Vaccinating the honeybees

By Asia Lie

Bees are one of the most essential creatures on our planet as one of the biggest pollinators of the world. More than 90% of the top 107 crops of the world are visited by bees, and although many food crops can self-pollinate or pollinate by wind, having diverse pollinators in the ecosystem is vital to food production.¹ Beyond pollination, they also provide honey and wax, and have been a part of human religion and iconography for hundreds of years.¹

For some context, bees live in organized family groups that consist of complex subpopulations working together for defense, labor, and reproduction. There are three main adult bee types: drones, workers, and the queen.² There is only one queen per colony, and she is responsible for reproduction by mating with drones: large, male bees who are tasked with mating with queens from other colonies.³ Worker bees care for her by supplying her food so she can lay her eggs, and the queen’s pheromones maintain the colony unity.² All workers are sexually undeveloped females, and they perform the labor of the colony: caring for the young and the queen, collecting pollen, and cleaning and guarding the hive.^2,3

Bee populations have been in marked decline in Europe and North America.¹ Honeybees are the easiest pollinators to “manage,” a word used to describe beekeeping and thus contribute to the 84% of European crops that depend on insect pollination.⁴ However, this decline in population has been noticed in both managed and wild bees. A number of causes could be contributing to this, including habitat changes, climate change, pesticides, and management practices.⁵ Another is disease, which this article focuses on.

American foulbrood (AFB) is a bacterial disease of honeybees that can weaken and kill bee colonies.⁶ It is caused by the bacterium Paenibacillus larvae and its spores can last for decades.⁷ Nurse bees (worker bees charged with caring for the eggs and larva) exposed to spores infect young larvae, where the bacterium multiplies in the gut and kills the larva, producing new spores. When house bees attempt to clean the dead remains, it can spread the spores across the colony, reaching the honey and other bees. From there, the hive can infect other colonies through the activity of robber bees, beekeepers, and drifting bees⁶, which are just three main methods of interacting with other colonies. 

It is estimated that around 25% of spore-producing colonies remain undetected, as symptoms appear late and the disease is largely visually undetected even if many spores are being produced.⁷ Because AFB is highly contagious and hard to detect, it has been easily spread by managed honeybee populations and industry in general,⁸ through contaminated equipment and general close interaction. Unfortunately, the most effective way of stopping the spread of AFB is to burn infected hives and bees⁹. 

To combat this, the world’s first honeybee vaccine has been approved in the US. Created by Dalan Animal Health, a biotech company, the vaccine contains inactive Paenibacillus larvae cells. The vaccine will be fed to worker bees that produce the royal jelly, which is consumed by the queen bee. Any developing larvae in the queen bee will then be immunized.¹⁰

Vaccines are typically used to prime the immune system of an animal to recognize and attack foreign particles if and when they are eventually introduced. This is done by introducing weakened or inactive particles.⁹ Often, they depend on antibodies, important parts of the immune system that recognize and confer memory of the particles they need to eliminate. This honeybee vaccine is unique in that insects do not have the antibodies that vaccines so often rely on.⁹Instead, insects have been shown to retain an ability to prime their immune systems by a phenomenon known as trans-generational immune priming.⁹ While many aspects of this phenomenon remain unknown, it has been discovered that the egg yolk protein Vitellogenin helps transfer information about diseases by carrying particles of bacteria or other disease agents.⁹

By orally introducing this vaccine to queen bees, the vaccine hopes to use the phenomenon of trans-generational immune priming to confer resistance to AFB to the queen’s larvae. Basically, it uses the parent to deliver a vaccine to the offspring. This development will hopefully have beneficial effects on honeybee colonies’ abilities to avoid infection, but it is still essential that studies continue to investigate how to protect a diverse range of pollinators from population decline. This vaccine is intended for beekeepers to supply to their hives, but will the vaccine also be able to protect wild bees? How can we administer it to wild bees without invasive intervention? What are the effects on the insect ecosystem as a whole and what might the consequences be if the technology does not produce the desired effect? 

The announcement of the world’s first honeybee vaccine is exciting and uplifting news as the decline of bee populations has been a growing issue for many years; however, it is essential that we continue working to understand insect interaction and behavior to figure out how to save a diverse range of pollinator species, including those in the wild.¹¹Because we depend so greatly on bees and pollinators, it is important we invest time and money into investigating why their populations are declining and how we can help stop it. The species of this world are all interconnected, so while focusing on the most convenient to us as humans makes sense, we can’t forget about the rest of them. 

References:

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