Luciana G. Brito, 1 Fábio S. Barbieri, 1 Rodrigo B. Rocha, 1 MárciaC.S.Oliveira, 2 and Elisana Sales Ribeiro Introduction

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1 SAGE-Hindwi Access to Reserch Veterinry Medicine Interntionl Volume 2011, Article ID , 6 pges doi: /2011/ Reserch Article Evlution of the Efficcy of Acricides Used to Control the Cttle Tick, Rhipicephlusmicroplus, in Diry Herds Rised in the Brzilin Southwestern Amzon Lucin G. Brito, 1 Fábio S. Brbieri, 1 Rodrigo B. Roch, 1 MárciC.S.Oliveir, 2 nd Elisn Sles Ribeiro 1 1 Embrp Rondôni, BR 364, km 5,5, Porto Velho, RO, Brzil 2 Embrp Pecuári Sudeste, Rodovi Wshington Luiz, km 234, São Crlos, SP, Brzil Correspondence should be ddressed to Lucin G. Brito, lucin@cpfro.embrp.br Received 8 November 2010; Revised 12 Jnury 2011; Accepted 28 Jnury 2011 Acdemic Editor: Guillermo Virkel Copyright 2011 Lucin G. Brito et l. This is n open ccess rticle distributed under the Cretive Commons Attribution License, which permits unrestricted use, distribution, nd reproduction in ny medium, provided the originl work is properly cited. The dult immersion test (AIT) ws used to evlute the efficcy of cricide molecules used for control of Rhipicephlus microplus on 106 popultions collected in five municiplities in the stte of Rondôni in the Brzilin South Occidentl Amzon region. The nlysis of the dt showed tht the cricide formultions hd different efficcies on the tick popultions surveyed. The synthetic pyrethroids (SPs) cricides were the lest effective ( %), followed by SP+ orgnophosphte (OP) ssocitions ( %) nd midine ( %). For the mcrocyclic lctones (MLs), the milbemycin ( %) ws the most effective, followed by spinosd ( %) nd the vermectins ( %). The phenylpyrzole (PZ) group hd similr efficcy (99.90%) to the MLs. Therefore, SP cricides, including ssocitions with OP, nd formultions bsed on midine presented low in vitro efficcy to control the R. microplus popultions surveyed. 1. Introduction Brzil is the world s sixth leding producer of milk [1], nd diry frming is n importnt source of income for smll producers s well s of industril jobs in Brzil nd in Rondôni stte, new Brzilin frontier for diry frming tht ccounts for 95% of milk production in this region [2]. Most diry herds in the Brzilin Southwestern Amzon re crossbreeds (Bos Turus Bos indicus) with vrying bloodline degrees. However, the incorportion of crossbreeds with greter percentges of turine breeds specilized for milk production, such s Holsteins, hs mde diry herds more susceptible to infesttion by ticks [3]. The climte conditions in the region re propitious for the estblishment of cttle ticks due to the predominntly equtoril climte, chrcterized by verge nnul rinfll of 2,500 mm nd verge nnul temperture of 24 C, with well-defined wet nd dry sesons [4]. Besides trnsmitting diseses, R. microplus impirs milk production becuse ech femle tick is ble to ingest 1.0 ml of blood from the host cow during its prsite phse, cusing weight loss of pproximtely 1 g nd reducing milk production by 8.9 ml. In economic terms, these ticks cost frmers round US$ 7.30/hed/yer when considering the production losses nd tretment costs [5 7]. Despite the disdvntges of using cricides, such s environmentl contmintion, potentilly hrmful residues in met nd milk, nd toxicity to workers who pply them, these drugs re still essentil to control tick infesttions in the world [8]. However, the intensive use of chemicl formultions leds to loss of efficcy of the bse molecules becuse of the development of resistnt tick popultions. The spred of this resistnce revels the limits on chemicl control of this prsite, mking it essentil to dminister these chemicls wisely [6].

