prevalence in calves and its effect on local water quality prior to abstraction and treatment.

spp., particularly , pose a significant threat to raw water quality and public health. Cryptosporidiosis, a gastrointestinal zoonotic disease, causes diarrhoea in dairy and beef production systems worldwide. Infected calves shed spp. oocysts in faeces, posing risks of contaminating surface water sources. Understanding the dynamics of contamination is crucial for effective water quality management. This study investigated spp. prevalence in neonatal calves and its potential impact on water quality before abstraction and treatment. The study analysed faecal samples from 1-3-week-old calves on two English dairy farms upstream of a water abstraction point. Initial screening used immune chromatographic assays (ICT) on 47 faecal samples. This was followed by DNA extraction and species identification, with subtyping. Raw and treated water quality data were analysed to determine oocyst counts. was the predominant species in calves at both farms, with subtype IIaA17G2R1 being the only subtype detected. Some calf samples revealed mixed infections with and . Raw-water samples ( = 214) revealed a 50.00% positivity rate for oocysts, with 22.43% (24/107) containing and the remainder 77.57% (83/107) . Water treatment significantly reduced oocyst counts ( < 0.001); however, due to the increase in popularity of bathing in rivers, oocysts present in raw river water may still prove a public health risk.