Influence of virus abundances in donor colonies and nurse hives on queens of Apis mellifera during the rearing process

Abstract

Background: Honeybees are one of the three most important animals for mankind. In order to safe and increase numbers of bee colonies for pollination, breeding of queens is necessary. For several decades, bees were selected on economic and behavioral aspects. With the appearance of the neozootic mite Varroa destructor beekeepers were forced to adapt their methods. V. destructor can act as a vector for many different bee pathogenic viruses and by this potentiates its devastating impact. Aim: Methods of rearing queens were not evaluated since the mites’ appearance. Beside scientific approaches, viruses received too little attention in regard to the rearing process of honeybee queens. Herein, we present a detailed analysis of virus abundances (Aparavirus, ABPV; Triatovirus, BQCV; Cripavirus, CBPV; and Iflaviruses, DWV, SBV, VDV-1) in breeding hives, donating first instar larvae, hives that are nursing these larvae until the pupa stage, and on queens of A. mellifera in a breeding apiary. Methods: Nurse and donor colonies of the queen rearing process were sampled in the year 2020 and analyzed by RT qPCR. Virus quantifications were correlated with queen mortalities and seasonal effects. Results: Virus detections increased in reared queens, however, the elevated virus titers did not increase the mortality of the queens until their exclosure. Moreover, we observed a lower interrelation between virus abundance in queens and their original donor colonies, than between nurse hives and their nursed queens. Conclusion: The bee pathogenic viruses ABPV, BQCV, CBPV, DWV, SBV and VDV-1 do not influence the mortality of bee queens during the rearing process. Whether respective virus loads result in sublethal or long-term effects remain to be elucidated.