Increasing botulism deaths among Great Lakes waterfowl

According to the CBC, botulism deaths among Great Lakes Waterfowl are on the rise, and zebra mussels are implicated. According to Dr. Katherine Welch of the Canadian Cooperative Wildlife Health Centre at the University of Guelph, "the die-offs are becoming more common. We first saw them in the late 1990s. They're increasing in frequency and expanse over the last few years."

The die-offs affect fish-eating birds and scavengers. This creates concerns for the long term effects on populations of cormorants, ducks, loons, grebes and gulls. According to the article, in October, more than 500 loons were killed by botulism after eating infected fish. The disease paralyzes the birds, causing them to drown.

These large-scale bird deaths are due to invasive species such as zebra mussels and round gobies. The zebra mussels create a low-oxygen environment where the toxin can grow, then round gobies, a bottom-dwelling fish, eat the zebra mussels and the disease works its way up the food chain to birds.

Fish with the disease swim differently and make themselves more obvious targets to the birds, meaning that birds are more likely to eat infected fish and thus contract botulism.

There's little that can be done to stop the deaths. "Until there's some change in the ecosystem of the Great Lakes, it's going to be a problem," Welch said.