Factors bearing on decisions to initiate onchocerciasis control programme in new areas

Factors bearing on decisions to initiate Onchocerciasis ControL programmes in new areas The Commission hasttcriteriatr which should on launching a campaign areas i dranm up the followiug be taken into accounE against onchocerciasis list of points or in making decisions in any nerd area or D 2. 3. 4. 5. 6. 7. 8. 9. The prevalence and severity of the disease among the popula-tion of the area, and the size and location of ihe affectedpopulat ion. The relative importance of onchocerciasis in relation to other diseases affecting the population: in terms of human suffering; productivity of labour; hindrance to land occu-pation; and the comparative ability to make an effective attack on these diseases. The distribution of onchocerciasis vectors and the trans- mission potenrial, including the presence of large breeding sites which may be a barrier to settlement of under-populated areas because of the potential for transmission if infectivepersons are sett.led. Costs or benefits which may accrue to the existing programme area as the result of the establishment of a nerd control pro- grammer oEr conversely, costs or benefits to the new programmefron the existing programme (e.g. control of reinvasion). The existence of potentially productive resources, land inparticular, the exploitation of which is significantly obstruc- ted by the presenee of onchocerciasis vectors. Evidence that population pressures would cause new and poEen-tially productive lands opened to be settl"ed, thus adding to the productive capacity of the region. The feasibility of the control of the disease through avail- able vector control technologies with or without the addition of chemotherapy. The interest. of nat.ional governrnents in an onchocerciasis control programme as evidenced by, inter alia, their commit- ments to (a) funding (including commFm"nEE a plan for progressive national takeover) ; (b) infrastructure development;(c) training and the creation of a career structure adequate to aEEract and refain the necessary personnel. The availability of internal and external financial- resources to mount and maintain an effective cont.rol programme, inclu- ding the resources required for the progressive nationaL takeover. lO. Initial availability of required nationally and internationally recruited personnel for carrying out Ehe control prograurme. ZF In considering these points it is important to understand their inter-relationship, to provide a fuller explanation of some and, their relevance to the major issues that must beabove all, to show faced in deciding new area. whether or not to start a control programme in a There are four major issues or questions. One, what benefits are likely to flow from control in the area? Two, what are the costs likely to be? Three, should control of onchocerciasis be given priority over campaigns against other diseases? Four, what are Ehe prospects of successful control in the light of what is known about (a) the degree of support that the control programme is 1ike1y to elicit from the government or governments in the new area or from outside governments or international institut.ions which will have to provide financing, and (b) the effectiveness of exist- ing control techniques and the availability of skilled personnel for the programme. The Benefits Benefits might accrue not only to the nelu area but atso to area or areas where control measures are already under way but have been handicapped by re-invasion of the vector from the uncontrolled area(point 4 above). Assessment of benefits to an existing programme area involves as accurate a determinaEion as possible of (a) the magnitude of the reinvasion, (b) the size and demarcation of the area or areas that are the sources of reinvasion, and (c) the extent to which the cost of the existing vector control programme could be reduced (or the effectiveness of the programme increased) by the institution of vector cont.rol in the new area. Benefit.s to the nerd area under consideration are of two types. The first type may be characterised as the potentialities for reduc- tion of human suffering, including the loss of eyesight, from the disease. These potentialities must be assessed in terms of "the prevalence and severity of the diseasetr (Point l) as measured by the number of people infected in areas of varying degrees of endemicity, the proportion of infected people suffering from varying degrees of blindness and the relationship of the number of infected peoples and areas of infection to the total population and area. The second type of benefit is economic as expressed by thepotential increase in production resulting from effective control of onchocerciasis. This benefit will be manifested in two ways. One results from potential improvements in human productivity following progressive reduction of the incidence of disease. This effect will occur above all as the consequence of the reduction in functional blindness; and its importance will accordingly depend on (a) the number of functionally blind adults est,imated to exist at the begin- ning of a control prograrnme and the potential increase in this number in the absence of a control programme and (b) the rate aE which the control prograrrne is likely to reduce the acEuaL and potential inci- dence of functional blindness. Favourable repercussions in human work capacity may also result from the progressive reproduct.ion of the physiological manifestations of onchocerciasis other than ocular lesions. Unfortunately, although some work to measure the loss