<em>Varroa destructor</em>: A Complex Parasite, Crippling Honeybees Worldwide

Abstract

The parasitic mite, Varroa destructor, has shaken the beekeeping and pollination industries since its spread from its native host, the Asian honeybee (Apis cerana), to the na&amp;iuml;ve European honeybee (A. mellifera) used commercially for pollination and honey production around the globe. Varroa is the greatest threat to honeybee health. Worrying observations include increasing acaricide resistance in the varroa population and sinking economic treatment thresholds, suggesting that the mites or their vectored viruses are becoming more virulent. Highly infested weak colonies, popularly dubbed &amp;ldquo;mite bombs&amp;rdquo;, facilitate mite dispersal and disease transmission to stronger and healthier colonies. Here, we review recent developments in the biology, pathology and management of varroa, and unearth old knowledge that was lost in the archives.

The first steps toward a global pandemic: Reconstructing the demographic history of parasite host switches in its native range

“…All Varroa mites (including families) clustered within diverse known haplogroups, i.e., mitochondrial lineages (4), with the exception of a newly described haplogroup (VJ Lombok 2) ( Figure S1 and Table S3). The haplogroup distribution observed in this study was consistent with the geographical origin reported for reference sequences used for comparison (4). Table S3).…”

“…One of the most dramatic and economically important switches involved the two ectoparasitic mite species, Varroa destructor and Varroa jacobsoni, which acquired the western honey bee (Apis mellifera) as a new host, ~70 and ~12 years ago, respectively (2,3). V. destructor, in particular, spread worldwide, causing extensive honey bee population collapses, whereas V. jacobsoni has so far remained in Oceania (4,5). Both mites were originally found on the sister species, Apis cerana, and came into contact with A. mellifera, which was brought in for purposes of beekeeping (6,7).…”

Bee Viruses: Routes of Infection in Hymenoptera

“…The developmental stage and tissues targeted by these viruses will be important for both their transmission strategy and their effects on the host. Mechanical and biological virus vectors can breach the anatomical and physiological host barriers to virus transmission, with potentially drastic consequences for host health, virus virulence evolution, and applied vector-virus virulence management (Traynor et al, 2020). Also important in virus transmission, as recently reported by Wang et al (2020) using a metabolomics-based approach, is the occurrence of diametrically opposite changes during virus infection of cells of different species origin, and we believe this phenomenon is possibly related to the type of infection (acute or persistent) that is triggered by the virus.…”

“…Another possible transmission route between non-Apis bees are parasitoids, parasites and commensals living in, on or with the host bee or its nest structures. Neither V. destructor, the highly potent vector of honey bee viruses in A. mellifera (Traynor et al, 2020) nor similar virus-transmitting mites parasitizing Apis bees in Asia (Forsgren et al, 2009, etc. see above in section "Vector-Mediated Transmission" in: Transmission of Viruses in Apis mellifera) parasitize non-Apis bees.…”

Characterization of Varroa destructor Mites in Cuba Using Mitochondrial and Nuclear Markers

“…At the colony level, low levels of infestation by V. destructor give rise to undetectable symptoms, but an increase in the number of mites leads to a progressive decrease in the number of bees (Fries et al, 2003). Eighteen haplotypes of V. destructor were described by Navajas et al (2010) based on 2700 base pairs of the mitochondrial genome, and recently a few more were described by Traynor et al (2020). From this wide variety, only two haplogroups successfully parasitize A. mellifera.…”