Cryptosporidiosis is an important disease in neonatal calves, causing watery diarrhoea, loss of appetite, and production losses. Dehydration from diarrhoea often results in the calf requiring rehydration or veterinary treatment to prevent calf mortality. Transmission of Cryptosporidium to calves still has some major knowledge gaps, such as the initial source of oocysts ingested by calves and how these oocysts can persist between calving periods. Some studies have examined the role of adult cattle in the transmission of Cryptosporidium oocysts, although these have yielded inconclusive results. In this study, highly sensitive oocyst extraction from faeces and detection techniques, sensitive to 5 oocysts per gram using a 50 g sample, were used to genotype faecal samples from adult cattle and their calves to determine if adult cattle could be a source of Cryptosporidium infection for their calves. On a dairy farm, faecal samples from adult cattle were collected twice per week for 0–3 weeks before calving and from their calves three times per week until they reached 3 weeks of age followed by twice per week until they reached 6 weeks of age. On a beef farm, samples were collected from both adults and calves at a single time point. Faecal samples were examined to compare species and multilocus genotypes of Cryptosporidium parvum. Results show that C. parvum was the most prevalent species on both the dairy and beef farms. The calves within each herd appear to have one predominant single multilocus genotype, whereas adult cattle have multiple distinct genotypes. Adult cattle on the dairy farm, tested before calving, in the majority of cases had a multilocus genotype that is different from that detected in their calves. On the beef farm, where samples were taken at the same time, the majority of adult cattle matched the multilocus genotype of their calves. This study shows that adult cattle display a higher diversity of C. parvum genotypes on both farms compared to the calves. The data also represent a detailed longitudinal prevalence study of the shedding profiles and genotype of Cryptosporidium parasites detected in dairy calves from birth to 6 weeks of age.

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