Main lines of devolution activities related to onchocerciasis in the original OCP area: revision 1

WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE oNcHocERcrAsrs coNTRoL PRoGRAMME IN WEST AFRICA (OCP) PROGRAMME DE LUTrE CONTRE L'ONCHOCERCOSE EN AFRIQUE DE L'OUEST EXPERTS ADVISORY COMMITTEE Fourteenth session Ouaeadoueou. 7-ll June 1993 ocP/EACl4.6 (93/tt0/devo/2.17) ORIGINAL: FRENCH l. MAIN LINES OF DEVOLUTION ACTIVITIES RELATED TO ONCHOCERCIASIS IN THE ORIGINAL OCP AREA REYISION I PRELIMINARY REMARKS The following text is a revision of document JPCI3.8 which covered both the original Programme area and C6te d'Ivoire's southern extension zone. However, today, all the OCP extension zones (southern extension in Cote d'Ivoire and western and south-eastern extensions) are under ivermectin treatment combined with larviciding or not. There is, therefore, no particular strategyproblem in these zones. On the contrary, in the original Programme area, where after many years of vector control OCP is getting ready to stop its activities for good but where the entomo-epidemiological results are not the same everywhere, it is appropriate to define clearly an onchocerciasis surveillance strategy, separating the zones already freed through vector control alone from those which, to attain the same level of protection, would necessitate large-scale ivermectin treatments, combined with larviciding or not. This document, therefore, covers only the original Programpe area. 2. GENERAL CONSIDERATIONS The original Programme area covers an area of 654,000 square kilometres which stretch over Benin, Burkina Faso, C6te d'Ivoire, Ghana, Mali, Niger and Togo. It was in this part of the Programme area that vector control, the only available means for the control of onchocerciasis, was started between 1975 and 1977 depending on the area (Annex l.). Today, discussing devolution i.e., the taking over by the Participating Countries of the activities which will help maintain and strengthen OCP's achievements, it is normal to consider first the part of the Programme which has already benefitted from 12 to 15 years of larvicide spraying operations. It is there that OCP can progressively hand over to the beneficiary countries the full responsibility for carrying out the residual activities related to the control of the disease. It should be noted that, today, transmission of the disease has been definitively interrupted in approximately 80% of the original Programme area. [n this area excellent epidemiological results have been recorded. The prevalence of onchocerciasis is less than 5% almost everywhere and there is no risk of onchocercal blindness anywhere. The advent of ivermectin (MectizanR) in the Programme in 1988 has provided the beneficiary countries with an effective tool for the control of river blindness, which is clearly within their technical, financial and human resources and which should be easier for them to handle than vector control through aerial spraying of larvicides. ocP/EACl4.6 Page 2 Armed with these achievements and the fact that the new drug makes it possible from now on to address the devolution process in real operational terms, OCP has stopped larvicide applications in aboul E0% of its original area. The blackflies are therefore returning, as foreseen initially. Today, the bites of these flies can, at best, only be a source of nuisance and not of onchocerciasis. In fact, the number of blackflies that carry the parasite responsible for river blindness is practically nil. It should, however, be noted that up to 1989 the western and south-western fringes of this original area in Mali and Cote d'Ivoire had been invaded by btackflies coming mainly from Guinea and Sierra Leone. Although this reinvasion has been completely brought under control since 1990, the entomo-epidemiological results are not yet quite satisfactory in these areas which had been infested by the reinvading blackflies for too long. A similar reinvasion phenomenon prevailed also in the south-eastern part of the original Programme area, in Togo and Benin. The problem has been solved by the southern extension of the Programme. Blackfly infiltrations from Nigeria, which, luckily, do not have the magnitude of a real reinvasion phenomenon, are observed from time to time in the Sota valley in Benin but the current ivermectin distribution campaigns in these two neighbouring countries have removed the risk of onchocercal blindness from this valley which is also under selective larviciding. Furthermore, there is a small localized focus in Burkina Faso, Pendie focus, where the epidemiological trends, though satisfactory from the public health viewpoint, are out of phase with the rest of the country by about ten years (slower decrease in prevalence). This is due io the fact that a residual transmission which was not detected in time continued and even intensified between 1980 and 1985. It is noteworthy that despite that, the intensity of the infection is low with a community microfilarial load (CMFL) of about one microfilaria per skin snip. Today, the risk of blindness in this Pendie area is nil because of the large-scale distribution of ivermectin t6at has been going on there since 1988, as well as vector control which, with effect from 1987, is being undertaken there through ground larviciding. In other localized zones in this original area, problems were encountered with larviciding operations as a result of the exceptional complexity of certain breeding sites of the vector as well as the resistance of some blackfly species to the insecticides, organophosphorus compounds, that have so far been the easiest