Report to the Scientific and Technical Advisory Committee on a visit to the Onchocerciasis Control Programme in the Volta River Basin Area: 19-31 October 1975

SCIENTIFIC AND TECHNICAL ADVISORY COMMITTEE oCP//STAC3.1 Th.i.rd meet ing ORICINAL: ENGLISH Geneva, 2-4 March 1976 RESTR I CTED 4gq.rq._ rte* 5 Report to the Scientific and Technical. Advlsory Commlttee on a visr.t to the Onchocerciasis Control Programme in the Volta River Basin Area 19-31 October 1975 by George S. Nelson Director, Department of Medical Helminthology, london School of Hygrene & Troprcal Medicrne tileport to the Scientific and Technical Advisory Conrnittee on a visit to the 0nchocerciasis Control lroglgrnrne in tle Vglta BlvelBqsrn lqrqa l9th - 3lst 0ctober, 1975 b-v George S. llel son Director, Departrnent of t!edical Helninthology, London School of Hygiene & Tropical tledicine I ntroducti on The visit was arranged as part of the schene designed to let members of the Scientific and Technical Advisory Cor,mittee see as much of the work of the Control Programme as possible. Thanks to the unstinted efforts of the 0irector and his staff opportunities vrere provided to see a great deal in the limited time available. An ilinerary of the nain aspects of the visit is attached to this report. 0n my return from 0uagadougou I visited Geneva to take part in the Expert Cormittee on the Epidemiology of Onchocerciasis from the lOth to the lSth of I'lovember. This provided an opportunit-v to discuss sorrre of my observations with Dr. Bellerive and other members of the ocp staff in tlHo headquarters. The main conclusion from th'is visit was that although the control programme seems to have been successful in some parts of the Phase I area the constant reinvasion by S.damnosum, especially in the south, is so disturbing to the morale of the field staff that a reappraisal of the control techniques and the phasing of the programme is necessary. Contro'l programmes based on methodologies which are known to be effective for example in the control of yellor fever, small pox, louse-borne typhus or even malaria in subtropical areas require administrative rather than scientific skil ls for their success. 0nchocerciasis is different especially on such a vast sca'le as the present programme. This is an operational research programme requiring 2large scale experimentation and the development and implementation of new techniques to meet changing conditions. The present staff recognises this need and although there is optirnism about the longterm success of the orograffine the routine vrork is so demanding in time and effort that there is insufficient time to tackle the research problems that are essential. The field staff has few opportunities for initiating research and there is considerable resentment to the farming out of local research problems to institutes and individuals who are not directly involved in the prograrme. A major deficiency is the lack of a central headquarters in 0uagadougou with laboratory and clinical facilities, where the OCP staff can collaborate with visiting scientists in solving many of the problems facing the programme. Unless this is provided it is unlikely that the prograrnme will attract or retain staff of high enough calibre to ensure the eventual control of the disease. Without a brain centre the body cannot function, it is a grave nristake to believe that the heart and brain of the programme can be in Geneva and only the torso in the programme area. It would help if there were more formal meetings in 0uagadougou where the professional staff could discuss the progress of their work and if there were more opportunities for the field staff to initiate and take part in the discussion on research needs with WHO staff in Geneva and with members of STAC either individually or by attending meetings of the committee. In the following report I have mentioned only a few of the problems that I encountered during my visit; some of these problems will require attention before the next meeting of the Scientific and Technical Advisory committee, others are longterm. I am convinced that the control of the disease is possible throughout the greater part of the programme area but this will depend entirely on the staff in the fie'ld; they are doing an excellent job under extremely difficult conditions but it will be necessary to establish a much better esprit de corps if the prograrme is to succeed. i 3I The satisfaction one gets from doing this type of work is the knowledge not only that one is succeeding in controlling the disease but also that one is successful in producing new knowledge and the resulting self esteem when people vrorking on similar problems recognise the quality of one's work. Epidemiology The purpose of the present surve.v is: 'l) to determine the prevalence of the disease in the area 2) to detennine