A Review of Preventative Methods against Human Leishmaniasis Infection

Abstract

Background

Leishmaniasis is an intracellular parasitic infection transmitted to humans via the sandfly. Approximately 350 million people are at risk of contracting the disease and an estimated 1.6 million new cases occur annually. Of the two main forms, visceral and cutaneous, the visceral form is fatal in 85–90% of untreated cases.

Aims

This literature review aims to identify and evaluate the current evidence base for the use of various preventative methods against human leishmaniasis.

Methods

A literature search was performed of the relevant database repositories for primary research conforming to a priori inclusion and exclusion criteria.

Results

A total of 84 controlled studies investigating 12 outcome measures were identified, implementing four broad categories of preventative interventions: animal reservoir control, vector population control, human reservoir control and a category for multiple concurrently implemented interventions. The primary studies investigated a heterogeneous mix of outcome measures using a range of different methods.

Conclusions

This review highlights an absence of research measuring human-specific outcomes (35% of the total) across all intervention categories. The apparent inability of study findings to be generalizable across different geographic locations, points towards gaps in knowledge regarding the biology of transmission of Leishmania in different settings. More research is needed which investigates human infection as the primary outcome measure as opposed to intermediate surrogate markers, with a focus on developing a human vaccine.

Author Summary

Leishmaniasis is a vector-borne parasite infection, transmitted to humans by sandflies. It is estimated to cause 1.6 million new cases of disease annually. Of the two main forms, so-called “visceral” and “cutaneous”, the visceral form is fatal in 85–90% of untreated cases. This literature review provides a comprehensive summary of all the available evidence relating to the impact of interventions against infection on the burden of leishmaniasis in people and highlights the absence of high quality evidence demonstrating an effect. Four broad categories of preventative interventions are identified, investigating a range of strategies, from protection of humans against infection, to interventions aimed one stage upstream of human infection (targeting the sandfly vector), and even further, to interventions targeting animal reservoir species. Based on the current lack of understanding of the dynamics of transmission of Leishmania, we conclude that scant resources might be best directed toward prevention of human infections, with a focus on development of a human vaccine.