Australian parasite discovery raises concern about neglected tropical diseases

A chance encounter in northern Australia with a previously undocumented parasite has allowed scientists to join important evolutionary dots, highlighting the need for closer monitoring of exotic and neglected tropical diseases.

A study led by researchers at the University of Technology Sydney (UTS) describes for the first time a unique Australian parasite in native biting insects that shares an evolutionary ancestor with the Leishmania group of "flesh-eating" parasites. Zelonia australiensis is found in a species of black fly that bites humans and other mammals.

Research into the evolution of Leishmania has already shown this parasite is adaptable, has jumped between distantly related animals and spread over vast distances. The disease leishmaniasis is potentially deadly and affects humans and animals via sandfly bites.

These latest findings, published today in PLOS Neglected Tropical Diseases, raise questions about the potential for the establishment of exotic pathogens in Australia. Although human-infecting Leishmania species are not native to Australia, imported instances of leishmaniasis are being reported more frequently.

The lead author of the study, Dr Joel Barratt from the School of Life Sciences at UTS, said that while Zelonia probably lacks the flesh-destroying capabilities of its exotic cousins, the finding is significant.

"In conjunction with previous research, this study provides clues as to what these parasites are capable of. They have invaded new lands in the past, adapting to infect new species.

"This raises an important question: do human activities provide an increasing opportunity for human-infecting species to take up residence on Australian soil? We know this has happened for other parasites in various places. The spread of malaria from Africa to Europe and the Americas is a prime example."

Dr Barratt said the research highlights the need for local health authorities and researchers to pay more attention to neglected parasitic diseases.

World Health Organisation data ranks leishmaniasis as second in global importance to malaria in terms of parasitic diseases caused by protozoa. Currently, it affects some of the poorest people on the planet, but the WHO lists climate change, urbanisation and population mobility as major risk factors for the spread of the disease.