DTIC ADA588066: Evaluation of ULV Applications Against Old World Sand Fly (Diptera: Psychodidae) Species in Equatorial Kenya

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by  Defense Technical Information Center

VECTORCONTROL,PESTMANAGEMENT,RESISTANCE,REPELLENTS
Evaluation of ULV Applications Against Old World Sand Fly (Diptera:
Psychodidae) Species in Equatorial Kenya
SETHC.BRITCH,1,2KENNETHJ.LINTHICUM,1TODDW.WALKER,3MUHAMMADFAROOQ,3
SCOTTW.GORDON,4JEFFREYW.CLARK,4FRANCISNGERE,4DANIELNGONGA,4
ANDCLIFFORDCHEPCHIENG4
J.Med.Entomol.48(6):1145Ð1159(2011);DOI:http://dx.doi.org/10.1603/ME11025
ABSTRACT Reducingpopulationsofphlebotominesandßiesinareasprevalentforhumanleish-
maniasesisofongoingimportancetoUnitedStatesmilitaryoperationsandcivilianpopulationsin
endemicregions.However,notenoughisknownregardingtheefÞcacyofDepartmentofDefense-
approvedpesticidesandequipmentagainstsandßies;speciÞcally,thepotentialforultra-lowvolume
(ULV)pesticideapplicationstocontrolOldWorldsandßyvectors.Inthisstudyweexaminetwo
sprayers, the Terminator ULV and the Grizzly ULV, with UV-labeled Duet and Fyfanon in four
combinationsagainstcagedPhlebotomusduboscqi(Neveu-Lemaire)andwildsandßypopulationsin
a natural environment in western Kenya. All equipment and Fyfanon have United States military
National Stock Numbers and both pesticides are registered with the United States Environmental
ProtectionAgency.CagedsandßieswererearedfromlocalP.duboscqiandtheareahaslongbeen
studiedbecauseofhighincidencesofhumancutaneousandvisceralLeishmania.Patternsofmortality
acrossgridsofcagedsandßiesshowedgreaterefÞcacyfromtheGrizzlyULVregardlessofchemical.
TheTerminatorULVperformedwellwithDuetbutwithalessuniformandoveralllowerrateof
mortalityacrossthespraygrid.Samplingofwildpopulationsbeforeandaftertreatmentssuggested
localpopulationsuppressionfromULVtreatments,aswellasapossiblerepellenteffectinnearby
untreatedareas.Surprisingly,ULVactiveingredientdepositioninferredfrompatternsofUV-labeled
dropletscapturedoncottonribbonsadjacenttosandßycagesinsprayplotsdidnotmatchpatterns
ofmortality.Wediscusstheimplicationsofthisstudy,theÞrstofitskind,forfuturemilitarypreventive
medicineactivities,includingrelativeperformancecostsandbeneÞtsoflargerorsmallersprayers,and
therelativestabilityofULV-inducedmortalitypatternsinvariedorsub-optimalconditions.
KEY WORDS Marigat, Kenya; phlebotomine sand ßy; Fyfanon; Duet; Deployed War Fighter
ProtectionProgram
SandßyvectorsofhumanLeishmaniaparasites,inpar- massivepesticidecampaignsagainstvectorsofmalaria
ticularsandßiesinthegenusPhlebotomus,poseasub- indicate that residuals such as DDT can be effective
stantialthreattothehealthofU.S.troopsdeployedto (NadimandAmini1970).Largescaleprogramsofap-
aridregionsintheMiddleEastandAfrica,andtocivilian plying residual pesticides other than DDT targeted
populationsinendemicregionsoftheworld.Reducing againstsandßiesarestillusedbymanycountriesand
populationsofphlebotominesandßiesinareasprevalent internationalagencies,andbytheU.S.militaryinIraq
forLeishmaniaisofongoingimportancetoU.S.military andAfghanistan(Colemanetal.2006),butthesepro-
operations.Historicalaccountsofcollateralreductionof gramscanbedifÞculttosustain(AlexanderandMaroli
sandßies,humancasesofleishmaniasis,orbothduring 2003)andshouldbeonlyoneelementinamultifaceted
systemtoreducesandßypopulationsandhumancases
Mentionoftradenamesorcommercialproductsinthispublication of visceral and cutaneous leishmaniasis (Britch et al.
