A tiny, silent fly bite can trigger a life-threatening, neglected tropical disease.

Health · Published 3 October 2026 Swipe more like this →

In short: Leishmaniasis is a parasitic infection transmitted by the bite of female sand flies, which are often one-fourth the size of mosquitoes. While many cases cause only skin sores, others progress to severe, potentially fatal internal organ damage. It remains a significant global health challenge, particularly in tropical and subtropical regions.

Leishmaniasis is caused by protozoan parasites from over 20 different Leishmania species. These parasites are transmitted to humans through the bites of infected female phlebotomine sand flies, which are most active from dusk to dawn. Because these flies are silent and tiny, many people do not notice the bite. While the disease occurs in approximately 90 countries, it is classified as a neglected tropical disease, often affecting the world's most vulnerable populations living in poverty.

The disease manifests in three primary forms. Cutaneous leishmaniasis is the most common, resulting in painless skin sores that can take months or years to heal, often leaving permanent scars. Mucosal leishmaniasis, a severe consequence of certain parasite types, destroys tissue in the nose, mouth, and throat. Visceral leishmaniasis, also known as kala-azar, is the most dangerous form. It attacks internal organs like the spleen, liver, and bone marrow, causing fever, anemia, and weight loss. Without treatment, visceral leishmaniasis is typically fatal.

Risk factors for the disease are deeply tied to socioeconomic and environmental conditions. Malnutrition, poor housing, and lack of sanitation create ideal breeding grounds for sand flies and increase human susceptibility. Furthermore, environmental changes such as deforestation and urbanization, alongside population displacement, can exacerbate transmission. While there are no vaccines or preventative drugs, protection against sand fly bites remains the primary defense. Diagnosis involves examining tissue samples or blood, and treatment strategies vary significantly based on the specific parasite species and the form of the infection.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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