The Transmission of Bancroftial Filariasis on Ukara Island, Tanganyika. III.—Biting-incidences on Man and Filarial Infections in wild-caught Mosquitos

Abstract

The seasonal biting-incidences on man of several species of mosquito inside and outside huts of villages on Ukara Island, Tanganyika, between 7 p.m. and 3 a.m. East African Standard Time are recorded. Anopheles gambiae Giles and A. funestus Giles were by far the most common indoor biters in both of the villages which received study: they were also taken biting outdoors in fair numbers. Tacniorhynchus africanus (Theo.) and T. uniformis (Theo.) were common outdoor biters in a village near a swamp, but were taken in only small numbers off human “bait” in a cone hut.A study of sleeping arrangements in huts showed that people between six and sixteen years of age were most exposed to the risk of mosquito bites at night, since they were least protected by covers and clothing.The inhabitants were bitten by Aëdes africanus (Theo.) and Aë. apicoargenteus (Theo.) outdoors by day, and by small numbers of A. gambiae and A. funestus in huts during daylight hours in April.The results are given in detail of dissections for developing filarial worms in over seven thousand mosquitos. Proboscis infections occurred in A. gambiae and A. funestus. Immature (thoracic) forms were found in A. pharoensis Theo., T. africanus, T. uniformis and Culex antennatus (Beck.).It is concluded that the biting-habits of A. gambiae and A. funestus point to them as more likely vectors of bancroftial filariasis than other species with developing filarial worms.