The parasite Cystoisospora suis causes diarrhea in pigs, especially in newborn piglets, and is capable of quickly spreading across farms. For this reason, pig farmers in Europe preventively use toltrazuril to control parasite development. In contrast to congeneric parasites in chicken, no resistance to this pharmaceutical compound was described in pig parasites until recently. In an article in Parasites & Vectors, researchers of the University of Veterinary Medicine, Vienna, have now for the first time confirmed that toltrazuril is ineffective against a Dutch isolate of the parasite. Even though antiparasitic resistance in pig parasites is developing slowly, monitoring of resistance should be intensified due to the lack of alternative treatment options, and increased hygiene measures should be taken to prevent pathogen spread.