Evaluation of formulations of permethrin (OMS 1821) furnished by wellcome as larvicides against simulium Damnosum S. L.: I. effects against S. damnosum S. L.

\YORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANTE ONCHOCERCIASIS CONTROL PROCRAMME IN THE VOLTA RIV[,R BASIN AREA PROGRAMME DE LUTTE CONTRE L'ONCHOCERCOSE DANS LA REGION DU BASSIN DE LA VOLTA ln rcply plcrs rcfcr to No VCü/0251 EVÀTUATToN 0F trORMULATIONS OF mRI\tETrnnI (offi 1B2l-) FURNISmD Iry ÏYELICOIffi AS IARVICIDES ÂGAINST SI],IUf,IU\I DAIllNOStIIl S.],. I EFFECTS ÀGAINST S. DA],INOSUI,{ S.I.a INSECTICIDDS Three formulations rÿere furnished by \Tellcome; (f) 2V1 ^,i. EC (registered narne Coopex) code 551/5/27 (2) 42.5% a.i. EC (experimental) code A l1-29L58 (l) 5V, ".i. Ec (experi.:mental) eode 511/12/4 TEST IlIIETHODS The close-circuit trough systen was used for prelinlnary 1"sf,ingo Coopex vras found to be superior to the trvo experimental formulations and was fi:rther evaluated by river trials. (See Annex I and 2 for details of nethod.s ) . TESî SITES Erraluatlon was carried out by OCP staff in Southem Togo. Slmu-Lfu-m damnosrxn s.l-. larrrae used. for the tests were obtained from sites where larnae are believed to have no:rnal susceptibility to aII inseeticldes. Hovr- everr susceptibtlity tests in Ivory Coast a3ainst larrrae resistant to teme- phos and cirlorphoxim shovred the resistant larvae to be 3 to 5 tlmes more 2susceptible than the rrnormalr' strain in Togo. Because of this obserrra- tion, trough and ri-ver tests vrere carried out ln Ivory Coast. They eonfirmed that the effective field d,ose in Ivory Coast is l-ess than in Togo. Studies are undervray to deterrnine if this effect is due to a r?negative correlatlonrr with organophosphate res:',-stance, a slight resist- anee to pyrethroids in Togo, or a simpre geographic yariation. For the erraluation of the effect o.f permethrin on the non-target fauna, it has been assumed that the higher effective field dose observed in Togo will be necessary for operational use. RESÛiîS A. Trough tests Results from 15 trough tests are sunmarized in tables 11 2, and 7. Data for temephos, the stand.ard OCP larvicide are shor,rn on table 5 for conparison. All the formulatlons are more aetive than temephos, with observed trtOO,s of 0.OI2 to OrO4 eompared with 0.1J to 0.27 for temephos. This dlfference is clear at the level of the IC95 (O.OO4 to O.OO7 vs. 0.066) as well as at the lerreI of the LC5O (O.OOO2 to O.OO1 vs. O.OOB for temephos). The test in Ivory Coast with the 42.5/"gc (leZ(fe)-Z f" Table 2) sholved that there was no cross resistance and. in fact somewhat better resufts (toû at o.o28 mglI vs. 94 at o.o1 in Togo) were achieved with the larvae resistant to temephos anC chlorphoxim. Al1 the formulations shol a lar6;e j-ncrease in concentration to go trom 9ü nortality t,o lOÿ1. fhis was true both in Togo and Ivory Coast. For this reason, comparative testing concentrated on determining thu ff100. 10@ effectiveness is necessary ix OC? operations, both for epidemiological reasons and to avoid selection of resistant strains. Comparative tests at the hlgher doses shorved COOIDX to be somewhat srrperior with an ffIOO of O.O25 mg/I j-n most cases, vs. O.O4 ngl1 tor t]ne 5dE.C. Tbe 42.5y'"8.C. never reached IOOU in the tests in Togo. On this basis the Coopex formula- tion was chosen for the ri-ver tests. . . .,/ ). 