Researchers hope study of brain worms in deer could help endangered moose

Every time Willow Bennett receives a cooler with a frozen deer head inside, she gets a little bit excited.

But the truly fascinating part comes later, when she skins the head, opens the skull and examines the brain.

"It isn't for the faint of heart or the weak in the nose," Bennett says. "It definitely doesn't smell great — it is carcasses. So it is a little mental leap to get over that you are cutting and opening deer heads."

Bennett is looking for tiny, string-like parasites called brain worms or meningeal worms that can live in the thin layer between the brain and the skull of deer.

The Acadia University undergraduate biology student is researching the prevalence of brain worms in Nova Scotia white-tailed deer — something that hasn't been studied in decades.

While deer can usually live out their natural lives happily enough with a worm infection, the same is not true for mainland moose, an endangered species in Nova Scotia. The worms penetrate the brains of moose and cause severe neurological effects, paralysis, and eventually death.

"It turns the moose into a zombie. So they can go blind, they go in circles and get hit by cars, they just don't seem like themselves. And that's why they usually have to be euthanized," Bennett said.

By working on understanding the prevalence and distribution of brain worms in deer, Bennett hopes other researchers can use her work to bring in conservation measures to protect mainland moose from infection.

Bennett's research supervisor at Acadia, professor emeritus Dave Shutler, said any direct application to moose is "a long way down the road."

"I don't want to get ahead of us, but it's, you know, there is the potential that we might want to medicate moose to prevent them from succumbing to the worm."

It is estimated there are fewer than 1,000 mainland moose in Nova Scotia.

Infection cycle involves slugs and snails

In deer, the worms mate on top of the brain and lay eggs that make their way through the bloodstream to the lungs. Deer then cough up the larvae, which are expelled through feces. Snails and slugs are attracted to the algae on deer poop, and while they feed on the nutrients in the feces, they also pick up the larval stages of the worm.

Moose don't intentionally eat slugs and snails, but they can inadvertently consume them while feeding on vegetation, and if they ingest the larvae, the larvae can travel up the spinal cord to the brain, destroying nervous tissue along the way.

The deer heads Bennett is studying were gathered by the Department of Lands and Forestry from roadkill and hunters.

So far, she's examined 85 deer brains, and found worms in about 40 per cent of them, with an average of three to five worms in the affected brains. Bennett hopes to study another 80 to 100 brains this fall as hunting season gets underway.

In order to get better geographic representation, she is hoping to get more samples from Digby, Yarmouth, Kings, Antigonish, and Guysborough counties.

Bennett is also analyzing the brains for mercury levels and coronavirus infection to see if those stressors could be a factor in higher levels of brain worms.