issolelyforthepurposeofprovidingspeciÞcinformationanddoesnot 2009,2010a,b).Residualpesticideapplicationsshouldbe
implyrecommendationorendorsementbytheU.S.Departmentof
used in conjunction with aerosol applications such as
Agriculture,theDoD,theU.S.Navy,ortheU.S.Army.Technicians
from the U.S. Army Medical Research Unit-Kenya (USAMRU-K) ultra-low volume (ULV) pesticide dispersal (Lofgren
providedexpertassistanceandsupportintheÞeld.USDAisanequal 1970),habitatreductionsuchasremovalofrodentbur-
opportunityproviderandemployer. rows(Faizulinetal.1976),physicalexclusionsuchasbed
1UnitedStatesDepartmentofAgriculture,AgriculturalResearch
nets(Zollneretal.2007),andpersonalprotectivemea-
Service,CenterforMedical,Agricultural,andVeterinaryEntomol-
ogy,1600SW23rdDr.,Gainesville,FL32608. suressuchasapplicationofDEETtoexposedskinand
2Correspondingauthor,e-mail:[email protected]. permethrintreatmentofclothing(Colemanetal.2006;
3NavyEntomologyCenterofExcellence,NavalAirStation,P.O. reviewedinKitchenetal.2009)toformanintegrated
Box43,Jacksonville,FL32212.
vectormanagementsystemofdefenseagainstsandßies.
4USArmyMedicalResearchUnit-Kenya,Unit64109,DPOAE
09831. However,fromtheperspectiveofU.S.militarypestman-
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1. REPORT DATE 3. DATES COVERED
2011 2. REPORT TYPE 00-00-2011 to 00-00-2011
4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER
Evaluation of ULV Applications Against Old World Sand Fly (Diptera:
5b. GRANT NUMBER
Psychodidae) Species in Equatorial Kenya
5c. PROGRAM ELEMENT NUMBER
6. AUTHOR(S) 5d. PROJECT NUMBER
5e. TASK NUMBER
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
Navy Entomology Center of Excellence,Naval Air Station,PO Box REPORT NUMBER
43,Jacksonville,FL,32212
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)
11. SPONSOR/MONITOR’S REPORT
NUMBER(S)
12. DISTRIBUTION/AVAILABILITY STATEMENT
Approved for public release; distribution unlimited
13. SUPPLEMENTARY NOTES
14. ABSTRACT
Reducing populations of phlebotomine sand ?ies in areas prevalent for human leishmaniases is of ongoing
importance to United States military operations and civilian populations in endemic regions. However, not
enough is known regarding the ef?cacy of Department of Defenseapproved pesticides and equipment
against sand ?ies; speci?cally, the potential for ultra-low volume (ULV) pesticide applications to control
Old World sand ?y vectors. In this study we examine two sprayers, the Terminator ULV and the Grizzly
ULV, with UV-labeled Duet and Fyfanon in four combinations against caged Phlebotomus duboscqi
(Neveu-Lemaire) and wild sand ?y populations in a natural environment in western Kenya. All equipment
and Fyfanon have United States military National Stock Numbers and both pesticides are registered with
the United States Environmental Protection Agency. Caged sand ?ies were reared from local P. duboscqi
and the area has long been studied because of high incidences of human cutaneous and visceral
Leishmania. Patterns of mortality across grids of caged sand ?ies showed greater ef?cacy from the Grizzly
ULV regardless of chemical. The Terminator ULV performed well with Duet but with a less uniform and
overall lower rate of mortality across the spray grid. Sampling of wild populations before and after
treatments suggested local population suppression from ULV treatments, as well as a possible repellent
effect in nearby untreated areas. Surprisingly, ULV active ingredient deposition inferred from patterns of
UV-labeled droplets captured on cotton ribbons adjacent to sand ?y cages in spray plots did not match
patterns of mortality.Wediscuss the implications of this study, the ?rst of its kind, for future military
preventive medicine activities, including relative performance costs and bene?ts of larger or smaller
sprayers, and the relative stability of ULV-induced mortality patterns in varied or sub-optimal conditions.
