Implications of co-infection of Leptomonas in visceral leishmaniasis in India.

Protozoan parasites Leishmania donovani (family: Trypanosomatidae) cause fatal visceral leishmaniasis (VL) and the infection relapses in apparently cured population as post kala-azar dermal leishmaniasis (PKDL) in the Indian subcontinent. In recent years co-infection of another Trypanosomatid parasite Leptomonas with L. donovani during VL/PKDL in this region has become prominent. The observation of clinically lesser-known insect parasite, Leptomonas in leishmaniasis is intriguing to researchers. The presence of Leishmania look alike Leptomonas in the cultures of clinical isolates of Leishmania has been worrisome to those, who prefer to work with pure Leishmania cultures for drug and vaccine development or immune response studies. The exact implications of such a co-habitation, which might lead to a delay in the diagnostics of VL and elevate mortality, need a thorough investigation. Also whether Leptomonas is involved in leishmaniasis manifestation needs to be ascertained. Thus we are currently witnessing a new paradigm of a parasitic co-infection in VL/PKDL cases in India and this review outlines various opportunities for further research in understanding such emerging co-infection.