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Sandfly

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A sandfly is a colloquial name for various species of flying, biting insects. These insects belong to the order Diptera, which is the group containing all true flies. They are most commonly found in sandy environments. In the United States, the term might refer to certain horse flies in the family Tabanidae, often called "greenheads." In other regions, it describes members of the family Ceratopogonidae, which are biting midges. These midges are sometimes called "no-see-ums" because they are so small.

Biting sandfly
Biting sandfly

Outside the United States, the name often refers to the subfamily Phlebotominae within the Psychodidae family.

Only female sandflies bite living creatures like mammals, reptiles, and birds. They do this to obtain protein from blood. This protein is necessary for the production of their eggs. Because they require this blood meal to reproduce, they are known as anautogenous reproducers. When a sandfly bites, it typically causes a small, intensely itchy bump or welt. These bites are often found in clusters because the flies attack animals in groups. This grouping behavior helps distinguish sandfly bites from mosquito bites. The intensity of the itch usually increases over a period of five to seven days before it begins to fade.

Sandflies are significant because they act as vectors for several diseases. A vector is a living creature that carries and transmits an infectious agent to another animal or human. Some sandflies carry the Chandipura virus, which is a deadly cousin of the rabies virus. An outbreak of this virus occurred in India in 2010. A subsequent endemic outbreak was recorded in Gujarat in 2024. Other sandflies spread leishmaniasis, a disease caused by various species of the genus Leishmania.

Parasite130072-fig1 Map of cutaneous leishmaniasis in North Africa
Parasite130072-fig1 Map of cutaneous leishmaniasis in North Africa

This disease is transmitted by different genera depending on the global region.

The transmission of leishmaniasis varies by geography. In Asia, Africa, and Europe, the disease is spread by sandflies of the genus Phlebotomus. In the Americas, the disease is spread by sandflies of the genus Lutzomyia. One specific type, Leishmania donovani, can cause spiking fevers, hepatosplenomegaly, and pancytopenia. Doctors can diagnose this by using a microscope to visualize amastigotes inside containing macrophages. This condition is treatable with a substance called sodium stibogluconate. Another disease, Carrion's disease, is caused by the bacteria Bartonella bacilliformis. This is transmitted by members of the Lutzomyia genus and is restricted to Andean areas of Peru and Ecuador, with historical reports in Southern Colombia.

In certain parts of the world, sandfly populations are very high. In the Caribbean, Belize and Honduras are considered notorious for their sandfly numbers. Travelers to these areas are often warned to use insect repellents with high concentrations of DEET. To prevent bites, people can use over-the-counter products containing DEET or picaridin. Some studies show that a specific extract of lemon eucalyptus oil is as effective as DEET. While most research on repellents focuses on mosquitoes, mosquito repellents are also effective against sandflies and midges. Effectiveness can vary between individuals, possibly because different species live in different areas.

Different cultures have unique views of these insects. In New Zealand, sandflies are taxonomically classified as black flies, specifically the genus Austrosimulium. Māori legend provides a fascinating perspective on these creatures. One legend says the god Tu-te-raki-whanoa created the stunning landscape of Fiordland. The beauty was so great that people stopped working just to gaze at it. The goddess Hine-nui-te-pō became angry at this lack of productivity. She created the sandfly to bite the people and force them to get moving. Another Māori legend claims these sandflies were able to revive the dead hero Ha-tupatu.

Understanding sandflies involves looking at biology, medicine, and even folklore. They represent a complex link between the environment and human health. By studying how they move through different ecosystems, scientists learn more about disease control. The way they reproduce and feed connects them to the wider food web. Their role as vectors connects them to the field of epidemiology, which studies how diseases spread. Whether viewed as a nuisance, a medical concern, or a character in a legend, the sandfly is a vital part of the natural world.

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Parasite130072-fig1 Map of cutaneous...
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