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

<i>Cryptosporidium</i> spp., particularly <i>Cryptosporidium parvum</i>, 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 <i>Cryptosporidium</i> spp. oocysts in faeces, posing risks of contaminating surface water sources. Understanding the dynamics of <i>Cryptosporidium</i> contamination is crucial for effective water quality management. This study investigated <i>Cryptosporidium</i> 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 <i>C. parvum</i> immune chromatographic assays (ICT) on 47 faecal samples. This was followed by DNA extraction and species identification, with <i>gp60</i> subtyping. Raw and treated water quality data were analysed to determine <i>Cryptosporidium</i> oocyst counts. <i>Cryptosporidium parvum</i> was the predominant species in calves at both farms, with <i>gp60</i> subtype IIaA17G2R1 being the only subtype detected. Some calf samples revealed mixed infections with <i>C. parvum</i> and <i>C. ryanae</i>. Raw-water samples (<i>n</i> = 214) revealed a 50.00% positivity rate for <i>Cryptosporidium</i> oocysts, with 22.43% (24/107) containing <i>C. parvum/C. hominis</i> and the remainder 77.57% (83/107) <i>C. andersoni</i>. Water treatment significantly reduced oocyst counts (<i>P</i> < 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.