2 2 Veterinry Medicine Interntionl There re reports in the literture of growing resistnce of cttle ticks to chemicl molecules in mny countries including Brzil, but the sttus is unknown of pesticide resistnce in cttle tick popultions in the Southwestern Amzon [6, 9 12]. Mny diry frmers in the stte of Rondôni hve reported the filure of tick control progrms in their herds nd hve requested ssistnce in choosing more effective pesticides, which ws the purpose of the present study. 2. Mterils nd Methods 2.1. Chrcteriztion of Are nd Sites of Collecting the Tick Smples. Between Mrch 2007 nd October 2009, engorged femle ticks were collected from 106 diry frms. The herds were formed of crossbreed nimls of Holstein (Bos turus) nd diry Gir (Bos indicus), with bloodline degrees vrying from 1/2 to 5/8. The herd size t most of frms rnged from 18 to 42 nimls, though one frm hd 116 nimls. The herds cme from diry frms in the municiplities of Jrú, Ouro Preto do Oeste, Ji-Prná, Presidente Médici, nd Rolim de Mour (Figure 1), ll locted between nd South Ltitudes nd nd West Longitudes. The predominnt climte in the region ccording to the Köppen clssifiction is megtherml, with the dry seson occurring in winter [13]. Diry frmers responsible for ech of the herds evluted were invited to respond to questionnire regrding the use of cricides, contining questions on the types used, frequency of tretments, nd ppliction method Collection nd Preprtion of Ticks. In ech frm, up to 250 engorged femle R. microplus ticks with length equl to or greter thn 4 mm were collected from cows nturlly infected, none of which hd received tick tretments for t lest 30 dys. The ticks were plced in identified plstic flsks free of cricide residues with lids contining smll holes, which were trnsported to the Embrp Rondôni Animl Helth Lbortory within 36 hours of collection for the evlution of the in vitro efficcy of cricides through the dult immersion test (AIT). Only smples in which no oviposition ws observed were nlyzed. In the lbortory, ll femles were seprted, crefully wshed, nd then dried on bsorbent pper. Engorged femles weighing between 160 nd 300 mg, with no signs of injury, were used in the tests Acricides. Technicl fipronil ws provided by Meril nd stored t room temperture nd ws used t finl concentrtion of %. The following commercil cricides were purchsed nd stored t 4 C; Tritox ectoprsiticide (12.5% mitrz, Intervet Schering-Plough Animl Helth), diluted with distilled wter to finl concentrtion of %; Flytick ectoprsiticide (15% cypermethrin, Vllé), t finl concentrtion of %; Altox ectoprsiticide (5% cypermethrin + 45% dichlorvos, Fort Dodge Animl Helth), t finl concentrtions of % nd %, respectively, Colosso ectoprsiticide (15% cypermethrin + 25% dichlorvos + 1% citronelll, Ouro Fino Animl Helth), t finl concentrtions of %, %, nd %, respectively, Butox ectoprsiticide (50% deltmethrin, Intervet Schering-Plough Animl Helth), t finl concentrtion of %; Dectomx injectble endectocide for cttle (dormectin 10 mg/ml, Pfizer Animl Helth), Ivomec injection for cttle (ivermectin 10 mg/ml, Meril); Bymec injectble endectocide (bmectin 10 mg/ml, Byer Helth Cre); Elector ectoprsiticide (2.46% spinosd, Elnco) nd Cydectin (moxidectin 10 mg/ml, Fort Dodge Animl Helth), ll t finl concentrtion of % Adult Immersion Tests. The AIT conducted followed the method described by Drummond et l. [14]. Ech group of 10 femles ws immersed for 10 minutes in 30 ml of the cricide solutions. Commercil formultions of mitrz; cypermethrin; cypermethrin + dichlovos; cypermethrin + dichlovos + citronelll; deltmethrin; spinosd were diluted in distilled wter ccording to the lbel recommendtions. For the evlution of the vermectins (ivermectin, dormectin, nd bmectin) nd milbemycin (moxidectin), the femles were immersed for 30 minutes in 30 ml of the solutions prepred ccording to the method proposed by Sbtini et l. [15]. To prepre the 1% fipronil solutions, 625 mg of technicl fipronil dissolved in 80 ml of PA cetone ws used, diluted in 120 ml of sterile distilled wter. All solutions described were kept under constnt gittion during the immersion period. Becuse of the lrge number of engorged femles, only the control ws prepred in triplicte, nd the field popultions were nlyzed with two replictes. Ech replicte ws performed with ten R. microplus femles with weights s homogenous s possible. The femles of the control groups were immersed in distilled wter for 30 minutes. After immersion in the pesticide solutions or distilled wter, ll the engorged femles were fixed with two-sided dhesive tpe in Petridishes (90 mm dimeter), which were identified by group, weight, pesticide, nd testing dte. The Petridishes contining the engorged femles were incubted in climte-controlled chmber t 27 ± 1 Cndreltive humidity of 85 ± 5%. After the oviposition period (14 18 dys), the eggs were weighed nd trnsferred to test tubes (150 mm in height 15 mm in dimeter closed with cotton blls). The identified tubes were plced in the climte-controlled chmber under the sme temperture nd reltive humidity conditions described previously, where they remined until the lrve htched. The htching rte of the R. microplus lrve ws bsed on visul estimtion of the percentge of unhtched eggs remining nd of egg shells from which lrve hd htched. The effectiveness of the cricides ws determined by the effect on the estimted reproduction (ER) of the engorged femles in tretment group. The percentge control (% control) of ER fforded by the cricides ws determined by compring the totl ER of ll tretment groups with tht of the control group ccording to Drummond et l. [14], clculted with the following formuls.

3 Ministro Andrezz São Felipe Veterinry Medicine Interntionl 3 Rondoni Stte locliztion Amzons Cndeis Jmri Cujubim Mchdinho D Oeste Bolivi Nov Mmoré Porto Velho Gujrá Mirim Buritis Cmpo Novo Alto Príso Monte Negro Gov. Jorge Teixeir Seringueirs Ariquemes Rio Crespo Cculândi Mirnte d Serr Jru Nov União Theobrom Alvord do Oeste São Miguel do Guporé Urupá Ouro Preto Novo Horizonte Vle do Anri Vle do Príso Teixeirópolis Nov Brsilˆndi Ji-Prná Pres. Médici Cstnheirs Rolim de Mour Snt Luzi Ccol Primver Mto Grosso Espigão D Oeste Piment Bueno Brzilin north region Cost Mrques São Frncisco do Guporé Alt Florest do Oeste Alto Alegre Precis Chupingui Vilhen Corumbir Cerejeirs Colordo do Oeste Pimenteirs do Oeste Cbixi Figure 1: Loction of the municiplities in the stte of Rondôni where the popultions of Rhipicephlus microplus were evluted for efficcy of the cricides. ER = Egg weight Engorged femle weight %htched 20, 000. (1) Estimted numbers of eggs in 1 g of Rhipicephlus microplus eggs %control= 1 ER of pesticide group 100. (2) ER of control group R. microplus popultions presenting control percentge greter thn or equl to 95% to the cricide were considered susceptible. In vitro efficcy of 95% is the threshold for the pprovl of n cricide product in Brzil ccording to federl regultions [16] Sttisticl Anlysis. For the interprettion of the results, the cricide fctor ws nlyzed in order to quntify the effect of the loction (municiplity) nd of specific cricide, long with the effect of the interction of both effects. The model s estimtes were obtined by employing the PROC GLM routine of the Sttisticl Appliction System (SAS) (SAS version 8.2; SAS Institute, Inc., Cry, NC) considering the rcsine of the squre root of the mortlity percentges. In the bsence of n interction, multiple comprison between the mrginl mens of the cricide fctor ws crried out using the Tukey-Krmer test, which is dequte for fctor nlysis with different number of repetitions. The estimtes of the confidence intervl of the men were interpreted s mesure of relibility of using the cricide bses in the region. 