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Veterinary Parasitology 188 (2012) 200– 202

Contents lists available at SciVerse ScienceDirect

Veterinary Parasitology

jou rn al h om epa ge: www.elsev ier .com/ locate /vetpar

hort communication

valuation of dicyclanil (CLiKZiN®) treatment for the early-seasonrotection of ewes against blowfly strike

atthew Walters, Richard Wall ∗

chool of Biological Sciences, University of Bristol, BS8 1UG, UK

r t i c l e i n f o

rticle history:eceived 21 December 2011eceived in revised form 10 March 2012ccepted 13 March 2012

eywords:lowflylimate changeicyclanil

a b s t r a c t

Protecting sheep against early season myiasis (strike) is a significant problem in northerntemperate farming systems, where fully-fleeced ewes and early-season lambs approachingmarket weight, are at high initial risk. Here, the prevention of early-season blowfly strikein ewes was examined on matched commercial sheep farms in south west England, using anew formulation of dicyclanil (CLiKZiN® pour on) with a short withdrawal period of 7 days.The ewes on seven farms received a prophylactic treatment with dicyclanil (CLiKZiN 1.25%pour-on suspension) in April 2011; ewes on three control farms received no treatment. Thelambs at all farms remained untreated. No adverse reactions to treatment were recorded. On

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the treatment farms no ewe strikes were recorded between April and June (10 weeks). Oncontrol farms, there were 16 strike cases in ewes over the same period, giving a cumulativeincidence of 31 cases per 1000 ewes. On the treatment farms only one lamb was struckwhereas at the control farms 10 lamb strikes were recorded. The data demonstrate thatCLiKZiN was highly effective at protecting ewes against early season strike-challenge.

. Introduction

In the UK, a characteristic seasonal pattern of sheeplowfly myiasis (strike) incidence is usually observed inost years (French et al., 1992). The first generation of

he primary agent of myiasis, the blowfly Lucilia sericata,merges in April/May and the initial strikes of early Springre usually seen predominantly in ewes, because theirong fleeces become wet and soiled by faeces, promotingigh blowfly egg and larval survival. Following shearing,we susceptibility is reduced. For spring-born lambs, thenitially short fleece results in lower susceptibility thanwes, but after weaning in summer, a combination of diar-hoea caused by temperature-dependent GI infection and a

rowing fleece leads to faecal soiling and rapidly increasesheir susceptibility to strike. Lamb strikes therefore gen-rally increase in incidence from mid-summer onwards.

∗ Corresponding author. Tel.: +44 1179289182; fax: +44 1173317985.E-mail address: richard.wall@bristol.ac.uk (R. Wall).

304-4017/$ – see front matter © 2012 Elsevier B.V. All rights reserved.oi:10.1016/j.vetpar.2012.03.016

© 2012 Elsevier B.V. All rights reserved.

However, the incidence of ewe strikes can increase againtowards the end of the season because of the re-growingfleece, particularly if the autumn is warm and wet (Frenchet al., 1992; Broughan and Wall, 2007).

For sheep farmers these spring strikes represent a par-ticular practical problem in both ewes and early seasonlambs. At present, most farmers in the UK do not treat theirewes prophylactically against blowfly strike before shear-ing (French et al., 1994; Bisdorff and Wall, 2008). Shearingusually occurs in June and once sheared, protection isoffered by the short fleece until, after some wool regrowth,when ewes can then be treated with a long-acting prod-uct with protects them for the remainder of the season.Farmers are understandably reluctant to apply products toewes at the start of the season, particularly since, if theyapply a long-acting product, a high proportion would beremoved with the fleece at shearing. For early lambs born

in January and February, many will be close to market-weight by the time the blowfly season starts in April/Mayand any product with a lengthy withholding period willresult in unacceptable delays in getting lambs to market.

ry Parasitology 188 (2012) 200– 202 201

Fig. 1. The cumulative incidence of strikes of untreated ewes at three

M. Walters, R. Wall / Veterina

This means that ewes and early lambs are particularly vul-nerable to fly-strike early in the Spring/summer and, if noprophylactic treatment is administered a warm spring willleave these animals exposed to high strike challenge. This isclearly a significant welfare and animal husbandry issue. Inaddition, in terms of fly population dynamics, early seasonstrikes, although relatively small in number, are dispropor-tionately important relative to strikes later in the season,because they allow the L. sericata population to establishand contribute, potentially exponentially, to future gen-erations. Any increase in strikes in this spring period istherefore likely to be reflected by a significant increase infly-challenge and potentially lamb strikes later in the year.

