Mind Controlling Parasite in Alberta!

Here in Canada we don’t often pay much attention to parasites. They are usually considered something you would get if you went travelling. The fact is, though, some disease-causing parasites are travelling here, putting both our domestic animal and wildlife populations at risk. In recent times the amount of animal trade and encroachment into wild spaces has increased the spread of animal parasites globally. Now one of the weirdest parasites known has moved into Alberta.

In the 1990s a small liver fluke was found in elk and cattle in the Cypress Hills Interprovincial Park, southeast of Medicine Hat, Alberta. This little worm was identified as Dicrocoelium dendriticum and it was the first time it had been observed in Alberta. This rather unspectacular looking worm, it is only 2-3cm long, does have a rather spectacular life cycle. Adults will shed worms in the feces of its elk or cattle host where they are ingested by terrestrial snails. The parasite replicates inside of the snail and grows so large the snail covers it in mucous and coughs out what is called a “slime ball”. These are then ingested by ants that, shortly after eating them, start to act really strange.

Infected ants clinging to a dandelion in Cypress Hills Interprovincial Park

Infected ants will climb up plants in the morning and at night and cling onto leaves and flowers. They remain here waiting to be accidentally eaten by a grazing animal so the parasites inside can move to the liver and complete the life cycle. What causes this weird behaviour is not exactly known but in every infected ant, one and only one of the parasites that it has eaten swims up through the ant, locates a large bundle of nerves underneath the ant’s jaws and wraps itself around, presumably driving the ant up and down from the plants in a daily cycle for the remainder of its life.

Our lab group from the University of Lethbridge has been studying various aspects to this unique system for several years now and are beginning to gain some insight into the effects this parasite can have on local animal populations, how it is distributed among wild and domestic populations, and where the risks of infection for grazing animals exist in the Cypress Hills. We are also using genetic techniques to track where this parasite may have come from. This is truly a fascinating system but also a great model system for understanding how parasites can travel to new places and infect local populations as well as how domestic and wild animals living in close proximity are sharing parasites, making management all the more difficult.

For more information on Dicrocoelium and mind controlling parasites visit my blog at zombieants.ca.

Submitted by Bradley van Paridon, PhD Candidate, University of Lethbridge