Leptospirosis is recognised by WHO, FAO and OIE as an important re-emerging zoonotic disease. A 1999 outbreak in northern Queensland with 160 cases notified for Cairns, Innisfail/Tully and the Tablelands highlighted the increased significance of leptospirosis in public health (Queensland Health 2002). The highest incidence of leptospirosis was in banana industry workers with 30.6 % in 2004, 25% of all notifications in 2003, and 17.9% in 2001 (Queensland Health data).
Furthermore, the recent emergence of a new serovar in Australia has potentially significant consequences for future human and animal health. Serovar Arborea has been reported in 61 human cases since 2001. There have been 15 isolations from two rodent species, Mus domesticus and Rattus rattus (Smythe, unpublished data).
In a recent survey of terrestrial mammals in the banana-farming Tully region in north Queensland (Rivera 2005), native rodents were identified as the carriers of pathogenic Leptospira. The findings by Smythe et al. (2002) also suggest a previously unrecognised role of flying foxes (Pteropus spp) in the ecology of leptospirosis, including the transmission of leptospira to other species residing under flying fox roosts, and an endemic leptospiral infection in flying foxes.
Leptospiral serovars have been isolated from bats in Indonesia (Alston and Broom 1958) and leptospiral antibodies have been identified in the spectacled flying fox (P. conspicillatus) (Emanual et al. 1964). Leptospiral antibodies have also been identified in long-tongued fruit bats (Sycnycteris crassa), fruit bats (Dobsonia moluccensis) and in P. temmicki on the Molucca Islands in Indonesia (Van Peenen et al. 1971).
The potential for flying foxes to introduce new exotic leptospiral serovars from Indonesia into Australia is supported by the recent identification of the previously regarded exotic L. interrogans serovar Cynopteri in flying foxes in northern Australia (Smythe et al. 2002) and more recently, Rivera (2005) identified antibodies against Cynopteri in a serum sample of a bush rat (Rattus fuscipes) that was captured near banana farms in North Queensland where flying foxes were found.
Using real time PCR, Cox et al (2006) confirmed the presence of DNA of pathogenic Leptospira in the kidney and urine samples of four species of pteropid bats in Australia, indicating the bats are hosts of pathogenic Leptospira spp. and shed leptospires into the environment.
Flying foxes may be an unidentified carrier, facilitating the spread and maintenance of leptospiral populations to rodents and then onto humans. They may also provide a pathway for the introduction of exotic serovars (Smythe et al. 2002) . Further research is required to determine the pathogenic leptospiral serovars carried by flying foxes, the role of flying foxes in the transmission of leptospira organisms to other animal species and to humans, and factors affecting the prevalence of leptospirosis such as seasons, locations, population abundance and other characteristics.