Getting out of a "sticky situation" - how the Leishmania parasite is transmitted
Professor Paul Bates, Biomedical and Life Sciences
10.10 am
The leishmaniases are a collection of human tropical diseases that are caused by various species of Leishmania parasites. The World Health Organisation has estimated that 350 million people are at risk of infection with leishmaniasis, with 12 million infected at any one time. Some species cause relatively benign but disfiguring skin ulcers, whereas others can be lethal infections if not treated with drugs. The different types of leishmaniasis are all vector-borne, meaning that they are transmitted by the bites of blood feeding arthropods. In the case of leishmaniasis transmission is by female sand flies, small midge-like insects found widely in the tropics. Inside sand flies the parasites undergo a complex developmental cycle, but ultimately differentiate into human-infective forms that are transmitted by bite.
However, the parasite faces a problem, which is how to ensure it gets into the human host in the face of an incoming blood meal travelling in the opposite direction. The solution is that the parasites secrete a sticky gel-like substance called PSG, short for 'promastigote secretory gel'. PSG creates a physical obstruction in the sand fly gut, a so-called 'blocked fly'. These sand flies have great difficulty in blood feeding, in fact the only way they can succeed is to first regurgitate the PSG to remove the blockage. This has the simultaneous effect of regurgitating the parasites as well, thereby achieving transmission in a simple but elegant manner. This new understanding is crucial to our ongoing efforts to develop vaccines against leishmaniasis.
Biography
Paul Bates obtained his PhD in Molecular Parasitology from the MRC National Institute for Medical Research in 1984. He then spent three years as a Fogarty Research Fellow at the National Institutes of Health in Bethesda, USA, before moving to the University of Glasgow in 1988. After six years working on leishmaniasis in Glasgow as a Wellcome Trust-funded Lecturer and Royal Society of Edinburgh Research Fellow, he joined the Liverpool School of Tropical Medicine in 1993. In September 2009, Paul moved to Lancaster to take up a Chair in Biomedicine in the School of Health and Medicine, Division of Biomedical and Life Sciences.
His main research interests centre on the tropical disease leishmaniasis, in particular the life cycle biology of Leishmania, transmission of Leishmania by the sand fly vector and the molecular biology of sand flies.