Expert Advisory Committee: fifteenth session: Ouagadougou, 6-10 June 1994: presentation of activities of the Vector Control Unit for the period May 1993-April 1994 (larvicides, aerial operations)

WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE ONCHOCERCIASIS CONTROL PROGRAMME IN WEST AFRICA PRoGRAMME DE LUTTE CONTRE L'ONCHOCERCOSE EN AFRTQUE DE L'OUEST EXPERT ADVISORY COMMITTEE Fifteenth session Ouaeadoueou. 6-10 June 1994 ocP/EACr5.7 ORIGTNAL: FRENCH Presentation of activities of the Vector Control Unit for the period May 1993-April 1994 (Larvicides, aerial operations) Larvicides The rainy season came quite late in the eastern zone but the situation returned to normal after the heary rains of July and August L993. The hydrological regime has therefore remained practically the same as in the western zone where a slight delay was observed, however, in the start of the period of rise in water levels in Cdte d'Ivoire and Mali. In the eastern zote, the larviciding coverage has been virtually the. same as in 1992/1993. For the'second consecutive year, the principal Oti has not been treated and the upper N'zi and some tributaries of the Comoe have been treated only occasionally. In the western zone,'the only notable fact is the definitive cessation of larviciding on the White Bandama at the beginning of February 1994. The Niger (near Bamako) and some of its tributaries (Fie, Faya, Dylamba) are still under larviciding but it has been carried out solely from the ground since 1 January 1994. This change in strategy has been dictated by budgetary considerations in view of the probable cessation of larviciding in 1995 on the Baoule and the Bagoe (with the exception of the Kankelaba) in Mali. The insecticide rotation, aimed at preventing possible blackfly resistance phenomena and limiting the effects of the larviciding on the non-target fauna, has once again demonstrated its efficacy. In the.eastern zone, all the insecticides, including temephos, were used to the east of the line separating the Mouhoun basin from the White Volta basin. To the west of this line, temephos was not used while the other organophosphorus compounds were used scantily. In the westernzone, the consumption of Abate was voluntarily increased during this period in order to determine better the limits of its use. Although a slight decrease in susceptibility has been recorded on some basins, this has not had an effect on the transmission. By authorizing the use of Vectron, the Ecological Group has put at the Programme's disposal, a seventh insecticide which will be used as from the month of June on some basins where the use of Abate is not recommended, particularly, in Cdte d'Ivoire, on the Comoe and the lower Bandama and, to a lesser extent, on the Marahoue and the Sassandra. This year, there has not been any particular problem with the ocPlE,ACts.T page 2 operational batches of Vectobac received, which seems to indicate that the company concerned now has fuIl control over the industrial production of this biological insecticide. 2. Aerial operations The aerial operations of the Kara and Odienne bases have been carried out without any major problem. The number of flight hours and the number of helicopters used in 1993 were in accordance with the estimates, i.e.,5 995 guaranteed hours, 652 additional hours and 109 helicopters/month, which represents, in terms of flight hours, a decrease of about 15Vo compared to L992. The accuracy of these estimates is due mainly to the fact that: (i) in L993, there were no social or political disturbances that could have disrupted the flight over the treated areas; (ii) the spraying system developed in L991 by the company has, once again, demonstrated its efficacy; (iii) there have neither been defective batches of Vectobac nor problems with the other insecticides; (iv) as has been mentioned in paragraph 1, the hydrological regime has been virtually similar to that of the previous period. The aerial contract between OCP and the aerial company, signed for a three-year period, is giving the Programme complete satisfaction with regard to the type of aircraft used and the spraying system, the experience of the pilots and mechanics and the seiiousness of the company in the management and maintenance of the helicopters. The Global Positioning System (GPS), which had so far been used only by the pilots who had acquired it themselves, would gradually form part of the aircraft equipment and the company has, for the first time, installed it on one of its helicopters. This system makes flyr.rg easier for pilots, especially during periods of poor visibility, and therefore saves a valuable-number of flight hours. In the whole Programme area, the highest larviciding coverage was recorded during the week of 6 to 11 September L993 (36th week/93), with 11 575 km of river treated, mobilizing the 11 helicopters under contract and using all the insecticides then available (Vectron was not yet operational). Conversely, the week of 28 March to 2 April L994 (13th week/94) experienced the lowest larviciding coverage (three larviciding helicopters) with 3 770 km of river treated, a complete cessation of larviciding in the eastern zone and the use, in the west, of only three insecticides, viz., a biological- origin insecticide, Vectobac , and two organophosphorus compounds, Abate and pyraclofos