Expert advisory committee ad hoc session, Ouagadougou, 11-15 March 2002: progress report by unit vector control (June 2001 to date)

,/ WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTI ONCHOCERCIASIS CONTROL PROGRAMME IN WEST AFRICA PROGRAMME DE LUTTE CONTRE L'ONCHOCERCOSE EN AFzuQUE DE L'OUEST EXPERT ADVISORY COMMITTEE Ad hoc Session Ouagadoueou. I I - l5 March 2002 EAC.AD.I Original: French February 2002 PROGRESS REPORT BY UNIT (June 2001 to date) A 2PART 1 VECTOR CONTROL (Rev. 1) JHIGHLIGHTS OF ACTIVITIES OF THE VECTOR CONTROL UNIT IN 2OOI HYDROLOGY AND AERIAL OPERATIONS 1. Hydrology The rainy season set in late in the Programme area, with an unequal distribution pattern in the entire basins. In the Eastern zone, a comparative study of the flows recorded in 2001 and that of 2000, shows a deficit in the all the basins except that of the sub-basin of the Kara, where exceptional spates were recorded. Subsidence was so sudden in this area that the cessation of flows was much earlier in 2001. In the Western zone, despite the late onset of the rainy season the rainfall figures recorded in 2001 were rather high, especially during the months of July and August. Rainfall was actually in excess in most of the basins, except in the Sassandra, Niandan and Upper Niger basins. In 2001, a total of 100 limni-metric stations, 52 of which had beacons, were exploited. This year, the hydrometric network is made up of 8l limni-metric stations, 34 of which have beacons. 2. Aerial contract and flight hours As obtained in the previous years, the concerted management of flight hours in 2001 in both zones, helped to limit expenses in flight hours to guaranteed hours planned to that effect. Thus, out of a total of 3001.6 hours guaranteed to the Company, 3001.7 hours were actually used for treatment.Year 2002 marks the end of the last four-year contract, signed with the Evergreen Company (EHI). Three helicopters are currently on contract with 1999.2 hours guaranteed to the company. The maintenance of Helicopters was satisfactory in 2001. Engine breakdowns lessened from 30% to 22Yo of total breakdowns; radio breakdowns dropped from l0% to 60/o, and battery failures from l3% to 0o/o. However, special attention must be given to the spraying system and the insecticide and kerosene pumps, whose breakdowns are on the increase. These breakdowns went from lo/o to 25Yo for spraying systems, and from 0 to 28%o for kerosene and insecticide pumps. 3. Use of larvicides The consumption of insecticides in 2001 went down from 60/o in. cost, as compared to that of 2000. It is also worth noting, in comparison with the three preceding years, a cut in the consumption of chemical insecticides, in favour of an increased use of biological insecticides. In addition, the concerted efforts of the VCU and National teams in managing insecticide and kerosene depots, helped to considerably minimize product losses which, represented 2.4%o of total stock in 2000, and dropped to 1 .5%o in 20Ol . These results could have been better this year had it not been the losses in products due to the poor quality of packaging and/or to the capping of barrels (pyraclofos, phoxim, etofenprox, permethrin). and to the ageing of stock (carbosulfan). On the whole, theft, leakage and contamination cost to the Programme $69,582 this year, as against $134,890 in 2000, i.e. a reduction of $65,308 (48.5%). 4RESULTS OF ENTOMOLOGICAL EVALUATION A) WESTERN ZONE The entomological results recorded from January to December 2001 are excellent for all the treated basins. None of the 57 capture points that are followed up regularly in the Western zone, showed an annual transmission potential (ATP) of savanna species higher than 100 during 2001. 1. Mid Niger In the mid Niger basin in Mali, animal filarial occupy an important place, and thus mask ATP reduction trends (savanna species ATP from 7 to 80 only in 2001). 2. The Sassandra In Cote d'Ivoire, reduction in ATP is higher than9lo/o in all the five control points. Since 1991 there has been a downward trend, and ATP figures for the savanna species have been below 100 since 1993 (except in Vialadougou, where it was 147 in 2000). This exceptional situation was only a false alert: no infected female was found there in 2001 (gross ATP:0). In Guinea Conakry, gross ATP reduction varies from 84 to 100% on the Upper Bafing and the Upper Bagbe. Annual Transmission Potential figures for savanna species have remained lower than 100 since 1993 on the five entomological control points (ATP savannah species : 0 at all capture points in 2001). Larviciding was finally suspended on 31 December 2001. 3. The Sankarani and Milo Reduction in gross ATP figures in the Sankarani and Milo basins varies between 93% and 100% at all the 13 entomological control points. Transmission has constantly decreased since 1990, and ATP figures for the savanna species have been lower than 100 since 1993. No O. volvulus transmission was reported in 2001 at all the capture points of the Sankarani and Milo basins, where larviciding was also finally suspended on 31 December 2001. 4. The Niandan In this basin, reduction in gross ATP figures varies between 85 and 100%. ATP of savannah species have remained lower than 100 at all the 7 control points since 1993. In 2001, only the capturing point of Sansambaya had an ATP/savanna of 28. 