2.3 Developing and evaluating new tools to study Leishmania transmission from sandflies

Area of research: Prevention
Research programme: Translational Science

Objectives:

(1) to develop a metacyclic-specific qPCR to detect Phebotomus argentipes sandflies infectious for Leishmania;

(2) to develop a transgenic parasite whose presence can be detected through bioluminescence-fluorescence imaging in infected sandflies and mice and used to study parasite transmission and dissemination dynamics in mice.

 

Expected results:

A novel long-term, non-invasive and low-cost surveillance system will be developed to identify hot-spots of Leishmania donovani transmission and collect data for better understanding of transmission field dynamics and prediction of possible outbreaks. The same approach can potentially extend to other vectors of disease, such as Anopheline mosquitoes.

At the same time, the bioluminescence-fluorescence imaging will elucidate parasite-host transmission dynamics providing important information regarding parasites dissemination inside mammalian host.

Summary:

Background: Visceral Leishmaniasis (VL), in India also known as kala-azar, is a neglected vector-borne disease that affects some of the poorest communities in the world. The target for elimination of VL (i.e. incidence below 1 case per 10,000 people), is 2020 on the Indian subcontinent. While areas such as Nepal and Bangladesh have achieved the goal already, others, such as the district of Bihar in India, have not. With such a variable situation between areas and with the incidence decreasing making the target of elimination quickly achievable, there is the urgent need of developing and establishing new methods that allow a better understanding of Leishmania transmission dynamics at both population and single-host level.

Methodology

The project will use molecular methods to investigate transmission at two different level: (a) spatial distribution of infected sandflies in Bihar (India), and (b) dissemination of parasites in mammalian host after infection.

a) RT-qPCR analysis will be used to quantify the expression of sherp gene expressed in infective metacyclic inside the vector;

b) A genetically modified Leishmania parasite will be developed using a bioluminescence-fluorescence dual reporter. Successful reporter transfection and integration will allow parasites visualization, through live-imaging, in live sandflies, mice and mouse tissues at high sensitivity (potentially locating as few as 100 parasites in a live mouse and even a single parasite at the organ level).