Expert advisory committee twenty third session, Ouagadougou, 23-27 September 2002: progress report by unit vector control (March to August 2002)

t{ WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE ONCHOCERCIASIS CONTROL PROGRAMME IN WEST AFRICA PROGRAMME DE LUTTE CONTRE L'ONCHOCERCOSE EN AFRIQUE DE L'OUEST EXPERT ADVISORY COMMITTEE Twenty-third Session Ouagadougou. 23 - 27 September 2002 EAC23.1 Original :French PROGRESS REPORT BY UNIT (March to August 2002) Part I = Part 2 = Part 3 = Vector Control Planning, Evaluation and Transfer Adminis tration and support serttices Page2toll Page l2 to 26 Page 27 to 29 t T A a2 PART 1 VECTOR CONTROL 3SALIBNT POINTS OF VECTOR CONTROL ACTIVITIES IN 2OO2 HYDROLOGY AND AERIAL OPERATIONS 1. Hydrology Rainfall was not homogeneous in the rvhole of the Programme area in 2002.In the Eastern zone, the rains were early this year compared to last year. Thus, the quantities of rains recorded in March and May are higher than those of the same months of 2001. From January to May, only February had no rains. In the Western Zone, a delay was observed in the resumption of the rains. This delay affected florvs during April and May 2002 in the majority of the basins except for the Niandan basin which had rains in time. In almost the whole of the river basins of the Western Zone, the fall in the water level of the hydrological year (2001-2002), compared with that of 2000-2001, was less marked until the fifteenth week of 2002, due to the positive hydrous results of the last season. This year, due to the reduction in the larvicide coverage the hydrometric network was also reduced by almost 28yo.It is now composed of 8l limnimetric stations 34 of which are equipped with beacons. 2. Aerial contract and flights hours The year 2002 marks the end of the last four-year contract signed with the Evergreen Helicopter Company (EHI). In view of the activities to be carried out in 2002 following the suspension of aerial larviciding in several basins in the Programme area, the air fleet was reduced from five to three helicopters, and from 3001.6 guaranteed hours to 1999.2 hours. Like the previous years, the concerted management of flight hours in 2001 in the two Zones made it possible to limit the expenditure in flight hours to the guaranteed hours envisaged for this pulpose; thus of a total of 3001.6 hours guaranteed to the company,3001.7 hours were ictually used for the treatments. The maintenance of the helicopters was satisfactory in 2OOl. Engine failures reduced from 30 to 22% compared to the total breakdowns, and radio breakdowns from l0 to 6Yo. No breakdown of batteries was noted. In spite of this good perforrnance, particular attention must be given to the spraying system of and the pumps for kerosene and insecticide whose breakdowns are on a considerable increaieithese breakdowns have increased from 7 to 25oh for the spraying systems and 0 to 28%o for the insecticide and kerosene pumps. The situation seemed to be well controlled for the first semester of 2002 as only two breakdowns were noted. 3. Use of the larvicides For the same larvicide coverage area, insecticide consumption in 2001 reduced by 6% compared to that of 2000. It must also be noted that the biological insecticides were favoured during the Lrvicide treatments.Thistendencycontinuedin2002; thequantityof B.t H-14usedaccounts forg6yoof the overall larvicide consumption during the first half of the year. 44. Product Losses The sustained effort of the VCU teams, the populations and the administrative authorities in the management of the kerosene and insecticide depots made it possible to reduce considerably the losses of products, thus passing from2,4o/o loss of total stock in 2000 to l.5oh in 2001. These results could have been much better this year, had it not been the loss of products caused by the poor quality of packing and/or covers of the barrels (pyraclofos, phoxim, etofenprox, permethrine), and the ageing of stocks (carbosulfan). On the whole thefts, leakage and contamination cost the Prograrlme, US$69 582 in 2001, against US$134 890 in 2000; that is, a reduction of US$65 308 (48.5%). No kerosene and insecticide loss was recorded in the Programme area from January to June 2002. RESULTS OF THE ENTOMOLOGICAL EVALUATION A) WESTERN ZONE The results from January to June 2002, compared with those of the same period of 2001, show a certain upward trend of the partial annual transmission potentials. However for the moment, the highest value of transmission of O. volvulus is 66 and relates to Fifa where nearly 70%o of the parasites found are different from O. volvulus. The Middle Niger in Mali: The ground larviciding as well as the distribution of the ivermectin will continue in this basin until the end of December 2002. Animal filaria occupy a significant place (84%) in the transmission and generally mask the downward trends of the ATPs in this basin. Nevertheless, the first half of 2002 is marked by the absence of infection on the Faya and