15. SUBJECT TERMS
16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF
ABSTRACT OF PAGES RESPONSIBLE PERSON
a. REPORT b. ABSTRACT c. THIS PAGE Same as 15
unclassified unclassified unclassified Report (SAR)
Standard Form 298 (Rev. 8-98)
Prescribed by ANSI Std Z39-18
1146 JOURNALOFMEDICALENTOMOLOGY Vol.48,no.6
agement systems, not enough is known regarding the Ngoka1983,Lawyeretal.1990)andLeishmaniavectors
efÞcacyofthecurrentarsenalofDepartmentofDefense (Minter1964),withabundantwildpopulationsofPhle-
(DoD)-approvedpesticidesandequipment,aswellas botomusspeciespresent,inparticularP.martiniParrot
otherU.S.EnvironmentalProtectionAgencyapproved andP.duboscqi(Kasilietal.2010).Weusedthelongest
pesticidesthatmaynotyetbeintheDoDNationalStock sectionofanL-shapedÞeld(centeredat0.470347(cid:3)N,
Numbersystem,againstphlebotominesandßies(Lin- 36.000474(cid:3)E)runningnearly270mlongeasttowestand
thicumetal.2007,Copeetal.2008,Dalton2008,Kitchen nearly 65 m wide north to south, bordered by a thin
etal.2009).Inparticular,weneedtoknowmoreabout marginofforestandsurroundedbysimilaragricultural
thepotentialforULV-deliveredpesticidestocontrolOld Þelds,dirtroads,andsmallirrigationcanals(Fig.1A).
WorldsandßyvectorsofLeishmania. Thegroundislevelwithold,packeddownfurrowsrun-
Ultra-low volume aerosol dispersal of insecticides ningeast-westwithacentral0.2-m-talland2.0-m-wide
againstinsectdiseasevectorshasbeencarriedoutfor moundrunningtheentirelengtheasttowest,andveg-
over 60 yr and is used routinely in mosquito control etationconsistedofgrasses(cid:4)0.1mtallandafewscat-
operationsworldwide(Lofgren1970,Mount1998).Al- teredforbs(cid:4)0.25mtall.
thoughtheefÞcacyofULVagainstmosquitovectorshas Sprayers and Spray Materials. We used two ULV
beenwellstudiedinmanyenvironments(reviewedin generatorsinthisstudy,theClarkeGrizzlyColdAerosol
Britchetal.2010a),nostudieshavebeenidentiÞedthat Generator(ClarkeMosquitoControlProducts,Roselle,
rigorouslyexaminetheefÞcacyofULVinsecticideap- IL)andtheTerminatorDieselULVSprayer/Compres-
plicationagainstsandßies.Insecticidaltreatmentsusing sor(ADAPCOSolutions&Technology,Sanford,FL).
malathion or resmethrin with a truck mounted ULV TheGrizzlyisa207-kgtruck-mountedULVsystempow-
sprayer,orpermethrinwithahandheldULVsprayer eredbya13.4kWBriggs&Strattongasolineenginethat
wereusedaspartofacomprehensiveandwelldocu- drivesarotarypositivedisplacementblower.Thisblower
mentedsandßyeradicationprogramatTallilAirBase providesairßowofupto10m3/min.TheGrizzlyhasa
duringOperationIraqiFreedom(Colemanetal.2006). laminar air ßow (IHPLAT) nozzle and the sprayerÕs
However,therewaslittleevidencefoundofsigniÞcant maximumßowrateis500ml/min.Laboratoryevaluation
reductionsinsandßiescapturedinoutdoortrapsafter byHoffmannetal.(2007)foundthattheGrizzlypro-
extensiveandrepeatedareaspraytreatments,although ducesD of3.5(cid:2)m,D of17.5(cid:2)m,andD of38.6
V0.1 V0.5 V0.9
longevityofindividualadultsandßiesmayhavebeen (cid:2)m,with56.4%ofdroplets(cid:4)20(cid:2)mwhenapplyingatest
affectedwithacommensuratedecreaseinvectorialca- materialofBVA13ULVoil.IntheÞeldwecarriedout
pacityforLeishmaniatransmission.Explanationsforthe acalibrationrunwiththeGrizzlyonßowratesetting#7
lackofsigniÞcantreductioninsandßypopulationsfrom anddeterminedittoproduceaßowrateof303ml/min
ULV applications at Tallil Air Base include replenish- for this study. The Terminator is a 65 kg truck- or all
ment of sand ßy populations from outlying untreated terrainvehicle(ATV)-mountedULVsystempowered
areas,timingofULVspraysnotcoincidingwithadult bya3.5kWYanmardieselenginethatpowersadirect-
sandßyactivity,orthepossibilitythatsandßieswerenot driveaircompressorthatproducestheairblastthrough
susceptibletothepesticidesorthemethodofdeliveryof twoventuri-stylestainlesssteelnozzles.Thecompressor
thepesticides(Colemanetal.2006). providesairßowattherateof0.3m3/minat690kPa,with
InthecurrentstudywelookattheefÞcacyofULV asprayßowrateof88.7Ð117.4ml/min.Laboratoryeval-
applications against Phlebotomus duboscqi (Neveu-Le- uationbyHoffmannetal.(2007)foundthattheTermi-
maire),anOldWorldsandßyvectorofLeishmania,ina nator with a No. 24 oriÞce produces D of 3.6 (cid:2)m,
V0.1
naturalenvironmentinequatorialwesternKenya.We D of17.2(cid:2)m,andD of38.8(cid:2)m,with56.6%of
V0.5 V00.9
comparetwoULVgeneratorsandtwoULV-formulated droplets(cid:4)20(cid:2)mwhenapplyingatestmaterialofBVA
pesticidesinfourcombinationsagainstsentinelcolony- 13ULVoil.IntheÞeldwecarriedoutacalibrationrun
rearedsandßiesaswellaslocalwildsandßypopulations. withtheTerminatorontheÞxedßowratesettingand
BothULVgeneratorsandoneofthepesticidesareap- determinedittoproduceaßowrateof60ml/minforthis
provedandlistedbytheDoDArmedForcesPestMan- study.