1In te:ms of Iarval behaviour, the Larvae become agitated almost instantly. Iiany stop feeding, and there is a very high percentage of detachment at the higher concentrations after 10 rnj-nutes. At l-orver oncen- tratlons, paralysls lnternenes, with the older larwae rernaini-:rg attached in distorted positi-ons. îhere is no evid.ence of recovery of moribond larvae. B. Biver trials Results from 6 river trials are suinmarized in tables 4 and 5. these results show that the mi:rimr:.m effective fielrl dose is between O.O1 and O.O2 ragl1 for 1O minutes (in îogo). This dose gives a carry similan to temephos at 10 x the dose (0.1 ng,/1 temephos at a ferv m1/see gives about t lrra, of 1O@ reduction). îhe relatively poor results obtained in the last tlro river tests in Togo (nel-lO and 71) are due to the fact that the rivers were drfing up and flovr between rapids lvas verl' slorv. In Ivory Coast, against larvae resistant to temephos and ch-l-or- phoxim, the minimum effective field dose may be as 1ow as 0.005 nrglt tor l-0 mln. Àgain carrjr could not be estimated because of lorv river discharge (tests R84-2 and 1)" Itro river trials have yet been earried out at higher dlscharges. It is hoped that this will show a performance equivalent to temephos (20 lm of 10@ reduction at 1OO m3/see). C, Comments on the physical properties of the formulations All these fo::nulations spontaneously form flne, white stable emulsions and are thus suitable for operational use. There is sone con- cern that the more coneentrated formul-ations might preclpltate in storage, but they seem i-nferior to tine 2O't anjruray. II. EFEtrCTS O}T }IO}I-{'ANG]]T FAUIIA COIi-DIîTOIIS A]ID IIgTHODS See annex l. .../4. 4AESUITS The results are presented in tr'igure 1, vrhieh shor';s the pereentage of j-ndividuals of the major taxa remaining in the gutter at various times after the application. The total number of individual-s in eaeh taxon present at the begiruei:rg of the experiment 1s 5iven on the left. Invertebrates began to detach J0 minutes efter the application of the che:rical. There ÿras a strong effect on t):e j-nvertebrates. I,{ost of the taxa were reduced b;r at least lgX rvithin JO minutes. îhe Diptera ( other th.an Simuliidae ) were the onl;r group not severely affeeted, nith only 5/,4% detachment. Ilven a;rong the Diptera, the less numerous Tanytarsini and Orthocladiinae were sensitive, rvith 88.ÿ, and, 82.% detaehunent respectively. Only the Chironornini anci Tanypodinae seemed to be IittIe affected. On the other hand the Epherneroptera, rvhich sirovred. a 95.Jfi reduc- tion, ryere even harcler hit than Simul-ium da.mnosum. Iinally the Trichoptera were also yerJr sensitive, being redu.eed to less tbarr 4CX of the nu,'nbers before the test. In this group, the younger i:nstars (f-Z) were almost cornpletely removed bi. the lnsecticlde, whereas oni-y 54.1y'" of the older larvae (lra instar and above) detacl:ed. l[o effect on L,lacrocrustacea or ilsh ivas observed du:r,Lng the passage of the insecticiC.e. r]ISCUSS IOII ,Às a measure of conparison, figrrre 2 (c1ata from Dejoux, tgZOI) presents data for temephos (an oper,'ttional I'.rrrici,le in the Onchocerciasis control ?rograrnne rvhich is consirlered ecolo;ical-I;' acceptable). It is clear that permethrin has a more drastic effect tiran temephos an,l that perrnethrin use would require very carefuf ecological monitoring. 