Giorgia Dalla Libera Marchiori
Giorgia Dalla Libera M. is a research assistant and 1st year PhD student at the London School of Hygiene and Tropical Medicine (LSHTM), studying Phlebotomus argentipes sand flies infected with Leishmania donovani parasites in Bihar (India) in order to develop a new surveillance method for Visceral Leishmaniasis.
“Phlebotomus argentipes is a very long name for a very tiny fly, not much bigger than the tip of a needle. However, never underestimate small insects. Like mosquitos, a sand fly, P. argentipes’ common name, can carry in its belly organisms that cause a very dangerous human disease. In fact, sand flies can be infected with leishmania parasites. When an infected sand fly bites a human being the parasites are regurgitated into the bloodstream and start their journey inside the new host.
In India, P. argentipes can be parasitized by Leishmania donovani, one of the specie of leishmania that causes Visceral Leishmaniasis (VL), also called Kala-Azar. VL is the clinical manifestation of infection and propagation of leishmania parasites in the human host. Differently from cutaneous leishmaniasis, where the parasite infection causes visible skin lesions, in VL the parasites affect the internal organs, colonazing spleen, liver and bone marrow. If not treated, the risk of death is close to 100%.
Great progress in fighting VL has been made in the Indian subcontinent in the last decades, with target of elimination (set, by WHO, as less than 1 new case in 10’000 people annually) closer than ever before. However, having less cases does not mean the parasite disappeared. It has become just harder now to track its movements inside a population. Therefore, we cannot relay anymore on a surveillance system that uses just human cases to map the pattern of transmission and predict outbreaks. Facing this new challenge arising from the drop in number of new cases, our group at LSHTM, led by Professor Mary Cameron, decided to explore a different approach: using P. argentipes, the vector, as the core of a new surveillance method. Using a molecular technique called RT-qPCR, we can differentiate between not infected sand flies, infected ones and, most importantly, infectious ones, which are the sand flies ‘ready to transmit’ parasites to humans. Once I receive the sand flies collected in villages in Bihar, one of the Indian North-Eastern states, (work done by my colleague Shannon McIntyre) my job is to analyse each one of them to spot the ‘ready to transmit’ ones. This method has the potential to identify the areas where human infections are more likely to happen and, with the support of mathematical models, make us understand transmission dynamics and outbreaks susceptibility.”