Transmission

In the peri- and post-elimination settings, a strong kala-azar surveillance framework will be required to measure ongoing transmission and ensure outbreaks do not occur. Molecular xenomonitoring involves detecting pathogen DNA or RNA in vectors. It has been used successfully to assess elimination endpoints for lymphatic filariasis in several countries, but requires technical development for kala-azar. 

Xenomonitoring for kala-azar requires a polymerase chain reaction assay to detect Leishmania donovani in Phlebotomus argentipes sandflies collected from areas where kala-azar transmission has been a concern. There are many advantage to this approach in that it is a less-invasive, ethically acceptable and potentially more cost-effective method of monitoring transmission in elimination settings than surveying human populations.

SPEAK India xenomonitoring studies commenced in June 2018 in Bihar and are a collaboration between researchers at the Rajendra Memorial Research Institute of Medical Sciences and the London School of Hygiene and Tropical Medicine. Main project objectives are to:

1. Determine the optimal framework for surveillance of P. argentipes 
2. Optimise a metacyclic-specific PCR assay for L. donovani RNA in P. argentipes to determine infectiousness of field-caught sandflies
3. Evaluate the cost-effectiveness, feasibility, and scalability of xenomonitoring as a surveillance tool
4. Analyse field and molecular data to inform modelling of transmission dynamics. 

Subramanian et al. 2020. 'Molecular xenomonitoring as a post-MDA surveillance tool for global programme to eliminate lymphatic filariasis: Field validation in an evaluation unit in India'. PLoS NTD 14(1): e0007862.

Poché et al. 2018. 'Bionomics of Phlebotomies argentines in villages in Bihar, India with insights into efficacy of IRS-based control measures'. PLoS NTD 12(1): e0006168.

Subramanian et al. 2017. 'Application of a household-based molecular xenomonitoring strategy to evaluate the lymphatic filariasis elimination program in Tamil Nadu, India'. PLoS NTD 11(4): e0005519.

Cameron et al. 2016. 'Understanding the Transmission Dynamics of Leishmania Donovani to Provide Robust Evidence for Interventions to Eliminate Visceral Leishmaniasis in Bihar, India'. Parasites & Vectors 9:25.

Rao et al. 2016. ‘Programmatic use of molecular xenomonitoring at the level of evaluation units to assess persistence of lymphatic filariasis in Sri Lanka’. PLoS NTD 10(5): e0004722.

Lau et al. 2016. ‘Lymphatic filariasis elimination in American Samoa: evaluation of molecular xenomonitoring as a surveillance tool in the endgame’. PLoS NTD 10(11): e0005108.

Tiwary et al. 2012. 'Prevalence of sand flies and Leishmania donovani infection in a natural population of female Phlebotomus argentipes in Bihar State, India'. Vector Borne Zoonotic Diseases, 12(6): 467-472.

LSHTM

Prof Mary Cameron

Ms Shannon McIntyre

Dr Miguella Mark-Carew

Dr Matthew Rogers

Ms Giorgia Dalla Libera Marchiori

RMRI

Dr Pradeep Das

Dr Vijay Kumar

Dr Vikram Pal Gandhi

Kundan Kumar

Ratnesh Kumar

Mukesh Kumar

Mukesh Kumar

Rahul Keshri

London School of Hygiene and Tropical Medicine (LSHTM)

Rajendra Memorial Research Institute of Medical Sciences (RMRI)

Bill and Melinda Gates Foundation (BMGF)