Treatment of Sassandra tributaries (Guinea): montiily report, April 1985

;Udm F.C. Pleszak VCU Consultanty'/estex Our ref. \$/vg11 /1g1in1.2. MEMORANDUM To Dr B. Ptrilippon Date 1 llay 1985Chief VCII Attention Dr D. Ba1-dry SUbJCCt TREATMINT OF SASSA}IDRA TRIBUTARTES (curNna) : MoNTirLy RrPoRT, APR]L 1985 Your ref. Originator Following briefings and equipment collection in Ouagadougou and Bamako, I arrived by prospection helicopter at Odienne on the-10 A[ri1, 1985. From the lOthr and throughout the month extensive prospection6 were camied out in the area. A special emphasis was placed on the easterly flowingtributaries of the River Sassandra (Boa, Bagbe, BafLng, etc.)r ed the northerlyflowing tributaries of the }?iver Niger (Oion, Sankarani, Gbanhala, etc.) During the period experimental treatment has continued and a closeliaison maintained r.rith the treatment pilots. Throughout ilre period the f\y count results have been carefully monitored and an attempt has been mad.e to cor-relate the results with the control activities undertaken. Although not presented herein, a complete chronolory of the monthrsbreeding site surweys has been recorded. A summary is given in lnne* 1. General comments are as folIows. Helicopter surveys $rere carried out along the rivers concerned with aview to assessing their overarl suitability for s. damnosum production. Thus therivers were sunreyed for numhers of breeding sitffif-suitrtrl" vegetable substrates, and number and species of lanrae/pupae. Collections r.rere made at21 sites on untreated river6. See Annex 2. Treated. rivers vrere a-Lso checked todetermine the effectiveness of the larvicidal treatrnent which due to there neverbeing any positive sites vras concluded to be 10026 eff'ective, - In 6eneral, the samples coLlected were 1or.r in number and often consistedof non-damnosum simuliids. what appeared to be the case ( as observed by othersincluaii!-Ti-Ti-atsh) was that, wrrilit there are mar\)r obvious breeding sites, theseconsisted mainly of roclgr outcrops having no suitatle vegetable substratesi andas such were not .suitable for attachment of larvaI S. dainosum. This fras naa tneresurt that during the month of ;\pri1 (disregaraine-fr;F:-m-n) there i,"s u"enno requirement to include any further river into the treatment ryc1e. However,it is felt that when the rivers begin to f1oru properly those that possess denievegetation along their banks may be especialty suitable at times of permanenthigh water for illinear breeding't in spite of ine lact< of classical breeding sites.Current\, the River Bafing which may offer substantial breeding potential has remained_Iorv, with 1itt1e flow and large areas heavily congested with the waterlettuce Pistia. Follovring negative proipections, and, if Gueasso (rrr,.". ir." rjm remains fid;rn be considutJd "" an indicator site ior the river, then at presentthere is no justification for including this river in the treatment ryc1e. Because the untreated Sassand.ra tributaries are careful\r monitored forla:rrae and pupae, the results of which are correllated to the DBR's at all thecatching points in the adjacent OCp area with particular attention to Lamodou(soa)r. Massadousou (sien)1 and Ngoloao"go"-(Bd;i;-;-;i";;-"."i""r is exercisedover the 8r€8r Therefore, as the treatmentr "r" currently initiated on an ad-hoc I -2- basis, should arqr river start to produce and reduce the current excellent level of DBRrs, then it would be recomrnended for immediate inclusion into the treatment rycle. Following a prospection of the River Dion on the l2/4 with Dr. Ba1dry and l'lr R. Lama it was recommended for, and included in the follouing treatment cycle (Or naldryts memo 23/4 reters). Althou6h the DBR at Tere fel1 from l!