Australia as a global sink for the genetic diversity of avian influenza A virus.

Most of our understanding of the ecology and evolution of avian influenza A virus (AIV) in wild birds is derived from studies conducted in the northern hemisphere on waterfowl, with a substantial bias towards dabbling ducks. However, relevant environmental conditions and patterns of avian migration and reproduction are substantially different in the southern hemisphere. Through the sequencing and analysis of 333 unique AIV genomes collected from wild birds collected over 15 years we show that Australia is a global sink for AIV diversity and not integrally linked with the Eurasian gene pool. Rather, AIV are infrequently introduced to Australia, followed by decades of isolated circulation and eventual extinction. The number of co-circulating viral lineages varies per subtype. AIV haemagglutinin (HA) subtypes that are rarely identified at duck-centric study sites (H8-12) had more detected introductions and contemporary co-circulating lineages in Australia. Combined with a lack of duck migration beyond the Australian-Papuan region, these findings suggest introductions by long-distance migratory shorebirds. In addition, on the available data we found no evidence of directional or consistent patterns in virus movement across the Australian continent. This feature corresponds to patterns of bird movement, whereby waterfowl have nomadic and erratic rainfall-dependant distributions rather than consistent intra-continental migratory routes. Finally, we detected high levels of virus gene segment reassortment, with a high diversity of AIV genome constellations across years and locations. These data, in addition to those from other studies in Africa and South America, clearly show that patterns of AIV dynamics in the Southern Hemisphere are distinct from those in the temperate north.

Outbreak of skin nodules associated with Riouxgolvania beveridgei (Nematoda: Muspiceida) in the southern bentwing bat (Miniopterus schreibersii bassanii), South Australia.

In 2009, an outbreak of white nodular cutaneous lesions was detected in one of only two known breeding colonies of the critically endangered southern bentwing bat (Miniopterus schreibersii bassanii), at Naracoorte, South Australia. Necropsies were conducted on 10 euthanized bats in September 2009. In October 2009, 123 bats were examined under anesthesia, with skin biopsies collected from 18 affected bats. Prevalence of skin lesions was 45.2%. The prevalence among males was three times greater than among females. The majority of lesions examined histologically were granulomas, typically centered on a nematode. A single lesion had epidermal hyperplasia with intracytoplasmic inclusions consistent with a pox virus; pox virions were identified on electron microscopy. Nematodes dissected from frozen lesions were identified morphologically as Riouxgolvania beveridgei, previously described in the eastern bentwing bat (Miniopterus schreibersii oceanensis). The factors contributing to this apparent disease emergence and outbreak remain undetermined. Lesions consistent with white nose syndrome were not identified.