Resume of the entomological situation with comments on future activities: the situation up to the week ending 24 June 1977

(t ! *yJ htfi ' From J.F. Ila3.sh, VCU MEMORANDUM To Maro Is. Bazln Attention 3 Progranme Dtrector// Drte 29 Jr:ne 1977 Our ref. Subiecr: BESUtrIE 0F [m ENT0UOI,0CI0AI SITUAIIO$ WIBH colftfnil[s 0I[ FUtIrnS ACIMIXES Im slluAllos uP To IHE U:EPK E}IDItrG 24 .]InrE Your ref. Phas.e I ControL has operatecl ln the sa.me nanner as in the prevloue two years withfalrly slmiLar cl.lsoharges of lnseotLotde. Relnvasion has again affeoted the Sandara YaJ.Ley and the leraba Rlver tn the Pont Routter nelghbourhood. FIy nu:nbers have exoeededl thoge reoordetl clurlng the oorresponcllng perLodl fn 1976 and appear eimlLar to the relnvaslon of 19?5 at both 0haussdc Siakaranantlougou(aanaana) and ?ont Routier (lerata). Both the nunber of fLtes antt the transmLeslon potentlal are dangcrousJ.y htgh. Eoweverr in nost other &reas, the sttuatlon ls quLte satisfaotoqfr betng better in the 3lack YoLta and Bougourlba valleys th,an La the prevJ.ous two years, though the Bul reglon oontlnues to be a problem. Phase III IIeEt Control, has proved extrenely d.lffioult at 1ow rater levels ancl sporacllo outbreaks of breed.tng havc been wtdespread. The oontrolletl arca has becn expanded to oover a scotion of the lflger Rlver at 3a^nako ancl at the trfiarkala Barrage. However, rr:tth rlstng water l-eveLse treatment of the l{lger at Ba,nako (not presaged. ln the fAC MlsElon rep6rt) rttl be euspendett after the treatment of 28 JunG. CarefuJ- aeri.al suryeys of the BantlX.agara area have show:n a YexT oonplex fl-uvlal- sttuatlon whloh ri"L1 requLre treatnent by helloopter lf it ls to be satlsfactorlly oontrollecl (not foreseen in the PAG Mlssloa repoft)o Resulte have not unexpeotedly been clisappolnttng wlth substaattal fly anrnbers throughout most of the southem half of the zoreo ilost of this area 1s wlthtn l-OO 1@ of uncontrollett breedtng sites outsltle the OCP and thc problem seema to be largely the resuLt of reinvasLon fron guoh areas. Eentative conoluslon The Phase III West zone of the OCP ls not the souroe of the fLles whieh have lnvaded the 3an<[ama and Leraba va3-1eye ln the years 1975 anct 1977. Moet of the Phase III ltest zone ls ttsel-f subJeot to reinvaslon j-n the earLypart of the ralny seaBotlo At a substantial number of sltese thle relnvaston is of epidemlologloal lmportanoe. The souroe of these flLes ls a matter of oonJeoture at the Present tlne. # oo: Dr R, I.te Berre a:*:-/-:- - ti 1977 -2- A relatlonshtp between the reinvaslon at Ch. Illaka (Sanaana) and Pont Routler (leraLa) is apparent as in 19?6. [he saTanna cytotypesyirJZs-i"b; ;=; "i"""iy tnv-olvedt but both the yah antl soubre eytotypes are also suspected from ?ont Routler. [he area of the lvory Coast south of Oclienn6 has been subJect to Lntenslve aerial prospeotlon and. a hitherto unknowu maJor breeding conplex has been l-ooateet on the Yanl trtbutary of tbe Marou6. Large quaatitles of nateriaL have been preserYetl for cytotaronomlo stucly for Dr VaJlne, posslbJ-9_)$S analysis 6y Dr Sennett ancl for cLassloal taronom1e stuay-uy ir^ts Qui116vdr6, Ga:ms and' others. Dr onar has co-operated with ir Garms in an atienpt to unraveL the oomplex situation coneeraing the tlifferent forms of the parasite onchocerca volvulus present in the area. At the tlme of the ftrst reinvasLonl active breeding sltes protlucing the relevant oyiotypes in a6jacent unconirol-Ied areas of Ivory Coast' were carefully plottett to t""g" scale maps. After 6lscusslons between Dr Garms' Dr Davtei ina Dr tre Berre, tt was cleclcletl' tol a) Treat the northera reaehes of the Maroud as these came lntoproarciion (fron about 1o June) b) Io exten6 treatnent to those parts of the Sassandra ancl tts trtbutarleswhichwereactlvelybreetllngapproprlatecytotypes at the ttrae reinvaslon cornneneedr Bhe treatment ls to be earrled out for an experiBental perlocl' of flve weers startins 5 Ju1y. By this meanEe it is hoped to cletemine unamblguousLY: a) IJYhether the control of the Upper Maroud resul-ts in a l-essening of retnvasloa as the seasoa progressest and b)whethertheUpperSassandraSasinoanbelnplicatedasthe source of the reinvading flies in the Bantlana YalJ-ey and the Pont Routler area of the