agementBoard(AFPMB2011),andbothpesticidesare Forspraymaterials,weusedFyfanonULV(Chemi-
registeredbytheU.S.EnvironmentalProtectionAgency nova,Inc.,Wayne,NJ)andDuetdualactionadulticide
forthecontrolofmosquitoesandotherbitingßies. (Clarke Mosquito Control Products, Roselle, IL). Fy-
fanonisa96.5%malathionoil-basedformulationrated
for ULV or thermal fog insecticide application. Mala-
MaterialsandMethods
thion is one of the most frequently used organophos-
Study Site. ThestudysitewasaÞeldattheKenya phateinsecticidesworldwide,targetedagainstabroad
Agricultural Research Institute (KARI) Marigat Field rangeofpestanddiseasevectorinsects.Duetisanoil
Stationlocatedinahotsemiaridagriculturalarea(cid:2)1.5 solublesynergizedsyntheticpyrethroidadulticidecon-
kmeastofthetownofMarigatand(cid:2)12kmsouthwest tainingprallethrin,Sumithrin,andtechnicalpiperonyl
ofLakeBaringo,withameanannualrainfallof(cid:2)654mm butoxide (PBO). The combination of prallethrin and
and mean high temperature of (cid:2)32(cid:3)C (KARI 2011). SumithrininDuetisdesignedtocauseagitationofmos-
Marigat is at just over 1,000-m elevation and (cid:2)50 km quitoes after chemoreception of prallethrin, drawing
northoftheequatorinwesternKenyaattheheartofthe them from a resting state to ßying and thus greater
RiftValley.Thisareahaslongbeenstudiedasafocusof contactwiththeaerosolizedformulation(Cooperband
Leishmania(McKinnonandFendall1955,Mutingaand etal.2010).BothFyfanonandDuetwereusedundiluted
November2011 BRITCHETAL.:KENYAULVSANDFLYCONTROL 1147
Fig.1. (A)Areamapshowingcontrolcagelocation(reddiamonds)attheKEMRI/USAMRU-KÞeldstation,CDCtraps
withinandbetweenspraygrids(redßags,Trap1ÐTrap4),andCDCtrapsinuntreatedoffsiteareastotheeast(redßags,
Ctrl1andCtrl2).Thesprayareasaredelineatedwithgridsof25feetsquares;thelefthandgridisthewestplotandthe
righthandgridistheeastplot.(B)Cartogramofcagepositionsandribbonscentered200feetalongand175feetdownwind
of300feeteast-westspraylineonsprayday1.(C)Cartogramofcagepositionsandribbons,centered200feetalongand
150feetdownwindof300feeteast-westspraylineonsprayday2.
1148 JOURNALOFMEDICALENTOMOLOGY Vol.48,no.6
in both ULV generators. We added Uvitex OB (Ciba searchsite,aroomtemperatureof(cid:2)28Ð30(cid:3)Cismain-
Corporation,Newport,DE)UV-ßuorescentdyeatthe tained year round, using space heaters in the cool
rateof4g/litertoeachtankofspraymaterialtoallowus seasonswhennecessary.