3. Results Through the responses of frmers, it could be observed tht SP cricides were used in most of the properties (87.3%). Substitution of cricide bses did not occur in systemtic form in ll frms, nd when it occurred, the reson given ws minly price nd ese of purchse of the cricides in the locl mrket. The frequency of tretments to control the cttle ticks ws weekly in 43.7% of the frms, nd the method of cricide ppliction most often used ws sprying on the nimls with mnul bckpck pumps. The men efficcy of the cricides nd their respective stndrd devitions ginst R. microplus collected from diry

4 4 Veterinry Medicine Interntionl Tble 1: Efficcy of different cricide bses on popultions of Rhipicephlus microplus collected from diry herds in the stte of Rondôni, Brzil. Chemicl group of function Min. efficcy (%) Mx. efficcy (%) Men efficcy (% ±SD) Amidin ± Cypermethrin ± 6.83 Deltmethrin ± 4.70 Cypermethrin + dichlorvos ± 4.10 Cypermethrin + chlorpyrifos ± 4.10 citronelll Dormectin ± 1.43 Ivermectin ± 4.29 Abmectin ± 2.22 Milbemycin ± 0.51 Spinosin ± 0.23 Phenylpyrzole ± 0.74 herds in Rondôni re presented in Tble 1. Avermectins, milbemycin, PZ, nd spinosin presented the highest men efficcies ccording to the AIT. Acricide formultions contining cypermethrin nd deltmethrin presented the lowest efficcy levels observed in the AIT, while the ssocitions of SP + OP nd SP + OP + citronelll presented intermedite efficcy in comprison with the other cricides evluted. The products bsed on midin were more effective thn the SP, but with higher confidence intervl. The dt obtined suggest tht citronelll enhnced the efficcy of the SP + OP ssocition. The mcrocyclic lctones (MLs) group, the spinosins, nd milbemycin showed high efficcy ccording to the AIT, s well s the PZ, ll with smll confidence intervl (Figure 2). Ivermectin, bmectin, nd dormectin hd lost efficcy on some frms, s shown by minimum efficcy vlues between 81 nd 86%. The vrince nlysis showed tht the cricides hd vrible efficcy, ccording to the F-test t 1% significnce (Tble 2). Nonsignificnt effects of the loction (L) nd of the cricide with loction interction (A L) indictes tht the effectiveness of specific cricide did not differ mong the municiplities, s the interction coefficient ws low (7.05%). 4. Discussion Presently, the Working Group on Prsite Resistnce (WGPR-FAO) recommends the AIT proposed by Drummond et l. [14] for the evlution of the susceptibility to cricides in cttle tick popultions, since it is fst, simple nd reltively chep method for the detection of cricide resistnce in the field [6]. Despite the high vrition of AIT results obtined for SP, OP, mitrz nd moxidectin s observed by Jonsson et l. [17], the AIT is vluble tool for the rpid nd chep detection of loss of susceptibility e d c c b f Cypermethrin Assoc1 Assoc2 Dormectin Milbemycin Spinosin Deltmethrin Amidin Ivermectin Abmectin Phenylpyrzole Men Men with confidence intervl with 95% of the probbility Cypermethrin + dichlorvos Cypermethrin + chlorpyriphos + citronelll Figure 2: Effectiveness of cricide bses observed in dult immersion test (AIT) in Rhipicephlus microplus popultions surveyed in Rondôni stte, Brzil. Mens followed by the sme letter do not differ ccording to the Tukey-Krmer test t 1% significnce. The br indictes the 95% minimum efficcy set by Brzilin federl regultions for the mrketing of cricides. Tble 2: Anlysis of vrince of the effects of the loction (L)ndof the cricides (A) on the susceptibility to cricides in Rhipicephlus microplus popultions collected