Preprint maps antiviral RNAi responses across Varroa mite life stages and finds evidence of vertical virus transmission

A preprint deposited on bioRxiv describes research into the antiviral RNA interference (RNAi) responses of Varroa destructor, the ectoparasitic mite regarded as one of the most serious threats to managed honey bee colonies worldwide. RNAi is the primary antiviral defence mechanism in invertebrates, and in other insects actively replicating viruses are degraded into 20–22 nucleotide virus-derived small interfering RNAs (vsiRNAs) of both sense and antisense polarity.

The researchers report that established viral infections in V. destructor produce a distinct 24-nucleotide antisense vsiRNA population, differing from the canonical insect pattern and suggesting mite-specific mechanisms of viral RNA processing. By profiling these small RNA signatures across multiple mite life stages, the team was able to infer both primary (active replication) and secondary (established) antiviral responses, providing a framework for studying infection dynamics without requiring direct virus quantification at each stage.

Critically, the data support vertical transmission of viruses through V. destructor — meaning viruses can be passed from one mite generation to the next, independently of honey bees. This has implications for understanding how bee-infecting viruses persist and spread in mite populations, and potentially for apiary management strategies that rely on mite control to reduce viral load in colonies.

This work is a preprint and has not yet been peer-reviewed. The findings should be regarded as preliminary pending independent evaluation.