Post control studies

ocP/E\clz/lrietinr paper no. I0 Expert Advisory Committee Twelfth session Ouaeadoueou. 10-14 June 1991Briefing session B June 1!!1 POST-CONTROL STUDIES Summary The objective of post-control studies is to confirm that the parasite has disappeared in the vector, after having shown epidemiologically that it has disappeared in man. In 1990, the post-control studies covered nine points: Konina, Samandeni, Nabere, Folonzo, ZiovZabre, f.oaba, Nangodi-rapids and Porga. Protocol : Four days of catching were done per week on each of these points. The blackflies caught on the first day by the OCP tearnwere dissectecl. Those of the following three days which came from villager-vector collectors have been partially dissected (parous-nulliparous). On the parous females, only the head is dissected in the search for infective O. volvulus larvae. Results The results obtained through epidemiological modelling have made it possible to define a level of one to two infective females per 1,000 parous flies. Below this thresholcl, larviciding can be definitely stopped. At Konina on the Banifing IV, the presence of a considerable number of infective females has led to the resumption of larviciding. At Folonzo on the upper Comoe, out of 1,581 parous females dissectedrthere is no infection. At Nabere on the Bougouriba, out of 18,881 parous females dissected, there were eight infective females, i.e., 0.42 infective females per 1,000 parous flies. Post-control studies have not been carried out at Karfiguela (Upper Comoe), Loumana (Tiao) and Fourkoura (Eastern trraba) because of the very low blackfly population Graphs corresponding to the different points have shown that the situation is very 1 2good ar Nabere, goocl at Ziou-Zabre, Nangodi and Folonzo and unsatisfactory at Zongoiri- rapids and Porga. Outlook for 1991 It is no longer necessary to conduct post-control studies again at Nabere on the Bougouriba since the results are excellent. It has therefore been decided to conduct them at Zambo. These studies will be carried out again at Ziou-Zabre, Nangodi, I-oaba, Zongoiri- rapids and Porga. They may also be undertaken at Karfiguela, I-.oumana and Fourkoura if the blackfly density is sufficient. They are currently being conducted at the road bridge on the [rraba and at Badikaha on the White Bandama.