The effect of diet on Apis mellifera larval susceptibility to Paenibacillus larvae

Abstract

Honey bees are threatened by changes in food resources. American Foulbrood (AFB), caused by Paenibacillus larvae,affects Apis mellifera larvae which progressively become more resistant to the disease with age. It has been suggestedthat nutritional limitations could result in increased susceptibility upon exposure to pathogens. This research, conductedon laboratory-reared honey bee larvae, aimed to analyze the effects of diet quality on the susceptibility of Apis melliferalarvae to P. larvae infections. The values of the lethal dose that killed 50% of the inoculated larvae (LD50) were determinedfor five strains of P. larvae (ERIC I). Virulence ranged from 2 spores/ll for the N15 strain to 906 spores/ll forthe Miramar strain. Different groups of larvae infected with half of the LD50 doses of P. larvae strains were fed Aupineldiet (with daily increases of glucose, fructose, yeast extract and royal jelly) and four different modifications thereof. Theresults show that the absence of a diet component tends to cause an increase in mortality associated with the infection,depending on the virulence of the strain and the component suppressed. Glucose and fructose suppression, and mainlyroyal jelly deprivation, affect larval susceptibility to AFB and their survival.