4 ONCHOCERCIASIS CONTROL PROGRAMME IN WEST AFRICA Expert Advisory Committee OCPIEACZ2 Twenty-second session OzuGINAL: FRENCH Ouagadougou. 4-8 June 2001 REPORT OF THE MEETING ON GROUND LARVICIDING OF BLACKFLIES DURING THE POST-OCP PERIOD - t I REPORT OF THE MEETING ON GROUND LARVICIDING OF BLACKFLIES DURING THE POST-OCP PERIOD 1. INTRODUCTION The meeting on ground larviciding was held at OCP/Ouagadougou on 22123 March 2001. Participants at the meeting included key technicians of the Programme involved in ground Iarviciding activities, representatives of hydrobiologists, the interim CPET and independent specialists (cf. List of participants in Annex 1 of this report). The objectives of this meeting, which was to ensure the application of recommendations made by EAC 21, were as follows: a) To discuss the efficacy of ground larviciding of blackflies in the post-OCP context; b) To address possible ecological problems relating to such activities; c) To ascertain progress made with respect to feasibility studies on ground treatment in target basins; d) To make concrete proposals for actions, which could re-state the protocols of on- going studies. Discussions centred mainly on the 5 river basins (tributaries of the Oti, Tinkisso, Niger, Mafou and Pru), on which transmission might not have been completely interrupted by 2OO2, but where larviciding will automatically cease due to the end of the Programme. 2. OPENING OF THE MEETING The Director of the Programme, Dr. Boakye A. Boatin, in his welcome address, called on participants to be open-minded during discussions, and to make relevant recommendations for the ground activities to be undertaken. Dr. L. Yameogo, chief of VCU, on his part, thanked participants for honouring the invitation of the Programme. He was full of praise for the presence of Dr. B Philippon and Dr. A. Yebakima at the meeting, which he hoped, would be an opportunity for sharing experiences in the area of ground larviciding. The proposed agenda (Annex 2) was adopted by participants, without any major amendments. A1 D -2- 3. GROUND BLACKFY LARVICIDING FOR CONTROLLING TRANSMTSSION IN THE OCP CONTEXT The chief of VCU, after presenting the larviciding coverage map for the OCP area, showed the results obtained on the Dienkoa and on the mid Niger, due partly to the ground larviciding. The excellent results obtained in these 2 basins, which have different characteristics, go to prove the fact that ground larviciding that is properly carried out could bring about a cessation in onchocerciasis transmission in a context where aerial treatment would continue in other basins. 4. GROUND BLACKFLY LARVICIDING FOR CONTROLLING TRANSMISSION IN THE POST.OCP CONTEXT Papers were presented by the national entomologist of Guinea on the activities undertaken or on-going ones on the Tinkisso, the upper Niger and the ft/afou. Additionally, the CAT of the Eastern Zone presented ground treatment activities that have been carried out on the Oti and its tributaries since 1997, as well as the on-going investigation on these rivers and on the Pru in Ghana. The national entomologist of tt/ali presented the outcome of ground treatment activities and those by boat on the mid Niger, in the vicinity of Bamako. Results on blackfly densities, as well as figures on annual transmission potential were presented by the ATO on the various basins that are mentioned. Entomo-epidemiological results show that the number of years during which transmission will have been controlled on these basins, before the end of the programme in 2002, will not be sufficient to bring down the risk of recrudescence to an insignificant level. It will therefore be necessary to continue with CDTI, entomological surveillance and ground larviciding activities for some time in these basins. Since ground larviciding is neither feasible nor efficacious in all cases, it was decided to choose a single criterion on the basis of which all the basins selected for ground larviciding (the Pru, tributaries of the Oti, the mid Niger in the vicinity of Bamako, the Tinkisso and Upper Niger-Mafou) will be examined. lt is to be noted, however, that in the post-OCP context, the surrounding basins will no longer be under larviciding, and may therefore be sources of contamination. The workshop addressed 9 items as follows 1. Characteristics of the basin. 2. Epidemiological situation and distribution of ivermectin. 3. Entomological data 4. Larvicides used and sensitivity of larvae to chemical insecticides 5. Evaluation of needs (human and material resources). 6. Points of capture, accessible points for prospecting and ground treatment; 7. Entomological evaluation of treatment 8. lVonitoring of level of sensitivity of vectors to the larvicides used; 9. Post-OCP larvicide supply channels, and possible coordination of ground treatment in the various countries. A2 -3- 5. WORKSHOP ON FEASIBILITY STUDIES ON GROUND TREATMENT IN THE SELECTED BASINS 5.1. Background Two working groups were formed, and it was agreed to focus discussions on the five basins presented under item 4. The Chief of VCU recalled that it was actually a brainstorming exercise. Participants were to put emphasis on the efficacy of ground treatment and the various strategies used, based on their knowledge and field experience. The first group worked on the feasibility studies of ground treatment on the Oti and its tributaries, the Keran, Kara and the Mo in Togo, and the Pru in Ghana. The second group reviewed the ground treatment options on the Tinkisso and on the Upper Niger/Mafou in Guinea, and on the mid Niger in the vicinity of Bamako, in Mali. Presentation of outcomes of the discussions and views on the various basins were annexed as follows: Annex 3: Ground treatment after 2002 on the tributaries of the Oti in Togo Annex 4: Ground treatment after 2002 on the Pru basin in Ghana. Annex 5: Ground treatment after 2OO2 in the basin of the Mid Niger in Mali. Annex 6: Ground treatment after 2002 in the Tinkisso basin in Guinea. Annex 7: Ground treatment after 2002 in the Niger-Mafou basin in Guinea 5.2. Summary of reports on workshops and plenary discussions The need to form and train teams that are able to carry out ground treatment activities was specially emphasised. The training will have to be carried out in the field by OCP technicians before the end of the Programme. Relevant information on the bio-ecology of vectors, their sensibility to the various larvicides, as well as characteristics of larvicides used under the Programme, will have to be included in the data to be transferred to the teams. lt was deemed appropriate to prioritise 8.f. H-14 and temephos for ground treatment, in order to minimise the impact on non-target fauna. Some surveillance of the aquatic environment will have to be carried out during the ground treatment period. A3 I -4- As much as possible, the VCU teams should try to write down figures for each of the foci, especially with respect to the intensity of bites and of transmission, the increment value that may be expected, with effect from the cessation of OCp activities, and CDTI coupled with manual larviciding, as compared to the CDTI strategy only. The prospects for keeping OCP entomological results at a level at least equal to the current one, must also be assessed. For the evaluation of treatment, captures/dissections must be parallel to the evaluation of the prevalence of infection with blackflies, using the molecular biology technique. Discussions centred also on the supply channels of larvicides after the OCP Programme. National structures should organise themselves, with the assistance of the Multi-Disease Surveillance Centre, which is being set up on OCP/Ouagadougou premises. Participants brought to the fore the need for coordination of actions and the sharing of experiences among teams of the various countries. Setting up a network of national entomologists will enhance the exchange of fruitful experiences. ln a bid to guarantee OCP gains and dynamics, participants wished mechanisms could be put in place so the various teams complement one another in the entomological, epidemiological and chemotherapy areas. The observations and suggestions made by participants on the various basins are summed up as follows: a. The Tinkisso: efforts will have to be concentrated on the Fifa stretch which constitutes the focus where transmission is not well controlled, and where access to breeding sites is possible in all seasons. b. The Upper Niger/Mafou: investigations carried out to date indicate that ground treatment for bringing transmission under control is not very feasible given the inaccessible nature of breeding sites on most parts of the river during the rainy season. It was suggested that investigations continue on access to important breeding sites, and that ivermectin distribution should be enhanced in this basin. c. The tributaries of the Oti: tests carried out on the Keran, Kara and the tVo show that ground treatment is efficacious during the dry season. ln the rainy season, however, it is practically impossible to carry out ground treatment due to the large number of breeding sites that are inaccessible, and the high risks of re-contamination by blackflies from adjacent rivers. A4 t i -5- d. The Pru: The outcome of investigations conducted to date show that this river is navigable downstream at Asubende, during the dry season. Studies to be conducted during the rainy season will help to confirm the navigability of the upstream part of the river for the control of breeding sites on this stretch by boat. This will enable the mapping of breeding sites to be completed, and also the identification of spraying points for effective treatment. The teams should take into account the suggestions made, and write up a final report on the feasibility of this activity by November 2001.