Scientific and Technical Advisory Committee seventh meeting, Brazzaville. 21-25 august 1978 : report of ecological panel

WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE Rcglonel Offlcc for Afrlca Burceu rrlglonal de I'Afriquc ONCHOCERCIASIS CONTS,OL PROGRAMME IN T}TE VOLTA RIVER BASIN AREA SCIE.ITIFIC AND TECHNICAL ADVISORY COMMITTEE Seventh meeting Brazzaville. 2l-25 August 1978 REPORT OF ECOLOGICAL PANEL The report of the meeting of the Ecological Panel held in Rome on 29 and, 30 May 1978 was presented to the Committee for information. It was felt that, since there are several matters particularly relating to larvicides and their application of interest to both the Ecological Panel and STAC, some way should be found to ensure that commonly accepted views are presented to the JCC. WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE 5 Regional Office for Africa Bureau r6gional de I'Alrique ONCHOCERC IAS IS CO].{TROL PROGRAMI\M IN THE VOLTA RIVER BASIN AREA SCIM{TIFIC AND TECHN ICAL ADVISORY COMMIT'TEE Seventh neeting BrazzaviJ-l-e, 2l-n,5 Aqgusl I97q OBJECTIVES The obJectives of the Programme, as defined by the PAG Mission Report and endorsed by aI1 countries concerned, were reviewed at the STAC meeting in 1977. Although there are differences in terminology which could be confusing if the PAG mission report objectives are read out of context with the body of this report and its technical annexeB, there is no conflict between the obJectives of the Programme as defined in the two reports. The STAC text, however, better focuses on key public health and socio- economic issues and is re-endorsed by the present Committee. It reads as follows: "... to reduce the impact of onchocerciasis to a sufficiently fow leve1 so that it no longer represents either a public health problem or an obstacle to socioeconomic development and also to maintain and adjust control activities so as to stabilize the disease at a tolerable 1evel". The tolerable level of disease was recently defined by a SAP/WG and impLies the absence of serious lesions of ocular onchocerciasis brought about by reduction of ATP to less than fOO or an annual biting rate of less than IOOO. Drring the short period since the beginning of complete coverage of the Programme area by larvicide applications, important advances have been made in the fields of vector biology and control and their relatronship to onchocerciasis transmission. The relative distribution and importance of the main species composing the S. damnosum 10 15 5Page 2 complex have been thoroughly investigated and the long fIlght ranges of the main vectors have been determined. The new findings do not require any fundamental changes in the objectives of the Programme. It has been established that the f1y can be removed from savannah river systems over a wide area and that it is possible to monitor and to delineate areas in which it becomes re-estabLished, either by movement from residual foci within the Prograrune area, or by invasion from outside. It should be possible, by the strategic application of larvicide, to maintain the numbers of flles at very low levels withln the Programme area. In some cases, there have been no new onchocerca infections at the second examlnation after three years, and the worm loads in existing infections will be expected to decrease. A very slgnificant reduction in the numbers of blind people in the population can be expected, and wlthin the protected area, progressive eye l-esions caused by severe O. volvulus infections will disappear. The existing drugs used for treatment of the disease have serious drawbacks, but the side-effects of DEC, which depend mainly on the response of the host to the presence of microfilariae kiIled by the drug, are less serious in patients with llght worm loads. Therefore, after several years, as the parasite loads decrease, the use of DEC, and of suramin, w111 become safer and a respite wilf be given during which new drugs and improved methods of treatment can be developed. This is the immediate and urgent concern of the proJects at present being carried out by the WHO Special Programme for Research and Training in Tropical Diseases. New methods of using DEC are being investigated, clinical trials are in progress with antlhelmintics and other antiparasitic compounds already in use in hurnan medicine, and new drugs, in collaboration with the pharmaceutical industry, are being screened. It is to be expected that, during the course of 15 years of control,, further develop- ment of the primary health care services of the seven countries concerned wilt take place, socioeconomic development will have taken place and the use of chemotherapy could progressively complement and perhaps largely replace vector control. Onchocerciasis control would then come within the broad framework of disease prevention and control measures carried out by the national health services. 10 r5 20 25 30