the severity of the disease and especially the amount of blindness due to onchocercias'is and 3) to provide data that can be used to assess the efficacy of the control measures. This .is a formidable undertaking for two teams operating over such an enormous area. I was fortunate in having the opportunity of working with one of the epidemiological units in Ghana. The organisat'ion was very impressive; the demographic study uras thorortgh; the cooperation of the people was good and the exam'inations were highly competent within the limits of the existing protoco l s. My main concern was with the parasitological techniques. If the parasitolog'ical data are to be used to determine the effect of the control measures they must be accurate, reproducible and sufficiently sensitive to detect light infections'in the younger age groups so that cohorts of negative cases can be followed to determine the effect of control measures on the incidence of the disease. Changes in prgv6lence and changes in intensity of infection are less sensitive measures of changes in transmission but the relationship between intensity of infection and the severity of the disease is so important that accurate intensity data are also essentia'|. 4Skin Snjp Techniques I worked wi th the laboratory assistant checking his microfi larial counts and at the same time using the same skin snip material to estimate the number of microfilariae escaping detection by the method he employed. It was soon obvious that the use of water rather than saline and the failure to remove the skin from the slide after emergence of the microfilariae to reveal those hiding under the snip, resulted in a serious underestimate of the number of microfilariae present. In 22 positive specimens examined by the'laboratory assistant he recorded a tota'l of lllg nricrofilariae. In the sarne 22 snips after removal of the skin I recorded .l729 microfilariae. in 58 negat'ive specimens examined by the laboratory assistant I found micro- filariae in 5, these were a'll young children with very low counts. Dr. Brinkman then took a batch of duplicate snips from the same site from another group of patients. The laboratory assistant examined one of the snips by the standard method, the other was placed in normal saline in a microtitre tray and 24 hours later the microfilariae were fixed by adding one drop of formal saline. The preserved specimens were taken to Ouagadougou for detailed counts and weighing of the skin snips. Unfortunately the laboratory facilities in 0uagadougou were inadequate so the material was taken to London. A preliminary comparison of this material showed that the counting of killed and preserved microfilariae is an extremely simple procedure: it avoids the necessity of examining live and wriggling specimens under difficult field conditions, it saves on the transport of'laboratory assistants to the field and it allows for a much more standardised procedure under far better laboratory conditions. Where there is pos sible confusion wi th Dipetalonema streptocerca the microfilariae can be examined after filtration and staining on millipcre filters using the technique developed in Togo by Scheiber and his col leagues. In the first batch of 39 snips examined by this method the laboratory assistant found 33 positive with a total of 1933 microfilariae whereas the ? 5preserved snips produced 36 positive with 4716 microfilariae. Both the filtration method and the simple formalin preservations methods are likely to prove much more sensitive for detecting light infections in children and in areas of low endemicity. The implications for the Programme are obvious. I have discussed the results with Dr. Kramer, Dr. Prost and Dr. Brinkman, and they are keen to improve the present rnethods. I have supplied them with some of the equipment to compare the various methods. llt was surprising to discover that there was no torsion balance available in the OCP area and no equipment for filtration even though WHO Expert Cormittees have recorrnended their use in special surveys.l Cl i nical Examinations Sufficient privacy was provided to carry out a thorough clinical examination. Dr. Brinkman took careful photographic records of all suspicious skin lesions with a view to establishing reliable clinical diagnostic criteria. Several cases of hanging groin were seen together with one caseof onchocercal elephantiasis of the scrotum. Another patient had a massive squamous epithelioma over the upper thigh where a large nodule had been treated with native medicines. Particular attention was given to detecting nodules around the head. It was interesting to note that the patients themselves were often better able to demonstrate head nodules than the physicians. The ocular examinations were exceptionally thorough. The mobile air-conditioned dark room mounted on the back