According to a paper in Frontiers in Veterinary Science in October 2022, an oral vaccination study in honeybees “constitutes a turning point” in insect disease management. The collaboration between European and American researchers investigated the safety and efficacy of a vaccination against American Foulbrood infection in honeybees. They report the “first-ever successful randomised placebo-controlled double-blinded trial using a classical vaccination approach to protect honeybees against a disease”.
AFB
American Foulbrood is a fatal bacterial disease that the study describes as “highly contagious”. It is caused by the spore forming Paenibacillus larvae and can infect bee larvae in the first 3 days of life. The Scottish government describes the spores as “resistant to extremes of temperature, chemical attack, and other adverse conditions”. Spores are transported by worker bees into a hive.
“Because of its virulent nature and detrimental effects on honeybee colonies, AFB is classified as a notifiable disease worldwide”.
The only effective means of treating the disease targets the vegetative state. Therefore, by the time a hive presents a clinical manifestation eradication is essential. Furthermore, the “growing concern” of AMR and antibiotic contamination means the use of antibiotics is “under growing scrutiny”. In the EU there is a zero-tolerance policy for antibiotic use in honeybee management. Unfortunately, this means the solution is burning the hive, equipment, and colony.
The bee all and end all
The study describes beekeeping as pivotal in the food supply chain, particularly as climate change and growing populations weaken food security. “Managed” bees, kept at “high densities”, are essential in functioning ecosystems and productive livestock.
“While honeybees are the most economically valuable pollinators, they are threatened by a variety of pathogens. Yet, safe and effective prophylactic solutions for disease prevention are lacking.”
Insects do not produce antibodies, but they can “prime” their offspring against “persisting pathogens”. They transfer pathogen knowledge in a mysterious “phenomenon” known as transgenerational immune priming (TGIP). Research on honeybees has revealed that this knowledge can be inherited with the “help” of the protein Vitellogenin, carrying immune elicitors. However, this is not the only way that insects prepare their offspring to face diseases. Transferal of “other signals, such as mRNA and proteins as well as epigenetic factors” has been suggested. The more that is understood about these processes, the more we can develop effective preventative strategies for disease management.
The trial
Previous research has proven that larvae can be protected from infections when the queens were injected with a “heat-killed P. larvae bacteria of the same strain”. However, with “limitations” and health implications for the queens, it is not the ideal method. As oral infection is the “natural way of infection” for many bacterial pathogens, other researchers have used similar methods in the past.
“Oral administration of an inactivated AFB bacterin to the queen bees is safe and induces protection in the next generation larvae.”
Two trials were carried out in different locations. The first was in Austria, using Apis mellifera carnica, and the second in Spain, using Apis mellifera iberiensis. Only hives that had enough larvae (30 in each) were enrolled. The queens, from local queen breeders, were “probably related but not sister queens”.
The researchers derived bacterin preparation from a strain that was isolated in 2018. It was a “proprietary aqueous suspension of inactivated P. larvae vegetative stage bacilli” and passed purity testing. It was then blended with “queen feed”, comprising 48 ml corn syrup per 500g powdered sugar, at a ratio of 1ml per 100g. The queens were vaccinated for 8 days and then released into hives.
Making a buzz
The results suggest an increase in disease resistance of up to 50% in the laboratory. Data indicate that the “innate immune response in insects” is enough to “decrease spore count” to “significant effect”. The authors call for further trials, but might this be a step towards more effective and efficient disease management? A future with “enhance[d] colony health” and safer pollinators would have myriad benefits.
To hear data from exciting new trials and learn more about vaccination come to the World Vaccine Congress in Washington 2023.
