N.S. researchers continue to map deer brain worms that kill moose

Nova Scotia researchers are continuing to build a heat map of the prevalence of brain worms in deer that are deadly to moose that contract the parasites.

Over half of white-tailed deer surveyed in Nova Scotia were infected by the meningeal worm, according to the Department of Natural Resources and Renewables. While deer can typically live with the worm, the same cannot be said for moose and other ungulates.

The infection is typically spread when a grazing deer accidentally eats an infected snail or slug. The parasites mate on top of the deer's brain and lay eggs that travel through the bloodstream to the lungs. The larvae are then coughed up, swallowed and passed in the deer's feces, making their way into the ecosystem where they can infect moose, causing weakness, impaired vision, deafness, paralysis and death.

"[The worms] don't know where their target is in the brain and so they start doing all kinds of neurological damage and it's actually quite painful to watch any footage of the moose that's gotten this," said Dave Shutler, a professor emeritus with the department of biology at Acadia University whose students partake in the research.

This month, the province awarded over $12,000 to Acadia University to continue the work. 

Jason Airst, a species at risk biologist with the Department of Natural Resources and Renewables, said mainland moose only exist in distinct pockets. He said the worm is one of the contributing factors to the population decline. 

"There's no treatment for it. It's just more or less a death sentence if it happens in a moose," Airst said.

Earlier this month, the province announced the suspension of the Cape Breton hunt because the population had dropped to 835 moose from about 1,500.

"We're very interested in trying to find ways to manage the moose population so they don't go extinct on the mainland," said Shutler.  "And now, of course, there's concerns about them going extinct in Cape Breton, given the dramatic decrease we've seen in populations." 

More deer could mean fewer moose 

Airst said higher densities of deer often have higher rates of brain worm.

"The idea being that the two populations separate not because they directly compete for food, but … indirectly due to the parasite," said Airst.

It is the third year of data collection for the project that has surveyed a total of 221 deer, but more samples are needed to better understand the level of infection across Nova Scotia. The province accepts heads at any Department of Natural Resources and Renewables office during hunting season.

"Because we're looking for a parasite in the brain, we prefer if the animal was not shot in the head, and we prefer the animal is as fresh as possible if they're going to submit this to us," Airst said.

The annual roadkill survey as well as the deer cull in Truro contribute deer heads to the research.

"It would be nice if we had a more representative sample of the province and it would be nice if we got more representative numbers from areas that have lower deer densities," said Airst.