Novel viral diversity and geographic structuring in the New Zealand West Coast blackfly (Austrosimulium ungulatum)

Abstract

Background Vector-borne diseases represent a major global public health burden, with climate change, land-use change and increasing human activity altering arthropod vector distributions and creating opportunities for infectious disease emergence. In Aotearoa New Zealand, insects commonly referred to as "sandflies" are blackflies belonging to the family Simuliidae. The West Coast blackfly, Austrosimulium ungulatum, is an endemic, human-biting species abundant throughout the South Island, yet its associated viral diversity remains largely unexplored. Methods Here, we used metatranscriptomic sequencing to characterise the virome of the West Coast blackfly and investigate patterns of viral diversity and community composition across geographical and environmental gradients. A total of 425 blackflies were collected from 19 locations spanning approximately 187 km. Results We identified 94 viral sequences across 16 orders and six phyla, all of which were putatively novel viruses. These included divergent lineages within families containing recognised vertebrate and arthropod pathogens, such as the Rhabdoviridae and Orthomyxoviridae. Viral community composition varied among sampling locations, but no significant associations were detected between land-use categories and viral diversity or community composition. In contrast, we revealed a weak but significant positive correlation between geographical distance and viral community dissimilarity, suggesting some degree of spatial structuring across the sampling range. Conclusions This study provides the first metatranscriptomic characterisation of the virome associated with the endemic West Coast blackfly, revealing substantial previously undescribed viral diversity and providing insights into the geographical distribution of arthropod-associated viral communities.