of a truck provided ideal conditions for work with a slit lamp and for recording the data. It was obvious that as with the skin manifestations there were many equivocal cases where the onchocercal etiology was uncertain. The raison d'ttre of the entire programrne is to reduce the transmission so that onchocercal eye disease is no longer an impediment to development; it is ironic that one of the first of the new economies has been to delay the appointment of a second ophthalmologist. It is realised 6that there are so few ophthalmologists available that recruitment has proved difficult but it was contended that a more vigorous advertisement campaign might have attracted more applicants. Dr. Thylefors has no understudy, if he were to leave the programme either due to il'lness or any other cause' the entire special survey programme would be immediately halted. If Dr. Thylefors'is to be retained by OCP it is essential that he should be encouraged to participate in research on various aspects of the ocular aspect of the disease. He must be provided with clinical facilities where he can study patients in more detail and where some form of treatment is available for selected cases. A doctor who is prevented from treating at least some of his curable patients must inevitably become frustrated. One of the ophthalmologist's function is to train local medical personnel. I had the opportunity of seeing Dr. Thylefor's careful instruction of an aspiring ophthalmologist from Mali. Data Analys'is The epidemiologist and the clinicans emphasised the need for a more rapid feed-back mechanism from those responsib'le for analysing the data. There was considerable concern that the parasitological and clinical data were accumulating in Geneva and that computerised analysis was not yet available. The epidemiologists and the entomologists were also worried at the lack of integration of the entomological and parasitological data. It was suggested that evidence of changes in transmission might be obtained more rapidly if rnore'intensive surveys were carried out in a few selected areas provided that the results of the analys'is were more rapidly available It was also suggested that use shou'ld be made of the existing computer programmes and the statistical expertise in London where computer analysis of the data from the Camerouns has been in progress for the past 5 years. It was recommended that Mr. T. l'larshall, statistician in the London School who is in charge of the Cameroun analysis, should be asked 7to help with the methodology to ensure compatibility of analysis of data from the two areas. Soci o I ogy Professor Pairaurtwas the sociologist with the team in Ghana' He was responsible for the demography and on the days of the survey he patiently interviewed everyone andwtththe help of the Chief he obtained information on missing families. As a result of his enquiries we discovered that most of the missing individuals urere busy with the ground nut harvest but by allor^ring them to finish their work in the fields 'in the morning and examining them in the afternoon a full attendance was achieved. Professor Pairault was uncomplaining about the rather mundane job that he was doing but the failure to estab'lish the Economic Developrnent Unit has meant that his expertise has not been adequately exploited. The impact of human behaviour on the transmission of the disease is probably the most neglected aspect of onchocerciasis research. The provision of alternative water supplies away from the rivers, changes in agricultural practices, changes in economic status with more protective clothing, the increased use of natura'l repellants all might reduce transmission but these and many other sociological aspects of the problem are not being studied. A major deficiency of the prograrme is the'lack of information on the effect of vector control on resettlement. I saw several new villages along stretches of the B'lack Volta; there are also tea plantations near Koloko and sugar estates near Banfora in areas where transmission was at one time active. There is considerable inrnigration into the prograffine area from the north but there is insufficient data to assess the significance of onchocerciasis control in relation to these settlements. This is a difficult problem to assess but since the long term financia'l support for the prograrme depends on producing convincing evidence of the economic benefits to the 8commun'ity a much more vigorous effort is required to produce this evidence. En tomo I ogy The purpose of the entomological programme is to interrupt or reduce transrnission. It is not a vector erradication prograrnme. The eventual objective is to ensure that the disease is no longer a public health problem. At the present time control of the vector is considered to be the only practical method of attaining this