M Youssefi, A Aminpour, F Arabkhazaeli
blackfly, dermatitis, iran, simulium
M Youssefi, A Aminpour, F Arabkhazaeli. Dermatitis caused by the bite of Blackfly in a 32 –year old man. The Internet Journal of Parasitic Diseases. 2007 Volume 3 Number 2.
Simulidae consist of more than 1700 species in 19 genera of which more than 40 are of medical and veterinary importance. Some of the most important genera of this family are
Eggs are laid in sticky masses in fast flowing water and hatching take a few days in warm condition on river floor. The mature larvae are poorly segmented, lightly colored and distinguishable by a blackish head with a prominent pair of feeding brushes. Larval maturation takes from several weeks to months and in some species larvae can overwinter. Pupation takes place in a slipper-shaped brownish cocoon (2). The pupa has respiratory gills projecting from the cocoon (3). After the 2-6 day pupal period, there is a mass emergence of adult flies. Typically longevity of adult black flies ranges from 2-3 weeks to as long as 25 days (2).
Adult flies feed on plant nectar, but in most species females require a blood-meal to obtain the protein necessary to mature their eggs (1). They are particularly active during the morning and evening. In temperate regions they may be regarded seasonal since adults die in autumn with new generations in spring and summer. Adults are strong fliers and are highly responsive to carbon dioxide and other host odors (2). Geographically these flies have worldwide distribution except some areas of the tropics like New Zealand, Hawaii and some minor island groups which are rendered uninhabitable by
A 32-year-old man from Khorram Abad city in Lorestan province, Iran, while camping in Gahar (around the mentioned city) was attacked by a mass of blackflies (figure 1). Few hours after, very sensitive pruritic red wheals appeared in the biting sites (figure 2). The lesions were present mainly on the lower legs and randomly distributed. They were pruritic for 2 weeks and healed without any treatment after 20-25 days. Dermatitis which is defined as superficial inflammation of the skin, characterized by redness, edema and usually itching (4) was diagnosed. The reaction is assumed to be type I hypersensitivity reaction due to the release of pharmacologically active substances which lead to vasodilatation and increased capillary permeability. The patient had no predisposing disease and his blood group was A.
Blackflies of the genus
There is an important difference between the biting habits of African and American species. The African
The flies' bites are seriously painful and due to the release of pharmacologically active substances such as histamine, leukotrienes, prostaglandins, platelet activating factor and eosiniphilic chemotactic factor (ECF) from IgE-sensitized basophils and mast cells after contact with antigens in the flies' saliva acute urticaria, which is one of the disorders due to hypersensitivity may occur. The condition is characterized by local wheals and erythema in the dermis can be due. In urticaria pruritis is the first symptom followed by the appearance of wheals. Acute urticaria is a self-limited condition and treatment is palliative. In hypersensitive persons bites can be fatal (4).
One of the few studies on blackfly distribution in Middle East by Crosskey 17 species belonging to 3 genera and 7 subgenera were identified from Iran and Iraq in 1970-1980 (7). The flies were isolated from Alborz Mountain, Kordestan and few regions near Caspian Sea. The isolated species in this study were as follows:
2 other species
Blackfly control is extremely difficult because of their small size and since the immature larvae are found in running water. The most practical control method is the application of insecticides to breeding sites in example application of organophosphate insecticides to water-courses which is then carried downstream and kills larvae (1, 2). The development of blackfly control in South Africa during the 1960s blackflies in the Vaal River was primarily with DDT; during the 1970s and into the 1980s blackflies were controlled using water-flow manipulation; when used at strategic times, water-flow manipulation could be used to enhance the effect of natural predator populations; and during the 1990s the organophosphate temephos and toxins produced by the bacterium
The authors would like to express their appreciation to Mr. Abbas Hatami and Abd-Allah Alinejad for providing the flies and larvae samples.