Native Bees are Also Struggling with their Own “Nosema” Pandemic
Sat, April 10, 2021

Native Bees are Also Struggling with their Own “Nosema” Pandemic



When the majority of the worker bees in a colony disappear and leave behind a few nurse bees to care for the queen and the remaining immature bees, Colony Collapse Disorder (CCD) happens. According to the US Environmental Protection Agency, this phenomenon poses a major long-term threat to bees. The beehive, which is an enclosed structure in which honey bee species raise their young and where the production of honey occurs, serves as an indicator of bee health. However, without worker bees, hives cannot sustain themselves, resulting in the loss of the bee colony.


Nosema infection in bees

Aside from CCD, a team of researchers from the University of Colorado at Boulder has found another threat for native bees: the Nosema fungal pathogen. This “pandemic,” as the researchers call it, has been infecting the native bee population around the world for the past two decades and continues to spread. Although a substantial number of studies have documented the Nosema infection across Canada, Kenya, and Europe, the bee pandemic has almost exclusively been observed in the European honeybee. Since honeybees play an important role in the pollination of commercial crops, the spread of the fungal pathogen can lead to reduced pollinator efficacy.

Their findings, which appeared in the journal PLOS Pathogens, show that almost nothing is known about the impact of Nosema pathogen on solitary bees that also make up approximately 20,000 bee species in the world.

Lead author Arthur Grupe II, who is also a postdoctoral researcher in the Department of Ecology and Evolutionary Biology, said via that more work needs to be done to better understand Nosema infections and their possible consequences to the ecosystems if native bees suffer the same situation when honeybees get infected. He added that native bees are incredibly important as they serve as pollinators in their local systems because honeybees are generally not found in these locations. Native bees likewise contribute to the pollination of crops in these places. Grupe highlights that one out of every three bites of the food people eat is due to a bee pollinator.

In the last 20 years, global bee populations, particularly honeybee hives, have been declining due to CCD. While researchers cannot pinpoint the singular cause behind the CCD phenomenon, bees as well as their colonies’ health are affected by the four Ps: pesticides, poor nutrition, pathogens, and pests.



The Nosema fungal pathogen: life cycle

The Nosema species belong to the spore-forming unicellular parasite called Microsporidia and are now recognized as a highly reduced lineage of fungi. It survives by infecting the cells in the midgut of bees. The moment the spore is ingested and it reaches the midgut, it will then germinate and inject its contents into the host cell. After that, it will reproduce and rupture the host cell to lay down spore walls. These spores then infect other cells in the digestive tract of bees or are passed out in the bees’ excrement, thus contaminating the floral resources and the nesting environment. If that happens, other bees also become susceptible to ingest the spores in the nest through fecal and oral transmission if at a floral resource if excreted.

Aside from the natural transmission of the fungal pathogen, commercial products like royal jelly, bee pollen, and honey can also be contaminated and these can disperse the pathogens.

The common symptoms of Nosema infection are microscopic lesions and dysentery within the Malpighian tubes and gut of the bees. This leads to host lethargy, frailty, and loss of workers that reduces the colony’s foraging ability. Some strains of Nosema lower the sperm count of bees and mutilate the male reproductive organs of bumblebees. This can negatively impact the ability of the next season’s queens to find new colonies.

Different strains, particularly Nosema ceranae and Nosema apis, are likewise appearing in new places, the authors added. The N. ceranae, which can remain dormant as a long-lived spore and is resistant to temperature, is causing year-round infection in hives and bees could flight it off seasonally.


Controlling the Nosema fungus

Grupe added that so far, Nosema bombi infections in the bumblebee population have been documented in Colorado, USA but the N. ceranae may also not be far behind. There are scientific advances when it comes to controlling the Nosema fungus. Some treatments include microbial supplements, breeding methods for resistance, and plant extracts. However, most studies in native bees have been focused only on DNA-based methods that test the presence of the pathogen in the bee and do not view it holistically in terms of how it can impact the bee’s population.

The authors believe that it is important for scientists to determine how these Nosema strains are transmitting around the globe and affecting the solitary bees as it could further the bee pandemic and lead to colony collapse.

According to Petpedia, an encyclopedia of Pets, there has been a 2.96 million decline in honeybee colonies in the past few years in the US alone. During winter last year, backyard beekeepers also lost 39.8% of their colonies. These numbers are very concerning because bees pollinate about three-quarters of vegetables, fruits, and nuts in the country.



Average winter loss per beekeeper

The average winter loss of backyard beekeepers (managed fewer than 50 colonies) stood at 41.6%, sideline beekeepers (managed between 51 and 500 colonies) at 33.6%, and commercial beekeepers (managed more than 500 colonies) at 27.7%. This is based on the National Management Survey by Bee Informed Partnership, a collaboration of leading research labs and universities in agricultural science.


Top beehive countries

India is the top beehive country with 13.04 million beehives followed by mainland China (9.04 million beehives), Turkey (7.94 million), Iran (6.60 million), Ethiopia (6.01 million), and the Russian Federation (3.18 million), according to database company Statista.

Since the CCD was detected, scientists from around the world have been working intensely to figure out the cause. Technologists have also been busy creating pollination methods to try to fill some of the gaps left by the bees that died or disappeared.

If bees continue to disappear in the environment, we humans would be left with little food sources at increasing prices. This is because the vast majority of plants we need for food rely on pollination, particularly from bees. Some plants would take time to grow while others simply die off without bees. They may be small in size but their importance should not be underestimated.