Mee, P. | Search bioRxiv

bioRxiv2024

Contrasting dynamics of two incursions of low pathogenicity avian influenza virus into Australia

The current panzootic of high pathogenicity avian influenza virus H5N1 demonstrates how viral incursions can have major ramifications for wildlife and domestic animals. Herein, we describe the recent incursion into Australia of two low pathogenicity avian influenza virus subtypes, H4 and H10, that exhibited contrasting evolutionary dynamics. Viruses detected from national surveillance and disease investigations between 2020-2022 revealed 27 genomes, 24 of which have at least one segment more closely related to Eurasian or North American avian influenza lineages than those already circulating in Australia. Phylogenetic analysis revealed that H4 viruses circulating in shorebirds represent a recent incursion from Asia that is distinct from those circulating concurrently in Australian waterfowl. Analysis of the internal segments further demonstrates exclusive, persistent circulation in shorebirds. This contrasts with H10, where a novel lineage has emerged in wild waterfowl, poultry and captive birds across Australia, and has likely replaced previously circulating H10 lineages through competitive exclusion. Elucidating different dynamics for avian influenza incursions supports effective disease risk identification and communication that better informs disease preparedness and response.

microbiology↗

bioRxiv2022

Urban population structure and local movement ecology of a native Australian mosquito involved in disease transmission

Dispersal is a critical factor in designing successful pest control measures as it determines the rate of movement across target control areas and influences the risk of human exposure to the species and its pathogens. Here we used a fine scale spatial population genomic approach to investigate the dispersal ecology and population structure of Aedes notoscriptus, an important disease transmitting mosquito, on the Mornington Peninsula near Melbourne, Australia. The species is suspected to be involved in the transmission of Mycobacterium ulcerans, the bacterium that causes Buruli ulcer, in this area. We sampled and reared Ae. notoscriptus eggs at two time points from 170 traps up to 5 km apart and generated genomic data from 240 individuals. We also produced a draft genome assembly from a laboratory colony established from mosquitoes sampled near the study area. We found low genetic structure (Fst) and high coancestry throughout the study region. Using genetic data to identify close kin dyads, we found that mosquitoes had moved distances of >1km within a generation, which is further than previously described for this species. A spatial autocorrelation analysis of genetic distances indicated genetic dissimilarity at >4 km separation, a fourfold higher distance than for a comparable population of the dengue mosquito, Ae. aegypti, from Cairns, Australia. These findings point to high mobility of Ae. notoscriptus, highlighting the challenges of localized intervention strategies targeting this species. Further sampling within the same area at two time points 6 and 12 months after initial sampling showed that egg counts were relatively consistent across time, and that spatial variation in egg counts covaried with spatial variation in Wrights neighbourhood size (NS). As NS increases linearly with population density, egg counts may be useful for estimating relative density in Ae. notoscriptus. The results highlight the importance of acquiring species-specific data when planning control measures.

ecology↗