/ pre- treatment to 38 post treatment, a more complete set of results is cumently being assimilated with a view to reducing the }evel of treatment. It has been the intention that ti'le nrajority of the helicopter suwey time be spent on the untreated rivers because, r,rith the increasing frequenc,y of the rains it r+as decided that slrorrld any river start t.o p-oduce it could be included in the treatment cycle and thus arrest any production at its initiation. As such, on\r cursory sur:veys have been carried out along the treated rivers vtith a gredter emphasis being placed upon the DBRts at the three main capturepoints as an indicator of treatment success. Treatments have been performed exceptionally well uith no operational problems being ex;lerienced or a41r envisaged within the area. Since the treatment machines are fitted r,rith BX spray nozzles the spray is emitted in fine droplets. Therefore the trace in the water, particular\y at the lovr doseage rates used, is very difficult to see. There is probab\y consi- derable loss of spray through drift and evaporation, and on the smal-Ier rivers by the swath exceeding the river width or impacting on surrounding vegetation. As a consequence there has been a tendanry for double dropping and possibly overdosing.ft is presumed that this is not only wasting Abate but also flight time. In general the results of the treatrnents appear to have been excellant. A11 the capture points have recorded Iow numbers of flies throughout the month with DBRts seldom entering double fi65ures. Refer to attached 6raphs. fhis hashad the effect that Massadougou, Lamodou, and Ngolodougou have al.L record.ed their lowest I'tsRrs ever, this is most clear1ry defined at Ngolodougou where the 1985 ItsRfor April is 215 compared r,rith B51o in 1!84, 2955 in 1983, and 10425 in 1982" ftre MTP have stiI1 to be calculated. The slight tendanry for increased DBRrs toward. the very end of April is probably attributable to the increased rainfall in the area together with unsuccessful B.t. treatments along the Sassandra. The situation vril1 be carefully monitored. to tfrto establish the source anC d.eal- vrith it accor-dingly. To reiterate the proposal made in the letter of 24/4/84 I would like to confirm tl:at the intention was not for a complete seizure of the treatment but a reduction to a more suitable l_eveI. Following discussions and agreement from Mr Zerbo on the subject, it is aSreed to follow your recomnendation to revievl the subject during l,l4r. Hor,lever,I would again like to put forlard my logic for ,vour further consideration. i. It is regarded that the pilots in general have a tendancy to overd.ose when in doubt and treat arSr breeding site re6ardless of its suita-bili ty for S. darnnosum S.1. there are generally , together with highproportions of other Simuliids. Surveys have confirnied earlier reports that 1ow numbers of aquatic sta5es of S. damnosum 11o oaa -)- iii. DBRrs at the main capture points have been low and parous rates have been high. Refer to the graphs. In view of the fact that the parous rates are invariably IOOiJ, it seems most likeIy that many, if not aII, of the flies caught are allochtonous. It isdifficuLt to believe that the parous rate sj-tuation is represen- tative of an aging autochtonous population. One may therefore conclude that as the Ieve1 of control is so good, the treatment stratery is perfect, or, there is appreciable over-treatment. IS earlier proposal for reducing the treatment rever was based on Z - reduced Abate