Coccidiosis, caused by the parasite Cystoisospora suis, is a common problem in Dutch and Belgian pig farms, with infection rates as high as 70% in Belgium. The parasite causes intestinal damage, leading to growth retardation and increased susceptibility to other pathogens. Despite the lack of visible diarrhea, the parasite is under-diagnosed due to the timing of its excretion. A new autofluorescence method and a more accurate PCR test are soon available for detection. Infected farms are advised to keep the environment clean, disinfect properly, and treat piglets with toltrazuril to prevent growth retardation and reduce infection pressure. Early treatment can improve piglet growth.