tovisualizedropletsoncottonribboncaptureapparatus, Westoredsentinelcagescontainingsandßiesincool-
describedbelow,andtolateruseßuorometricquanti- ers containing moistened towels during travel to the
tation to estimate droplet deposition across the spray studyareafromtheÞeldstation,andwaiteduntil(cid:2)30
Þeld.Immediatelybeforeeachsprayrunweremoved20 minbeforetheanticipatedspraytimetoafÞxcagesto
ml of dye/pesticide solution from the spray tank and posts.Afterawaittimeof10minaftertheendofeach
applieditto30feetofcottonribboncoiledinaplasticbag spraysentinelcageswereremovedfromthepostsand
until it was completely absorbed, and allowed to dry. transported in coolers directly to the KEMRI/
Theseribbonswerelaterßuorometricallyanalyzedto USAMRU-KÞeldstationwherethe10-minmortalityfor
determinetheexactconcentrationofdyeineachspray eachsentinelcagewasimmediatelyrecorded.Surviving
run. This posthoc analysis was necessary because the sandßiesweretransferredtonewcagesandsupplied
Uvitexdyepowderhasbeenobservedtoshowarange with a sugar water source. We recorded subsequent
ofsolubilitydependingonspraymaterialandconcen- mortalityat12hand24hpostsprayforeachcage.Con-
tration. trolcageswerehandledseparatelybutwithtiming,stor-
TestGridsofSentinelSandFlyCages.Tomeasurethe age, and mortality tallying methods identical to cages
efÞcacyofULVapplicationswesetuptwogridsofcaged usedinthesprayplots.Wecalculatedthemean,range,
sentinelsandßiesinthestudyareabasedontheexper- median,andinterquartilerange(IQR)forallmortality
imentaldesignÞrstdescribedinRogersetal.(1957)and databyplotandspraytrialwithMicrosoftExcel.The
latermodiÞedasinBritchetal.(2010a).Wedeployed IQRisgivenindataunitsandisameasureofthespread
gridsof25sentinelcagesina150feet(day1)or125feet ofdataaroundthemedianvalue,boundbythe25thand
(day2)by200feetarraypositioned25feetdownwind 75th percentiles.Thus,theIQRignoresoutliersabove
ofa300feetsprayline(Fig.1BandC).Weused122-cm and below the most frequently observed values. Low
whitepolyethyleneTread-InPosts(Jeffers,Dothan,AL) IQRvaluesindicatethatthemajorityofobservationsfall
tosupportsentinelsandßycagesatthepositionsillus- intoanarrowrangearoundthemedianvaluebecausea
tratedinFig.1.WeafÞxedonecagetoeachpost61cm treatmentgenerallycausedaconsistentresponse.How-
abovethegroundbyusingadisposablehookandloop ever,highIQRvaluesindicatethatdataaremorebroadly
cabletie(Fig.2A).Inbothplots,eachpostwaslabeled scattered owing to a noticeable variability in the out-
withauniquealphanumericcodefromA1toE5(Fig.1), comeofatreatment.
andthiscodealongwiththedateandtypeofapplication Standard CDC downdraft incandescent light traps
wascopiedontoeachsentinelcage.Inadditiontothe (JohnW.HockCo.,Gainesville,FL)baitedwithCO
2
twogridsof25sentineltestcages,wesetupalineofÞve from dry ice were positioned at six locations running
sentinelcontrolcagesattheKenyaMedicalResearch westtoeastthroughthestudyarea(Fig.1A).Weplaced
Institute/U.S. Army Medical Research Unit-Kenya onetrapinthewestplot,onetrapbetweentheplots,and
(KEMRI/USAMRU-K) Þeld station within the KARI twotrapsintheeastplot.Wealsoplacedtwoadditional
propertylocated(cid:5)0.3kmtothewestofthewestplot trapsfurthertotheeastinanuntreatedarea.Weran
(Fig.1A). thesetrapsfortwonightsprecedingtheÞrstspray,the
Thesentinelcagesweremadefromcylindricalpa- nightimmediatelyaftertheÞrstspray,thenightimme-
perfoodcontainers(8.5cmindiameterby4.5cmin diately after the second spray, and Þnally one night
depth;NeptunePaperProducts,Newark,NJ)withthe thereaftertoobtainarelativemeasureofefÞcacyofthe
paperdisktopandbottomreplacedwithamberLu- ULVapplicationsonlocalwildsandßypopulationsdom-
mitescreening(32by32meshperinch;BioquipProd- inated by P. duboscqi, P. martini, and Sergentomyia
ucts,RanchoDominguez,CA)heldinplacewithtwo schwetziAdler,Theodor,&Parrot.Wepredictedthat
rubber bands and the original paper lid bezel. The wild sand ßy numbers would drop postspray in both
hookandloopcabletieisslippedthroughoneofthe treatedplots,butwouldremainstablepostsprayatlo-
rubberbandstoholdthecageonthepost(Fig.2A, cationssampledtotheeastinuntreatedareas.