'r 'De joux, C. 1978. Action de llAbate srlr les invertébrés aquatiques. Vf . Effets des premiers traitenents du Sassand: a. Rapport ORSTOII Souaké, 1.Io.25, 22 p. mimeo. ...//5. 5ft should be kept in mind hovrever that these results reflect the short-terrn effect of a slngle application in a river not subject to regular insecticide treatrnent. îhe long-term effeets of vree)lly treatment cou-l_C be more or less severe. In the case of the Trichoptera, for example, vhich have a long life cycle, the drastic effect on thc young j-nstars couLrl restrlt in serious reducti-on of the population over ti..e long-tern slnce the older lnstars v,rortlrL not be replcced as thelr matr:red. OD the othcr hand, past exoeriettce has shown that the fauna trad justs'r to repetitive treatnents. Fron the ecoJ-o3ical vie',vroint, an insecticide rust be re jeeted if it produces a permanent struct,"ral anti/or quantitative disequilibriurn in the aqu-atie ecosystem. The resuLts prescntcrl hcre eannot be uscd to decide vrhether permethrin will have srrch an effect until an operational triaJ- has been carried out. It is csse:itial_ to stress that the present trial vras carried out uncldr very loiv di,scharge vrhen the effects on non- target fauna are the nost d.rastic vrith an7 insectici,le. A 1esser effeet can be expected when river d,ischai.ilcs are tr:igh:r. ITI. DISCT]SSIOII A]D CO}ICIUSION The Coopex 2& nc formulation of perrncthrin is an effeetive Simulirl'o damrg larvieide at a dosi:rg rate of o.o1 to o.o2 m6l1 for ro m1n. îhe pro- duct emulsifies spontaneously j:r the river anri disperses well . The earr;r ts acee;ltable in relation to the diseharge. The t,vo otirr:r fornr:lations funrished. (42.5% EC and 5ü r;e) ou somewhat i-nferior. Although there is no mortality among fish or macrocrustacea the effect on the non-target farara is more severe tiran that of temephos. In this respect a long-term trial is necessary bcfore it ean be deciried if the product is ecô1ogica11y acce5rtable or not. ïV. REC0lylilllIIDATI0N Ân operational trial i:r an entire river basin for 6 months to one year (dry and wet season conditions) with carefrr} evaluation of the effects on non-target fauna should be carried out. The carry srrould be rretermineri at higircr discharges. îhe ninjmr:rn effective field dose a3ainst larvae resistant to temephos and ehlorphoxim sho'*ld be rrerified. The loss of aetivity in storage shourd be investigated. 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Grtglrr u..d rrtrnrlvrly la ler tort ttrto. It ber b..! furth.r rodifkd by thc ocp flrottrlilof,rlolroh ?olr, Lorr, îogo. L§ÿaa oollaat.d h thr fhld rrr tllorrd to.ttroh throrclvtt o! a litærblaplrtr ly14 l,l tbo bottol of r trmgi rtdr ntrr tl rrolrculrtrd vlth â purp. Thr p).eto lr tbrl trrarlrrrrd to r ..oond troEê làrro lnlrcttoldo hrr rlnrdy bccn rlxrd lnto tho rcctrculetlng vrtrr. lftrr rsprciflc.rPotur. tlrr, tho plrtr 1r flarlly tranrfGrcd to a thlrd trough vlth claari vltcr vhcro thrrortrllty 1r uotrd rltor 2l bollr. Tcohnlcel drtrllr tho trou6hr uId rrr oonrtructrd of rlurlnlur and palnted vhlto. 'the t-,,urllir arc B0 cr ]oag,L5 cr vidc ead I cr dorp. thry arr clorrd rt oac cnd. tL thc othar rud, a constr.i:,.Èd r.ctlon or llp,I! cr long, 8.8 cl Yld., rnd 2 cr drrp 1r rttrchrd.  