Buruli ulcer (Mycobacterium ulcerans infection) is a destructive geographically restricted infection that affects skin and soft tissue. Australia is one of the only developed countries reporting significant local transmission but typically only in defined endemic areas. In Victoria, endemic regions are not geographically fixed and there has been a progressive westward advance of the endemic zone from the original Bairnsdale region, first to Westernport, then to Phillip Island and the Mornington Peninsula, and most recently to the Bellarine peninsula. The state-wide annual incidence of Buruli ulcer is approximately 1-2/100,000 but some endemic towns have experienced rates of up to 770/100,000 of the local population. Our research team has discovered that up to 50% of ringtail possums in Victorian endemic areas have PCR-positive faeces suggesting colonisation of their gastrointestinal tracts, and a proportion of these animals have clinically apparent Buruli ulcer. We now have 3 independent lines of evidence suggesting that mosquitoes may link humans to possums but lack definitive laboratory proof that mosquitoes act as vectors. In Queensland, in contrast to Victoria, the geographic range of the most endemic area north of Cairns has remained fixed since the 1950s, but the incidence in this zone varies markedly from a typical baseline of 3-5 cases per year to more than 60 in 2011. Although coastal Victoria and the tropical north are markedly different environments, we have recently found preliminary evidence of a potential marsupial reservoir in north Queensland analogous to colonised possums in Victoria.
paul.johnson@austin.org.au