The oral vaccination with Paenibacillus larvae bacterin can decrease susceptibility to American Foulbrood infection in honey bees—A safety and efficacy study

Abstract

Pollination services to increase crop production are becoming more and more important, as we are facing both climate change and a growing world population. Both are predicted to impact food security worldwide. High-density, commercial beekeeping has become a key link in the food supply chain, and diseases have become a central issue in hive losses around the world. American Foulbrood (AFB) disease is a highly contagious bacterial brood disease in honey bees (Apis mellifera), leading to hive losses worldwide. The causative agent is the Gram+ bacterium Paenibacillus larvae, which is able to infect honey bee larvae during the first 3 days of their lives. It can be found in hives around the world with viable spores for decades. Antibiotics are largely ineffective in treating the disease as they are only efficient against the vegetative state. Once a hive shows the clinical manifestation of the disease, the only effective way to eradicate it and prevent the spread of the disease is by burning the hive, the equipment, and the colony. Because of its virulent nature and detrimental effects on honey bee colonies, AFB is classified as a notifiable disease worldwide. Effective, safe, and sustainable methods are needed to ensure the wellbeing of honey bee colonies. Even though insects lack antibodies, which are the main requisites for trans-generational immune priming (TGIP), they can prime their offspring against persisting pathogens. Here, we demonstrate an increased survival of infected honey bee larvae after their queen was vaccinated, compared to offspring of control queens (placebo vaccinated). These results indicate that TGIP in insects can be used to majorly enhance colony health, protect commercial pollinators from deadly diseases, and reduce high financial and material losses to beekeepers.Classificationbiological sciences, applied biological sciences

Trans-generational immune priming against American Foulbrood does not affect the performance of honeybee colonies

“…The treatment conditions in our study mimic queen transport but were arguably more controlled than the varied conditions that the queens might be exposed to during transport in the mail. Further, similar methods used in other studies have not resulted in significant queen failures (13,16). A likely reason for the queen failures then are problems during mating, such as bad weather conditions during mating or the drone quality.…”

“…To conclude, we could not find any significant trade-offs resulting from TGIP. These results have important practical applications, as TGIP has been recently suggested as a tool to fight infections by "vaccinating" honeybees against pathogens (16,30). Our results support the use of TGIP as a tool in fighting American Foulbrood.…”

“…Similarly mixed results have been found with bacterial pathogens. Recently a study found no evidence for TGIP in honeybees against a bacterial pathogen European Foulbrood (Melissococcus plutonius) with oral priming (15), while other studies have shown TGIP against other bacterial pathogens using either oral (16) or injection route of priming the honeybee queen (17).…”

“…Honeybees have been used as model species for TGIP in multiple studies (10,11,(13)(14)(15)(16)(17)30) and TGIP has been shown to be effective against one of the most devastating honeybee diseases worldwide, American Foulbrood (AFB), caused by the spore-producing bacterium Paenibacillus larvae (31). AFB infects honeybee larvae after an oral exposure, and infection requires the permeation of the peritrophic membrane in the gut (32).…”

American Foulbrood—Old and Always New Challenge

“…Dickel et al conducted the first experimental trials of an oral vaccination against AFB disease, which represents a new milestone in the management of bee and other insect diseases [ 72 ].…”