in the stte of Rondôni, Brzil. Source of vrition D.F. S.S. (Type III) M.S. F Acricide (A) Loction (L) ns A L ns Coefficient of vrition 7.05 D.F.: Degrees of freedom; S.S. (Type III): Type III sum of squres; M.S.: Men squre error; F: F-test estimtes; : Significnt t 1% probbility; ns :Not significnt. to certin cricide nd should be used with this specific objective in resistnce mngement progrms. According to the nlysis of vrince, there were no differences of susceptibility to specific cricide mong the different municiplities, which demonstrtes tht the cricides evluted presented similr efficcy ginst the different R. microplus popultions evluted. The efficcies of cypermethrin nd deltmethrin on the R. microplus popultions studied vried from 48.33% to 70.5% nd 61.22% to 76.84%, respectively. These efficcy levels differ from those found in other regions of Brzil. Pereir [11], in the stte of São Pulo, observed efficcy of 25.39% for deltmethrin nd 31.10% for cypermethrin, while Furlong et l. [12], in Mins Geris, reported verges of 15.3% for deltmethrin nd 9.1% for cypermethrin. The differences in efficcy of these cricies observed between the different Brzilin sttes cn be relted to the wy they re used, such s indequte sprying, underdosge or

5 Veterinry Medicine Interntionl 5 overdosge [18], nd/or high frequency of use cusing the development of resistnt popultions [19]. The occurrence of synergism in cricide formultions contining SP nd OP ws observed by Lndim et l. [10]. They investigted tick popultions collected in the region of Uberb (Mins Geris) nd observed tht the formultions contining this combintion were more effective thn formultions contining SP or OP lone. The uthors reported tht SP nd OP used seprtely hd mximum efficcy levels of 43.6% nd 46.7%, respectively, while the SP + OP ssocitions showed efficcy between 75.5 nd 97.7%. This result ws lso observed by Furlong et l. [12], who reported smll increse in efficcy of cricides contining combintion of SP nd OP on R. microplus popultions from the sttes of Mins Geris, Rio de Jneiro nd São Pulo. However, in the present study we did not observe ny significnt increse in efficcy of the SP + OP formultions compred with those contining only SP ginst tick popultions from Rondôni. Furlong et l. [12] lso evluted the efficcy of formultion contining SP + OP + citronelll, which demonstrted men efficcy of 74.1%, close to its men efficcy observed ginst cttle tick popultions in the present study. The men efficcy of the cricide formultions contining SP, SP + OP nd SP + OP + citronelll cn be considered unstisfctory for the control of R. microplus in the surveyed frms, considering 95% s the minimum efficcy for pprovl of n cricide ccording Brzilin federl regultions [16]. Severl Brzilin uthors hve studied the efficcy of mitrz on R. microplus popultions using the AIT. The results hve shown different susceptibility levels. In the Southest region, Mendes et l. [9] evlutedticksfrom17 rnches from the stte of São Pulo nd reported n verge efficcy of 77.44%, similr to our results (77.2%). Furlong et l. [12] evluted the susceptibility to mitrz on 196 R. microplus popultions from the sttes of Mins Geris, Rio de Jneiro, São Pulo nd Goiás nd found 47.9%. In the Northest region, low efficcy of mitrz ws reported in the sttes of Pernmbuco (40.5%) by Sntn [20] nd Bhi (30.95%) by Cmpos Junior nd Oliveir [21].Nevertheless, in the South region, stisfctory results were obtined in the stte of Prná bysouzetl.