the Dylamba. At Tienfala, the partial ATP is 16 both for the transmission of O. volvulus and that of all the parasites. The Sassandra in COte d'Ivoire and in Guinea Conakry Larviciding was definitively stopped at the end of December 2001 on the Upper Sassandra in C6te d'Ivoire. The reduction of the crude ATP there was higher than 95 % in 2001 on the five monitoring points. Trends have been on the decline since 1991 and the savana ATPs lower than 100 since 1993 (except at Vialadougou where this ATP was 147 in 2000). This exceptional transmission was only a false alarm as no infected female was recorded there in 2001 (crude ATP : 0). Larviciding was stopped on December 31, 2001 on the Upper Sassandra in Guinea Conakry. The reduction of the crude ATP there varied between 89 and 100 % on the Upper Bafing and Upper Bagb6. The savana ATP has remained lower than 100 since 1993 on all the five entomological monitoring points (savana ATP: 0 on all the capturing points in 2001). 1 2. 53 Sankarani and Milo in Guinea Conakry In the basins of Sankarani and Milo, the reduction of the crude ATPs varied from 78 to 100 o/o onall the thirteen (13) entomological monitoring points. Transmission has been dropping steadily since 1990 and savana ATPs have been lower than 100 since 1993. No transmission of O. volvulus was recorded in 2001 on all the capturing points of the basins of Sankarani and Milo. Larviciding was stopped here on December 31,2001. Niandan in Guinea Conakry Larviciding is being maintained in this basin until the end of December2002 due to its role as a barrier between the untreated zone and that still under treatment. The reduction of the crude ATPs varied between 97 and 100% in 2001. The savana ATPs have remained lower than 100 on all the seven (7) monitoring points since 1993. In 2001 , only the capturing point of Sansambaya presented savana ATPs reaching 28. Upper Niger-Mafou in Guinea Conakry Larviciding will continue in this basin until the end of December 2002. The reduction of the crude ATPs varied between 87 and 100 % and the trends have been on the decline since the beginning of the combined treatments of larviciding and ivermectin in 1989 (except in Balandougou, Ser6koroba and Yalawa). The resumption of the transmission on the Mafou since 1996 is due mainly to forest flies (savana ATP lower than 100). However, at Yalawa, savana ATP above 100 were observed in 1996 and 1997. The specific actions implemented made it possible to obtain good results with savana ATPs of 35 in 1999 and 2000. No transmission of O. volvulus was recorded in Yalawa in 2001. The partial ATP of O. volvulrzs is lower than 100 for first half of the year of 2002. Tinkisso in Guinea Conakry Larviciding and specific actions will continue in this basin until the end of Decemb er 2002. The trends of crude ATPs are falling, with a reduction from97 to 100 oh.The rise in the transmission since 1995 seems localised around Fifa where the savana ATP went up to 510 in 1998. The specific action implemented made it possible to again obtain good results in 1999. The ATP of O. volvulus by the savana species in 2001 was 2l in Lab6ro,42 in Konden, and 7l in Fifa. This year, the transmission was intense in the first six months with partial ATPs of 66 in Fifa and 63 in Lab6ro. It is zero for the moment in Konden. B) EASTERN ZONE In this zone, the excellent results recorded on the basins of Mono and Sio in Togo, and the tributaries of the Volta Lake in Ghana and Togo, both on the entomological level since the establishment of the extensions in February 1988 (ATP lower than 100 for nearly l0 years) and on the epidemiological level, made it possible for the final suspension of larviciding in these basins on December 31, 2001. The difficulties met relate especially to the basins of the Pru in Ghana and the tributaries of Oti in Togo and in Benin on which a particular stress is laid in this document. 4 5 6 61. Pru The captures started in 1978 while the larviciding and the distribution of the ivermectin started only rn 1988. We thus have l0 years of data of pre-control on this basin. The black fly population is made up almost exclusively of savana species of S. dantnosut?l. A very intense transmission (ATP:3330) was recorded in 1978. The identification by DNA probe of the parasites collected from January 1993 to December 2000 showed that 2Oo/o of these parasites are forest O.volvulus ;48% of savana O.volvultts and32o/o of other parasites. Larviciding was suspended from the 33'd week in 1988 and 1989 for studies of xenodiagnosis and the impact of the ivermectin on the transmission. From 1990, lower Pru was treated up to 2002 with the ,.u.n OCP larvicides used in rotation. In the dry season ground larviciding is implemented. The reinforcement of prospecting teams and ground larviciding allowed for a suspension of the aerial larviciding for 26 weeks in 2002 against 13 for the same period of 2000 and 2001 . Although having decreased to a significant degree, the annual transmission