5. Upper Niger-Mafou In this basin, the reduction in gross ATP figures varies between 73 and l00yo, and there have been downward trends since the beginning of combined treatment (larviciding and ivermectin) in 1989 (except at Balandougou, Serekoroba and Yalawa). The relapse of transmission on the Mafou since 1996 is mainty due to forest blackflies (corrected ATP of savanna species lower than 100). However, at Yalawa, savanna ATP figures that are higher than 100 were recorded in 1996 and 1997. Specific actions that rvere carried out achieved positive results with ATP figures of 35 for the savanna species in 1999 and 2000. No O. volwrlus transmission was noticed at Yalawa in 2001. 56. The Tinkisso In the Tinkisso basin, there is a downward trend in gross ATP figures, with a reduction of between 75 and 100%. The increase in transmission since 1995 seems to be around Fifa where ATP figures for the savanna species went up to 510 in 1998. Specific actions that were implemented helped once again in arriving at good results beginning 1999. The results recorded in 2001 were satisfactory: Savanna species ATP of 2l atLabero and 7l at Fifa. 7. The kolente, Kaba and Mongo In these basins, the decrease in gross ATP figures in December 2000 was 80% at Badekanti (Kolente); 86%o at Kabanihoye (Kaba); andl4o/o at Pont Mongo (Mongo). ATP figures for the savanna species have remained lower than 100 at all the 7 control points since 1993. No O.volvulus transmission by savanna blackflies was recorded in 2001 (Savanna Sp.ATP:0 for all capture points of these rivers). B) EASTERN ZONE In this zone, excellent results were recorded in the basins of the Mono and Sio in Togo, and on the tributaries of the East Volta Lake in Ghana and in Togo, at two levels: entomologically and epidemiologically, since the Extensions were created in February 1988 (ATP lower than 100 for nearly 10 years). This called for the final cessation of larviciding in these basins on 31 December 2001. The difficulties encountered had to do, mainly, with the basins of the Pru in Ghana, and the tributaries of the Oti in Togo and Benin, on which special emphasis is placed in this report. 1. The Pru Capturing started in 1978, whereas larviciding and ivermectin distribution started only in 1988. We therefore have 10 years of pre-control data on this basin. Blackflies are almost exclusively made up of the savanna species (S.damnosum). A very high transmission rate (ATP : 3330) was recorded in 1978. Identification by DNA probe identification of harvested parasites from January 1993 to December 2000 showed that 20%o of these parasites are of the forest O.volvulus, while 48o/o are of the savanna O.volvulus, and32oh of other parasites. Larviciding was suspended beginning from the 33'd week in 1988 and 1989 in order to carry out xenodiagnostic studies, and to study the impact of ivermectin on transmission. From 1990, Lower Pru was treated until 2002, with 7 OCP larvicides, which were used in rotation. In the dry season, ground larviciding was carried out. Though the ATP figures have dropped significantly, they were around the tolerance line of 100, precisely between 63 and 189, during the period between 1997 and 2001. The situation has basically not improved despite the intensification measures that were adopted in 1996197 (expansion of the larvicide coverage, accompanying pilots, increased surveillance of tributaries, intensification of prospecting and ground treatment). Corrected ATP figures for January through December 2001 is 140. 26 The tributaries of the Oti (Kara-Keran-Mo) Capturing has been going on since 1976 at 7 points on the Keran, at 4 points on the Kara and at 6 points on the Mo. The vector species found from January 1994 to July 1997 are mainly as follows: On the Keran: 98% of savanna species;2oh of forest species; On the Kara: 84oh of savanna species; l6% of forest species; on the Mo:52o/o of savanna species;48% of forest species. Transmission here is mainly due (92%) to the savannah female species, and 8% to the forest species. DNA probe identification of harvested parasites on the Keran, Kara, Mo from January 1993 through July 1997 indicated that about 72oh of larvae are of the O.volvulus type (ll% of forest O.volvulus and 6loh of savanna O.volvulus), and the remainingZSYo are not of the O.volvulus species. The Keran-Kara-Mo (tributaries of the Oti) have been under aerial larviciding since 1977 up to date. In 1993, larviciding, which had also started in 1977 on the Oti (main river) was suspended following the good entomological and epidemiological result obtained. Larviciding on the Lower Keran and lower Kara was also suspended. a o In 1997, following the poor entomological results obtained in May-June, special measures were taken to enhance the efficacy of control operations. These actions were mainly to i) intensiff ground larviciding in support of aerial treatment; ii) increase larvicide coverage by including Lower Keran and Lower Kara up to their confluent with the Oti; iii) treat the main Oti River before its spate for four to six weeks; iv) reinforce treatment of the Upper Oueme which could be the source of re-invasion of blackflies of the Upper Keran and Kara. The analyses of entomological results shows that the ATP on these rivers significantly decreased only from early 1988, when larviciding started in the South-eastern extension. Apart from the exceptionally high transmission levels recorded in 1997, the situation on these basins is as follows: - On the Lower Keran, gross ATP figures which were around 1500 prior to the beginning of operations dropped by nearly 9OYo, and even lower if account is taken of the results of thes past two years where transmission has been below the tolerance level (77 and 7 in 2000 at the two capture points (Titira and Tapounde) which were the most affected, and 72 and 28 in 20ol). - On the Kara and the Mo, the situation has been under control since 1994, with ATPs below the tolerance level. On the whole, though the entomological results have improved on the Pru and on the tributaries of the Oti, as compared to the situation that prevailed before the operations started, it is important to keep the level of operations for some more years to ensure that the reservoir of parasites is eliminated in these areas, and thus avoid a premature relapse of the disease. 