dosages, - treatments restricted to breeding sites considered to be highly pro duc tive. Having stated that, it is realized. that the area is currently subjectto climatic/environmental change and that ti:erefore, nry logic is probab\y nottrue at the present time. Be t]:at as it maq/, I tirink it vould be uorthwhile to implement my proposa1 at a different time of the ;rear uhen climatic and hydrolo-gical conditions are more stable. cc Dr Ba1dry Dr l/alsh Dr Agoua Iilr Zerbo I"lr Colussa LL/4 L2/4 L3/4 Lr/4 L6/4 t7/4 tB/4 ?2/4 23/4 Annex 1 BREIiDING SITE SUIiVXYS MADE DUIING APiIIL ]-985 Boa, Boua and Bafing (urith Dr Baldry) Dion (with Dr Ba1dry and R. Lama) Bo", Sassandra and Bagbe (vrith Dr l'Ja1sh) Bafing (r',,ith Dr \,/aIsh) Dion ( l- eadr,:aters ), Loro, Lof f a, Sanl,ou and Suessou Kourou Ke1le, Gbanhala and Gboroni Dion and Beni (r,ith Dr Ba1dry and 1.1. Lena) Bafinfir Borho and Mboo Trtbutaries of Dion i.e. Beni, Tooma, l'iaradalar Monsoro, Tourou Kouan, ltlafbe and Sysss6u Bafinl , I.hoo, Kotre, Gouan and Bolho Kourou Kelle, Gbanhala, Kourai, I'Iilo and Dion (v,ith G, Nigbei) Bafing, Gouanr Shon, l.fboo, Sua and Srressou ('i-tt't G. Zerbo) ?5/4 ?6/4 30/4 Annex 2 COLLtrCNIONS OF LARVAIJ AND PUPAE I,IADB DIIIT]NG APRIL 1985 All larval samples vrere preserved immediately in cold carnoyr atd will at the earliest time be transported to either Banako or OuagadouSou where a cytotaxonomic identification will be carried out. Ihe following is a list for April. It is envisaged that a complete list uiIl be included in the definitive report (if not before). Lt/4 Boa 7'41 1,I, 8'4 t,I l2/4 Dion g'33 N, g'4O N, g'42 N, 9'49 N, 9'50 N, 9'54 N ]':6,/4 Dion B'59 N, roro B'50 w, loffa B'11 N, suessou 8'35 v'l LZ/4 Gbanhala 9'45 N, 9'58 N 22/\ Mboo 8')5 w 2)/4 .Torrrou 9'11 N, Monsoro 9'12 N 26/\ Mil-o 9'L4 t,'l . )o/4 Bafing 8'oI N, shon 8'23 N, sua 8'3? w All pupal eamples urere reared in the laboratory at Odienne and will be transported to the University of Salford where an identification by neane of cuticular hydrocarbon analysis (OI,C) will be performed by Dr Angela Phil1ipa. The list for April in addition to tl'ose already taken by Dr l,/alsh is as followe ; 22/4 Muoo 8'35 w 26/4 Milo 9'14 vll p/4 sua B'3? w 3 - Dny RuNNtNo l'lenn bBR's f) (.? (r.N "'-oo ti) {a64o I l t'.<I t 'r( ij' v:--6't- I @ axI x JI tl I x , xI I 0\ (o o l.) + l\ o 1., o A, N 1.,t r,r a\ N a (, o fl o :E <- + - + x \ odlPo ,a\> 1 x i I Iotdt,Do9 PtrS / >i I r 3 oV k-l <_I t\ if i t/ rl De a,0 og \ qt lr1 {l a qr t l, (, t- ,ot l.) .il :/ , I I x J t * I II x' I x II II t-- ,t , x I i i I l lr I i ! ! I I I * I x + I Y II Ix I !.{ a ,i '+ dI r ; )0 \ s{)rtt I It I Ir ldo !6 eaeous9o I ffi lr _ii'r) .<- I l. cunn tn ' mealL DBF! - 3 aqy -+- -tr C d '6 P, I I I -f-tf) t) N, I + o @ F} -n LO 0 / I 2L lrl 1t 3o o ( t o\o -,o os llo { I' I 1 + +- .qt4tdPa*tttr' '{' I ;1,\l + l + lr ri + I -to o/n P.rrau t + .D(.c - (9 m(Ii r P o o o C I -). \(-.1 -t ) P 9 IqctI8,c I bo 2 + G I to l2 t+ Ito r$ i 2'o' r 2Z 2.t zb zg 30 5a il g ii, + \ I' l 3 -Dnv RUNNING Mreu DBRs lg85 eoo ,.ro c\ oi I 'Tl (-o \", I I 'I f T tr(rrocr \\ \ \ ! I I I + I I I I I I { \ oL G) o p f G a le o Iv t$ l.f f P F l.l (c (, o Gr 91 + -o gr \-9 u$(J x I x t l II/s @ F x\ x ,1 ! I T I It\ I + I x I xI x/ \ !/rI tl \o I$ I't Ul N, \ \ \ \ \ 5:\ \ \ \ t + + l -i ( t + I .[rlut '.t+o\r:Ll'*lri -r,. ,. tt \ \ \ --O^ - {sA -\qe_< !--- ;Bif,i + tt + EI I I i ?'o p:rrcS f 3 2leti t'rtt;,')r,1, ,'r,eor 1 rf 3 rtoJ- a Dt- t \ (/\ :) rneqn -. DBR s(rs o€, _3 aog runnjn$ \) h)I t- I I T1 rE h)t xiitol 'l --t- t-1. 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