Zelonia australiensis under the microscope. Credit: The University of Technology Sydney
The discovery of an undocumented parasite in Northern Australia has shed light on the need for closer monitoring of exotic and neglected tropical diseases.
The study, which was led by researchers at the University of Technology Sydney (UTS), describes the newly discovered Zelonia australiensis in a species of black flies that share an evolutionary ancestor with the Leishmania group of “flesh-eating” parasites.
The research has shown the parasite is adaptable and has jumped between the distantly-related animals and spread over vast distances.
The disease is potentially deadly and affects humans and animals by sandfly bites.
The researchers said they’d like to now examine the potential for the establishment of exotic pathogens in Australia.
Joel Barratt, Ph.D., of the School of Life Sciences at UTS, said that while the parasite likely lacks the flesh-destroying capabilities of its relatives, the findings could lead to other breakthroughs.
“In conjunction with previous research, this study provides clues as to what these parasites are capable of,” Barratt said in a statement. “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,” he added. “The spread of malaria from Africa to Europe and the Americas is a prime example.”
According to the study, which was published in PLOS Neglected Tropical Diseases, Leishmania includes approximately 53 species, 20 of which causes leishmaniasis in human beings. It is still unknown when and where the disease first arose but respected theories suggest that it may have originated in the Palearctic and dispersed to the New World via the Bering land bridge. Another theory suggests that the disease originated in the Neotropics.
“The success of Leishmania species, the complexity of their dixenous life cycle, and the intricacy of their host-parasite interactions implies a relationship between host, parasite and vector that has evolved over millions of years, certainly predating the appearance of humankind,” the study states.
According to the study, the researchers were able to trap midges and flies at a specific location that is considered suitable for the isolation of other tropical trypanosomatids and would provide an opportunity to re-isolate the Australian Leishmania parasite.
The insects were then pooled and crushed with a spatula in a Phosphate buffered saline and the resulting suspension was used to inoculate a Leishmania culture medium.
According to Barratt, the research shows the need for local health authorities and researchers to pay more attention to neglected parasite diseases.
Leishmaniasis ranks second in global importance to malaria by the World Health Organization (WHO) in terms of parasitic diseases caused by protozoa.
The WHO lists climate change, urbanization and population mobility as major risk factors for the spread of the disease, primarily in some of the world’s poorest countries.
By taking an evolutionary perspective, Barratt said it will help recognize how adaptable life is and will allow scientists to mitigate future risks. Damien Stark, Ph.D., a co-investigator and microbiologist at St. Vincent’s Hospital in Sydney, said leishmaniasis cases have been on the rise in the past decade.
“With more international tourism and migration of refugees from endemic regions, leishmaniasis has emerged as an increasingly imported infection within Australia,” Stark said in a statement.
“So far no cases of local transmission have been reported and it was thought Australia lacked an insect vector that might be capable of transmitting Leishmania. Our research shows that may not be the case.”
