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Interviewee: Michael Otterstatter, University of Toronto
Commercially raised bumblebees are often used to help pollinate crops in greenhouses. But when accidents happen, like when a truck transporting hives crashes on the highway or when air vents leading outside greenhouses are large enough, bees can escape captivity and mix with their wild cousins.
New research shows this can be a problem, because commercially bred bumblebees are not as healthy as those in the wild.
“We found that these bees harbored incredible loads of disease. So the same bees that are used in greenhouses are in fact very sick bees and carry many parasites that you don’t see at nearly the same level as wild populations.” says Michael Otterstatter.
Otterstatter is a bee researcher at the University of Toronto. Worried about the high level of infection in these bees and its possible impact on the wild population, he developed a mathematical model to predict how one specific parasite might spill over from commercial to wild bees. This parasite, called Crithidia bombi, not only makes bumblebees sick, it is also known to impair a bee’s ability to think and find food, which can lead to slow starvation. What’s worse, the parasite can prevent the birth of a new queen bee, jeopardizing the survival of the hive after the winter season. If this dangerous pathogen was being passed from commercial bee to wild bee, then the model should predict this transmission.
And, as Otterstatter states, “the model told us, given everything that we know about this system, that yes, spillover was indeed likely to happen.”
As they wrote in the online science journal PLoS One, Otterstatter and his team next collected wild bumblebees living near commercial greenhouses. They collected individual bees right outside the greenhouses, then proceeded to capture bees farther and farther out from these central locations. The greenhouses all housed sick bees, many of which could easily escape their enclosure through vents leading outside, a practice the researchers observed happening more than once.
Once the bees were returned to the lab, Otterstatter and his team tested the feces of the captured specimens in order to detect traces of the parasite. What they found was good news for their model but bad news for the bees. The lab tests backed the computer model. Wild bumblebees were getting sick from interacting with their domesticated neighbors. Far more sick than even the researchers had imagined.
“We had this amazing bubble of infection around the greenhouse where up to fifty percent of wild bumblebees would be infected”, says Otterstatter.
Though the rates of infection dropped dramatically as they moved away from the greenhouses, Otterstatter remains concerned. The parasite hasn’t spread very far from the greenhouses, but that doesn’t mean it can’t. His model also predicted that it would take very little to push this spillover into a full-fledged epidemic among the wild bumblebee population. The model made it clear that if pollinating season had lasted a few weeks longer, and diseases had just that extra time to move out from the greenhouses, the infection could have reached a tipping point.
As Otterstatter describes, “this is a wave of infection that would form at the greenhouse, and it would spread outward, away from the greenhouse into the wild bumblebee population, and it would infect a very large proportion of the wild bumblebee population, potentially up to 100 percent of the wild bumblebees.”
That sort of epidemic would be catastrophic for the survival of all bumblebee species, not to mention the damage it would inflict on the agricultural industry, which relies on pollinators such as bumblebees to service crops. Luckily, Otterstatter is nowhere near finished with his investigation into the plight of bumblebees. He is now studying how to block the spread of the parasite, and wants to encourage commercial bee breeders to keep their bees healthy from the start. That way, wild and domestic bumblebees can keep on buzzing.
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