renovablc rctÀI plat6 rêsts :r th. bottor of thlrIlP' lJrtcr 1r puaprd lnto thr olorrd rnd of th. trou8h rnd floyr ovcr thc plùt. r: thô rlp into . r.sèrvolrto be rsplrrtod by thc purp rgrin. srlll rltctrio ctntrifu6el punpr ylth a dlscharro of èbout 22 l/a]n. ertutrd, eud th' v'locltt otar th. ottaohralt pletr lr rbout 0r?r/rec. For tho attac5rrrrÈ rnd obrarvrtionsyltcrl, th' r'!'rvolr i!. prarttc ratt.-buckât hordlug about 60 lltrrr. ror tho Êxpol.rs !yot.r, a IoIttrc raarrrvrr' pot il urrd lt I r.t.rÿolr to roducr thc uount of lnarctlcrdc nocdcd. Rlv.r ÿat.r lt ut.dat rll ltrgrr for routlnl trrtr. rtr cbrreotrrlrtlce (terpcrrùurc, pE, turbtdlty) ara carafully notrd. Lrrvtc arc colbotrd by rllovla3 th.lr ttrturrl rupportr fro! thâ rlvcr. Thcy rrr trrülport.d hplrrtlc bagr ln rn lorbor. Cerr la t.ta! to r.prrrta thr larvtr fror üc 1or by à lay.r of frrrh Irrvrt or81116' ^rthoqb thr rqulpreat orn bo uæ'd rt thr rlvrrrtdc urlng a portrblc .r.ctrlc grurrrtor, thle typrof t..t 1r uruelly dono la. lrborrtory rà1ch lry bo tt sorr dlrtrncr fror thr collrcLtng point. ?br vogrtetloa rlth tùo lrrvro Lttrohrd lr plrcod ln thr .tt.chr.!t trough. tha lrrrer lrturrllylrrvc thr y.t.trtlo! to mrt r ataolg.r oUiront r.d thrr rttrch to tho pleto in thr llp, vhlch ber tùrhlShrrt vrloclty 1l the trogL. ?àl rerrrr §. r.ft lo:. 21 hourr to .Drur. rlrt ettÀch..ot. Ll,rrrr nàiobpuprtr durlag thlr portod trr tltrlaatrd Jurt beforr .rpo!u:... Thc pletc urually oontalDs about l0O r.tur.lrrvrc rnd aaÿ.nl hundrod youug lrrver. ?hr lervlcldr forrulrtloo, *. rpproprlrtrry dlrutcd rltb tttrtlllcd vrtar irradlatery prlor toth. t..t. ?hr qutntlty E.o.ttlrÿ for thr lorcrt oonc.ntrÀtlon l.r rdded b), plpcttê ro thr reacrvolr of th.erporur' trough vtth tbr purp ruaalag. ?br lntrotkidr lc arlorcd to clrculat. for ! rlnutcs üo obtrln runlfor' dllprrrrl. lddlt'loDrl larotloldo 1r rddrd to lhe aarr tyrtcr to obteln rhe hi,h.r oonc.ntrrtlon,in r trtt rrfur. lbr plrtc fror thr rtttohrrnü trough 1r nov carcfu).Iy llftrd out r6d placer) Ln th, ?rpotur. troughfor e dcftncd pcrlod, usurlly I0 tlnutor. Lerveo drtrchln| durlag tbr cxporuro prrlod rre caught ln r nct attached to tne rip of th. trough. Âftor thc 'rPotur. P.r1od th. Pltt. Ud thr E.t arê tranaforrcd to e boi,lr:r8 LnDu,lh. lt tho codrf e Z4-hour obt'rvatlo[ prrlod, tho dotrohrd lrrver lu thr nct, lr vc]l as aoy deacl onas s.,,rrr attachrd to '-ho prrtc lr' prat'r"'d la llcohor for couatlag. (l flrrt corlcction 1r uruelly rade ? hours rft.r .rposur.slncr rort larver drtech ln thlr prrlod rsr thr 1e171; try dccorporr tf lcft too lon{t). Iire livlag lrrrrrare klllrd vlth hot ÿetrr rld elro prrrrvod ln tlcohol for countlng. Totrl Durb?r crporcd, Ilvlag, endcred, rrc rrtebllrbrd t.p.nt.l, for rrturo (6tl-7tu larter) aad young (rrt-5tl lnsùar) Irrva.. Lervrraxpolrd to l[..otlcldr rad pnpethg durla3 tbr tort tr. not couDtrd crc.pt for th. coDtrol vhrri thry trlaoludrd ln thr nurbrr rurvlvlng. lbc urual confonrtlon of r tctt lr r rrn6r of ! conccntrrtlonr end an u.troated coutror ylthtvo rcpllcrt?r rt ,..ch oonoaûtrrtlo[. p[ooat rortrllty ts calculetad at râoh conccatr.tloD td couo.rFtrrtlon/rorteltty llnrr rrtrbllrhod by probtt uelyr1r. ^IIIEI 2 SIXULII,}T LÂRVICIDE SCREE}TITG IN THE OIICEOCERCIÀSIS CO}ITROL PROGRAHI{E IETEOD: Rlvcr Trlal Rlvcr