potential oscillates around the tolerance level of 100, more precisely between 63 and 189 from 1997 to 2001. The situation basically did not improve in spite of the stringent measures put in place in 1996 / 1997 (extension of the larviciding coverage, accompaniment of the pilots, increased monitoring of the tributaries, intensification of the prospecting and ground larviciding). The corrected ATP from January to December 2001 is 140. For the first six months of 2002, the ATP for O. volvulus is seven' 2. Tributaries of Oti (Kara-K6ran-M6) Captures have been going on since 1976 in 07 points on K6ran, 04 points on Kara, and in 06 points on M6. The vector species seen from January 1994 to July 1997 are primarily: - on K6ran - Kara -M6 98 o% savana,02 o/o forest 84 o/o savana, 16 %o forest 52 o/o savana, 48 o/o forest The transmission there is due mainly (92%) to the savana females and 8 oh to the forest females. The identification by DNA probes of the parasites collected on K6ran, Kara, MO from January 1993 to July 1997 indicates that approximately 72o/o of the larvae are O. volvulus (ll % of forest O. volvulus and 6lYo of savana O. volvulus) and the remaining 28 o/o are not O volvulus o K6ran, Kara, M6 (tributaries of Oti) have been regularly treated by air since 1977 to date. In 1993, the larviciding which also started in 1977 on Oti (main river) was suspended following the good entomological and epidemiological results recorded. The suspension also concerned the lower K6ran and the lower Kara. o In 1997, following the poor entomological results recorded in May - June, special measures were taken to increase the effectiveness of control operations. These actions consisted primarily of : i) intensification of the ground larviciding in support of air treatments; ii) increase in the larvicide coverage by the inclusion of the lower K6ran and lower Kara and their confluence with Oti. iii) treating the main Oti before the increase in water level for four to six weeks. iv) reinforcing the treatments of Upper Ou6m6 which could be the source of the blackflies re-colonising the upper K6ran and the Kara. , 7The analysis of the entomological results shows that the annual transmission potential on these rivers started reducing significantly only from 1988, date at which larviciding began in the south-eastern extension. Beside the exceptionally high transmission recorded in 1997, the situation on these river basins is as follows: - on the lower K6ran, the crude ATPs which was around 1500 before the beginning of the operations were reduced by almost 90%o and even more if one takes into account the results of these last two years where the transmission is below the tolerance level (77 and 7 in 2000 at the tri'o catching points (Titira and Tapounde), which were the most affected, and 72 and 28 in 2001). The partial crude ATPs for the first six months of 2002 are 14 at Titira and 40 at Tapound6, thus by far lower than the tolerance level; - on Kara and M6, the situation in terms of transmission of the human onchocerciasis is well controlled since 1994 with O. volvulus ATP of below the tolerance level. The blackfly densities during the first six months of 2002 were everywhere lower than those of the same period of the previous years. Nevertheless on the M6, an increase in population was recorded during the last weeks of May and June. Generally, even if the entomological results improved on the Pru and the tributaries of Oti compared to that which prevailed before the beginning of the operations, the current situation of the transmission on M6 which is to be seen in relation with the cessation of larviciding of the eastern tributaries of Lake Volta requires great caution. It is therefore important to maintain the pressure for a few more years to ensure the elimination of the parasite reservoir in these zones and thus avoid a premafure resurgence of the disease. Ou6m6/0kpara The situation is satisfactory on the upper Ou6m6 with an annual transmission potential below the tolerance level at all the points visited. On the other hand on the lower Ou6m6, even if the situation is satisfactory in Atcherigb6 and Aguigadji with ATP below the tolerance level, the O. volvulus ATP remains higher than 100 in Mb6t6koukou. The same situation prevails in Kaboua and Djabata. OPERATIONAL RESEARCH Blackfly Movements and identification of vectors and parasites Generally, the data collected during 200112002 are of a particular importance as they mark the end of activities undertaken relentlessly for three decades, and emphasise the main trends to be considered for a suitable planning of the operations necessary for the maintenance of the achievements of the Programme. Within the framework of the actions initiated by VCU for a detailed analysis of these trends, a particular accent was put on the study of blackfly movements, a phenomenon which could, in some cases, compromise the effectiveness of the activities for the maintenance of the achievements, particularly