Mites in the genus Tropilaelaps (Acari: Laelapidae) are ectoparasites of the 
brood of honey bees (Apis spp.). Different Tropilaelaps subspecies were 
originally described from Apis dorsata, but a host switch occurred to the 
Western honey bee, Apis mellifera, for which infestations can rapidly lead to 
colony death. Tropilaelaps is hence considered more dangerous to A. mellifera 
than the parasitic mite Varroa destructor. Honey bees are also infected by many 
different viruses, some of them associated with and vectored by V. destructor. 
In recent years, deformed wing virus (DWV) has become the most prevalent virus 
infection in honey bees associated with V. destructor. DWV is distributed 
world-wide, and found wherever the Varroa mite is found, although low levels of 
the virus can also be found in Varroa free colonies. The Varroa mite transmits 
viral particles when feeding on the haemolymph of pupae or adult bees. Both the 
Tropilaelaps mite and the Varroa mite feed on honey bee brood, but no 
observations of DWV in Tropilaelaps have so far been reported. In this study, 
quantitative real-time RT-PCR was used to show the presence of DWV in infested 
brood and Tropilaelaps mercedesae mites collected in China, and to demonstrate a 
close quantitative association between mite-infested pupae of A. mellifera and 
DWV infections. Phylogenetic analysis of the DWV sequences recovered from 
matching pupae and mites revealed considerable DWV sequence heterogeneity and 
polymorphism. These polymorphisms appeared to be associated with the individual 
brood cell, rather than with a particular host.