NTDs

Counselling in Kenya

Neglected tropical diseases are a medically diverse group of infections caused by a variety of pathogens including viruses, bacteria, protozoa and helminths. The 17 neglected tropical diseases prioritized by WHO are estimated to affect more than 1 billion people worldwide and are endemic in 149 countries.

Why NTDs?

Until recently, NTDs saw little attention from all but a small handful of dedicated supporters. In January 2012, a varied set of partners came together in London under the banner of Uniting to Combat NTDs to discuss the importance of attaining the WHO 2020 goals for neglected tropical diseases. This coalition of pharmaceutical companies, donor groups, implementing partners, national NTD programs and other supportive partners demonstrated their commitment to meeting the goals for 10 of 17 NTDs through the signing of the London Declaration. Since then, they have been collaboratively working together to address the neglected disease burden of in some of the world’s hardest to reach areas.

2014 saw the Bill & Melinda Gates Foundation pledge their continued support to control or eliminate NTDs high on the international research agenda, at a forum held at the Institute Pasteur, Paris in April. Partners to the 2012 declaration pledged to maintain the momentum for the 2020 goals. Driving new treatment innovations and developing new tools and strategies to successfully interrupt the tranmission of Visceral Leishmaniasis was high on this agenda.

Current challenges in Visceral Leishmaniasis

  • Visceral leishmaniasis, also known as kala-azar, is the second largest parasitic killer in the world. Transmitted via sandflies carrying the leishmania parasite, the disease is characterized by fever, weight loss, swelling of the spleen and liver, and anaemia. If left untreated, the fatality rate in developing countries can be as high as 100% within 2 years.
  • Post-kala-azar dermal leishmaniasis (PKDL) also plays an important role in maintaining and contributing to onward transmission of the disease, acting as an asymptomatic reservoir for parasites.
  • Current control strategies for VL involve wide-scale indoor residual spraying (IRS) as well as mass screen and treat programmes. Part of these disease control programmes are two key forms of surveillance – passive and active case-detection or searches. Active case search is an essential component of the VL elimination strategy on the Indian subcontinent, helping to reduce disease transmission by shortening the infectious period of patients.

Why diagnostics are essential in VL control strategies

As these control strategies transition from wide-scale to focal IRS, the criteria and threshold for when and how to change programme strategy is being considered, as well as the role mass screen and treat programmes will play. A robust surveillance system with appropriate diagnostics technologies is an essential component of this.

Currently, the most effective diagnostic tests for leishmaniasis are invasive and potentially dangerous, where tissue samples are required from the spleen, lymph nodes, or bone marrow. These tests require lab facilities and specialists not readily available in resource-poor, endemic areas.

Dipstick testing, while more easily and commonly used, only establishes whether a patient is immune to kala azar based on presence of the parasite. However, it cannot be used to distinguish between past infection, re-infection, or relapse.

The Diagnostics Modelling Consortium exercise aims to identify the product profile for field-based diagnostics which are best suited for IRS and case-finding strategies.

Project Methodology

The exercise is based around analysis of existing VL models and data available from ongoing VL programmes in Bihar, India. A critical part of the exercise is to conduct a landscaping of existing VL models and gaps that can be addressed with emerging data.  Key issues being addressed include: 

  • What is the role of asymptomatic cases in transmission, particularly across the clinical spectrum of post-kalazar dermal leishmaniasis (PKDL)?
  • What is the profile of care seeking behaviour as related to incubation period and disease progression?

Key Research Questions

The primary research question aims to address "What product profile for a field-based diagnostic is needed to ensure the success of indoor residual spraying (IRS) and mass screen-and-treat (MSAT) strategies to reduce and interrupt transmission for visceral leishmaniasis?"

Other secondary questions include:

  • To what extent is transmission sustained by asymptomatic infections?
  • Given different scenarios for (1), what profile of diagnostic is needed to interrupt transmission?
  • How does this differ to a passive case reporting and reactive treatment strategy?
  • Does the diagnostic product profile vary by transmission setting or stage of the program?

 

 

Key people: 
Dr Christine Rousseau
Prof Azra Ghani
Dr Sophie Allauzen
Dr Deirdre Hollingsworth
Dr Emily Adams
Dr Kat Rock
Dr Sake de Vlas
Dr Epke de Rütte
Dr Daniel Bontje
Dr Lance Gordon
Dr Sandra Laney
Dr Julie Jacobson
Mr Aryc Mosher