CU Boulder entomologist studies how to protect nature’s most important pollinators from deadly parasites

Samuel Ramsey, an assistant professor of evolutionary biology at the University of Colorado Boulder, is renowned for his expertise and effervescent enthusiasm for everything related to bugs. He's made a cicada music video on his “Doctor Buggs” YouTube channel and appeared on CBS Mornings to warn the public about spotted lanternflies, a destructive invasive species.

But perhaps Ramsey’s most important contribution to science has been his groundbreaking research on deadly parasites causing a steep decline in the honey bee population. Through his public appearances and nonprofit, the Ramsey Research Foundation, he’s also raising awareness about how we can change our international response to help nature’s most important pollinators survive.

The importance of bees to life on Earth can’t be overestimated. Through pollination, they help sustain the life cycles of wildlife habitats and produce one-third of the global food supply, including apples, coffee, nuts and potatoes.

“With the sheer number of people and the amount of food that we want to grow on a regular basis, it requires us to dramatically increase the efficiency of agricultural systems, and that is what honey bees are built for,” Ramsey says. “It’s important for how we do life.”

Studying a deadly parasite

Ramsey made his first splash in the scientific community when he was a doctoral candidate at the University of Maryland, where he researched the deadly bee parasite Varroa destructor. Entomologists had long held that Varroa fed on bees’ blood, but Ramsey realized that this picture of Varroa’s feeding habits was incomplete.

“My path to studying honey bees is a bit circuitous because I became obsessed with the Varroa mites before I became obsessed with honey bees,” Ramsey says. “Part of what drew me to them was the fascinating history of how they got here and how they became such a dominating parasite on this planet.”

When Ramsey finished his dissertation, he presented a new picture of Varroa: Imagine a tick as large as a Frisbee lodged onto your body, transmitting crippling viruses; but instead of sucking your blood, it dissolves and feasts on your liver. This is what the Varroa destructor mite does to honey bees, and the mites have spread from Southeast Asia to the rest of the globe in a matter of just decades.

“There was a time where Varroa was restricted to just a tiny region of the world. But there was a host shift several decades ago when people started sharing brood from Apis cerana (the Eastern honey bee) with Apis mellifera (the Western honey bee) to make the Western honey bee colonies “stronger” in the area, Ramsey says.

“Southeast Asia is the only region of the world where every single honey bee species exists. That's the cradle of civilization for them, except for the Western honey bee, which was brought back in” by humans, Ramsey explains. When the Western honey bee branched off and evolved outside of Southeast Asia, “they lost a lot of their parasite suppression genes.”

The Western honey bee now lives on every continent except Antarctica as a domesticated insect. “And so now Varroa, as of last year, fully has a cosmopolitan distribution by having finally reached Australia,” Ramsey says. The losses have been devastating: Last year, North America lost 48% of its honey bees, with Varroa as the main driving force.

Ramsey’s discovery of Varroa’s food source being bees’ fat body tissue, and not their blood, helped generate a new understanding of how Varroa thrives across the globe, which could chart new paths to protecting Western honey bees.

A new mite emerges

Since his dissertation, Ramsey’s research has shifted to a new parasite threatening Varroa’s global dominance over bees—one that is even faster and more efficient in invading colonies and reproducing its species: Tropilaelaps.

Like Varroa, Tropilaelaps was originally contained in Southeast Asia until it jumped hosts from the giant honey bees to Western honey bees. It emerged later than Varroa and is currently spreading around the planet in a similar pattern.

“The possibility that Tropilaelaps can take over is quite substantial,” Ramsey says. “While honey bee losses for some countries they’ve entered were around 2% or 4% per year, those losses have now gone up higher than 64%. That is really devastating for the beekeeping industry, economy and ecology of those areas.”

Although Tropilaelaps poses a new threat to the global honey bee population, many nations have shown reluctance to tracking its spread.

“No one wants to be blamed for Tropi mites going from their country to another. So, for some of these regions, it has been difficult to convince people to do proper reporting of whether those parasites have been in their borders. They might not be able to trade bees and bee products freely to other countries because of the concern,” Ramsey says. “There are geopolitical concerns that are all pulled into that.”

Another major obstacle to international research has been the hesitance of wealthier nations to invest resources in other countries to study and manage the transmission of Tropilaelaps.

“So little research was conducted on this organism when it was transiting through what we call ‘developing nations,’ which is not my favorite term in the world, because these organisms were not impacting major economies,” Ramsey says. “Unfortunately, that particular way of looking at things reduces people down to just their GDP. It doesn’t account for the importance of those human beings, their livestock and their bees.”

When Tropilaelaps reached Pakistan about three decades ago, the country experienced a 100% loss of its western honey bee population. “We have ignored it knowing it has the capacity to do that kind of damage,” Ramsey said at the 2023 American Beekeeping Federation Conference.

Making research progress

Despite these challenges to international research on Tropilaelaps, Ramsey and other entomologists have made recent headway in conducting research on the mite in Thailand. With donations to the Ramsey Research Foundation, Ramsey was able to fund his investigation into the behaviors of Tropilaelaps inside highly protective honey bee brood cells. This work is currently in review for publication. 

“Inside the colony, there are these hexagonal cells that can be used to either store food or store the developing bees,” Ramsey says. “Nurse bees will create a wax covering over the cells when their larva reaches a certain age and starts to transition towards being a pupa. It’s at that time that Tropi mites are able to smell the age of the immature bees and jump into the cell.”

Once inside the wax-sealed cells, mites are protected “from basically everything,” including pesticides and the adult bees themselves. “I quickly realized anything that won’t penetrate that wax capping is not going to be effective at controlling those mites,” Ramsey says.

“So we started looking at different forms of treatments that could penetrate the capping and go after them, Ramsey says, adding that in the United States, a substance called formic acid has been shown to reduce the mite’s population substantially.

Ramsey and other scientists have been experimenting with other possible treatments that include applying heat to the brood cells to control Tropilaelaps. “It could potentially be a promising nonchemical means of treating this set of organisms,” Ramsey says. “We’ll have to see more data.”

Learning pandemic lessons

Although Ramsey thinks the international response has been timid in solving the growing crisis, perhaps some lessons have been learned from the COVID-19 pandemic.

“When COVID-19 hit, I think it laid bare just how unprepared many of us have been for something like this,” Ramsey says. “So, thankfully, groups like the United States Department of Agriculture APHIS (Animal & Plant Health Inspection Service) and National Geographic have partnered with me, noticing that I have a lot of passionate for this subject and optimism that we can win this time! I’ve already built out infrastructure in my research apparatus in Southeast Asia to study these things, so all the pieces are there.”

Those partnerships support research about these organisms and contribute data to emergency response plans, Ramsey says. “We’ve picked up the pace and I think before the Tropi mites arrive, we will have a solid emergency response plan in place.”

Much remains unknown about Tropilaelaps, but Ramsey is currently raising funds through his Fight the Mite Initiative to conduct more research on the parasite across the globe. The Ramsey Research Foundation shares critical data with experts and the public alike to help stop this mighty mite.

“We are working really hard to make sure the general public has greater access to this kind of information,” Ramsey says. “(I try) to do everything I can to make sure that I’m holding the door for others.”

“It is my sincere hope that as we try to make research more broadly available, as we try to find funds to build up these communities, more and more of the general public will be behind us in these initiatives and provide their support whenever possible.”

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Ramsey is the Marvin H. Caruthers Endowed Chair for Early Career Faculty at CU Boulder. You can learn more about his research and initiatives at the Ramsey Research Foundation.