Image above: a bumblebee in a snapdragon blossom, a perfect fit.

While humanity has been struggling with the coronavirus pandemic since January 2020, bees have been infected with their own pandemic – a unicellular fungal pathogen known as Nosema – for the past two decades. This infection has been documented in such far flung places as Canada, Kenya and Europe and is causing the most common and widespread disease in adult honeybees.

The pathogen is also impacting solitary and native bees, and the extent is as yet unknown. A year ago we wrote a post, A Ghost in the Making, about how Nosema has brought the rusty-patched bumblebee to the brink of extinction.

This is equivalent to a bee pandemic, according to recent scientific studies.

Nosema is a fungal pathogen that infects the stomachs of bees, where it germinates and survives. Strains of nosema responsible for most infections in bees are Nosema ceranae which was identified from the Asian honeybee and causes year-round hive infections. So far only Nosema bombi has been documented in Colorado and it infects bumblebees. Nosema apis was the only unicellular honeybee pathogen known until 1996.

As the pathogen travels through the bee’s digestive tract it can make the bee ill and infect other cells in the bee’s body. It also then contaminates pollen, flowers and hives that come in contact with the sick bee.

Some available treatments are microbial supplements, natural plant extracts and breeding methods that build resistance.

Prior to these recent studies on solitary and native bees, the pathogen was almost exclusively known to infect European honeybees which are the most commercial pollinators.

This 3:15-minute video from Bee Health discusses and shows Nosema symptoms:



A spillover of these pathogens represents a massive threat to native bees. This can happen when infected honeybees from commercial hives leave the fungus on flowers and then native bees pick it up while foraging. Since native bees never encountered this pathogen before they could be highly susceptible to its negative effects.

This could also happen in reverse, where a new and more aggressive strain of Nosema mutates in native bees and can find its way into the commercial honeybee communities when they forage on contaminated flowers. They would have no resistance to the newer version of the pathogen.

Until now, research into the impact on solitary and native bee populations has been limited. Researchers believe it is critically important to understand how the Nosema strains travel around the globe and affect native and solitary bees, which represent the majority of all 20,000 bee species on the planet. These strains could create widespread bee colony problems and more bee pandemics. It can lower the sperm count of bumblebees which will reduce their reproduction over time.

There are even more far reaching implications. Ecologists worry about flowers as well as bees.

Arthur Grupe II, lead author and postdoctoral researcher in the Department of Ecology and Evolutionary Biology at University of Colorado, Boulder, says more research into understanding Nosema infections in native bee species needs to be undertaken to know if native bees suffer a similar fate to honeybees when infected, and also to evaluate the potential consequences to the native ecosystems.

Native bees are very important pollinators of local crops and ecosystems, and some flowers have only one type of bee or insect that is the right size and weight to pollinate them. If that species were to go extinct the flower would have to adapt quickly or die off. All bees are challenged in recent decades by monoculture, scarcity of quality nutrition, pesticide, pests, pathogens. Colony collapse disorder (CCD) is a phenomenon that happens when the majority of worker bees in a honeybee colony disappear and only leave behind a queen, food and some nurse bees to mind the remaining immature bees.

Flowers also act as a place where solitary bees meet mates, so if those flowers no longer exist, bees would have to adapt to a new way and place to find their reproductive partners.

According to study co-author and assistant professor of Ecology and Evolutionary Biology, Alisha Quandt, it is important that people do the necessary surveillance work, so we learn more about the biology of what is happening.

We depend on pollinators for every third bite of food we eat. It’s time for people to sample more native bees and get a good handle on their current health status.

The study was published in the journal PLOS PATHOGENS and is included for those who enjoy reading scientific studies.