Campylobacteriosis in New Zealand: Results of a case-control study

Study objective. To identify and assess the contributions of major risk factors for campylobacteriosis in New Zealand. Design. Case-control study. Home interviews were conducted over nine months using a standardised questionnaire to assess recent food consumption and other exposures. Setting. Four centres in New Zealand with high notification rates of campylobacter infections - Auckland, Hamilton, Wellington, and Christchurch. Participants. Case patients were 621 people notified between 1 June 1994 and 28 February 1995 as having campylobacter infection. Control subjects were selected randomly from telephone directories, and were matched 1:1 with case patients in relation to sex, age group, and home telephone prefix. Results. Risk of campylobacteriosis was strongly associated with recent consumption of raw or undercooked chicken (matched odds ratio 4.52, 95% confidence interval 2.88, 7.10). There was also an increased risk with chicken eaten in restaurants (matched odds ratio 3.85; 2.52, 5.88). Recent consumption of baked or roasted chicken seemed to be protective. Campylobacteriosis was also associated with recent overseas travel, rainwater as a source of water at home, consumption of raw dairy products, and contact with puppies and cattle, particularly calves. Conclusions. Improperly cooked chicken seems to be associated with a large proportion of campylobacteriosis in New Zealand. Thorough cooking of chicken in homes and restaurants could reduce considerably the incidence of this disease.