in the river basins harbouring alternatively balckfly populations of various origins. This refers in fact to the basins of the zone of transition forest-savana characterised by the presence of savana species of S. damnosum s.l. some of which are involved in migratory movements from the 3 I 8south-west towards the north-east at the beginning of the raining season and in the opposite direction at the beginning of dry season. Due to the seasonal nature and the magnitude of these movements, it is important to stress that not all the foci concerned benefited from the activities of the Programme for the length of time necessary for the stop of the transmission. Even if such a situation relates only to Sierra Leone, it could be alarming insofaias the research undertaken in 1988/1989 on re-invasion showed that the North of this country is regularly affected by the blackfly migrations as evoked above. Besides, these observations are in agreement with the data recently recorded within the framework of special studies mainly based on the cytotaxonomic and molecular biology (microsatellites) techniques oi identification. In iact, these studies, still in progress, show that the S. sirbanum populations are actually implied in the great movements covering the river basins of Mali and Guinea. These migrant populalioni of S. sirbaium could well come from non decontaminated areas of the North of Sierra L.br., due to the proximity of this foci, and its geographic position in relation to those of Guinea and Mali (South-westA{ord-east axis). To verify this assumption, of many samples collected in 2002, simultaneously in the river basins of North Sierra Leone (Seli and Kabi-Mongo of Guinea (upper Niger/Iv1afou, Milo and Niandan) and of Mali (Baoule) are currently being analysed by the DNA laboratory of O-CP in collaboration with the IRD of Monfpellier. The iarvae samples will also be analysed in collaboration with a specialist in cytotaxonomy from the "Noguchi Memorial Institute for Medical Research " in Accra. Similarly, the infectivity of flies in the north of Sierra Leone between December 2001 and June 2002 were compared with that which prevailed there in 1996. Only six (6) infectious females were captured in Yirafilaia and Kaba Ferry. The identifications carried out by the DNA probes indicated five females carrying savana O volvulus and one female infected by larvae of animal origin. In 1996, at the same period record was made of 22 infectious females at the points of Musaia, Yirafilaia and Arfanya. No infectious fly was found at the time of the study 2002 at points Musaia and Arfanya. Samples collection in connection with the blackfly movement study are also in progress in the Eastern Zone. The analyses of these samples will undoubtedly make it possible to appreciate the magnitude of the blackfly movements on the iouth-west/north-east axis covering the basins of Pru in Ghana, the tributaries of Oti in Togo and those of the Niger in Benin. For these studies and for routine entomological evaluation, the molecular biology laboratory continued to ensure the identification of the parasites collected by the entomological network to enable the correction of the transmission parameters. The infecting larvae of 291 infectious females collected in the zones under larviciding, were thus identified during the 2000-2001 entomological year. The females carrying parasites of animal origin accounted for 7\Yo. The zones having a high rate of human parasites are the special intervention zones. The partial results obtained up to June 2002 is identical to what was observed for the previous period. A particular stress was laid on the treatment of the infections coming from the specific intervention zones. The identification of parasites also related to parasites coming from the APOC countries. 2. Follow-up of blackfly sensitivity to insecticides Due to the strict application of the restrictive measures recommended for optimum results of the insecticide rotation strategy, the risks of appearance or intensification of resistance to organo- phosphorus are considerably minimised at this period of end of the Programme. In addition to the tests carried out within the framework of the routine monitoring, this period is also marked by the continuation of the investigations initiated in 1999-2000 to evaluate the sensitivity of the blackfly 9populations in the river basins where vector control activities were stopped after several years of intensive larvicide treatments. In the Western Zone, these investigations showed that on the majority of the rivers no longer under larviciding for at least five years, the sensitivity of the blackfly populations has been generally normal to temephos and phoxim, and intermediary to pyraclofos. The weakest level of sensitivity were observed at Markala-barrier on the Niger (NN300) where resistance to the pyraclofos became obvious. Concerning the basins on which the treatments were recently stopped (Sankarani and Milo in Guinea), the