of work capacity has been started, it is as yet difficult to draw con- clusions regarding the effect of the non-ocular manifestations of onchocerciasis. t Ia The second way in which the economic benefits of a control pro- graurne might accrue is through the opening up to settlement and Pro- duction of areas which, owing to the prevalence of the vector, have been utilised or under-utilised. (Points 3 and 5). This pre-supposes that. there are significant areas with considerable economic potential- which are at present virtually uninhabited and unutilised because the existence of nearby breeding sites of the vector creates a high risk of widespread and acute infeetion by onchocerciasis. The economic potential may consist of good agricultural land or of mineral resour- ces. The existence of land with such potential will nor by itself guarantee a flow of benefits. There must be evidence that the land is realIy needed for developtrent. Where there is a mineral resource potential-, it would be necessary to demonstrate that the governmenE is anxious to develop these resources and that their development would make a significanE contribution to the diversification and growth of the national product. Where it is a question of agricul- tural potentiaL, it would be necessary to marshal convincing evidence eirher (a) that there exist within a reasonable distance of the unoc- cupied areas other areaa where population pressures on available Land resourcea have become acute and where people have a sufficient incen- tive to move to unutilised land freed from the danger of onchocercia- sis, or (b) that the unutilised area is particularly suitable for a crop or crops which are important to the economy, cannot be grown in other parts of the country on an adequate scale and can be produced in the hitherto unoccupied area with manpower resources that could be mobilised elsewhere (sugar cane might be a case in point). In asses- sing the economic benefits of realising the production potential of areas hitherto unutilised or under-utitised owing to the prevalence of onchocerciasis, account must be taken of the often substantiat investments in infrastructure that wiLl need to be undertaken in such areas to bring about effective settlement and the potential production(net of extra investment foLlowing effect). By and large, little reliabLe analysis has been done to assess the reaL economic benefits (net of the costs in addition to the con- trol prograurme necessary to realise some of these benefits) result- ing from onchocerciasis control measures. The Costs The second question relates to the determination of the costs of a control programme and of the phasing of Ehese costs during successive stages of the control prograrilDe. Principal determinants of costs will be, for vector control, the number and geographic distribution of breeding sites (Point 3), including the length of streams which will have to be subject to larviciding, and, for epidemiological monitor- ing and chemotherapy, the ntrnber, location and distribution of infec- ted people (Point l). The experience of the OCP with the costs of the various types of operations involved in a control programne will be invaluable in arriving at, a cost estimate for any new area under consideration. Account. wiIl, of course, have to be taken of the l-atest developments respecting the technology of vecEor control and the effeetiveness of chemotherapy both in determining how effective a new control programme is likely to be and what, it will cost (Point 7) tn In calculating costs of a control operation some consideration may have to be given to the need for a contingency allowance toparry the possibility of reinvasion of the new controlLed area by vectors continuing to breed in an uncontrolled area. However, if there is a strong probability of such a reinvasion, the best way of obviating the danger may well be to make sure from the beginning that the new controL prograrme is extended to the entire area where the vector breeds. .If the flight patterns of the vectors indicate that the only possibility of reinvasion is from an area already under effective control, then obviously reinvasion will be no real threat and will not affect costs. The magnitude of costs will depend significantly on whether the area proposed for control (a) adjoins an area already under a control prograrnme in such a way that control operations can be more economically carried out by the already existing organisation as an added responsibility, or (b) is of such size and extent that a nerr project and new organisation will be necessary. In the first case, the cost of control operations in the new area are likely to be lower than the costs in the pre-existing control project primarily because the overhead costs of the control organisation are unlikely to increase significantl-y. In other words, the marginal or incre- mental cost of extending the geographic scope of the existing con- trol organisation may well be considerably lower than the average costs experienced prior to expansion of the controL area. Where the choice betl^reen extending t,he operations of an existing control organisation or the establishment of a new organisation is not clearly obvious, a careful estimate of the comparative costs of these turo solutions will be necessary. The Cost-Benefit Ratio In theory the flow of costs and benefits of the proposed con- trol project over time should be quantified and reduced to rrpresent values" by applying a discount rate, thus finally arriving at a cost,-benefit ratio. This ratio could then be compared with that of other possible health