inset).Eachsentineltreatmentandcontrolcagecon- BoththeFyfanonandtheDuetwereusedineach
tained (cid:2)20 colony reared P. duboscqi sand ßies in a ULVgenerator,totalingfourseparaterunsonthetwo
mixtureofmalesandfemales.Thesandßiesusedin experimentalplotsofcagedsentinelsandßies.Onthe
thetreatmentandcontrolsentinelcageswerefroma Þrstsprayday,theTerminatorwasrunwithDuetatthe
P.duboscqicolonyrearedinMarigatattheKEMRI/ labelrateof1.23oz(undiluted)peracre,fromwestto
USAMRU-K Þeld station from parent progeny that eastonthenorthedgeofthewestspraygrid,andthe
were100%ÞeldcaughtintheMarigatareain2007.The GrizzlywasrunwithFyfanonatarateof3.5oz(undi-
colony is periodically infused with new wild caught luted)peracre,fromeasttowestonthenorthedgeof
ßies approximately once per year to counteract de- the east spray grid (Figs. 1B and 3A). With the wind
clinesincolonynumbersfrommiteactivityduringthe primarilyfromthenorth-northeastat1.4Ð2.1mph,the
cool seasons, the most recent infusion having been opposingtraveldirectionsallowedustorunthesprays
September, 2009. The colony is reared according to simultaneouslyintherelativelysmallavailablestudyarea
theKEMRIprotocolusinghamstersasabloodsource. withlessconcernofcross-contaminationofplots.Onthe
AlthoughincubatorscalledforbytheWRAIRsandßy secondsprayday,theTerminatorwasrunwithFyfanon
rearing protocol are not available at the Marigat re- at3.6oz/acre,fromeasttowestonthesouthedgeofthe
November2011 BRITCHETAL.:KENYAULVSANDFLYCONTROL 1149
Fig.2. (A)SentinelsandßycagesbeingremovedfromcoolersandafÞxedtopostsinthewestplotonthesecondspray
day;lookingsouth.Cottondropletcaptureribbonshavealreadybeenattachedinpositionbetweenthepostsateachcage
position.Upperleftinsetshowsapproximatelocationofoneofthetermitemounds(2.5mhigh);lowerrightinsetshows
close-upofsentinelcageandadjacentcottonribbonattachedtopole.(B)Viewofthewestplotonthesecondsprayday
showingthesandßycagesanddropletcaptureribbonsinposition,withtheTerminatorULVbeingoperatedfromatruck
bed;lookingnorthwest.
1150 JOURNALOFMEDICALENTOMOLOGY Vol.48,no.6
Fig.3. Firstspraydaymortality(A)andsecondspraydaymortality(B).Colorrampshowsbreakdownofmortality
frequencyin10%blocks.CDClighttrapsbaitedwithCO arerepresentedbysmallredßagsandlabeledTraps1Ð4.Twocontrol
2
CDCtrapswerelocatedinalinetotheeastofTrap4ontheothersideofthetreelinevisibleattherightedgeofthemap
(seeFig.1A).
November2011 BRITCHETAL.:KENYAULVSANDFLYCONTROL 1151
Fig.4. MortalityobservedinwildsandßypopulationsovernightimmediatelyaftertheÞrstsprayday(day1;A),overnight
immediatelyafterthesecondsprayday(day3;B),andovernightimmediatelyaftertheexcessFyfanonsprayday(day4;
C),basedonCDClighttrapdata.Positivevaluesrepresentreductioninsandßynumbersoverprespraypopulations.Negative
valuesrepresentanincreaseinsandßynumbersafterspraytrials.
