The occurrence of a gastrointestinal illness among a class of 96 undergraduate veterinary students in New Zealand prompted laboratory and questionnaire-based investigations. Cryptosporidium parvum was the only enteropathogen identied in 4/7 faecal specimens analysed. The C. parvum isolates carried a rare IIa GP60 allele, indicating a point-source outbreak. The infection source could not be microbiologically traced, but the investigation suggested contact with calves during a practical class as the most likely exposure. The inferred median incubation period was 5 days (range 011 days), and the median illness duration was 56 days (range 223 days), corroborating previous observations in experimental cryptosporidiosis. Disease was self-limiting, characterized by abdominal discomfort, diarrhoea, and in some cases, vomiting. Originating from a rural area and having had previously handled ruminants were associated with a signicant risk reduction in males. All the three students who reported chronic use of steroid inhalers for treatment of asthma were cases. This case highlighted, once again, the potential hazard for explosive outbreaks of cryptosporidiosis. In 2006, we investigated an outbreak of gastrointestinal illness in a class of 96 veterinary students, in which C. parvum was identified as the sole enteropathogen in multiple faecal specimens. A 100-l water sample was collected from one of the drinking water taps on the same day of the investigation and filtered on-site using a commercial filter (FiltaMax, Idexx Laboratories, USA), at a ow rate of 2 l/min. A 200-ml sample was also collected in a sterile bottle, placed on ice and transported to an environmental microbiology laboratory for analysis for the presence of Escherichia coli bacteria. The same day, the dairy farm that provided the calves for the practical class was visited. The farm was situated about 5 km from LATU. Faecal specimens from nine calves aged >30 days were submitted on ice to IVABS Unfortunately, the calves actually used in the class had been sold and could not be traced, and other calves aged <1 month were not present at the day of the visit as the calving season had ended. Seven faecal specimens submitted by students were analysed for the presence of enteropathogens. The three specimens initially analysed at the regional diagnostic laboratory tested negative for Campylobacter and one tested positive for Cryptosporidium. All the seven specimens submitted to IVABS tested negative for rotavirus, Salmonella spp., norovirus and Giardia, and four tested positive for Cryptosporidium oocysts by immunouorescence. There were 25/80 cases among respondents to Q1 (31% attack rate), and 15/64 among respondents to Q2 (P=0.35). Nine out of 25 cases (36%) sought medical advice during the course of the illness. All 64 respondents to Q2 had attended the calf-handling practical (Table 2), and none of them responded as having drunk tap water at LATU during the same practical, arguing against a water-borne source of infection there (Table 2). Sixteen out of 25 cases (64%) reported diarrhoea and abdominal discomfort in Q1; six (24%) abdominal discomfort, diarrhoea, and vomiting; two (8%) abdominal discomfort only, and one (4%) vomiting only. Although a single negative water sample was of limited value to completely rule out a water-borne outbreak of cryptosporidiosis, Q2 indicated none of the respondents had drunk tap water during the practical class, leaving direct zoonotic transfer through contact with calves as the most likely route of transmission. An attack rate of 31% was estimated based on the responses to Q1. 

What pathogen was connected to the outbreak?
{'answer_id': 274819, 'document_id': 447650, 'question_id': 142258, 'text': 'C. parvum', 'answer_start': 1281, 'answer_category': 'SHORT'}