Only four genera in the Simuliidae family, Simulium, Prosimulium, Austrosimulium, and Cnephia, contain species that feed on people, though other species prefer to feed on other mammals or on birds.
Simulium, the type genus, is the most widespread and is a vector for several diseases, including river blindness.
Preferred timing and location of bites varies by species, though feeding always occurs during the day and is usually sited on areas of thinner skin, such as the nape of the neck or ears.
Mature adults can disperse tens or hundreds of kilometres from their breeding grounds in fresh flowing water, under their own power and assisted by prevailing winds, complicating control efforts.
Swarming behaviour can make outdoor activities unpleasant or intolerable, and can affect livestock production; during the eighteenth century, the “Golubatz fly” (Simulium colombaschense) was a notorious pest in central Europe.
Even non-biting clouds of black flies, whether composed of males or of species that do not feed on humans or do not require a blood meal before egg laying, can form a nuisance by swarming into orifices.
Bites are shallow, and accomplished by first stretching the skin using teeth on the labrum and then abrading it with the maxillae and mandibles, cutting the skin and rupturing its fine capillaries.
Feeding is facilitated by a powerful anticoagulant in the flies’ saliva. Itching and localized swelling and inflammation sometimes occurs at the site of a bite; swelling can be quite pronounced depending on the species and the individual’s immune response, and irritation may persist for several days to weeks.
Intense feeding can cause “Black Fly Fever”, with headache, nausea, fever, swollen lymph nodes, and aching joints; these symptoms are probably a reaction to a compound in the flies’ salivary glands. Less commonly, severe allergic reactions may require hospitalization.
River blindness:
Black flies are central to the transmission of the parasitic nematode Onchocerca volvulus, which causes Onchocerciasis, or “river blindness”. It serves as the larval host for the nematode and acts as the vector by which the disease is spread.
The parasite lives on human skin, and is transmitted to the black fly during feeding. Simulium pruinosum bite is thought to be involved in the pathogenesis of Fogo Selvagem, the endemic form of pemphigus foliaceus, a bullous dermatosis.
Information Sourced from:
