Report of mission for larvicide river and susceptibility test with temephos in to the eradication of the vector of onchocerciasis in the Tukuyu focus located in South-Western Tanzania, East Africa: 18 September to 22 October 1999

REPORT OF MISSION 18 SEPTEMBER TO 22 OCTOBER 1999 Larvicide river trials and susceptibility tests with temephos in relation to the eradication of the vector of onchocerciasis in the Tukuyu focus located in South-Western Tanzania, East Africa. Prapared by M. Tel6 Barro E nto m o I o g i c a I a n d I n secti c i de Research Assrsfanf WHO/ONCHO, Odienne (C6te d'lvoire) FOR INTRODUCTION The project for the eradication of the vector of onchocerciasis in the Tukuyu focus in the United Republic of Tanzania plans to carry out larviciding with temephos, the anti- blackfly insecticide chosen for that purpose. Before such important work can be carried out, we were commissioned by the Chief VCU a.i. on behalf of the African Programme for Onchocerciasis Control (APOC) to undertake an investigation mission to Tanzania from 18 September to 22 October 1 999. 1/ Mission Objectives To determine the actual carry of temephos ; To determine the susceptibility of S. damnosum s.l. to temephos for establishing baseline data ; To train local staff (on how to carry out river trials and susceptibility tests) 2/ Mission Planning a) Morning The first briefing session brought together Drs Akpoboua L.K.B., ATO/OCP Ouaga;L. Yam6ogo, Chief VCU a.i./OCP Ouaga;Y. Bissan, CRE/OCP Ouaga; Bertha T. Maegga (NIMR Tukuyu) ; Dr M. Noma (APOC/Ouaga) and myself. This meeting defined the goal and objectives of the mission (as stated above) b) Evening The second briefing session brought together only Drs Y. Bissan, CRE/OCP Ouaga, Bertha T. Maegga (NIMR Tukuyu) and myself. lt dealt with the practical organization of the field work to be carried out and the travel schedule : 13.09.99 15.09.99 16.09.99 17.09.99 18.09.99 19.09.99 20.09.99 Departure from Odienne for briefing in Ouagadougou Arrival. Briefing in Ouagadougou. Administrative arrangements for travel (TA, etc... ). Departure from Ouaga for Bouake. Departure from Bouake for Abidjan. Administrative arrangements for the transport of the temephos supply. 21.09.99 22.09.99 23.09.99 26.09.99: 1 8.10.99: 20.10.99: 21.10.99: 22.10.99: - Mr Kalinga Akili K.M. : - Mr Mwaikonyole Adam - Mr Donald Charles : - Mr Kibweja Addow : Research scientist !ll. Senior Laboratory Assistant. Laboratory Assistant lll. Laboratory Assistant lll. Departure from Abidjan for Johannesburg. Departure from Johannesburg for Dar-Es-Salaam. Stop over in Dar-Es-Salaam: o Visit to WHO Office in Dar-Es-Salaam o Courtesy visit to the National Director of NIMR lnstitute for Medical Research) Departure from Dar-Es-Salaam for Tukuyu. Departure from Tukuyu for Dar-Es-Salaam. Departure from Dar-Es-Salaam for Johannesburg. Departure from Johannesburg for Abidjan. Departure from Abidjan for Bouake. (National 3/ Technical activities carried out Prospection and evaluation of larval breeding sites (see summary table) ; Susceptibility tests (see results in annex) ; River trials (see results in annex) ; Training. 3.1- Training Three (3) technicians of the "National lnstitute for Medical Research" in Tukuyu took part in the work accomplished during the entire mission. They had a practical introduction to susceptibility testing and river trials. They were : 3.2- Comments 3.2. 1 - The prospections The three main rivers of the Tukuyu focus were visited as follows 1 point on the middle course of the Kiwira river ; 5 points on the Mbaka river; 3 points on the tributary of the Lufilyo Kasyabona River ; 4 points on the main course of the Lufilyo River. 2 ln all of the breeding sites prospected, the presence of S. damnosum s.l. was noted. However, there was low aquatic S. damnosum S.l. population compared to the overall blackfly density in this area. Upstream on the Mbaka and Lufilyo rivers, a series of breeding sites stretching down from the mountain ranges was noted. The current velocity of the rivers at mid-course gradually decreases and a more noticeable presence of the aquatic stages of S. damnosum s.l. could be observed. These aquatic stages significantly increase in abundance compared to other species as the rivers enter the swamp areas on their way to Lake Nyassa. The water temperature in all the rivers is very cool (ranging from 18'to 25" maximum) with clear waters. The turbidity level observed was < SJTU "Jackson Turbidity Unit". 3.2.2- Accessibility Accessibility to the upper stretches of the rivers is difficult if not impossible. Nonetheless, some extra efforts must be made to determine the limits of the distribution of S. damnosum s.l. in all the rivers concerned. The limits defined on the attached map need to be refined. Upstream from the given limits, S. damnosum s.l. is in low proportion. 3.2.3- Susceptibilitv of the laruae to temephos The results of the tests show satisfactory susceptiblity levels. Tukuyu is in fact a vast region of banana, coffee and cocoa plantations, with huge fields of maize, potatoes and other crops. These farms are certainly treated with chemical products which are carried by rainfall runoff into the watercourses. Therefore, the presence of moribund larvae calls for caution. Moreover, when the test results are analysed, one realizes that the dosage of temephos for CL95 of the restricted mortality rate (i.e. dead larvae only) rises to 0.66 mg/I. A very satisfactory susceptibility level of the S. damnosum s.l. larval population to this product in West Africa is 0.4 mg/l at the very most. The species of the S. damnosum s.l. complex encountered in East Africa, especially in the Tukuyu focus situated in the South-Western part of Tanzania might be genetically different from those colonizing the watercourses of West Africa. Could this possible difference alone explain their level of susceptibility to temephos ? We think that other factors may be involved. For instance, the chemical products used for the treatment of the plantations should be taken into account. As a result, the possibility of a faster selection of the tolerating individuals cannot systemAtically be excluded due to the probable increase in the dosage of temephos (0,4 l/mr'"') because of the very low temperature of the water (18'- 19") and of the poorness of materials in suspension. J However, given the seasonal cycle of the eradication campaign (ust a few weeks of sprayings during the dry season) ; - the frequency of the treatments (10 to 14 days cycles). We do not think the susceptibility of the S. damnosum s.l. larvae in the Tukuyu focus will decrease significantly during the campain 3.2.4- River tials with temephos Two (2) trials were carried out during the mission, the first one on the Mbaka river which was chosen by Dr Maegga and the second one on the Lufilyo river. a) Trial on the Mbaka river The results obtained show a good carry. For a discharge of 4.3 m3/sec at the dose of 0.3 l/m3 or 0.1 mg/|, the actual carry (OOo/o drop off) was 7.060 km (from the spraying point to the confluence with the main tributary, the Mwalisi river). Breeding site N" 4 located at 6.5 km from the said confluence was not totally cleaned up. A 95.3% mortality rate for all larval stages was recorded and 93.2o/o drop off for the mature larvae only. We think the effective carry was influenced by the following limiting factors : 1) the dilution of the mass of insecticide at the confluence of the Mwalisi river whose discharge was about 0.6 m3/sec ; 2) the clarity of the water in the river Mbaka (turbidity < 5JTU "Jakson Turbidity Unit") which indicates insufficient materials in suspension. lt has been demonstrated that the efficacy of temephos is related to the turbidity level of the water (absorption of the active matter of temephos by the particles in suspension which are then ingested by the larvae) ; 3) in all likelihood, the temperature of the water also has affected the treatment which was carried out at a temperature of 25'C. However, it could be that before the mass of insecticide reaches breeding site n'7 (see prospection map) the temperature had already cooled off very significantly. The mean temperature recorded during our stay in the area was 18' - 19'. We know that temperatures below 21"C constitute a limiting factor for the toxicity of organophosphorous compounds, especially temephos. 4 b) Trial on the Lufilyo river The stretch chosen for the trial was about 15 km long (14,5 km precisely). During that season, most of the small tributaries of this watercourse do not flow. However, 6 were still flowing but their discharge rate was in our opinion insignificant (about 0.5 m'/sec). Taking into account the observations and suggestions made by Drs P. Guillet and F. Walsh on the dosage of temephos, we increased the dosage to 0.4 l/m3/sec (which gives a concentration of 0.133 mg/l). The stretch used for this trial went as far as the confluence point with the Rumakali river which is the biggest tributary on this part of the Lufilyo, with a discharge rate comparable to that of the main river. Due to the inaccessibility to this watercourse beyond its confluence with its main tributary, the Rumakali river, no evaluation was made before and after the treatment beyond the last breeding site a few meters upstream from the confluence point. When the rainy season comes, all of the small tributaries will be flowing. lt would then be wise to take this hydrological situation into account and adjust the number of spraying points, as well as treat all the tributaries hosting S. damnosum s.1.. A first test treatment should be carried out, then based on the results of this treatment, a decision should be made on whether to adjust the treatment or not. Lastly, the water gauge on the Lufilyo river at Lufilyo-village should be updated and put to use, specially when measuring the discharge rates become difficult to perform. ln that connection, it would be desirable to approach the hydrologists of the region to try and find the ways and means to obtain reliable data on the discharge rates when these cannot be measured due to the swelling of the watercourses. 3.2.5- Obseruations During our stay in the area, we were able to observe that a) some of the catching points were not appropriately located in relation to the activities of the riverside populations ; for instance : at Kambasegela, on the Mbaka river, the catchers were sitting right next to the washerwomen (at less than ten meters'distance) ; at Tapio, on the Lufilyo river, the catchers work all day amongst the sellers of pancakes, fruit, etc. b) the dissections were clearly inadequately performed due to the incompetency of the principal dissector in determining the physiolical age of the flies and above all his inability to recognize onchocercal larvae. 5 4/ Suggestions and Recommandations 4.1- Suggesfions 1- ln order to obtain appropriate baseline data and for a better evaluation during and after the eradication campaign, we suggest the following : a) sensitization and awareness raising of all the catching teams on the importance of their work ; b) retraining of all technicians on the technical and practical aspects of entomological evaluation, especially dissection, the differentiation of S.damnosum s.l. from the other species and the screening of larvae during susceptibility tests ; c) further training of the team's scientist. 2- ln order to have baseline data in respect of blackfly susceptibility to temephos in all the basins of the Tukuyu focus, we suggest the following : a) the conduct of a susceptibility test on the main water courses and their major tributaries before the beginning of larviciding operations and after the eradication campaign if it proves to have not been effective ; b) the sampling of all blackfly species before the beginning of larviciding operations ; c) a cytotaxonomic identificatiion of all the flies of the S. damnosum s.l. complex in the entire hydrological network of the Tukuyu focus. 3- At the start of the dry season which is the period chosen for the beginning of larviciding operations, the water level in the Mbaka, Kiwira and Lufilyo rivers might be high. lt would then be difficult, if not impossible, to measure the discharge rates ; therefore, we suggest that steps be taken to get in touch with the hydrologists of the region to find the ways and means to estimate the discharge rates pending the decrease of the water level for the classical gauging of the discharge rates. 4- From the information we received, most of the water gauges installed in the basins concerned are located either at the farthest end of the rivers upstream or downstream. These water gauges are therefore difficult to exploit on the middle portion of the rivers which is the favourite place for the breeding of S. damnosum s.l. ; furthermore, no water gauge is installed on the main tributaries. ln addition, the present gauges were installed a long time ago. Therefore, we suggest the following : a) to the extent possible, new gauges should be installed in the middle portion of the main rivers and on the main tributaries of those rivers ; 6 b) the taring scales of the existing gauges should be updated 4.2- Recommandations 1- Given that new solutions of temephos would be necessary for any future susceptibility tests, we recommend : a) that steps be taken to provide the team with temephos technical solution (active matter), absolute alcohol, electronic precision scales (satorius), small weighing equipment. b) that an assessment of the knowledge of the team in charge of the tests be made if possible before the beginning of operations (espacially in the area of screening of tested larvae). 2- Given the following factors which limit the efficacy of temephos ; the clarity of the water which indicates poorness of materials in suspension ; the water temperature which may be above 20' ; the great number of small tributaries which may be flowing until the beginning of the dry season ; for better effectiveness and an excellent carry, we recommend : a) a dosage of 0.4 l/m3/s ; b) monitoring of the aquatic entomofauna before the beginning of the treatments and aquatic monitoring during and after the eradication campaign to assess the impact of the larviciding on the non-target aquatic fauna ; c) that a study of the life span of blackfy larvae be immediately undertaken to determine the appropriate frequency of the treatments. 3- The presence of S. damnosum s.l. upstream from the limits of the already defined area was revealed by our different prospections. a) that new prospections be initiated to update the access to the upstream portions of the different watercourses ; b) that in each basin, the farthest breeding site be located in order to establish the first spraying points. 4- Taking into account the proven and recognized qualities of B.T. H14 in West Africa i.e. : ease of handling, efficacy against blackfly larvae, good carry of the Teknar formulation, high selectivity (insignificant effect on the non-target fauna), no risk for the non target aquatic flora in case of overdose, and given the fact that a development of resistance to temephos cannot be totally excluded, we recommend : That trials with Teknar be performed before the beginning of larviciding operations in the hydrological catchment area of the Tukuyu focus for : 7 1) a rapid reconnaissance of the geographical location of the rivers and their tributaries; 2) a quick summary of the entomological results ; 3) avoiding any confusion in the names of the rivers or tributaries (some tributaries have the same names). We recommend that the rivers and tributaries chosen for the trials as well as the catching points be coded. 5/ Acknowledgements We wish to express our sincere thanks to all those who, directly or indirectly, have assisted us in our mission, especially the staff of the National Institute for Medical Research (NIMR) at the Tukuyu station, namely the entomological team of the station l/lessrs : Kalinga Akili, the team scientist, ft4wai konyole Ad am, Sen io r Laboratory Assistant, Donald Charles, Laboratory Assistant, Kibweja Addow, Laboratory Assistant, The drivers, Mr Sylvester and Miss Victoria for their contribution to the work accomplished. Our special thanks to Dr l/ohamed Amri of the "Disease Prevention Control" at the WHO Office in Dar-Es-Salaam, for all his help during our stop-over in the Tanzanian Capital. Our gratitude and special thanks also to Dr Bertha T.A. Maegga, the NIMR Officer who spared no effort to make our mission successful. Finally, our gratitude and sincere thanks to the persons named below, for their practical advice and more particularly for the trust they showed toward us in giving us the responsibility of this important mission : Dr A. Seket6li, Director APOC/Director a.i. OCP, Ouagadougou, Dr L. Yam6ogo, Chief VCU a.i., Ouagadougou, Dr L.K.B. Akpoboua, Administrative and Technical Officer (ATO), Ouagadougou, Mr. Mamadou Sarr, Chief ATS Western ZonelOdienn6, COte d'lvoire, Dr Y. Bissan, Coordinator of Entomological Research, Ouagadougou. 8 o\ .= (gE o E o a J 1' s =EL o s s N + (5 oF s o)(Et(E o)c :>J o(u z(o o)C '= o oo z(U E G oo 0) E tr- Ec uJ .= o)q) m E .o (trL#C ooc oo o) ro o IL : : :'t : : : :i:.) : : :J f : . .J.E .'A- .:rEi <48: :g :od : a.6 :38 : $E iE= : i.P *E#' :o=-..9"=8a' ip E ioE =- : E O : :=i o-r :'E o- : :E rE rEEr+E H E sn s s E gJEaOtrtFt ^\-b$!b(Jc#I_ \o-o\oro {=il5 >\o tilE*l PBIj-l EEl!olxEl ;EI EEI(6cl =ol =olE 'lBlt 5 lql €sl @lFI utl rulrl >lFl JI ml FI o-l u.tl ol al =lal ol -lol zl ol ol -l =l z a Ir.l trl ol 'r.rl(El ol t-l {.rl CI olEI ol EI ol cl ol xl(Ul rrl ol +.1x ol EO:fEE ?lso .oclg E6l-:EF.UA; g or Ei n$€eE Foo5000 o Lq) z o)a -oo -o o o _o oo o o- E(E a * LIST OF MATERIALS REQUIRED FOR SENSIBILITY TEST HANDED OVER TO DR BERTHA T.A. MAEGGA NIMR TUKUYU TANZANIA Platic cover Cutter Soft forceps Fine tip forceps Nalgene note book Thermometer Cold box Bowl 1 little bottle Pipet 0,5 Pipet 1 ml Pipet 2 ml Pipet 5 ml Pipet 25 ml 50 ml volumetric pipet 60 ml dilution bottle [t/leasuring cylinder 0,5 ml Measuring cylinder 1 little Fly collection tube Petri dish Elastic bands Lids for collection tubes Alconox soap Hyflo water pump Plastic tubing Air stones Conductivity meter Comparator Scrubbing eponge Filter paper Katadyn pump Deionising filter catridge Catadyn filter Bijou bottles 30 ml sample bottle Enamelled tray Aluminium box lce chest (medium size) 4cm 1 6 (3 fine tip, 3 round tip) 2 1 1 50 10 1 packet 1 packet 1 packet 1 packet 2 2 30 1 1 500 10 2 packets 2 1 packet 1 4m 4 1 1 3 1 packet 1 1 1 26 20 2 1 1 l0 LIST OF MATERIAL FOR SUSCEPTIBILITY TEST AND RIVER TRIALS TO BE SENT IF NOT AVAILABLE LOCALLY Adaptor socket Table lamp Electric cable lce chest (small size) Funnel Timer Tape measurer 10 little plastic bucket lVleasuring cylinder 1 little Measuring cylinder 0,5 little 2 1 30m 1 1 1 1 1 1 1 ll