We hypothesised that haematological
malignancies increase the risk of acquiring zoonotic Salmonella or Campylobacter
gastroenteritis. The population-based study comprised all first-time Salmonella/Campylobacter
gastroenteritis cases in two Danish counties (1991-2003), with age- and gender-matched controls from the background population. We linked the study cohort to registries to obtain data on
malignancies,
chemotherapy (yes/no), and main comorbidities diagnosed before Salmonella/Campylobacter
gastroenteritis. Based on this design, we determined incidence rate ratios (
IRR) in conditional logistic regression analyses, and we used weighted mean regression curves to evaluate fluctuations in risk 0-5 years after the
malignancy diagnosis. Sixty-eight of 13,324 cases (0.5%) and 29 of 26,648 controls (0.1%) had haematological
malignancy before their Salmonella/Campylobacter
gastroenteritis. Comorbidity-adjusted
IRR for Salmonella/Campylobacter
gastroenteritis in patients with haematological
malignancy as compared to patients without
malignancy were 4.46 [95% confidence intervals (CI), 2.88-6.90] for all individuals, 8.33 (95% CI, 4.31-16.1) for Salmonella, and 2.17 (95% CI, 1.15-4.08) for Campylobacter. Stratification on
chemotherapy treatment did not change these estimates. In time-related analyses,
IRR were 7-8 in the first 2 years after the haematological
malignancy diagnosis and 4-5 in the following 3 years. Patients with haematological
malignancy had increased long-term risk of enquiring Salmonella or Campylobacter
gastroenteritis.