Confirmed toltrazuril resistance in a Dutch field isolate of cystoisospora suis
P. Waijers1, E. Willems2, T. Tobias2, A. Joachim3
1De Varkenspraktijk, Mill, the Netherlands
2Royal GD, Deventer, the Netherlands
3Institute of Parasitology, Department of Biological Sciences and Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria
Material and Methods
• 3800 sow farm with piglets up to 25 kg
• Cocciodiosis despite proper use of toltrazuril
Background and Objectives
Despite routine use of toltrazuril, diarrhea due to Cystoisospora suis is frequently observed. In most cases, however, the problem is effectively controlled by thorough cleaning and disinfection and strict adherence to instructions on the SPC. If, nevertheless, clinical symptoms continue to occur, it is advisable to consider resistance to toltrazuril. In this study, we present a second case of toltrazuril resistance in the Netherlands on a 3800 sow farm with piglets up to 25 kg.
Results
Oocysts were detected by autofluorescence in 12 out of 13 samples. Toltrazuril (20 μM) showed an efficacy of <20% in contrast to the susceptible reference strain (Wien-I) that showed an efficacy of >95%. Efficacy of diclazuril was only 15% for the isolate from the Dutch farm compared to >98% in the reference strain.
Discussion and Conclusion
Toltrazuril resistance of Cystoisospora suis originating from the Dutch sow farm was confirmed in-vitro. As there is no alternative on the market, this has a large impact for the farm. The farm now has entirely focussed on hygiene and started to use a disinfectant that is effective against oocysts of C. suis. Further studies to evaluate the extent of toltrazuril resistance of C. suis on Dutch farms will be evaluated.