The Globe and Mail By Eric Atkins December 16, 2014
The honeybees responsible for pollinating one-third of the food we eat face a host of threats, from bloodsucking mites and viruses to pesticides and climate change.
But researchers at the University of Guelph have taken a big step toward fighting the most destructive and widespread killer of honeybee larvae, a disease known as American foulbrood.
For the first time, scientists have identified a toxin released by the pathogen, and come up with a drug that could stop the disease that is prevalent in North America, Europe and other parts of the world.
“What we’ve found is an important factor that we can inhibit in this honeybee disease,” said Rod Merrill, a Guelph biochemist and co-author of the study to be published in the December issue of the Journal of Biological Chemistry.
American foulbrood, named for the smell of infected hives and the country in which it was first identified more than a century ago, is spread easily among honeybee colonies by spores carried by adult bees. The spores are eaten by larvae, which die but also spread millions more spores into the hive.
“The next generation is kaput. It’s not toxic to the adults, but that ultimately destroys the hive,” Prof. Merrill said in an interview. “And then what happens is robber bees go into the hive and steal the honey, which is contaminated with the bacterial spores, and then they drag it over to their hive, so it just proliferates.”
Hives infected with the bacteria quickly fail, and beekeepers must burn the hive and all associated equipment to ensure the spores are destroyed.
There is no cure for American foulbrood. Antibiotics used to control the disease have proven ineffective as resistant strains have developed.
Field tests to be conducted on hives in the spring will show whether the drug is effective at controlling American foulbrood, said Prof. Merrill, who began the research more than two years ago.
The drug that could treat the disease is not an antibiotic, but an anti-virulence compound that controls the toxin that kills the larvae but does not prompt the bacteria to mutate by threatening their survival.
“Research takes a long time. So right at this moment I can’t say what the impact will be in treating American foulbrood,” Prof. Merrill said. “However, I can say it’s going in the right direction that we need to characterize the toxins produced by the organism that causes American foulbrood or the impending crisis for the honeybee is going to get worse.”
Long winters, virus-bearing varroa mites and pesticide exposure have contributed to declines in honeybee populations in North America and Europe. In Ontario, declining honey production and mounting costs of replacing dead bees have been blamed in part on neonicotinoid pesticides that are used to grow corn and soybeans.
In response, the Ontario government recently said it plans to impose rules that would reduce the use of the systemic pesticide by 80 per cent by 2017. Farmers who plant seeds treated with neonics would have to show their fields are susceptible to grubs, worms and other yield-destroying pests.
The move is opposed by the chemical companies that sell the pesticide-treated seeds and the Grain Farmers of Ontario, which says the restrictions will take away an important tool farmers use to protect their harvests.
A new poll of 1,000 Ontarians shows nearly 80 per cent support the provincial government’s plans to restrict the use of neonics, which scientists say impair bees’ foraging abilities and contribute to colony failure.
The poll, released by the Canadian Association of Physicians for the Environment, Friends of the Earth Canada and the Ontario Beekeepers’ Association, found support for the restrictions was strongest (85 per cent) in Southwestern Ontario, the heart of Canada’s corn-and-soybean region. Support was weakest, 60 per cent, in the central part of the province.
“Our food security depends on healthy pollinators,” said Gideon Forman of the Canadian Association of Physicians for the Environment. “Ontarians are aware of the current crisis and want the government to take action to protect bees.”