leraba' o)IYhetherthisextensloEhasanybeneftcialeffectlnthe Phase III Vest &re&r Reinvaston studies ?hase II Fo11owlng the oaset of the ral-ny sesson-and the beginniag of f3'owin the Red volta, sissiu ""0 ipp""-frnit" volta val1eys, an infJ',x of flies aeens to nirr"-occurred. -ii """""a1 cases, ureettng had successful'y taken place within a few days of the cornnencement of flow' In additlont treatment was probably not oarried out in a sattsfactory Elanner (posstbly the result of excessiie treatm"ii-"p""q).. At the tine of writing; tbe situation is unsatrsfactory r;-;;";;-oi'in"-si-ssili, Bed volta and white volta valleys and comp*r"i ,oravourably witb the sttuatiou iu L976. -7- Phase III Ow"ing to the varlous attnlnlstrative problemsl oontrol has hltherto been oonflned. to Iogolese territory. This ls a very dllfflcult area to treat andl in addition, the quality of treatment leaves much to be clesirecl and. results have not been very lnpressive. Eoweverl owing to the paucLty of pre-control info:matLon, lt ls not possibLe to clraw manyfira conoluslons. In the UB Va11ey, the southernmost polnt In the control zouer fJ.y nunbers are, however, consid.erabLy ln exoess of those recorcled ia 1976. Parous rates suggest that treatnent is probably lnad.equate but the problem uay well be reiaforcetl by the relnvaslsn. lack of atlequate pre-oontroL records acts as a serrere coastraint tn lnterpreting the present resul-ts. GeueraL aonolusj-ors - Phase II and III East Control acttvX-ty has thus been disappolntiag for 1977. Some of the reasons for thls appear to ber a) lack of appreciation of the speed at whlch colonLzatlon wouLd take place. b) Intrinsio tLiffl-cultLes arisiag from the rapld changes ln water leveIs resultLng in outdated lnstructLons to pilots coaoenrl.g tlosing rate, e.B. the gauge readlngs at Pd Brl<lge1 Retl Vo1ta, were 3 0.14 metres at U.00 h on 22 Jrtte J.P. Wa1sh 0112 metres oa 25 June Ouaga sector team 0.10 netres at 18.00 h on 24 June G. Zerbo 1.BO metres at 20.00 h on 26 June Mrs B. YlaLsh(strll- rising) Under nornal oircr.mstancesl the reacling uade by the sector tean oa 2J June wouLdl have been nsecl in planniag the treatments for the week s6mmslglng 27 Jure. Fortunatelyr a routlne hyctrobiology vislt brought to J-ight a sharp rise ln water levels. lack of ad.equate background expertence of the p11ots and their too frequent ehang€-oY@xr Excesstve speed of treatnent. (ls f understancl itl the plLots have their acconnoctation paid for when on duty travel but there Ls no al3-owance for foocl so, iu effectl they lose money when away from base). e) Inactequate brieftng and supernlslon by aerlal operations staff. Expaas lon of activlties ln Phase III East Knowletlge of pre-control bitiag rates and transnlsslon potentlals is inaclequate throughout the Phase III East ErBBr Howeverl the Porga and llatitlngou sub-sectors are part of the same fluvial systen as those under controL in Togo. For this r€asonp control should start once adlequate last minute prospeotions antl proper fltght plans are preparecl. ) d) -4 ?art of thls area is tl.ensely populated. so there wiLl- be a major beneftolaLpubIla relatloas and pol-itlcal effeot. Coatrol should thus enoonpass the whole PenctJarX. Basta as soon as teohnically feaslbIe. However, with the preeent lneclequaeLes.in the existlng controL activitlesl the absenee of eyerl oae fril-l year of pre-control clata, the Iliger tributartesin Bealnl Bogo the trllekrour Al-lbou antt Sota ae well as the whole lfia,mey sub-sector shouLd be left untreated at the moment, though the Mekrou shoul-d be inclutlecl ia the routlne aerial surveillance. Resumd of the work beinE carried out in the proposecl rrextenslon zonesll Ivory Coast As part of the reinvaslon study, we have been monitoring seven sites outeide the preeent OCP area, with acltlttional sttes being stutlted by IRO, Bouak6 tn the Sassandra-Marou6 basins. Itris stutiy wtII be terninatedin August. No work is being undertaken by ug ln proposed extension areas of the Nzl and Comoe systems. Sorae pre-controL data exlsts for previous years in the IRO fi1es. This may be satisfactory for certatn sites stuclietl ln detatl by Dr Philtppon bute tn many caeese it cloes not cover the fuII breed.ing seaaon and. ln other casesr d.issections undertaken by tralnees clearly underestlmate the