Potential vectors of loiasis and other tabanids on the island of Bioko, Equatorial Guinea.

The biting flies Chrysops dimidiatus Wulp and C.silaceus Austen (Diptera: Tabanidae), vectors of Loa loa (Cobbold) (Nematoda: Onchocercidae) on the African mainland, were found to be widespread on the island of Bioko (Equatorial Guinea) during 1996-2001. These tabanids were particularly prevalent in the southern part of Bioko, indicating potential transmission of loiasis on the island. The only other tabanids previously recorded on Bioko, Tabanus argenteus Surcouf (from 1915) and Haematopota near heptagramma Speiser (from 1933), were also collected. The possibility of loiasis being endemic on Bioko contra-indicates ivermectin treatment of onchocerciasis cases, due to risks of adverse side-effects.

Use of odour-baited sticky boards to trap tabanid flies and investigate repellents.

Tabanid flies were captured in a sheep pasture in Hungary using black plastic boards (30 x 30 cm), coated with an adhesive sheet, which were either unbaited or baited with ethane-ethiol or Swormlure-4. Five species of tabanid were caught, of which Tabanus tergestinus was caught in the greatest number (87% of 192). The sex ratio of T. tergestinus on unbaited boards was not statistically significantly different to equality. However, on baited boards, males were significantly more numerous, probably due to a repellent effect of the odours on female tabanids. Because of the importance of repellents in tabanid control, this result encourages the exploration of a wider range of compounds as tabanid repellents than are used at present. Sticky boards offer a simple technique for trapping both sexes of tabanids, especially males, which are poorly represented in many tabanid traps.