[22], where the men efficcy of mitrz ws bove 95% for ll 17 R. microplus popultions tested. Cmilo et l. [23], evluting the susceptibility of 20 cttle tick popultions in the stte of Rio Grnde do Sul, observed the presence of resistnce or low efficcy in the mjority of popultions nlyzed. The low efficcy observed for SP, OP nd mitrz in the studied re cn be ssocited to the development of resistnce to these molecules in locl popultions of R. microplus in the stte of Rondôni. Possibly the indequte use of these cricides t the frms studied, such s ppliction of sub-lethl doses, sequentil use of the sme chemicl group for long periods nd short intervls between tretments, hs fvored the development of resistnce [24]. Since 1999 the Rondôni government hs hd policy [25]of providing resources to locl diry frmers to encourge them to geneticlly improve their herds using Europen breeds (Holstein) s crosses. This inititive hs been resulting in significnt gins in productivity. However, Bos turus breeds incorported to increse milk production my lso hve fvored infesttions of R. microplus. In generl, producers tend to reduce the intervl between tretments in persistent nd hevy tick burdens rther thn trying new tretment strtegies, thus fvoring the development of resistnt popultions of R. microplus. With respect to the MLs, ivermectin, dormectin nd bmectin presented efficcies <95% in some cses. However, these compounds re not recommended for use on lctting cows, since they leve residues in the milk. However, these compounds cn be used on other ctegories of herds to reduce the non-prsitic instrs in pstures s prt of n integrted mngement progrm, s observed by Cstro [8]. The spinosins re indicted for use on lctting cows nd demonstrted excellent efficcy on the tick popultions ssessed, proving to be potentilly good cricide to control ticks in the studied re. The PZ group lso ws highly efficient to control the cttle tick popultions evluted. This efficcy (99.90%) is higher thn tht reported by Furlong et l. [12] (88.5%) in tests on 723 R. microplus popultions from vrious Brzilin sttes. The nlysis of the susceptibility to different cricides with R. microplus popultions from diry frms in the stte of Rondôni contributes to the rtionl nd strtegic use of cricides in tht re, which is responsible for bout 85% of milk production in the Southwestern Amzon. The dequte use of efficient cricide molecules ssocited with integrted mngement prctices to control cttle ticks cn contribute to the sustinbility of diry frm opertions in the region. Such mesures re importnt to dely the development of resistnt R. microplus popultions. Acknowledgments The study received finncil support from Ntionl Council for Scientific nd Technologicl Development (CNPq, Process no /2005-9) nd the Rondôni Diry Sector Chmber (Proleite) for funding. The uthors lso thnk Antonio Xvier do Nscimento of the Embrp Rondôni Animl Helth Lbortory for his vluble ssistnce in conducting the lbortory tests. References [1] USDA, Diry World Mrkets nd Trde, Circulr Series, 2008, Finl Dec08 PSD.pdf. [2] IBGE, Municipl Livestock Reserch, 2009, [3] N.N.Jonsson,A.L.Mtschoss,P.Pepper,P.E.Green,ndJ. Ansell, Resistnce of Holstein-Friesin cows to infesttion by the cttle tick (Boophilus microplus), Veterinry Prsitology, vol. 89, no. 4, pp , [4] G. Fisch, J. A. Mrengo, nd C. A. Nobre, A generl review on the Amzon climte, Act Amzonic, vol. 28, no. 2, pp , 1998.

6 6 Veterinry Medicine Interntionl [5] N. N. Jonsson, D. G. Myer, A. L. Mtschoss, P. E. Green, nd J.Ansell, Production effects of cttle tick (Boophilus microplus) infesttion of high yielding diry cows, Veterinry Prsitology, vol. 78, no. 1, pp , [6] FAO, Acricide resistnce: dignosis, mngement nd prevention, in Guidelines Resistnce Mngement nd Integrted PrsiteControlinRuminnts, pp , Animl Production nd Helth Division, Agriculture Deprtment, Food nd Agriculture Orgniztion of the United Ntions, Rome, Itly, [7] N. N. Jonsson, The productivity effects of cttle tick (Boophilus microplus) infesttion on cttle, with prticulr