triale luvolvc llrrt the relcctlon of s lultablc §. dalnoarlr e.l. brccdlng rlver, cithcr uaII, rcdlur, or ltrgc ln a glvcn lealoD dependlng on thc requirercnta and crpcctatlona of the chcrtcal, aftcr inltlal laboratory rcreeuing. Âu adcquatc .trrtch of riÿar ir flrrt surveyed by hellcoptcr. Laadlugr arc rade at cÿery PoteDtlel brccdlng slt. and the posltive sitcs, (presencâ of eggs, Iarvac, pupec), arc identlficd vlth colourcd plaatic strips for carlcr prospcction and verificatloD èftGr lnrectl- cldc trcatrcnt. thc brcadlng !1t.r arc cercfully rapp.d aud rclcvent factorr includlrg topcraturc, turbldity ead pE of thâ rrt.r 8rc rccordcd. Thê dltchlrSâ of the rlver at or near the point of trcatrcnt la detcrrlned clther by rcading the vatcr gaugc at the polnt (if one is avallable), or by rcaaurlng lt vltb a current reter or float. hce treatrcnt polnt har be€n chosen in thc particular ctretch of tha rlycr to be used, the arouDt of forrulation regulred to 6ive the desired concentretiou for 1.0 uinuter of rlver diacharge 1r calculated. It ig usually diluted ulth & convenlcnt arount of rivcr yater Just before aPpllcetlon. The actual application nay be carried out by pourlng or yith a hagd prclsure sprayer ia thc carc of !!all ttrcaE!. A boat and a plerced drur ray alao bc uaed. In thcrc two carcs, thr appllcEtlon cau be thed to last I0 aiuutcs. The application can elro bê donc frour the alr ullag a hcllcoptcr. Fror the air, the insecticide lay bc pourcd through an outlct 1n thc ridc of the râcbiD., or sprayrd lnto the rivcr uairg the equ!.plent uscd ln rouüinc operatlonr. Àcrla1 application Is essentially lnstantaneous, but tho applicatlon is aade in rlovly- rovlng ratcr tota dlrtencr rbovÊ tho first raptds 1n ruch a ray that thc lnrccticldc front lprcads out to gire I longcr lrpo.urG ln the rapidr. Evaluation of the cffect of the chericel, on the Iarval ctage of the vector ir crrrricd out 2tl hourt or 48 hourr aftcr appllcatloa. The vhole portion of river 1s again survcyed by helicopter Ènd the proportlon of larvae uhlch have dctached ls estitatod. ^rIlrEI J COI{DIIIOTS AltD I{EIHODS FOR THE EVALI]ÂTION OF THE II{PACI ON lroH 1^R0E1 FlUilÀ 0F PERXETHRII| 2ü/ t.t. EC (CoopEr) ^ppLItD roR slxulIult coNlRoL Conccntratlon : 0.015 rgll for l0 rinutcg Appllcatlon l(cthod : hcllcoptcr Locatlon aod datr of tcrt! xono Rivcr at ÂtchinedJi (Togo). 2G,21 ltovcrbcr l9B3 Rlvcr dlccharec z O.6 t3/acc. l'lethod of lnvcrtieatiou: Slngle gutter placed in thc rlvcr. thtr trthod ia barrd on the rrasurclcnt of the drift (detachrent) of benthlc equatic organlsr. this phcnorcnon occurs naturrl).y ln a dally cyclr, but 1r vcry ruch lncrcercd by the pÈ!.a8r of toxic ratcrlal r. thr guttrr (a rcctlon of PVC pipr h long by l2cr ln dlerctrr) r.pr...rtr a rtrctch of rlvcr ln rlnlaturr. It lr placcd in thc rlver 2,1 houra bcforc thc applicrtlon of lnarctlcldo aad colonlrcd by adttlng Datural. supportr (rtonca, grasr ctc.) vith adhcrlug organlur. It lr urually placcd a fcv hundrcd tctror bclou thr polut of applJ,crtlon of thr lntcctlcldc. I nrt 1r rttaoh.d to the dovnstrcar end of thc guttarreud.detacblng orgaulrrt Àra coll€ct.d r,t lntcrvtlr aftcr thc palregc of thc inrecticidc. Tblr rcthod tbul pcrlltr an analysis of the dynatlcr of thc cffccts of thc inrcctl- cldcr, aa ycll rr tbc global reduction of cach group of organiur.