Queen mandibular pheromone suppresses early nosema infection
The honey bee disease caused by the microsporidian Nosema (Vairimorpha) ceranae is the most widespread intestinal disease affecting adult worker bees worldwide (Chen et al., 2008; Fries, 2010).
The article describes fumagillin as the only antibiotic approved to control nosema disease on the US market, while noting restrictions in most countries, particularly in Europe, because of concerns about harmful residues in bee products. Unfortunately, fumagillin is less effective against N. ceranae than against the long-established pathogen Nosema apis. Its toxicity to bees and pathogen resurgence further limit its use (Huang et al., 2013). This has prompted research into alternative treatments, without consistent practical results.
Field studies (Botías et al., 2012; Simeunovic et al., 2014) found that queen replacement suppressed the pathogen to a degree similar to fumagillin treatment, with queen age significantly influencing infection.
Surprisingly, the effects of queen pheromone, or synthetic QMP commercially available since 1997, on nosema disease in caged bees and field colonies remain largely unexplored, despite occasional use of QMP in disease studies (Cho et al., 2022; Huntsman et al., 2021). We therefore conducted a controlled cage study, infecting bees with serial doses of purified N. ceranae spores in the presence or absence of synthetic QMP. Our results indicate that QMP inhibits infection in terms of both infection incidence and disease development.
Infection rates and intensity: caged bees exposed to queen mandibular pheromone (QMP) had significantly lower infection rates than “queenless” bees not exposed to the pheromone. In the QMP group inoculated with 312.5 spores through serial dilution, qPCR detected infection in only three of the 56 inoculated bees.
Queen mandibular pheromone (QMP) can therefore be concluded to exert significant suppressive effects on nosema disease development. The study highlights that these effects are stronger during the early stages of disease, when lower infectious inoculum doses are involved. The effects appear to diminish as the infectious dose increases. Higher doses with a 12-day incubation period also produced nonsignificant effects in a preliminary study. Although the underlying biological mechanisms remain unclear, the results support earlier field observations and underline the importance of maintaining an adequate circulating level of queen pheromone within the hive, recalling that young, high-performing queens raised and selected by professional breeders are central to this aim.
Adapted from the short communication The effects of queen mandibular pheromone on Nosema (Vairimorpha) ceranae infections in caged honey bees — Wei-Fone Huang, Ama Safo-Mensa, Evan Palmer-Young, Jay D. Evans, Yanping Chen
Available online 20 July 2024, Journal of Invertebrate Pathology
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