westspraygrid(Fig.2B),andtheGrizzlywasrunwith MappingBioassayEfficacyDataandInferredActive
Duetat1.23oz/acrefromwesttoeastonthesouthedge Ingredient Deposition. We mapped grids using 0.6 m
oftheeastspraygrid.Achangeinwinddirection,from resolution grayscale digital orthophotoquadrangles
thesouth-southeastonthesecondsprayday,hadforced (GeoEye,Dulles,VA)intheArcGIS10geographicin-
us to ßip each plot and driving direction to permit a formation system (GIS; Environmental Systems Re-
simultaneousspraywithoutcross-contamination(Figs. search Institute, Redlands, CA). We mapped bioassay
1Cand3B).Inaddition,wehadtomovetheE1toE5line mortalitydataontheimageofthestudyareaintheGIS
ofsentinelcagestoalinenorthoftheA1toA5lineof byassigningthevaluesofthemeanofthe10minand12h
sentinelcagestomakeroomforthevehiclesatthesouth mortalityfrequenciestotheirrespectivepolepositions
edgeofthespraygrids. andcarryingoutaninversedistance-weighted(IDW)
SamplingSprayDropletDepositionintheTestGrids. interpolationanalysisforeachgrid.Interpolationwith
At1mfromeachsentinelcagepositionweinserteda IDWestimatesacontinuoussurfaceusingobservedval-
secondpostforstretchinga1mlengthofcottonribbon uesfromadeÞnedsetofpoints,andgraduallyconstrains
paralleltothespraytruckdrivingdirection(Figs.1and the inßuence of more distant points when estimating
2). These ribbons were positioned to capture dye-la- valuesatanygivenpoint.TheIDWparameterswereset
beledspraydropletsatthesameheightasthesentinel tothedefaultexponentofdistanceof2,whichcontrols
cageateverysentinelcageposition(Fig.2A).Thiswas thesigniÞcanceofsurroundingpointsonaninterpolated
animprovementfrompreviousexperiments(Britchet value, and an arbitrary Þxed search radius of 400 feet
al. 2010a) where ribbons were only deployed at the from each interpolated point to take into account all
centralcolumnofÞvecagesperpendiculartothespray valuesinagrid.Toenhancevisualizationoftheinter-
line.TheuniquealphanumericcodefromA1toE5in polated surface, we added null values to corners and
eachplotwascopiedontoeachdropletsamplingribbon, midpointsofasquare7.6mfromtheoutermostobserved
alongwiththedateandtypeofapplication.Welater valuesinthegrid.Wecolor-codedtheresultinginter-
ßuorometricallyanalyzedribbonsfordepositionasde- polatedsurfaceusingaredtobluecolorramp,where
scribedinBritchetal.(2010a). redssymbolized80Ð100%mortality,yellowssymbolized
1152 JOURNALOFMEDICALENTOMOLOGY Vol.48,no.6
60Ð80% mortality, greens symbolized 30Ð60% mor- both the Þrst and second spray trials, which similarly
tality,andbluessymbolized0Ð30%mortality(Figs.3A contributedtomortalitycountsat12h.
and B). Similarly, we mapped inferred active ingre- Third,12hmortalityincontrolcagesinbothspray
dient deposition data on the grids using the ßuoro- trialsshowedmedianvaluesof45%and35%(Table1);
metric analyses of the droplet capture ribbons and whereas,medianvaluesat12hpostsprayintreated
used the same red to blue color ramp to partition cageswere100%mortalityinthreeoutoffourcases.
inferredactiveingredientdepositionvaluesonascale ThefourthcasewastheTerminator/Duetapplication
of0Ð1(cid:2)g/cm2(Figs.5AandB). intheÞrstspraytrialthatshowedamedianvalueof
40%.Althoughthisvaluecloselymatchedcontrolcage
medianvalueof45%at12hpostspray,theIQRforthe
Results Terminator/Duet application was 45, indicating a
widespreadofhighandlowmortality,comparedwith
Weather Conditions. Windsweremeasuredat1Ð2
anIQRofonlyÞveinthe12hpostspraymortalityfor
mphonbothdays,andthetemperatureontheÞrstspray
daywas31.1(cid:3)Cwith63.4%relativehumidity(RH)atthe thecontrolcagesfromtheÞrstspraytrial.Thewide
spread in mortality values in the Terminator/Duet
timeofspray,whichwasjustafterduskat1843hours.
application was consistent with spatial variation in
The temperature and RH were not recorded on the
mortality across the grid consistent with an uneven
secondsprayday.Thesecondspraytookplacetwodays
application of pesticide (Fig. 3A); versus a narrow
aftertheÞrstspraydaybecauseoftheabsenceofsufÞ-
spreadinmortalityincontrolcagessomewhatequally
cientwindvelocityonthedayinbetweenthetwoap-
affectedbyenvironmentalexposure.
