Epidemiology and Infection

Gastroenteritis

Retrospective cohort study of an outbreak of cryptosporidiosis caused by a rare Cryptosporidium parvum subgenotype

A. GRINBERGa1 c1, W. E. POMROYa1, R. A. SQUIRESa2, A. SCUFFHAMa3, A. PITAa1 and E. KWANa1

a1 Massey University, Institute of Veterinary, Animal and Biomedical Sciences, Palmerston North, New Zealand

a2 School of Veterinary & Biomedical Sciences, James Cook University, Townsville, Australia

a3 Hawke's Bay District Health Board, Hastings, New Zealand

SUMMARY

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 identified 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. A total of 25/80 respondents to a questionnaire were defined as cases using a clinical case definition (31% attack rate). The inferred median incubation period was 5 days (range 0–11 days), and the median illness duration was 5–6 days (range 2–23 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 significant 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.

(Accepted October 06 2010)

(Online publication November 19 2010)

Correspondence:

c1 Author for correspondence: Dr A. Grinberg, Infectious Diseases Group, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11 222, Palmerston North (4442), New Zealand. (Email: a.grinberg@massey.ac.nz)

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