In recent years, the most widely used products for blowfly control in the UK have been cyromazine (vetrazin 6%pour-on, Novartis Animal Health) and dicyclanil (CLiKZiN5% pour-on, Novartis Animal Health) (Bisdorff and Wall,2008). They claim to protect sheep for 10 weeks and 16weeks respectively from blowfly strike by L. sericata, andhave withholding periods of 28 and 40 days, respectively. Anew formulation of dicyclanil (CLiKZiN 1.25% pour-on sus-pension, Novartis Animal Health) was released in 2011; ithas a claim to protect sheep against blowfly strike for 8weeks and has a withholding period of only 7 days. Thisproduct may have a particular value in allowing farmersto treat animals in spring to protect ewes prior to shearingand early season lambs prior to sale, in addition to its uselater in the blowfly season. The aim of the work describedhere, therefore, was to examine the first of these scenarios,the use of dicyclanil (CLiKZiN 1.25% pour-on suspension)to protect ewes against early-spring blowfly strike.

2. Methods

Ten commercial flocks in south west England were usedin the study. The farms were selected to match for as manyflock-level blowfly-strike risk factors as possible: all farmsearly-lambed between December and March, sheared ewesin June/July, were at an altitude of below 250 m and hadflocks of about 200 ewes. All flocks were separated by atleast 5 km. Throughout the course of the trial, each flockwas grazed on permanent grassland pasture. The animalsused in the trial had no previous insecticide treatment forthe control of ectoparasites in the 2011 season. All thefarms had experienced strike in previous years but nonehad a history of unusually high strike incidence. The farmswere allocated to the treatment or non-treatment groupsat random. There was no bias in geographical distributionand all were located in the counties of Devon, Cornwallor Somerset in south west England. Farmers were con-tacted initially by telephone, this was followed up by letterexplaining the protocol and an initial farm-visit. All farm-ers were provided with a labelled note-book in which theywere asked to record each case of strike. Dates of lambing,weaning, lamb sales or other flock size changes were noted.

Seven farms were allocated to the treatment group. Ateach of these farms, all ewes were treated between the

18th and 20th of April 2011. The weights of the eweswere estimated by the farmer in accordance with normalfarm management practice. All of the ewes in the trial fellinto the over 50 kg category and dicyclanil (CLiKZiN 1.25%

farms in s.w. England, day 1 is the 17th of April 2011. There were no strikesin ewes treated with dicyclanil (CLiKZiN 1.25% pour-on suspension) atseven separate farms over the same period.

pour-on suspension) was applied by the study investiga-tors at the recommended dose of 36 ml per ewe, usingthe four stroke method recommended by Novartis AnimalHealth. No other ectoparasite insecticide was applied to thesheep prior to or during the trial, unless they contractedblowfly strike. At the three control farms, all ewes remaineduntreated. Lambs were untreated at all ten farms.

Each farmer carried out daily inspections of all sheep. Ateach of these inspections any struck animal was recordedand the position of each strike noted using in the pre-prepared recording booklets. Individuals that were struckwere treated with a therapeutic dose of 1.25% (w/v) high-cis cypermethrin (Crovect Pour-On®), their ear tag numberwas recorded and they were removed from the trial. Inspec-tions and strike recording continued until shearing in lateJune. The farmers were all contacted regularly to check onthe progress of the study and to deal with any issues orenquiries. The study was ended on the 20th of June 2011.

3. Results

No adverse reactions to treatment were recorded. Onthe seven treatment farms, where a total of 1434 eweswere present (mean flock size 205) there were no cases ofblowfly strike in the ewes during the course of the study.At these farms, there was also only one strike on a lamb.On the three control farms, among the 524 ewes included,16 were struck, corresponding to a prevalence of 31 strikesper 1000 animals. Strikes on the control farms began in lateApril (the onset of the blowfly season was relatively early in2011) and increased steadily over the course of the spring(Fig. 1). In addition, at the control farms, 10 lamb strikeswere recorded.