and the most effective insecticide to use. Consequently, while the entomo-epidemiological results in those zones are still acceptable from the standpoint of public health, they are not as satisfactory as those recorded in the greater part of the original programme area. Finally, it should be pointed out that there is an occurrence of considerable movements of migrants with onchocerciasis into certain river basins where transmission of O. volvulus has been completely interrupted and where OCP has stopped vector control, as for exarnpte in tt eBanifing IV basin in Mali. These migratory movements deserve therefore to be monitbred very closely and appropriate measures in the form of treatment of immigrant patients need to be taken. In the light of the above, it is easy to understand that, during the fourth Financial phase(1992-1997), OCP will have to continue the larviciding operationsln about 20% of its original area. The vector control will be s'trengthened where necessary, by the treatment of the population with ivermectin. However what will attract particular attention during this period, wiit be the activities which the countries concerned will carry out themselves in the freid zones as part of devolution as a proof of their determination to protect and strengthen OCp's achievements. These activities are defined in the devolution plans prepared by the seven countries in the original Programme area and which have been already approved by the Joint Programme Committee, the Programme's supreme decision-making body. These devolution plans, which the countries hare undertaken to revise in order to take into account the present socio-health and economic situation, lay emphasis on the pressing need to integrate onchocerciasis control into other ongoing health activities in the countries. ' For the specific case of onchocerciasis which directly concerns us here, the overall strategyfor the control or more appropriately for the maintenance and strengthening of OCi;s achievements will be based on the above-mentioned basic data. 3ocP/EACl4.6 Page 3 STRATEGY FOR THE MAINTENANCE AND STRENGTHENING OF OCP'S ACHIEVEMENTS tN THE ORIGINAL PROGRAMME AREA It has been demonstrated that after l4 years of complete interruption of transmission of the onchocerciasis parasite, the risk of recrudescence of the disease hecomes very low and even negligible. This period corresponds to the maximum life-span of the a.iult worm in man. The risk of recrudescence after the cessation of vector control operations depends, among other factors, on the existence of a residual parasite reservoir, the density of the biting female vector and the immigration of infected individuals. The Participating Countries should therefore be vigilant and, as part of the devolution, take steps aimed at preventing any serious recrudescence of onchocerciasis, i.e., to prevent any intense and generalized resumption of transmission which may result in high rates of incidence of the disease and which may finally bring about new cases of onchocercal blindness. The strategy to be adopted for the attainment of this objective is based on four main principles lines: - Information, Education and Communication (I.E.C); - epidemiological surveillance; - ivermectin treatment of migrant onchocerciasis-patienS; - ivermectin treatment of populations in zones where recrudescence of the disease would be detected. The implementation of this strategy would require an adequate training of staff at all levels. 3.1. Information. Education. Communication(I.E.C) Activities to raise awareness to be carried out through information, education and communication with the authorities and the population are fundamental to devolution. First of all, the governments of the Participating Countries will have to be made aware of the importance of the maintenance of onchocerciasis control which should be included in their main public health priorities. Once the politicat will of the governments has been aroused, education and community mobilization efforts will have to be initiated since the control of the disease will be increasingly dependent on epidemiological surveillance and ivermectin treatment. Community mobilization plans are therefore necessary in each country. Studies on the knowledge, attitudes and practices will enable the identification of gaps in the knowledge on onchocerciasis and the attitude towards the disease and the return of the blackfly after the cessation of larviciding. Such studies will enable the definitive identification of the appropriate means applicable for the dissemination of public health messages. 3.2. Eoidemioloeical surveillance In the areas where larvicide sprayings have been carried out successfully for many years, an active epidemiological surveillance by mobile teams will be the most appropriate means for early detection of any possible recrudescence of infection. However, passive epidemiological surveillance by fixed health centres or by the rural communities themselves should not be neglected because it can also provide important epidemiological information (suspected onchocerciasis-patients, immigrant onchocerciasis-patients, etc). Active epidemiological surveillance will consist of parasitological surveys based on skin snips in comnlunities at high risk, living close to the vector's breeding sites. For further details on the methodology of these parasitological surveys, the reader is requested to refer to the OCP manual entitled "Manual of procedure for skin snip surveys'(Document JPC9.9A, Annex l). ocP/EACl4.6 Page 4 Villages in which this epidemiological surveillance is carried out are called'surveillance' villages or'sentinel' villages. During these epidemiological surveillance surveys, particular attention should be paid to the presence of immigrants and to the identification of their places of origin. Besides, apart from classic epidemiological monitoring surveys, special studies on human migration should be organized on a larger scale to gather further information on this important phenomenon which can be an important factor in the resumption of transmission among the local populations in certain zones with high blackfly densities. 