7OPERATIONAL RESEARCH AT VCU 1. Blacklly movement and identification of vectors and parasites The research activities that have been made priority these last three years are meant to enhance our knowledge in the genetic variability and the vector capabilities of the S. sirbanum, the blackfly species, which is the main cause of transmission of onchocerciasis in the savanna regions of the OCP Programme area. In terms of bio-ecology, the importance of this savanna species is linked to its involvement in the periodic migrations that are observed at the beginning of each of the main annual seasons: the rainy season (migration from the south-west to the north-east, during the spate period - June-August), and the dry season (migration from the north-east to the south-west, in the harmattan period "November-March"). After being controlled for several consecutive years, these large-scale movements could soon resume on a higher note, given the massive build-up of blackfly populations, following the cessation of vector control activities in all the Oncho foci, which have been made "healthier" by the Programme. Thus, the basins selected for our investigations in the Western zone, are located in Guinea (Upper Niger-Mafou and Milo), in Mali (Baoule and Faya), and in Sierra Leone (Seli and Kaba-Mongo). As for the Eastern zone, the investigations are carried out on the tributaries of the Oti in Togo (Keran-Koumongou, Kara and Mo), and on those of the Niger in Benin (Mekrou and Alibori). On the basins that have been selected, blackfly samples (larvae and adults) are harvested simultaneously at different points during the migration periods. These samples are then carefully analysed per various techniques at OCP: morpho and/or cytotaxonomy, heteroduplex analysis (HAD) and micro-satellite markers. The analysis of samples harvested on the basins of Guinea during the 200012001 period showed that at the beginning of the rainy season, the S. sirbanum populations move from the basin of the Mafou (adjacent to the border region of Guinea-Sierra Leone) toward the Milo basin located further north. These observations confirm those which have, for about a decade (1987-1997)), helped to notice blackfly large-scale movements, which are favoured by dominant winds. Thus, movements noticed from the Mafou toward the Milo are only a stage of the migration of S. sirbanum populations from the northern basins of Sierra Leone (Seli Kaba/lMongo, Bagbe) to those in the east of Mali (Baoule, Faya). This may soon be ascertained through the analysis of samples that were harvested during the 2001- 2002 period. In addition to sample harvests that allow for following up the blackfly migration trends, operations are also initiated in order to estimate the risk of transmission linked to these large-scale movements. In actual fact, experimental surveys on transmission, conducted in April-May 2001 on the Milo at Morgbedougou, brought to the fore the great variability in compatibility befween the S.sirbanum and various strains of the O.volvulus that are encountered in the migration foci. Thus, in managing future cases of recrudescence, after the end of the Programme, it would be appropriate to take this vector- parasite compatibility factor into account, given the incidence it could have on onchocerciasis transmission in natural conditions. For these studies and the routine entomological evaluation, the molecular biology laboratory continued to carry out the identification of parasites collected by the entomological network, so as to enable the correction of transmission parameters to be carried out. The infective larvae of 381 infective females collected in the areas under larviciding, were thus identified during the past entomological year. 8Among the infective females captured, 67.7% were bearers of parasites of animal origin. Special emphasis was placed on the treatment of infections from the areas of specific intervention. The identification of parasites also dwelt on parasites from APOC countries. 2. Susceptibility of blackflies to insecticides In the area of follow-up and management of the phenomenon of resistance of blackfly populations to organophosphorous compounds, actions are now ongoing, not only to maintain the efficacy of the vector control effort, but also to take stock of the susceptibility on the river basins that are yet to be treated but which have been under high insecticide pressure for several consecutive years. With regard to this last category of river basins, the results that are already at hand show a relatively good situation in the western zone, where a campaign of sensitivity tests is being undertaken since November 2001. Actually, on most of the watercourses where there is no longer larviciding for the past 5 consecutive years, susceptibility is normal to temephos and to phoxim, and intermediate to pyraclofos. The lowest levels of sensitivity were noticed at Markala-barrage on the Niger OIN300), where resistance to temephos was observed. As for the basins on which larviciding stopped recentll (Sankarani and Milo in Guinea), the larvae populations show a general normal sensitivity