Lethal infection thresholds of Paenibacillus larvae for honeybee drone and worker larvae (Apis mellifera)

• Published in: Environmental microbiology Vol. 12; no. 10; pp. 2838 - 2845
• Main Authors: Behrens, Dieter, Forsgren, Eva, Fries, Ingemar, Moritz, Robin F.A
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.10.2010; Blackwell Publishing Ltd
• Subjects: Animal and Dairy Science; Animals; Apis mellifera; Bacterial Load; Bees - microbiology; Body Size; Female; Husdjursvetenskap; Larva - microbiology; Lethal Dose 50; Male; Microbiology; Mikrobiologi; Paenibacillus - pathogenicity; Paenibacillus larvae
• ISSN: 1462-2912; 1462-2920; 1462-2920
• DOI: 10.1111/j.1462-2920.2010.02257.x

We compared the mortality of honeybee (Apis mellifera) drone and worker larvae from a single queen under controlled in vitro conditions following infection with Paenibacillus larvae, a bacterium causing the brood disease American Foulbrood (AFB). We also determined absolute P. larvae cell numbers and lethal titres in deceased individuals of both sexes up to 8 days post infection using quantitative real-time PCR (qPCR). Our results show that in drones the onset of infection induced mortality is delayed by 1 day, the cumulative mortality is reduced by 10% and P. larvae cell numbers are higher than in worker larvae. Since differences in bacterial cell titres between sexes can be explained by differences in body size, larval size appears to be a key parameter for a lethal threshold in AFB tolerance. Both means and variances for lethal thresholds are similar for drone and worker larvae suggesting that drone resistance phenotypes resemble those of related workers.