larval populations show generally a normal sensitivity to phoxim and intermediary to the other trvo organo-phosphorus. Data collected on the rivers under larvicide treatment indicate a case of resistance to temephos on the Niandan in Bagou6 (ND500). The analysis of the results of cytotaxonomic identification revealed that the larvae having tolerated the strongest concentrations of temephos (1,25 and 2,5 ppm) belong primarily to the S. damnosum s.s. species (approximately 44 oh), whereas the lowest levels of sensitivity to pyraclofos are observed in the S. sirbanum which constitutes approximately 72o/o of the larvae living or dying at 0,078 ppm. It must be pointed out that among these less sensitive larvae appear a considerable proportion of S. damnosunt s.s. / ,S. sirbanum hybrids (respectively 26 % and 1 I o/o of the larvae having tolerated the strong amounts of temephos and pyraclofos) In the Eastern Zone, no case of resistance to organo-phosphorus was encountered during the last three years (2000,2001 and2002). The cytotaxonomic identifications seem to show the same trends as in Western Zone, i.e. the more or less pronounced sensitivity of the savana species (5. sirbanun and S. damnosunt s.s.) be it temephos or pyraclofos. 3. Transfer activities: training and recycling of the nationals Within the framework of operational research at VCU, the main activities undertaken during this last decade is intended to prepare for the post-OCP. In fact the technicians and the national teams are implicated more and more in the planning and/or the implementation of the entomological research activities. They also take part in special sessions of training, in order to improve individual performances and to reinforce the operational capacity of the countries which will be taking on entomological activities soon. Thus, since 1998, VCU research teams have ensured the training of national entomologists capable not only to plan and supervise the residual activities, but also to analyse the data collected, interpret the results and make the decisions essential for the maintenance of the achievements of onchocerciasis control. The training currently going on relates to the third generation of entomologists made up of l4 trainees from six OCP countries (Benin, Guinea, Mali, Niger, Sierra Leone and Togo), and of one APOC country (the DRC). This will change the total number of entomologists trained by the VCU research team to 37, including32 OCP countries as indicated in the table below. 10 National entomologists trained by OCP - Current Status Countrv Number of entomologists TOTALS (envisaged)1998 Bouak6 2001 Odienn6 2002 Odienn6 (in progress) Benin I 1 I 2 Burkina Faso 1 ., 0 3 Cdte d'Ivoire I I 0 2 Ghana ) I 0 3 Guinea 1 0 ) 1 Guinea -Bissau I I 0 7 Mali 1 0 ) I Niger I 0 I I Senegal I I 0 2 Sierra Leone I I ) ) Togo I 3 I 4 DRC (APOC) 0 0 5 5 TOTALS t2 11 t4 37 4 Collaboration with external institutions Within the framework of the blackfly migration studies, relationship was established with the department of parasitology of the "Noguchi Memorial Institute for Medical Research", Achimota, Ghana, for cytotaxonomic identification of vectors. For this same study, the OCP laboratory collaborated with that of the IRD (ex-ORSTOM) of Montpellier to carry out the identification of vectors by microsatellites. In the collaboration which continues this year, the role of the IRD consists primarily of the supply of starters for the microsatellites, quality controls and assistance in the analysis and the interpretation of data. The IRD also contributes to the training of the laboratory staff, bearing the cost of the stay of technicians in its facilities at Montpellier. Collaboration also continued with Dr. T.R. Unnasch's laboratory at the Division of Geographic Medicine, University of Alabama (UAB), Birmingham. The UAB carried out the quality control of the identifications of parasites and vectors by traditional techniques (DNA probes, Heteroduplex). The past year was particularly marked by the conception of a new data-processing programme for the analysis of data obtained by the pool screening technique. This programme enables a link with the results of routine dissections. The molecular biology laboratory of the Programme was also involved in the collection of nodules and the preparation of DNA for research works on resistance to ivermectin. Furthernore, the laboratory took part in the preparation and the use of the DEC patch test for epidemiological evaluation. It also l1 contribute to the development of the immunological test of Prof. Weil by undertaking evaluation missions in OCP and APOC countries. In the field of hydrobiology, collaboration continued with institutes (Water Research Institute, Achimota, Ghana; "Centre national de recherche agronomique", Bouak6, C6te d'Ivoire), and national team for onchocerciasis control in Guinea. Exchanges are also maintained with the IRD and the World Bank in the field of the environmental activities in general. 7