsh terrain and brutally cold temperatures are not the only dilemmas Arctic dwellers face.Dr. Emily Jenkinsand her team of researchers at the University of Saskatchewan’sWestern College of Veterinary Medicinehave identified parasites in the gastrointestinal tract of carnivores from northern Canada asEchinococcusspp, a small tapeworm no larger than a mustard seed. Despite its miniscule size,Echinococcusis extremely dangerous.
Echinococcus multilocularisandE. canadensisare two species of the parasite that arepresent and emergingin Canada. Although the parasiteoccurs worldwideandmany cases of human echinococcosis have been diagnosed elsewhere, few Canadians are aware of the growing risk. The World Health Organization considers人体包虫病是一个“被忽视的热带disease,” butEchinococcusis not restricted to the tropics – and it appears to be becoming more common, even in regions as cold as the Canadian North.
In the Arctic,E. canadensisoften useswolvesasdefinitive hosts– hosts that are required for the parasite to survive or reproduce – but can infect coyotes, foxes and othermembers of the dog family, including pets.鹿、麋鹿、鹿和其他cervidsusually serve asintermediate hostsin which the parasite undergoes development and asexual reproduction.E. multilocularisalso uses dogsas definitive hosts, but typically circulates inrodentintermediate hosts.
Echinococcusis a public health concern because it also infects people.Echinococcosis, a condition where a large cyst develops in the liver, lungs or other organs, can develop when people consumeEchinococcuseggs shed by definitive hosts, often pet dogs that have scavenged on wildlife carcasses.Dogs, as both intermediate and definitive hosts of the parasite, are also at risk ofdeveloping echinococcosis.
“The cysts can affect people in the same way that a tumour would,” says Joy Wu, an undergraduate research student working in the Jenkins lab. “Just like cancer, echinococcosis can be a very serious illness that may require surgical or chemotherapeutic treatment.”
Of particular concern is that, when infected, intermediate hostsshow no clinical signs. This means owners of infected dogs may have no idea their pets are carrying the parasite in their gastrointestinal tracts. This puts humans at high risk of being infected unknowingly.
At the Jenkins lab, adultEchinococcusworms were collected and counted from the intestines of wolverines, coyotes, wolves, red foxes and arctic foxes that had been trapped or hunted in the Yukon and Northwest Territories for other purposes. Researchers then confirmed that the worms were eitherE. canadensisorE. multilocularisusing a technique known aspolymerase chain reaction, or PCR.
With PCR, researchers extract DNA from the worms, amplify it, and then analyze it to determine which exact species the worm is. This allows researchers to know what species the worm is without having to rely only onmorphology, which can be very unreliable since both worms look very similar.
The researchers found thatE. canadensiswas highly prevalent (76%) among wolves in the Yukon, whileE. multiloculariswas highly prevalent (26%) in Arctic foxes from islands off Inuvik in the Northwest Territories. By determining how common these parasites are, researchers are trying to gauge whether people living in the Canada’s north face increased risk for infection.
“If we see that the parasite is present in more wildlife than it has been in the past, then we can predict that it is more likely for humans to come into contact with it since it is more abundant in the population overall,” Wu says. “If more wild animals are infected, the parasite can spread between more animals more quickly, and domestic animals and people who come into contact with wildlife will be at a much higher risk of becoming infected.”
Rajnish Sharma, a graduate student working in the Jenkins lab, says that “based on a qualitative risk assessment,E. multilocularishas been ranked as the most important zoonotic parasite in the North from a public health point of view.” He saysEchinococcus“has been an emerging parasite in the Canadian North due to multiple factors, including climate change and people-wildlife interfaces.”
Climate change and increasing interactions between people and wildlife mayalso be allowingEchinococcus– and possibly other parasites – to increasein the rest of Canada.
Echinococcuseggs are extremelyresilient to cold temperatures. For example, researchers had to freeze samples at â€“80Âº C to inactivate any eggs before they could safely analyze them. Even with the extreme cold tolerance ofEchinococcus, Sharma predicts that the parasite will become even more abundant in the Arctic if temperatures were to increase. Rising temperatures and longer summers in the Arctic will extend the breeding season and allow more wildlife to survive in these regions. More wild animals means not only more hosts available forEchinococcusand other parasites to infect, but more sources of infection for animals and people altogether.
Few Canadians are aware of the risk that is emerging in our backyards.Echinococcus, a dangerous parasite known to be the cause of a widespread disease in the tropics, appears to be spreading and becoming more common in Canada – including in northern regions. As climate change continues to progress and the breeding and migration patterns of northern wildlife shift in response, we may – to our regret – find ourselves becoming far too familiar with this tiny tapeworm.
Join us every Monday this month to readworksby our other Pitch and Polish graduates:
January 7, 2019:Veterinary researchers seek clues to more effective treatment for deadly dog disease, by Nolan Chalifoux
January 14, 2019:Llama drama: Research into the mechanics of llama ovulation reveals a rare tumour, by Kylie Hutt
January 28, 2019:Ramp walking helps diagnose lameness in dogs, by Emma Thomson
February 4, 2019:Multidisciplinary collaboration helps researchers solve complex, real-world problems