objective but it is hoped that more effective chemotherapy will be available during the later stages of the programme to supplement vector control. The brief visit that I made to Bobo-Dioulasso, together with the discussions I had with the entomologist and the trip by helicopter to see the dosing parts of the Black Volta were very interesting but quite inadequate to assess the success or otheruise of the Phase I operation. I saw only a small part of the area and I saw very little of the work of the evaluation teams and I had no opportunity to dissect adult flies for infection. Also I had no opportunity to visit the problem area in the South where reinvasion is a major problem. l4y general impression of the contro'l operation was that it was highly efficient and that there was excellent collaboration between the entomrlogists and the aircraft and hel'icopter p'ilots. Formidable d'ifficulties have been overcome, including the replacement of the damaged aircraft and he'licopters and the problem of supply of insecticides but there are still serious problems with ground transport and there is a feeling of uncertaintly about the quality and rel'iability of supplies of insecticide and spare parts. I was present at the weekly briefing. I saw something of the mapping and I listened to the reports of the entomological assessment teams. There seems litt'le doubt that S.damnosum is under control in most of the central and northern part of the Phase I area but there are problems of reinvasion not only in the South but also in the East along the Black Volta from the 9t unsprayed Phase II area and also in the South West and North West in l4ali' It is perhaps ironical that the most expensive and most effective control area has been the Gr6chan rapids where there is no disease because the area is uninhabited except by a few hippopotamuses' In September 11,000 litres of Abate were used costing'10 u's' dollars per litre, much of this was poured into rivers where there is either no transmission or where reinvasion is resulting in fly densities that are not significantly less than in the precontrol period' for example the Bandama river. It would be a d'ifficult decision to stop the routine application of insecticide in these rivers for fear of reinfestation of other rivers now apparently free from breeding S.damnosum. This'is particu'larly the case with the present philosophy which aims at elimination of all S'damnosum breeding in the central area with progressive expansion of the cleared zone as the control of the periphera'l areas is expanded in Phase II and Phase III' Experience over the past 6 rnonths suggests that reinvasion in the South is not a temporary migration due to peculiar climatic changes' it isa!g]]yoccurrence.InafewcatchingstationsontheBandamariver daily biting rates have remained at over 50 for many months with no evidence of local breeding. l'lost of the f]ies are parous and the infection rate remains high. A]though there is no rea't evidence it is thought that the flies originate from breeding sites at lease 100 km to the South' Dai]y migrations of this extent might have been expected from experience e'lsewhere' The likeliest flight route is along the rivers. If this is the case then the application of adu'lticides might provide an effective barrier' Large scale experiments are necessary but the present staff is too invo'lved with routine control measures to give the problem the attention'it deserves' The frustration is all too obvious because the area involved is politically sensitive and it is one of the areas earmarked for resettlement' It is also a problem that will not be solved by the Phase II expansion because the IO invasion comes from outside the programme area. There is a need to rethink some of the present objectives and to study different methods of control. Some of the finartcial and other resources at present employed in treating rivers where there is no immediate onchocerciasis problenr rnight be better spent in operationa'l research in the southern invasion areas. The Entonrological Evaluation Units provide fairry reriabre information on biting densities and on the parous rates of flies but it is admitted that the area covered is inadequate. The recorded infection rates are of doubtfui value since Garms has shown that not all the infective larvae are O.volvulus and up to the time of my visit no attempt was being made to identify the larvae from routine collections. A helrninthologist in the Centre Muraz was supposed to be helping to identify larvae but he had made no effort to collect larvae since Garms' visit and he seemed to have no idea how to set about collecting reliable reference material. It would be better for Dr. Davies to investigate the problenr with the help of Dr. Garms or with help from my Department rather than rely on a helminthologist who has