Mites as vectors for honey bee viruses

The European honey bee, Apis mellifera, is of great importance not only for the honey they produce, but also as vital pollinators of agricultural and horticultural crops. The economical value of pollination has been estimated to be several billion dollars, and pollinator declines are a global biodiversity threat. Hence, honey bee health has great impact on the economy, food production and biodiversity worldwide. A broad spectrum of pathogens affect the honey bee colony including bacteria, viruses, microscopic fungi, and internal and external parasites (i.e. mites). Hemophagous honey bee mites within the genuses Varroa and Tropilaelaps act as biological and mechanical vectors for certain honey bee viruses. Varroa destructor is currently considered the major threat for apiculture. The damage caused by this mite is thought to be a crucial driver for seasonal colony losses worldwide and V. destructor acts as a vector of several different honey bee viruses. Moreover, the global spread of V. destructor has resulted in a significant change in the relative prevalence of the different viruses in honey bee colonies. Different Tropilaelaps subspecies were originally described from the “giant” honey bee, Apis dorsata, but a host switch occurred to A. mellifera, for which infestations can rapidly lead to colony death. Tropilaelaps mercedesae causes severe damage to beekeeping with A. mellifera in China and recent studies have shown that also this mite can act as a biological vector for at least one of the honey bee viruses.