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RCPV (2014) 109 (589-590) 33-37

Resistncia mltipla anti-helmnticos num rebanho ovino no sul do Brasil

Anthelmintic multiple resistance in sheep flock in southern Brazil

Fernanda C.C. Santos*; Andria Buzatti1;

Marciele M. Scheuermann1; Victor F.B. Roll2; Fernanda S.F. Vogel1

1Laboratrio de Doenas Parasitrias (LADOPAR), Universidade Federal de Santa Maria (UFSM),Avenida Roraima, 1000, Bairro Camobi, Santa Maria, Rio Grande do Sul (RS), Brasil.

2Departamento de Zootecnia, Faculdade de Agronomia Eliseu Maciel, Universidade Federal de Pelotas (UFPel),Campus Universitrio, Pelotas, RS, Brasil.

Summary: The control of gastrointestinal endoparasites in li-vestock relies on antihelmintic drugs administration, being thisperformed inadequately, resulting in stimulation of parasite re-sistance. The aim of this experiment was to evaluate the effi-ciency of 5 active principles against gastrointestinal endoparasi-tes in a sheep flock in the southern Brazil. For this, 54 sheep weredivided into 6 groups with 9 animals in each. The active princi-ples tested were moxidectin (T1), ivermectin 1% (T2), levamisoldisofenolat (T3), oxfendazol (T4) and levamisole hydrochloride(T5), administered orally according to the manufacturers ins-tructions. Examinations of egg counts per gram of feces (EPG)and fecal culture were performed at days 0, 7 and 14. For statis-tical evaluation, analysis of variance for repeated measures andcomparisons of means by LS Means test (p

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xidectin have been reported previously (Waruiru etal., 1997; Molento e Prichard, 1999; Armson et al.,1995). The inadequate management of anthelminticsand their indiscriminate use are among the main ope-rative factors that lead to the occurrence of this phe-

nomenon (Fao, 2003).The aim of this experiment was to evaluate 5 active

principles administered orally in a sheep flock natu-rally infected in the southern Brazil.

The experiment was conducted in the Agricultu-ral College of the Federal University of Santa Maria(UFSM) installations, localized in the Central De-

pression of Rio Grande do Sul, Brazil. It was used 54sheep, both sexes, aged from 2 to 6 years, Texel x Ilede France. The flock remained in the same paddockof native grassland, continuous grazing, with waterad libitum. The last administration of anthelminticwas performed 45 days before the beginning of theexperiment.

The sheep were randomly divided into 6 groups of9 animals, each group representing an active prin-ciple to be tested. The active principles tested weremoxidectin (T1), ivermectin 1% (T2), levamisol di-sofenolat (T3), oxfendazol (T4) and levamisol hydro-chloride (T5), respectively. The T6 was the untreatedcontrol group. The doses followed the manufacturersrecommendation and were all orally administered(Table 1).

Table 1- Dose of active principles tested according to treatment.

TREATMENTACTIVE

PRINCIPLEDOSE

1 Moxidectin 1mL/10 kg BW

2 Ivermectin 1% 2,5mL/10 kg BW

3Levamisol

disofenolat1mL/10 kg BW

4 Oxfendazol 1mL/9 kg BW

5Levamisol

hydrochloride1mL/10 kg BW

6 Control -

The animals received all treatments on the same day,which was considered day 0. Fecal samples from allsheep were collected at day 0, 7 and 14 for the examsegg counts per gram of feces (EPG) and fecal cultu-re in pool of the groups, according the methodologydescribed by Gordon e Whitlock (1939) and RobertsSullivan (1950), respectively. Treatment efficiency wascalculated by fecal egg count reduction test (FECR).

Statistical analysis was performed with data transfor-med in square root (x+1) by repeated measures analysis.It was obtained the main effects means, interactions of

pairs (treatment x time) and the mean comparison testwas performed by LS Means (p

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The results of this study indicate that oxfendazolwas completely ineffective in the flock examined, asno FECR was observed in treated animals. Moxidectinand ivermectin 1% have retained some efficacy in theflock described, clinical improvement of the affectedanimals may be expected in the short term, but the lowmean of FECR (21-62%) is a cause of concern and in-dicates a considerably reduced efficacy of this drug.Levamisol hydrochloride presented 88% efficiency atday 7, but at day 14 it droped to 68%, considered lowmean. Levamisol disofenolat was the only drug with

high efficiency (>95%). In a fully effective anthelmin-tic, a FECR of at least 95% (and a lower 95% confi-dence interval) has to be expected (Coles et al., 1992).

For the repeated measures analysis it was chosenARH structure due the lowest value for Akaike In-formation Criterion. Based on the repeated measuresanalysis there was no significant effect of treatment(p = 0.0150), time period (p = 0.006) and interaction

between treatment and time (p = 0.0002).As shown in Table 4, there was no difference in EPG

values between groups in day 0. On subsequent days, itwas observed that moxidectin, levamisol disofenolat andhydrochloride presented reduction in EPG values on day 7,whereas in the control group and in oxfendazol treatment

there was no EPG reduction in the same day. Ivermectintreatment presented a rise in EPG value according to time,indicating in this case parasite resistance to the product.

Table3- Percentage of helmint larvae identified in coproculture according to the treatments moxidectin (T1), ivermectin (T2), levamisoldisofenolat (T3), oxfendazol (T4), levamisol hydrochloride (T5) and control group.

TREATMENT GENRES

DAY EFFIENCY EFFIENCY

0 7 14 0-7 0-14

Haemonchus 84 88 100 0 0

1 Cooperia - - - - -

Trichostrongylus 6 - - 100 100

Ostertagia 10 12 - 0 100

Haemonchus 87 79 74 9 14

2 Cooperia 3 7 - 0 100

Trichostrongylus 7 13 - 0 100

Ostertagia 3 - - 100 100

Bunostomum - 1 26 0 0

Haemonchus 99 22 37 77 62

3 Cooperia - 2 10 0 0

Trichostrongylus 1 76 53 0 0

Ostertagia - - - - -

Bunostomum - - - - -

Haemonchus 90 48 86 46 4

4 Cooperia 4 - - 100 100

Trichostrongylus 5 5 14 0 0

Ostertagia - 47 - 0 0

Bunostomum 1 - - 100 100

Haemonchus 82 70 99 14 0

5 Cooperia - - - - -

Trichostrongylus 16 25 - 0 100

Ostertagia - - - - -

Bunostomum - - 1 0 0

Chabertia 2 - - 100 100

Haemonchus 92 96 99 - -

Control Cooperia 2 4 - - -

Trichostrongylus 2 - 1 - -

Ostertagia - - - - -

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Table 4- Variance analysis of repeated measures of moxidectin(T1), ivermectin (T2), disofenolato of levamisole (T3), oxfenda-zole (T4), levamisole hydrochloride (T5) and control group (T6)in a sheep being evaluated by EPG (square root x+1) on days 0,7 and 14 post anthelmintic administration.

TREATMENTDAY

0 7 14

1 49,28 A, a 22,60 B, a 23,30 B, a

2 30,57 A, a 58,30 B, b 55,98 B, b

3 38,10 A, a 4,01 B, a 10,38 B, a

4 39,45 A, a 37,64 A, b 49,44 A, b

5 56,60 A, a 13,22 B, a 22,10 B, a

6 41,70 A, a 45,45 A, b 49,67 A, b

Means followed by different capital letters in the samerow differ significantly (p

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