transmlssion potentials. Thusl tn qy opinionl whilst ad.equate clata ts avalIable eoncerning breeding sltes of the varlous eytotypesl infornatLon eoncerntng ABRts anct ATlls is not aclequate at this time. Info:mation eoncerning breecling sttes contained ln the report by Dr B. ?htlippor- No LZ5/Oneho/Tecb/ll of 3 Juae 1977 ts not aclequate. Ile eertaLnly require detailed lists of cytotype dete:mlnations giving exaetlocalitiesl dates of col-lection and actual nu.mbers of each cytotype cletemlned in order to tlistinguish between sites yiel-ding pred.ominantly saYanna cytotypes and those sites where savanna cytotypes may be of purely sporadlic dry season occurrence. Doubtless, the proposeil bourxdary of the extenslon takes lnto consitleratton these facts but the bastc data must be available toyCU. Dr Qu1116v6r6ts lateet quarterly report gives tlata of the requlretl exactitutle. Ghana 1. Ilestel4 aqqe (fintampo) lYe have falrly adequate ilata over two years from our slte near Klatampo, whieh has, however, provetl of 11ttIe epldemioS-ogical significarlce. 2. Central area Dr VaJlme has matle a long serles of cytotype collections from the main breetling river which we hane considered as a posslble gource of re- invacting flies, but we have almost no d.ata coacerning ABRts and ATPrs. Regul-ar coLleotlons are now betng unctertaken to obtain this data at the site aLread.y being studietl by Dr Vajimer It -5 - 7. Eastern areag (votta Region) IIe have one yearts data from two sites in the north adJacent to the OCP area. In adtlitionl Mr Zerbo has marle some stutlies further south atdiffereat seasons. Eowever, the cytotype distributlon ancl transillsslonpicture 1s very compJ-icatetl aati a oonslderable number of further investiga- tions is requlred. At Akosombop Dr Rayboulct has made a small lnvestigation of the cytotypes comlng to bite man and the degree to whi-ch these cytotypes are attracted. by poultry and other clomestic anlmals. Tog_o From aerlal surveys carrled out by Dr le Berre 1n 1975 ancl Mr S. Sowah recently, we have a fatrly good generaL ld.ea of the potentlal. breedingplaces. 1)r VaJlne has made a few cytotype dete:mlnatione. However, the ABB ancl ATP ts not ]orown from even a single site ln the proposecl extension 8f€&r 3eaj.n General looowJ-edge concernlug breeding d was col-lectecl by Dr Quelennee in the 195ols been untlertaken. Slnee August 1976, we have at two or three sites just south of the pres OCP data concerning ABRts and ATPis exist. istribution of S. ilamnosum but no aerlal surveY has been making reguLar catches ent OC? bouadarY. Ho Pre- Concluslou Ivory-!-gqE_t Ghana' Togot Benln Although the proposett Ivory Coast extenston area 1s relatively welJ- known, I do not thlnk-lt ls known wel.L.enough_to merlt control without constclerab1efurtherstutly.niver@_aataa1soseemstobein- aa.equate. Valuable lnfo:matton shouLtl be iorthoomtag from the experlmental control to be undertaken la July which wtII aLso glve a so1icl basis to oost estlnateg. Both Dr Davles ancl I feel strongl-y that in any eoatrol undertakea in this areal the result ts unllkeIy to produce a satisfaotorT "pia.rforogical situation in the Sassandra Va11ey itself, although there niy Ue sol1e alleviatlon of the present shocking situation' Unlese thei;;=y Coast Government are ararL of thlsr OCP may stancl accused of being d.lshonest and eertalnly ctoubts will be cast on our abiltty to d'eliver thettentomoLoglcal- good"tt.- Ilowever, the 197? experiment shouLd settle thls r.atter. Possible extension areas are poorly kaown entonoJ'ogical1y anci much Lnvestigatory work ts requiretl. Hyarof|gtcal lnfozuatlon would' requtre considerable lmprovenent especlally in Ghana and' Benln' GeneraL At the present tlne, OCP anct the a.ertal Contractor are barely able to adequately tackle the oc? ""." "" originally p]-annett' ln the ?AG Elsslon report. Any exiengion of oontroL shoul6 thus bnly be contempLatetl tf it is fel-t that lt may have a beneflclal effect on the oc? area as origtually tleflned. Thls shol].d' be macl" o"ty clear to the SoYerDments coacerned' It must be adni.tted that certaln Lxtensions, though highly desirable from a rnedlcall socloS-ogical and eoonomlc point of viewl may not. be feaslble lnviewofexisttnghowletl'geandconstralntsimposedbypoJ.lttcal consitlerations.