Australian Leishmania lifecycle investigation

  • Annette Dougall

    Student thesis: Doctor of Philosophy (PhD) - CDU


    In 2003 an unknown Leishmania species was isolated as the cause of cutaneous lesions in red kangaroos (Macropus rufus) located in the Northern Territory. This was the first identification of natural Leishmania infection in Australia and the parasite was characterised as a unique species.

    The lifecycle of Leishmania typically involves a mammalian host and transmitting phlebotomine sand fly vector. This study aimed to investigate the lifecycle of Australian Leishmania by incriminating both a vector and reservoir of the parasite.

    Traditional methods for Leishmania diagnosis were utilized in the investigation including in vitro culture, cytology, histology, and serology, as well as the development of a new specific Australian Leishmania real-time PCR. Native marsupials commonly found in the Darwin rural area were opportunistically sampled and screened for Leishmania. Serology and real-time PCR assisted in determining the parasite's geographic range and its natural mammalian hosts. New clinical cases of cutaneous leishmaniasis were identified and characterised in northern wallaroos (M robustus woodwardii), a black wallaroo (M bernardus) and agile wallabies (M agilis). Overall, antilopine wallaroos (M antilopinus) and agile wallabies presented with high exposure and tolerance to the parasite, implicating them as reservoirs.

    To incriminate a vector, phlebotomine sand fly trapping was undertaken in two hot spot areas of known transmission and were subsequently screened for Leishmania. No association between Leishmania and sand flies was found. Subsequently, alternative vectors present in the Darwin rural area were investigated for infection giving startling results. For the first time, evidence linking the day-feeding midge, genus Forcipomyia, subgenus Lasiohelea as the biological vector of Leishmania is presented. This finding will have massive implications in the understanding of the Leishmania lifecycle worldwide.

    Elucidating the complete lifecycle of Leishmania in Australia is vital to predicting the effects of an exotic introduction or an endemic expansion of the parasite. This knowledge is fundamental for ongoing disease surveillance and Australian biosecurity.
    Date of AwardJan 2010
    Original languageEnglish
    SupervisorShelley Walton (Supervisor) & Deborah Holt (Supervisor)

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