4. Discussion

When considering treatments for the prevention ofstrike, under some circumstances it may be desirable to runtreated and untreated animals in the same flock, to ensurethat they all experienced identical fly challenge. However,

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Wall, R., Ellse, L., 2011. Climate change and livestock disease: integrated

02 M. Walters, R. Wall / Veterina

uch a design may be flawed if there is any risk of the trans-er of product from treated to untreated animals. To avoidhis possibility treated and untreated animals need to ben different flocks. This then introduces concerns about thenfluence of possible differences in fly challenge at the dif-erent farms. This possibility can be minimised by ensuringhat there are a sufficiently large number of replicates tovercome any natural farm to farm variation; here 10 farmsere used, 7 with treated ewes and 3 with untreated ewes.

In the treated flocks, no flystrike was observed in any ofhe 1434 ewes, indicating that the dicyclanil product wasighly effective at preventing myiasis. In contrast 16 of the24 untreated animals were struck over the 10 week studyeriod. This incidence is slightly higher than might haveeen expected over this period in an average year and sug-ests that these months were highly conducive to strike in011 (Fenton et al., 1998). The untreated lambs in the flocksf treated ewes had a lower strike incidence than the lambsn the untreated control flocks. The exact cause of this dif-erence cannot be determined from the present study but its possible that some transfer of product occurred betweenwes and lambs.

Feedback from farmers with flocks in the treatmentroup at the end of the study was positive and all con-idered the product to be more effective as a preventativereatment than other short-acting products that are avail-ble. However, most did not usually treat their ewes earlyn the season, preferring to treat reactively until afterhearing. This approach to early season strike managementay however become increasingly unsustainable. Since

ystrike incidence is strongly dependent on patterns ofemperature and rainfall, in the future changing climaten northern Europe (Murphy et al., 2009) may result inubstantially higher levels of strike challenge earlier in thepring and lasting later into the winter, than is currentlyhe case (Wall et al., 2011). Warming of 2–3 ◦C is predictedo double the strike rate in lambs and give four times thennual strike rate in ewes while allowing L. sericata to bective throughout winter in the most southerly parts of

he UK (Rose and Wall, 2011; Wall and Ellse, 2011). Underhese conditions, ewes are likely to be at a substantiallyigher risk of flystrike earlier in the season because of their

ong winter fleece which retains moisture and faeces. Any

itology 188 (2012) 200– 202

climate-induced increase in challenge in this spring periodis therefore likely to be reflected by a significant increasein ewe strikes and, also subsequent, lamb strikes. With achanging pattern of flystrike it may be important to alterthe current strike prevention strategies with a greater needfor more routine strategic early-season control.

Conflict of interest statement

We are grateful to Novartis Animal Health for theirfinancial support of this study.

Acknowledgements

This work was undertaken with the agreement of theUniversity of Bristol ethical review committee (referenceno: UB/09/008). We would like to thank all the participatingfarmers for allowing us to work with their sheep.

References

Bisdorff, B., Wall, R., 2008. Sheep blowfly strike risk management inGreat Britain: a survey of current practice. Med. Vet. Entomol. 22,303–308.

Broughan, J.M., Wall, R., 2007. Faecal soiling and gastrointestinal helminthinfection in lambs. Int. J. Parasitol. 37, 1255–1268.

Fenton, A., Wall, R., French, N.P., 1998. The incidence of ovine myiasis bythe blowfly Lucilia sericata in sheep pastures in northern Europe: asimulation model. Vet. Parasitol. 76, 211–228.

French, N.P., Wall, R., Cripps, P.J., Morgan, K.L., 1992. Prevalence, regionaldistribution and control of blowfly strike in England and Wales. Vet.Rec. 131, 337–342.

French, N.P., Wall, R., Morgan, K.L., 1994. Ectoparasite control on sheepfarms in England and Wales; the method, type and timing of insecti-cide application. Vet. Rec. 135, 35–38.

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