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SANDFLIES (Psychodidae)

Sandfly Fevers

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There are some medically important species that are vectors of various fevers, such as Leishmania, Pappataci fever, Kala-azar and Oroya fever, especially in tropical regions. Service (2008) reported that there are almost 1,000 species in six genera. Those that draw blood from vertebrates are in the genera Phlebotomus, Lutzomyia and Sergentomyia. Phelobotomus species are absent from the Americas but range in parts of Africa and Asia. They typically are active in drier savannas. Lutzomyia are restricted to the Americas where they are abundant in the forests of Central and South America. Sergentomyia species also are not found in the Americas but rather Central Africa and Asia. However, they do not generally encounter humans and are not vectors. Service (2008) listed the most medically important species are Phelebotomus papatasi, P. sergenti, P. argentipes, P. ariasi, P. perniciousus and Lutzomyia longipalpis and L. flaviscutellata.

In addition to Leismaniasis, sandflies are involved as vectors of other diseases affecting humans. Bartoneliosis is a disease found in mountainous areas of the Andes of South America. It is caused by Barionella bacilliformis and vectored by Lutzomyia verrucarum, L. colombiana and other Lutzomyia species.

There are also seven viral serotypes of sandfly fever, often called "Papataci Fever." They occur in the Mediterranean region but extend into Egypt and India and possibly China. The principal vector is Phlebotomus papatasi. Other forms of the virus occur in Central and South America, vectored by Lutzomyia trapidoi and others of the genus. Female sandflies become infective about a week after a blood meal. Eggs containing the virus are laid which give rise to infected adults. Various mammals are suspected as reservoir hosts.

CHARACTERISTICS & DEVELOPMENT

The moth flies and sand flies have abundant scales on their wings. They are small to very tiny insects with a large number of hairs on their bodies. When at rest adults may hold their wings roof like over the body.

The habitat is in moist shady areas but can also be found in drainages or sewers. Adults may occur in bathrooms that they enter via sink drains. Larvae inhabit decaying vegetable matter, moss, mud or water.

Oviposition is not directly in water but occurs in ground holes, termite mounds, masonary cracks in poultry houses and around the roots of forest trees, etc. (Service 2008). The larvae feed as scavengers on organic matter and rotting vegetation. The genus Phlebotomus occurs in partially arid areas, but their larvae still develop in a high humidity environment. Larvae pass through 4 instars in about 20-30 days, which of course varies with temperature and different species. The 4th instar larva may go into diapause if conditions are unfavorable. Overwintering is in the larval state in colder climatic areas.

Adults feed on plant sap and other sweet secretions, but the females draw blood from vertebrates. Lutzomyia species restricted to the Americas and Phlebotomus species elsewhere attack humans and other mammals. They are all especially active during sunset and at night and in outdoor darkened environments, such as forests. Most species require blood meals to lay viable eggs, but a few autogenous species lay viable eggs without a blood meal. All adults are weak fliers and will not spread far from their breeding sites, but windy conditions can drive them greater distances. Other adult behaviors are noted by Service (2008).

CONTROL

Insecticide control of vector sandflies is effective until resistance sets into the fly population. Therefore, the use of repellants is preferable. To reduce diseases caused by sandflies some efforts have been made to eliminate reservoir hosts from populated areas. Further efforts to control the vectors remain experimental, especially as the breeding sites of most sandflies are not easily found.

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Key References: <medvet.ref.htm> <Hexapoda>

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