a1 Department of Public Health Medicine, South Glamorgan Health Authority, Abton House, Wedal Road, Cardiff CF4 3QX
a2 PHLS Communicable Disease Surveillance Centre (Welsh Unit), Cardiff CF4 3QX
a3 Cardiff Public Health Laboratory, University Hospital of Wales, Cardiff CF4 4XW
a4 Cardiff Environmental Services, Wood Street, Cardiff CF1 1NQ
a5 Environment and Health Division, Newport Borough Council, Newport NP9 4UR
After a nursery school trip to a dairy farm, 20 (53%) of 38 children and 3 (23%) of 13 adult helpers developed gastrointestinal infection. Campylobacter jejuni was isolated from 15 primary cases and from 3 of 9 secondary household cases. A cohort study of the school party found illness to be associated with drinking raw milk (relative risk 5·4, 95 % confidence interval 1·4–20·4, P = 0·001). There was a significant dose response relationship between amount of raw milk consumed and risk of illness (X2-test for linear trend 12·1, P = 0·0005) but not with incubation period, severity of symptoms or duration of illness. All 18 human campylobacter isolates were C. jejuni resistotype 02 and either biotype I (number 16) or biotype II (number 2). Campylobacter was also isolated from samples of dairy cattle and bird faeces obtained at the farm but these were of different resisto/biotypes. Educational farm visits have become increasingly popular in recent years and this outbreak illustrates the hazard of exposure to raw milk in this setting.
(Accepted June 24 1996)