San Diego, Calif., (March 21, 2018) – Honey bees are responsible for the annual pollination of at least $17 billion worth of US crops, but face severe health challenges. Nosema ceranaeis a fungus thatcauses a common and widespread infection that is associated with poor colony health and Colony Collapse Disorder. Currently, Nosema diseaseis primarily treated with a single antibiotic. Because of the potential for antibiotic resistance and the transfer of resistant genes in humans, it is desirable to find an alternative treatment, one that relies upon the natural honey bee immune system. Based upon data from bees reared in the lab, we found thatfeeding honey bee larvae heat-killed N. ceranaspores can activate honey bee immunity and substantially reduces infection levels when these “immunized” bees are exposed to Nosema as adult bees. The proposed research will test if this “immune-priming”, a vaccine-like treatment can also work (1) in naturally-reared honey bee larvae, (2)in beesimmunized as adults, and (3) in field tests of colonies. To test the effectiveness of our treatments, we will measureindividual bee infection level, the number of infected bees per treatment, bee immune gene activation, and effects on bee longevity.

OBJECTIVES: Honey bees are responsible for the annual pollination of at least $17 billion worth of US crops, but face severe health challenges. Nosema ceranaecauses a common and widespread infection that reduces honey bee health and is primarily treated with a single antibiotic. Activating insect immunity against fungal infectionsprovides a natural countermeasure that should be difficult for pathogens to evolve resistance against. This has been demonstrated with heat-killed bacteria, but it remains unclear if this strategy would work with a heat-killed fungal pathogen like Nosema cerana.In our preliminary data, we show that autoclaved N. ceranaespores fed to A. melliferalarvae reared in vitro (immune priming) and subsequently fed live Nosemaspores as adults have infection levels reduced by 85% upon adult death. The proposed research would test the efficacy of this immune priming treatmentin vivo and with field colonies. If successful, we will have developed a new treatment against N. ceranaeand created a potentallytransformative approach to treating honey bee fungal diseases. Specifically, we will determine if immune priming conveys protection against infection when administered in vivo to (1) larvae or (2) adults upon emergence. Based upon these results, we will test if (3) immune primingeither larvae or young adults in field colonies boosts colony immunity against Nosema infection. We will measure individual bee infection level (midgut spores/bee), number of infected bees per treatment, bee immune gene activation, and effects on bee longevity.Overall goal:We will test if immune priming activates honey bee immunity againstN. ceranaeand therefore decreases subsequent infection when bees are exposed toN. ceranae.Ourspecific objectivesare as follows. We will determine if immune priming conveys protection against infection when administeredin vivoto (1) larvae or (2) adults upon emergence. Based upon these results, we will test if (3) immune priming either larvae or young adults in field colonies boosts colony immunity againstNosemainfection. We will measure pathogen prevalence (proportion of infected bees per treatment), abundance (spore counts /bee), immune gene activation, and effects on longevity.

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