Sandflies and Disease: What You Need to Know About Leishmaniasis Risk
"Uncover the changing patterns of sandfly distribution and the rising threat of leishmaniasis in urban environments."
Leishmaniasis is a parasitic disease transmitted by sandflies, posing a significant health risk in many parts of the world. In Brazil, American Visceral Leishmaniasis (AVL) is a growing concern, with the sandfly Lutzomyia longipalpis identified as the primary vector. This disease, traditionally associated with rural environments, is increasingly found in urban areas, altering its transmission patterns and raising new challenges for public health.
A recent study in Barra do Garças, Mato Grosso, Brazil, sheds light on this changing landscape. Researchers investigated the sandfly population in urban neighborhoods, examining the influence of environmental factors on the density of L. longipalpis. Their findings reveal important insights into the adaptation of sandflies to urban settings and the factors driving the spread of leishmaniasis.
This article will explore the key findings of the study, explaining the implications for public health and what individuals can do to minimize their risk of exposure. Understanding the changing ecology of sandflies is crucial for effective prevention and control efforts.
Leishmaniasis and Its Global Scope
Leishmaniasis is caused by Leishmania parasites and transmitted by sandflies, with the disease affecting mainly poor regions, according to WHO. More than 20 Leishmania species are known to infect humans, and infected female phlebotomine sandflies transmit them. WHO identifies visceral leishmaniasis, also called kala-azar, as the most serious form and cutaneous leishmaniasis as the most common. PAHO reports that it developed the Regional Leishmaniasis Information System, SisLeish, in 2012 to consolidate information and support surveillance, risk-area identification, and analysis.
Vector Control: Established Limits and Emerging Tools
Traditional insecticide-based approaches to controlling sand flies are not always effective and can harm the environment, according to a 2025 review. That review examines biological and genetic control approaches, including sterile insect techniques, in which sterilized male sand flies are released to reduce populations. It also summarizes approaches reported to have succeeded under laboratory and field conditions and considers how they might be incorporated into integrated vector management as an alternative sustainable strategy. A 2024 review separately describes progress toward paratransgenic control of Leishmania through microbial studies in sand flies.
Tracing Leishmaniasis Through History
A 2017 historical review traces the genus Leishmania to the Mesozoic era and discusses its subsequent geographical distribution. It also surveys evidence of the disease in ancient times and early accounts of infection in the Middle Ages. The review follows the later discovery of Leishmania parasites as the causative agents of leishmaniasis. A separate overview notes that understanding evolutionary relationships between sandflies and Leishmania is important for forecasting transmission patterns and informing management.
Urbanization and the Rise of Sandfly Vectors
The study in Barra do Garças revealed a diverse sandfly population, with L. longipalpis being the most prevalent species. This is concerning because L. longipalpis is a known vector of Leishmania infantum chagasi, the parasite responsible for AVL. The presence of this vector in urban areas indicates a shift from the disease's traditional sylvatic (wildlife) cycle to a peridomestic (around the home) transmission pattern.
- Environmental changes: Deforestation, urbanization, and agricultural expansion alter natural habitats, forcing sandflies to adapt to new environments.
- Poor sanitation: Accumulation of organic matter, such as decaying leaves and animal waste, provides breeding grounds for sandflies.
- Presence of domestic animals: Dogs, chickens, and other domestic animals serve as blood sources for sandflies and can maintain the parasite's life cycle in urban areas.
- Climate factors: The study found a correlation between rainfall and L. longipalpis density, with higher sandfly populations observed during the rainy season due to increased humidity and vegetation cover.
Surveillance and Vector Monitoring in Recent Studies
A study titled “Environment-based strategy for monitoring early colonization of Lutzomyia longipalpis at the city scale” reports a scoping review of environmental, social, and biotic variables associated with vector occurrence or abundance, prioritizing variables suitable for operational use. An updated investigation of visceral leishmaniasis in Mato Grosso recorded 30 human cases from 2019 to 2021 across 16 municipalities. The investigation also reports that earlier studies and its findings indicate the disease occurs in different biomes in the state.
Resistance and Gaps in Vector Knowledge
WHO published two guidance documents in 2023, including a report on determining insecticide concentrations for monitoring resistance in sand flies. This reflects a practical challenge for control programs: insecticide resistance needs to be monitored. A 2026 review of Leishmania–sand fly interactions identifies gaps and limitations in current knowledge and calls for more comprehensive, systematic studies of how vector–parasite interactions affect transmission and control. Leishmaniasis is transmitted by infected female sand flies, and its different forms affect people in different ways, with skin sores common in the most common form, according to CDC.
Protecting Yourself and Your Community
The findings from Barra do Garças highlight the importance of understanding the changing dynamics of leishmaniasis transmission. As sandflies adapt to urban environments, preventive measures must be tailored to address the specific risks in these settings.
What Military Studies Can Add
A 2025 systematic review and meta-analysis focuses on leishmaniasis among military personnel deployed to endemic regions. It examines infection rates, regional variation, and the effectiveness of preventive measures. The review identifies knowledge gaps relevant to reducing sand-fly exposure and Leishmania transmission during deployments. Its findings are specific to military populations, a group the sources describe as exposed while serving in endemic areas.
A One Health and Neglected-Disease Perspective
A 2025 One Health review classifies leishmaniasis as a neglected tropical disease caused by Leishmania protozoa. Infected female phlebotomine sandflies can transmit the parasites to humans and other animals. The review describes cutaneous leishmaniasis as causing ulcers and scars, while visceral leishmaniasis is systemic and can lead to life-threatening disease. This framing places the disease in both human and animal health contexts.
Here are some steps you can take to protect yourself and your community:
<ul> <li><b>Maintain good sanitation:</b> Remove organic waste and debris from around your home to eliminate breeding sites for sandflies.</li> <li><b>Protect domestic animals:</b> Use insecticide-treated collars or sprays on dogs to prevent sandfly bites and consider vaccinating them against leishmaniasis.</li> <li><b>Use personal protection:</b> Apply insect repellent to exposed skin, especially during peak sandfly activity periods (dusk and dawn). Wear long sleeves and pants when possible. Use bed nets while sleeping, especially if your home is not well-screened.</li> <li><b>Support public health initiatives:</b> Advocate for community-wide vector control programs, including insecticide spraying and environmental management.</li> <li><b>Stay informed:</b> Keep up-to-date on the latest information about leishmaniasis risks and prevention measures in your area.</li> </ul>