A project undertaken at the School of Life and Environmental Sciences, The University of Sydney, and supervised by Emily Remnant
The Western honey bee Apis mellifera is host to a range of diverse viruses, which under normal conditions rarely cause overt disease. Varroa mites began to parasitise A. mellifera during the 1950s, and have since spread to nearly all managed honeybee colonies globally. The spread of Varroa has led to widespread colony losses due to virulent viruses that Varroa transmits to bees, which has changed the honey bee viral landscape. Few opportunities exist to observe changing viral dynamics in honey bees during the early stage of Varroa invasion. A recent incursion of Varroa into Fiji in 2018 has provided an opportunity to survey honey bee virus dynamics at the forefront of invasion, and explore how mites affect the viral landscape of a Varroa-naïve bee population.
Hive inspection in Nadi, Fiji (Credit: John Roberts)
We confirm the likely origin of the Varroa jacobsoni mites in the Fiji incursion to be Papua New Guinea, based on their mitochondrial genotype of the invasive mites and their ability to parasitise the honey bee species present in Fiji (Apis mellifera).
Dr John Roberts (right) briefs staff from the Biosecurity Authority of Fiji prior to a hive inspection.
We observe a diverse viral landscape in the Fiji population of honey bees. Honey bees that are free from Varroa have lower virus levels overall, in line with predictions that Varroa increases virus levels. The viral landscape of Varroa-free honeybees in Fiji was dominated by Lake Sinai Virus (LSV), a virus which is not associated with disease, and we find evidence that LSV is displaced by the more virulent Sacbrood virus by the arrival of Varroa. We do not observe evidence of two major pathogens, Deformed wing virus and Slow bee paralysis virus, in the Fiji populations. These viruses are a common consequence of Varroa infestation elsewhere in the world, indicating that the situation in Fiji is novel compared to other Varroa incursions. We identify eight novel viruses present in Fijian bees that are not currently associated with Varroa, however we recommend monitoring these viruses over time as new associations with mites could establish.
Dr John Roberts (centre right) with staff from the Biosecurity Authority of Fiji at Nadi Airport (Credit: Patrick Cape)
The Fiji incursion provides a novel opportunity to survey honeybee virus dynamics at the forefront of early invasion and explore how mites affect the viral landscape of a Varroa-naïve bee population. As Australia contends with our first major incursion of Varroa destructor, identified in Newcastle, NSW in June 2022, our research in Fiji could inform the potential scenarios that might occur in Australia should Varroa become established.