Leishmaniasis affects up to one million people annually – how can it be prevented?

Around 700,000 to one million new cases of leishmaniasis occur each year, often in areas where poverty, environmental disruption and weak health systems intersect.

Leishmaniasis is part of a group of diseases called ‘neglected tropical diseases’ that mainly affect vulnerable communities in tropical regions. These diseases have very limited resources available to research, prevent, treat and control them.

The true burden of leishmaniasis is poorly understood, and without increased and improved resources, it will continue to cause severe health, social and economic impacts.

Sandflies thrive in warm, humid climates and their habitats include rock crevices, caves, tree holes and people's homes. Sandflies bite from dusk to dawn. Biting can also occur during the day in dark rooms indoors or shaded outdoor spaces, especially if people disturb sandfly environments.

Several factors are driving leishmaniasis to spread to new places. For example:

• Climate change is expanding the range of sandflies. Rising temperatures and altered rainfall create ideal breeding conditions for sandflies. This has been linked to increased climatic suitability for leishmaniasis in Europe in the last two decades.
• Changes in land coverage can disrupt sandfly habitats and increase human exposure to insects. This includes urbanisation, making changes to vegetation, developing new farmland and using intensive agricultural practices.
• Extreme weather events, like floods and droughts, add to the problem. They weaken healthcare systems, making it harder to control the spread of the disease. They can also force people into conditions that increase their exposure to sandflies.
• Poor housing and domestic sanitary conditions due to poverty can create breeding and resting sites for sandflies, giving them easier access to humans. Crowded housing and homes with livestock in or nearby are also ideal spaces for sandflies.
• Epidemics can also occur when non-immune people move into areas with high leishmaniasis transmission. This has been seen during conflicts, such as the visceral leishmaniasis outbreaks in South Sudan and the cutaneous leishmaniasis outbreak in Syria.

While anyone exposed to infected sandflies can be affected by leishmaniasis, some are more at risk of disease, often individuals with weaker immune systems. This can include people living in poverty, children, elderly people and immunocompromised individuals.

Several strategies are needed to prevent and control leishmaniasis.

One example is case management. Early diagnosis and effective, prompt treatment is critical for disease control in most settings. It helps monitor the spread of disease and reduce transmission. However, existing diagnostics and treatments are limited.

Other key strategies include implementing:

• a strong surveillance system to detect outbreaks
• interventions to control leishmaniasis in reservoir hosts, such as dogs
• campaigns and activities to raise awareness and knowledge of the disease
• vector-control methods such as using insecticide-treated bed nets, insecticide spray and protective clothing

Leishmaniasis is curable, but treating it is challenging, particularly in low-income communities.

Existing treatments have several limitations and have largely remained the same since the 1940s. The available treatments are given mainly by injection and can require storage at a specific temperature. They can also have toxic side effects, variable efficacy, can require hospitalisation, and are often expensive.

Limited knowledge about the disease, including among healthcare workers, can lead to misdiagnosis. This can delay treatment and hinder control efforts.

Another challenge is the lack of access to effective treatments, often in countries with the highest disease burden. While the World Health Organization has made significant efforts to improve equitable access, more needs to be done to ensure treatments are available to the people who need them.

More funding, research and global collaboration are needed to better understand, monitor and respond to leishmaniasis. This should include advancing research to develop new tools and treatments, upskilling healthcare workers, and improving disease surveillance and healthcare systems. Additionally, there is a need for tailored prevention, diagnosis and treatment approaches based on factors such as the disease form, the sandfly and Leishmania species, the environment and more.

At Wellcome, we’re helping to reduce the burden of leishmaniasis by supporting the Drugs for Neglected Diseases initiative (DNDi) to develop safer, more affordable treatments. We’re supporting the development of new products to tackle neglected tropical diseases through strategic funding with the Global Health Innovative Technology Fund. We’re also exploring opportunities to fill key research gaps that will improve our understanding of the drivers of leishmaniasis and how to control it.

Through our work, we want to ensure that leishmaniasis receives the attention and resources needed to effectively treat it.

The World Health Organization has set two global targets for leishmaniasis for 2030. First, to eliminate visceral leishmaniasis as a public health problem by reducing the case-fatality rate to less than one percent. Second, to ensure 85% of all cases of cutaneous leishmaniasis are detected and reported, and 95% of reported cases are treated.

However, greater global investment and action are needed to achieve these goals and ensure that effective treatments are available to everyone.