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Much of the explanation for the Kenyan bees' resilience may lie in different farm practices, researchers said.


Honeybees in East Africa Resist Deadly Pathogens

Bees in Kenya stay healthy despite parasites and viruses that collapse U.S. and European hives.

A surprising finding about East African honeybees lends new hope to the fight against colony collapses in the West. Scientists have discovered that bees in Kenya have strong resistance to the same pathogens responsible for the deaths of billions of bees elsewhere in the world. (See "Gold Dusters" in National Geographic magazine.)

Entomologist Elliud Muli, a beekeeping expert at the International Center for Insect Physiology and Ecology (ICIPE), teamed up with researchers at Penn State University to survey beehives in all of Kenya's major ecosystems: savanna, mountains, tropical coast, and desert. They measured the sizes of hives and the numbers of bees and tested them for parasites and pesticide contaminants.

In a paper published today in the online journal PLOS ONE, the researchers report that honeybees in Kenya are infested with the same nasty pests and diseases that wipe out hives elsewhere—but what's surprising is that they don't succumb. Hives remain healthy even where a combination of pathogens are present.

"That resilience—I was amazed by the lack of manifestation of ill health in the bees," says Muli.

Vanishing Bees in the West

In hives afflicted with colony collapse disorder (CCD), the name given to a mysterious condition that began killing U.S. honeybees in 2006, adult bees simply vanished from hives, leaving the queen behind. According to a report issued last year by the U.S. Department of Agriculture, since that time U.S. commercial beekeepers have lost some ten million hives and $2 billion.

Though some of that is due to normal wintertime attrition, the report said, CCD is thought to have at least doubled normal losses and in some cases wiped out more than 90 percent of hives. It was a particularly major threat to crops pollinated by bees trucked in by commercial keepers—especially almonds in California, which require the services of 60 percent of all hives in the U.S.

CCD had no smoking gun; scientists finally determined that no one pathogen or chemical or environmental problem was to blame. Instead, it was an onslaught of many factors, all of which continue to weaken and wipe out hives nearly a decade later. Varroa mites plague colonies throughout the Western world, and since invading the U.S. in 1987 have "caused hives to crash all over the place," says Penn State's Christina Grozinger, a coauthor of the Kenya study. The gut parasite Nosema is another menace. Beekeepers keep up a constant chemical battle to fight off these two killers but often lose. (See "The Plight of the Honeybee.")

Though many pesticides are deemed safe for use, components in them weaken bees' resilience, as do other chemicals applied to the crops they pollinate. Poor nutrition from a monoculture diet and the stress of being carted from state to state are factors. There are also viruses that join forces with parasites to knock the insects out. "It's now well accepted that our honeybees are dying because of the synergistic effects of multiple stressors on their immune systems," Grozinger says. "We have worn them down bit by bit until they can't take any more."

The "Africanized" honeybees (also known as killer bees for their aggressiveness) that have invaded the American Southwest have been reported to be more resilient to pests than other honeybees are. They come from stock brought in the late 1950s from Africa to Brazil that then hybridized with European bees—so they're not to be confused with the East African bees Muli, Grozinger, and their colleagues studied.

Into Africa

Muli and Penn State co-author Maryann Frazier first detected Varroa in Kenyan honeybees in 2009. Nosema hadn't been seen there before—but in the current study both pests proved prevalent in all but the most remote study areas surveyed.

"Finding Nosema at all was a big surprise, and finding out that Varroa was already so widespread—we didn't expect that, either," says Grozinger.

But the biggest surprise was a happy one. "When we did the analyses on how the pests were impacting colony health, we didn't see any significant effect," Grozinger says. Hives were fat with bees doing their jobs normally despite the pesky parasites.

Good Genes or Good Practices?

What explains the resilience of the East African bees? One source of it may lie somewhere in their genes, a possibility that, if true, could lead researchers to building a better bee for Western applications. "Finding those resistance mechanisms and trying to selectively breed for them, there's certainly a lot of interest in doing that," Grozinger says.

But she and her colleagues believe much of the explanation for the Kenyan bees' resilience lies in different farm practices. So far, African bees live relatively free of human input. The study found very low levels of just a few pesticides in Kenyan hives, when there were any at all.

Beekeeping in Kenya is typically a small-scale family affair done for honey; most crop pollination still relies on wild colonies. Bees colonize hollow logs and keepers mostly leave them alone, as is the traditional way.

And whereas in the West new hives are started with queen bees that are commercially produced and mailed to beekeepers, in Kenya "domesticated" bees come from natural swarms (with naturally existing queens) that have, naturally, split in two—meaning, Muli says, there was a healthy "mother hive" to begin with. He speculates that when bees leave a big hive to start anew, they may be breaking the development cycle of any mites that are present.

Most important, Muli adds, in Kenya "there's no manipulation of colonies, no renting out of bees, no colonies packed on trucks like sardines and shipped off for pollination purposes."

Back to Nature?

Sweeping changes by commercial farmers in the United States to "get back to nature," Kenyan-style, are unlikely. Still, improving bee health through practices that reduce chemical use and give bees access to diverse flowering plants can make a difference in the insects' health, Grozinger says. "There is more and more interest from farmers to maintain pollinator-friendly habitat on their lands," she says. "Diverse landscapes lead to more diverse pollinator populations, which leads to better crop pollination, which ultimately benefits farmers and consumers alike."

Kenyan beekeepers, meanwhile, should copy Western practices as little as possible, the study authors say, if they want to keep their hives healthy—and in particular refrain from treating them with pesticides even though Varroa and Nosema have crept in. For now, at least, "the wild Kenyan bees have their own resistance," Grozinger says. "It would be a mistake to mess with that."

The way beekeeping is done in the West, says Muli, "has eroded the genetic pool through commercial breeding of queens and propping up sick colonies through use of medication—colonies which would otherwise be long dead.

"For us, instead, it's survival for the fittest, and mother nature seems to be getting it right," he adds. "She's giving us a broad genetic pool of honeybees capable of dealing with any environmental shocks on their own."