During the summer and fall of 2012, more than 1,500 documented loons washed ashore in northern Lake Michigan, dead from avian botulism.
Brenda Moraska Lafrancois, regional aquatic ecologist with the National Park Service, is working with a host of other partners – universities in Michigan and Wisconsin, the U.S. Fish and Wildlife Service, Petoskey's Tip of the Mitt Watershed Council, Departments of Natural Resources for Michigan and Minnesota, as well as many others – to study the avian botulism outbreaks.
But they have to rely on testing the shoreline where they suspect the botulism toxin is present, and less on experimenting with the toxin in the lab.
That's because the toxin and the bacteria that produces it is restricted by the Centers for Disease Control's National Select Agent Registry. Researchers can have only half a milligram of the toxin in their labs at any time, and cannot culture the bacteria at all.
An indirect measurement
Researchers work around the restriction by looking for the presence of genes from the Clostridium cells in lake sediments, decaying algae, in invertebrates and in fish.
"We know that toxin production occurs only if there's lots and lots of these cells. And it's strongly linked to water temperature," said Lafrancois, who is based in Ashland, Wis. "And we could investigate what happens when there's certain kinds of nutrients available."
But basically, researchers are relegated to looking for genes in lake water, around where they suspect botulism outbreaks have occurred, or in organisms, such as zebra or quagga mussels.
"We're doing that, and doing that successfully, and we're increasingly able to link the number of cells to different kinds of conditions. But it's always going to be an indirect measurement, when it would be more preferable to look at things directly," said Lafrancois
"That's informative, but that's not measuring the toxin, and there's just a lot of variability in the environment. If you measure a couple feet over, you might get a different sample or result."
Wind, air temperature, water temperature, lake currents – these all can affect sampling. Too, all of those factors – particularly temperature and the presence of rotting plant vegetation or nutrients from agricultural run-off – can impact the botulinum toxin production.
"If we could study this in a lab setting, we could control for all of those factors," said Lafrancois.
Testing the environment
In addition to testing for the bacteria gene, researchers are developing a more efficient way to detect the botulism toxins in dead animals.
Researcher David Blehert, a microbiologist with the U.S. Geological Survey's National Wildlife Health Center in Madison, says studying where the toxin outbreaks occur will help solve how birds ingest the toxin. But the test researchers use now to detect the botulism toxin is clunky.
Scientists first spin down blood taken from a bird suspected to have died of botulism in order to separate blood cells from the serum they float in. They use the serum to conduct the test, for which they use three mice, said MDNR's Tom Cooley.
One mouse is a control, and gets injected with the serum. The second mouse gets the serum plus an antitoxin for type E botulism. The third mouse gets the serum and an antitoxin for type C botulism.