3.3. Ivermectin treatment of infected immierants All immigrants found to be positive by skin-snip test or highly suspected to have onchocerciasis during epidemiological surveillance or special migration studies, should be treated with ivermectin. Of course, the presence of immigrant onchocerciasis-patients in an area is not synonymous with recrudescence of the disease but their treatment with ivermectin is undoubtedly a measure to prevent it. 3.4. Ivermectin treatment of oooulations in zones where recrudescence would be detected If, after an active epidemiological surveillance, it is proved that there is recrudescence in an area, a large-scale ivermectin treatment campaign will be undertaken. At present, it is recommended to give this treatment once per year for a relatively long period (about l5 years). The procedure for this ivermectin distribution is explained in detail in the OCP manual entitled "Manual of procedure for ivermectin distribution and monitoring of adverse reactionsn Revision 2 (document JPCl3.9). N.B. The strategy defined above fully applies today to the freed zones in the original Programme area. On the contrary, in the zones in the original Programme area where entomo-epidemiological results are not yet quite satisfactory, epidemiological surveillance cannot be instituted at the moment for detection of recrudescence of the disease. In these zones, large-scale ivermectin treatment will be instituted and it should be seen as a complement to vector control with a view to controlling onchocerciasis more effectively. EPIDEMIOLOGICAL SURVEILLANCE AND IVERMECTIN TREATMENT ZONES IN THE ORIGINAL PROGRAMME AREA IN 1993 To facilitate the coordination of the actions of the different partners concerned with devolution activities in the field (Participating Countries, OCP, NGOS, etc.), it seems appropriate, after the account that has just been made on the overall strategy, to define clearly the zones which will be subjected to epidemiological surveillance and those eligible for ivermectin treatment in the original Programme area. It goes without saying that the information, education and communication activities will cover all the zones, with specihl emphasis on those where the risk of recrudescence is presumed to be greatest. Since larviciding is still being continued in about 20% of the original Programme area, it should be foreseen that changes would occur in the delimitation of zones as the insecticide sprayings come to an end. The zones presented below therefore relate to 1993 only. Annex 2 shows, among other things, the zones of the original Programme area where preparations are being made towards the cessation of vector control operations. The collection of parasitological data, which will enable decision-making as regards the stopping of these larvicide treatments, is therefore necessary in this part of the OCP area. Consequently, for the moment, these zones will not be subiected to larce-scale ivermectin treatment. 4 ocP/EACt4.6 Page 5 4.1. Eoidemioloeicalsurveillancezones See Annex 2 for the location of the zones and Annex 3 for the entomo-epidemiological criteria for their delimitation. It should be noted that the river basins in which this epidemiological surveillance will be undertaken are no longer subjected to larviciding operations. The epidemiological surveillance surveys in these zones come under the full responsibility of the Participating Countries concerned. OCP will, of course, continue to play its role of adviser and catalyst. 4.2. Zones elieible for laree-scale ivermectin treatment Annex 2 shows also the zones where it is justified to make large-scale ivermectin treatments. As shown in Annex 3, they are zones where the entomo-epidemiological results are not yet fully satisfactory. The general considerations presented earlier give the main reasons for these partially satisfactory results : reinvasion by blackflies from untreated areas, larviciding difficulties due to the complexity of certain breeding sites, resistance of the blackflies to the organophosphorus compounds, residual transmission that went unnoticed for a long time. All the basins concerned with this ivermectin treatment will continue to be treated with larvicides by OCP. As in the OCP extension areas, the onchocerciasis control strategy in these zones will therefore be based on vector control and ivermectin distribution under the direct responsibility of OCP during the fourth Financial Phase. However, the national teams of the Participating Countries will remain the main actors in the ivermectin treatment of the populations in these zones. 4.3. In all the other zones outside those mentioned above, the prevalence of onchocerciasisis negligible and likewise the possibility of its transmission. Consequently, only passive epidemiological surveillance wilt be undertaken in the course of routine medical examinations at fixed health centres. As regards active surveillance, it will be conducted only exceptionally on the basis of an indication of new local infections revealed by passive surveillance. 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