neither the expertise nor the enthusiasm for the job. The same deficiency in laboratory accommodation exists on the entomological side as in the parasitology side of the programme. The lack of a central OCP laboratory is a major deficiency which cannot be remedied by farming out research activities to institutes such as the Centre lluraz. Any serious attempt to identify the larvae in S.damnosum will involve studies on (a) the morphology of the'larvae (b) the host preference of S.dam{osum in different areas (c) a survey of filarial parasites in the animal and bird host (d) transmission experiments to study the susceptibility of S.damnosum to infection with suspected parasites (e) the inoculation of larvae from S.damnosum into animals and birds to recover adult vJonns. There is usually no difficulty in distinguishing species of filariae of other genera but since there are other species of Onctrocerca in domestic and wild animals I tl1 in the area special attention will have to be given to this problem. It would be particularly interesting to examine s.damnosum in areas where there is very little contact with man to see if the flies are infected and with what type of infective larvae. Apparently there are such areas in the Phase III zone. Studies on the types of infective larvae in S.damnosum are of obvious significance in relation to the transmission of 0.volvulus. The proper identification of different species of filariae in the flies may also be of value in studies on migration and on the different cytotaxonomic types. Trypanosomi as i s The UNDP financed Trypanosomiasis Survey Unit under the direction of Dr. D.H. Molyneux is already established in Bobo-Dioulasso. Discussions were held with various people involved and everyone seemed to be keen to be closely associated with the onchocerciasis programme. Sleeping sickness is a hazard already experienced by ocp entomological staff. Dr. i,lolyneux agreed that'it might be of value to screen OCP fieldstaff at regular intervals to detect early infections. irne last case was only detected in a'late stage of the disease.] A pilot project for the control of riverine tsetse is being planned for one of the river systems in Niger by FAO staff. It is proposed to use helicopters to spray ultra low volume insecticides as adulticides. I met the field officer in charge, Dr. Jan Van Veghten, and he said that S'damnosum is present on the rivers selected for the pilot tsetse control project. We had discussions together with Dr. Le Berre but I sensed some antagonism and little enthusiasm to make this a joint operation. This is unfortunate because the use of ultra low volume spraying may be of some value in limiting the migration of S.damnosum into cleared areas and also because sleeping sickness and onchocerciasis are so intimately related in terms of ecology and resettlement. 12 In concluding this report I would like to acknowledge the marvellous way in which all the staff in the Programme area went out of their way to he'lp make this short visit so worthwhile. I regret that my visit causdso much inconvenience, I regret the interruption of the routine work but I hope that the opportunity for scientific discussion was of sorne value. I am particularly grateful to Dr. Z'iegler for organising the 'itinerary and for his hospitality and to Dr. Le Berre who was unstinting in his help even though he only returned to Bobo-D'ioulasso on the day of my visit. t I ti nerary '13 of Visit bv G.S. Nelson to the 0nchocerciasis Control Programme Area lgtn 0ctober Left London 20th 0ctober a.m. Arrived 0uagadougou p.m. Meeting with the Director and staff for a General Review of the Prograrnme. Various aspects of the work were presented by: Dr. Ziegler, Dr. Thylefors, Dr. Kramer, Dr. Brinkmann, Dr. Baldry, Mr. Walsh, Dr. Davies, Professor Pairault, Mr. Fatoyinbo and Dr. POnS 21 - 24th 0ctober Visit with the Epidemiological Unit to Lawra [Kramer, Brinkmann, Thylefors , Pairault and Bi nz] 25 - 26th October Ougadougou. Discussions with Kramer, Brinkmann, Prost 27th 0ctober 28th October 29th 0ctober 30th 0ctober 3lst October and Davies Bobo-Diou'lasso Attended weekly briefing and review of Vector Control Preliminary Discussions with Dr. Le Berre and Mr. Hendericksx Helicopter flight with Le Berre and Davies to observe insecticide application on the Black Volta Visits to Koloko, Sikasso, Loumana, Gr6chan and Banfora Discussions with 0r. l{olyneux and Dr. Jan Van Veghten on UNDP Trypanosomiasis programne Discussions with Le Beme and Baldry V'is'i t to Centre Muraz wi th Dr. Davi es to meet Dr. Prod t hon Return to Ouagadougou a.m. Discussions with the Director Discussions with Dr. Walsh l4eeting with Kramer, Thylefors, Brinkmann, prost, pairault and t'lalsh for final discussions on the epidemio]ogy To Paris (delay due to strike by Airport workers) To London.lst November