Treatment against coccidiosis in Norwegian lambs and potential risk factors for development of anticoccidial resistance—a questionnaire-based study

Abstract

The objectives of this study were to investigate the use of anticoccidials in Norwegian sheep flocks and identify farms with management procedures likely to select for drug resistance. Data were obtained by a questionnaire sent to all members of the Norwegian Sheep Recording System in October 2015. The data set consisted of 1215 answers, corresponding to 8.5% of Norwegian sheep flocks. Anticoccidials were used in 82.7% of flocks. Main treatment was at turnout (38.6% of treated flocks) or 1 week after turnout (32.4%). Interestingly, clinical signs possibly related to coccidiosis were observed by almost 40% of the farmers after treatment, which might be an indication of drug resistance. Correlations between the apparently reduced anticoccidial efficacy and management conditions, such as the size of the farms, were found. From the farmers’ perspective, metaphylactic treatment was used in 88.5% of treated flocks, of which approximately one third had no history of clinical coccidiosis. Even though farmers seem aware of the importance of good drenching routines based on reliable estimates of weights and calibration of drench guns, drench gun used for anticoccidial administration was never calibrated in 12.1% of the flocks. Finally, dose estimation was made by visual appraisal in 27.5% of the flocks, which can lead to incorrect dosing. Based on the present study, it cannot be determined whether the apparent treatment failure was related to management practises, incorrect administration of the drug, other infections or actual anticoccidial drug resistance.Electronic supplementary materialThe online version of this article (doi:10.1007/s00436-017-5400-7) contains supplementary material, which is available to authorized users.

Field evaluation of anticoccidial efficacy: A novel approach demonstrates reduced efficacy of toltrazuril against ovine Eimeria spp. in Norway

“…Norwegian sheep farms (n = 80) were selected based on a previous questionnaire study performed in October 2015 ( Odden et al, 2017 ). The inclusion criteria were: a) treatment with anticoccidials annually for at least four years, b) coccidiosis-related symptoms in lambs treated with an anticoccidial, and c) flock size of more than 60 winter-fed ewes.…”

“…( Taylor, 2000 ; Daugschies and Najdrowski, 2005 ). However, these measures are often labour intensive and can be difficult to implement, and chemoprophylaxis with anticoccidials is therefore frequently used, in addition to hygiene measures for control of clinical coccidiosis in sheep farms ( Taylor and Kenny, 1988 ; Platzer et al, 2005 ; Saratsis et al, 2013 ; Odden et al, 2017 ). Metaphylactic administration of a single oral treatment with toltrazuril in the prepatent period has been shown to be effective at reducing clinical signs and maintaining adequate growth rates in different production systems ( Gjerde and Helle, 1986 , 1991 ; Taylor and Kenny, 1988 ; Le Sueur et al, 2009 ; Saratsis et al, 2013 ).…”

“…The emergence of ACR in poultry and pig production systems ( Lan et al, 2017 ; Shrestha et al, 2017 ), along with anecdotal reports of reduced ACE in Norwegian lambs ( Odden et al, 2017 ), demonstrates the need for a FECRT-type method to evaluate drug efficacy in live animals. However, due to the reasons outlined above, the standard FECRT ( Coles et al, 1992 ) currently recommended by WAAVP for evaluation of anthelmintic efficacy is unsuitable for use with coccidia.…”

Controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine Eimeria spp.

“…Management strategies that decrease the need for anticoccidials by reducing the infection pressure, possibly achieved by applying strict hygienic measures, and improved flock and pasture management should be actively encouraged by veterinarians and agricultural policy incentives [11]. Additionally, farmers should be informed about the importance of correct drenching techniques, including dosage estimation and drench gun calibration, as these have been shown to be inadequate in several farms [12].…”

“…Suggested strategies to control ruminant coccidiosis include pasture management, adequate nutrition, and hygienic measures [10,11]. However, these measures are often difficult to implement in practice, and the main control approach is often metaphylaxis with anticoccidials [12][13][14][15]. Metaphylactic administration of a single oral dose of toltrazuril in the prepatent period has been shown to be effective at reducing clinical signs and maintaining adequate lamb growth rates in different production systems [13,[15][16][17][18][19].…”