programmes or, indeed, with those of develop- ment projects in fields other than health. It is unrealistic, however, to expect that this can be done,partly because the rrstate of the art" does noE permit an acceptable quantification of most of the benefits and partly because the whote process would be unduly time-consuming. For instance, no feasible way has yet been found to put a value on the diminution of human suffering which is one of the principal benefits of a health pro- gramme. And a considerable part of the purely rreconomic" benefits such as those resulting from the ability to develop areas which previously have been too dangerous to occupy owing to the vector population cannot be quantified without prolonged and detailed investigations. Thus, while costs can probably be quantified, within a toler- able margin of error, a qualitative judgement will have to be made of the benefits on the basis of whatever evidence can be marshalled. D nI The Relative Priority of Onchocerciasis Control It is obviously desirable also to arrive at an informed judge- ment on the priority which an onchocerciasis programme should be accorded by comparison with other possibLe campaigns to deaL with other serious health problems or diseases (Point 2). Experience has 'shornrn that the resources - finance and skilled manpower - avail- able for public health programmes in Africa are extremely limited and that accordingly decisions on priorities cannot be avoided. rhe first step in the determination of priorities should be togather evidence that would permit a comparison of the prevalence and severity of onchocerciasis with that of other widespread dis- eases such as malaria, schist,osomiasis, guinea worm, gastro-intesti- na1 infections, trachoma, tuberculosis, measles, tetanus, etc. What do we know about the relative numbers of people infected by each of these diseases or disease complexes and about the impact of each of these on morbidity and mortality? Above all, can we arrive at some comparison of the number of people incapacitated for work by various diseases? what can be said about the probable impact of incapacities on productivity, particularly in agriculture in savanna Africa where at certain times of the team all family labour needs to be mobilisedif output is not to suffer severely. Admittedly, the evidence available on this subject is far from satisfactory. There are stilL large gaps in our knowledge about the incidence of disease, morbidity and mortality. I^Ie are only beginning to grapple with the question of the impact of disease on hunan pro-ductivity. Thus, untit the area of ignorance is substantially reduced, we shall have to content ourselves with estimates and, in sone cases, reasoned surmises. The determination of appropriate priorities does not depend solely on the comparative impact which prevailing endemic diseases have on the population. Of equal importance is the availability of an effective, feasible means of attack (preventive, curative or a Icombination of both) on any specific diseases or groups of diseases and the cost of waging such an effective campaign. Malaria, for exampte, is presumably the most widely prevalent disease in rural- Africa and has greater impact on the population than onchocerciasis,but, whereas cont.rol of t.he vector of onchocerciasis appears to have been proved effective, a comparable campaign against the mosquito vectors of malaria can hardly be adjudged either feasible or effec- tive at this time. Diseases which can, in varying degrees, be prevenEed by identical means can, for instance, be grouped. This would be true of diseases that would be reduced by effective provision of adequate supplies of hrater, safe for drinking and washing, complemented by improvements in personal hygiene and environmental sanitation. n 1' I a The Availability of ResoUrces and their Comnitment The last question affecting decisions whether or not to initiate onchocerciasis control operations in a new area relate to the availa- bility of qualified staff to start the operations and the willingness of all the parties concerned to find the resources and undertake the commitment necessary to see the project to a successful conclusion. The initial availability of qualified personnet is an issue only when a new organisation is to be created and staffed to undertake the con- trol operations. There must be reasonabLe assurance in such a case that professionals which are likel-y to be in short supply, such as medical entomologists and epidemiologists, can be found. The govern- ment or governments of the country or countries in the proposed area must suppty evidence of their willingness to (a) contribute signifi- cantly to the financing of the project for its duration, (b) assume progressively, at appropriate tiues in the future, responsibility for various control operations aE the national or regional 1eve1, and (c) with a view to this assumption of responsibil-ity, collaborate fu1ly with a programrDe for the training of the requisite national personnel and provide for these trained people conditions of employnent and career opportunities that will give them an incentive to stay on thejob. Similarly, there must be a reasonable assurance that aid-giving governments and institutions will pledge sufficient ext.ernal resour- ces to ensure the financing of the project not only while it is being carried out by an internationaL organisation, but also during the transitional period when the national government or governments of the area will be assuming responsibility both collectively and indiv- idually for operation of the programre. I