plicationdays.Thesecondspraywascarriedoutat1651
Fourth, mortality values in treated cages at 12 h
hourswhenwindswerefavorable,notwaitinguntildusk
postspraygenerallymatchedmortalityvaluesat24h
incasewindsceasedastheyhadthepreviousday.Atthe
postspray, largely because most sand ßies in most
startofthetrialontheÞrstsprayday,windspeedfrom
treatedcagesweredeadat12h(Table1).Theone
thenorth-eastdirectionindicatedbytheblueline(Fig.
exceptionwastheTerminator/Duetapplicationinthe
3A)waslightandthedirectionßuctuatedfromnorthto
Þrstspraytrialthat,owingtotherelativelylowmean
north-east as the vehicles with ULV generators drove
mortality of 48% at 12 h, showed nearly double the
westtoeastfortheTerminatorandeasttowestforthe
meanmortalityat24hpostspray,andamedianvalue
Grizzly.Atthestartofthetrialonthesecondsprayday,
of95%at24h.Incontrast,meancontrolcagemortality
windspeedfromthesouth-eastdirectionindicatedby
betweenthe12hand24hcountsonlyincreasedby
theblueline(Fig.3B)waslightandthedirectionßuc-
abouthalf,withmedianvaluesof60%inbothspray
tuatedfromsouth-westtosouth-eastasthevehicleswith
trialsat24h.
ULVgeneratorsdroveeasttowestfortheTerminator
Tocompensateforenvironmentallylinkedmortal-
andwesttoeastfortheGrizzly.
ityincontrolcagesthatnodoubtcontributedtomor-
PatternsofMortalityinTestGrids.Wefoundthat
talityintreatedcages,wecalculatedthemean10min
sandßiesfromcontrolsentinelcagesweredyingat12h
and12hmortality.AsshowninTable1thisfunction
postsprayandingreaternumbersat24hpostspray(Ta-
on the data provided a conservative perspective on
ble1),mostlikelybecauseofphysiologicalstressesof
efÞcacyofthemachine/pesticidecombinations.For
livinginthecages.Althoughcontrolcagemortalitywas
instance,capturingthefactthatapplicationswiththe
highat12hpostsprayinbothtrials,weobservedseveral Terminatorhadlessinitialknockdownthanapplica-
indicatorsthatpesticideandnotenvironmentalexposure tions with the Grizzly, but tempering the apparent
wasresponsibleforthemajorityofmortalityobservedin 100%12hkillacrossmostofthegridsinbothofthe
cagesfromthespraytreatmentgrids.First,mean10min GrizzlytrialsandoneoftheTerminatortrials.The10
postspraycontrolcagemortalitywas0%fortheÞrstspray min/12hmeanalsocreatedacorrectioncloselycom-
compared with 80% in the Grizzly/Fyfanon plot, and parabletoAbbottÕscorrection,butallowingsomemar-
mean10minpostspraycontrolmortalitywas6%forthe gin for moribund individuals at 10 min that were
second spray compared with 33% in the Terminator/ clearlyaffectedbythepesticide.These10min/12h
Fyfanonplotand81%intheGrizzly/Duetplot(Table1). meanmortalityvalueswereusedtodevelopthemor-
These high values in most spray plots indicate rapid tality interpolations across the spray Þelds and visu-
knockdownfromthepesticidethatwasnotobservedin alizetherelativeefÞcacyofthedifferentsprayevents
thecontrols. asshowninFigs.3AandB.
Second, although the Terminator/Duet plot in the OntheÞrstsprayday,lookingatthe10min-12hmean
Þrstsprayshowed4%meanmortalityat10minpostspray mortality,weobservedmortality(cid:5)95%atovertwothirds
(Table1),barelyhigherthancontrolmortalityof0%, ofthepositions(range,50Ð100%,mean89%;Table1)
many sand ßies observed to be still moving but most withtheGrizzly/Fyfanonapplicationontheeastplot,
likelyintoxicatedandmoribundat10minintheTermi- comparedwithmortalitylowerthan40%attwothirdsof
nator/Duet plot, and thus not counted as dead, were thepositions(range,8Ð50%,mean26%;Table1)withthe
amongthedeadat12hpostsprayintheTerminator/ Terminator/Duetapplicationonthewestplot(Fig.3A).
Duet plot. Moribund sand ßies were not observed in The Grizzly/Fyfanon application in the east plot pro-
controlcagesat10minpostsprayineitherspraytrial,but ducedhighmortalityoutto175feetfromthesprayline,
moribundindividualswereobservedintheGrizzly/Fy- impacting nearly every cage position with very high
fanon,Terminator/Fyfanon,andGrizzly/Duetplotsin mortality.Conversely,theTerminator/Duetapplication