reference to Bos indicus cttle nd their crosses, Veterinry Prsitology, vol. 137, no. 1-2, pp. 1 10, [8] J. J. De Cstro, Sustinble tick nd tickborne disese control in livestock improvement in developing countries, Veterinry Prsitology, vol. 71, no. 2-3, pp , [9] M. C. Mendes, C. J. Verissimo, C. N. Kneto et l., Biossys for mesuring the cricides susceptibility of cttle tick Boophilus microplus (Cnestrini, 1887) in São Pulo stte, Brzil, Animl, Plnt Snity nd Environmentl Protection, vol. 68, no. 2, pp , [10] V. J. C. Lndim, E. A. Silv, J. M. V. Pes et l., Dignosis of the sitution of resistnce to cricides in Boophilus microplus in beef nd diry cttle in the Uberb region, FAZU Journl, vol. 3, no. 1, pp , [11] J. R. Pereir, In vitro efficcy of comercil formultions of ixocidides in engorged femle of Boophilus microplus collected of diry cttle t Príb Vley in the stte of São Pulo, Brzilin Veterinry Prsitology, vol.15,no.2,pp , [12] J. Furlong, J. R. Mrtins, nd M. C. A. Prt, The tick of cttle nd resistnce: we hve to celebrte? AHorVeterinári, vol. 27, pp. 1 7, [13] M. J. G. Silv, Climtology of Rondôni stte, Secretri de Estdo do Desenvolvimento Ambientl,PortoVelho,Rondôni, Brzil, 2010, [14] R. O. Drummond, S. E. Ernst, J. L. Trevino, W. J. Gldney, nd O. H. Grhm, Boophilus nnultus nd B. microplus: lbortory tests of insecticides, Economic Entomology, vol. 66, no. 1, pp , [15] G. A. Sbtini, D. H. Kemp, S. Hughes, A. Nri, nd J. Hnsen, Tests to determine LC 50 nd discriminting doses for mcrocyclic lctones ginst the cttle tick, Boophilus microplus, Veterinry Prsitology, vol. 95, no. 1, pp , [16] Brzil, Ministry of Agriculture, Livestock nd Food Supply, Ordinnce No. 48, Technicl Regultion for licensing nd license renewl of ntiprsitic products for veterinry use, Diário Oficil, no. 92, Section 1, [17] N. N. Jonsson, R. J. Miller, nd J. L. Robertson, Criticl evlution of the modified-dult immersion test with discriminting dose biossy for Boophilus microplus using Americn nd Austrlin isoltes, Veterinry Prsitology, vol. 146, no. 3-4, pp , [18] M. W. Binchi, N. Brré, nd S. Messd, Fctors relted to cttle infesttion level nd resistnce to cricides in Boophilus microplus tick popultions in New Cledoni, Veterinry Prsitology, vol. 112, no. 1-2, pp , [19] J. Furlongnd J. R. S. Mrtins, Resistênci dos crrptos os crrpticids, Juiz de For: CNPGL-EMBRAPA, (Boletim Técnico 59), [20] V. L. A. Sntn, Sitution of chemicl control of Boophilus microplus (Cnestrini, 1887) the sub-regions in the re of forest nd wstelnd in the stte of Pernmbuco, bsed on in vitro efficcy of cricides in engorged femles. Disserttion in Veterinry Science, Federl Rurl University of Pernmbuco, Recife, Pernmbuco, Brzil, [21]D.A.CmposJr.ndP.R.Oliveir, Invitrovlutionof cricides efficiency to Boophilus microplus (Cnestrini, 1887) (Acri: Ixodide) from bovines t the region of Ilhéus, Bhi, Brzil, Ciênci Rurl, vol. 35, no. 6, pp , [22] A. P. Souz, A. A. Srtor, V. Bellto et l., Efficcy of cricides in diry cttle herds in southern region of Prn stte, Brzil, Agronomy nd Veterinry Sciences, vol.2,no.1,pp , [23] G. Cmillo, F. F. Vogel, L. A. Sngioni, G. C. Cdore, nd R. Ferrri, In vitro evlution of cricides efficiency to bovine s ticksofriogrndedosulstte, Brzil, Ciênci Rurl, vol. 39, no. 2, pp , [24] M. C. L. Silv, R. Neves Sobrinho, nd G. F. C. Linhres, In vitro evlution of effectiveness of chlorfenvinphos nd cyhlothrin for the control of Boophilus microplus (Cnestrini, 1887) in diry frms of the microregion of Goiâni Goiás, Brzilin Animl Science, vol. 1, no. 2, pp , [25] SEAPES, Reltório nul de 2007, Secretri de Estdo d Agricultur e do Desenvolvimento Econômico e Socil. Governo de Rondôni. Porto Velho: SEAPES/RO, 2007.

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