to phoxim and an intermediate sensitivity to the other two organophosphorous compounds. In the blackfly foci that are still under larviciding, the first tests that were clear resistance to temephos on the Niandan River at Bagoue (ND500). The same operations will very soon be undertaken in the Eastern zone, where 2001 show a good overall situation of the basins visited. Thus, the general before the end of Programme activities could be taken into account in the activities in relation with the aquatic environment. in2002 indicate a some results obtained in to be presented planning of local 3. Transfer of residual activities to Participating Countries In addition to the active participation of nationals in research activities VCU, progralnmes are specially drawn up to transfer key entomological knowledge to local teams will have to upkeep the gains of the Programme. It is in line with these special programmes that research team carry out residual entomological activities. To this end, training and re-training at all levels that are deemed useful for the success activities, which will have to be conducted right after the cessation of special emphasis is placed on the following: a Initiation in ground larviciding of staff of the various national or vate bodies. It is worth mentioning here the example of the SCB (Study and Deve Company for banana project in controllingcultivation), which received assistance from the Programme for blackfly nuisance on the Bandama in Cote d'Ivoire. Periodic training and re-training of entomological technicians of OCP and/or of other national an operational potentialstructures. This aspect of transfer aims at equipping the countries that will enable them take up future large-scale entomological acti of the post-OCP era. The training of national entomologists capable, not only of planning supervising residual activities, but also analyzing the data collected, interpreting the and making necessary decisions at the operational level. These entomologists have drawn up, surveys (i) on detecting potential recrudescence of transmission, or supervised a (ii) on the impact of 9a o ivermectin on transmission, and have supervised work relating to the control of blackfly' nuisance in some countries, with the logistic and financial support of states. These activities were conducted with the participation of village inhabitants. The tool used for the entomological surveillance of the post-treatment type mentioned above, is the DNA detection of O.volvulus in the head batches of these crushed blackflies, which was an important activity in the laboratory. The results of these works carried out in 1999 and 2000, show that the rate of infectivity of blackflies are below the tolerance line of 0.5 infective females/1000 females captured for all the study points, except for some points, where the number of flies required was not obtained. Some of the challenges to be taken up by the national coordinators are the transportation of the biological material through the national means for data transmission and the acquisition of resources for making this surveillance activity sustainable. Specialised Oncho training modules have, besides, been produced for national technicians and entomologists. Training of the staff of national teams, through the molecular biology laboratory, in the preparation and use of the DEC test for epidemiological evaluation. Training of personnel of the Unit in areas other than onchocerciasis as part of post-OCP preparation, but also for improving their knowledge, and making them more operational. In this connection, the technicians had training on malaria, sleeping sickness, bio-information etc... a 4. Collaboration with external institutions As part of studies on blackfly movements, collaboration was sought with the department of parasitology of the Noguchi Memorial Institute for Medical Research, of Achimota, Ghana, for identiffing the cytotaxonomy of vectors. For the same study, the OCP laboratory collaborated with that of IRD (ex-ORSTOM) of Monpellier, for the identification of vectors by micro-satellites. In the collaboration which will continue this year, the role of IRD will be limited, basically, to the supply of primers for the micro-satellites, to verifuing knowledge, quality control and technology transfer. Collaboration also continued with the laboratory of Dr T.R. Unnasch at the Division of Geographic medicine of the University of Alabama in Birmingham (UAB). The latter conducted quality control of the identification of parasites and vectors, using the classic techniques (DNA-probe, Heteroduplex). Last year was particularly marked by the conception of a new computer software for the analysis of data obtained by the blackfly crushing technique. This prograrnme enables a comparison to be made with the results obtained through routine dissection. The molecular biology laboratory of the Programme was also involved in the collection of nodules and in the preparation of DNA for research on the resistance to ivermectin. Additionally, the laboratory took part in the preparation and utilization of the DEC mono-test for epidemiological evaluation. It contributed to the finalising the immunological test of Pr. Weil, by undertaking evaluation missions in OCP and APOC countries In the area of hydrobiology, collaboration continued with the Water Research Institute of Ghana. the National Centre for Research on Agronomy of Bouake, C6te d'Ivoire, and the National Oncho control team of Guinea. Exchanges were maintained with the IRD and the World Bank in the area of environmental activities in general.