The epidemiology of listeriosis in pregnant women and children in New Zealand from 1997 to 2016: an observational study

BACKGROUND: Listeria monocytogenes causes the foodborne infection listeriosis. Pregnant women, infants and immunocompromised children are at increased risk for infection. The aim of this study was to describe the trends in the epidemiology of disease notifications and hospital admissions due to listeriosis in pregnant women aged 15 to 45 years and children aged less than 15 years in New Zealand (NZ) from 1997 to 2016. METHODS: In this population-based descriptive study, listeriosis notification and hospitalization rates from 1997 to 2016 were analyzed. Notification data were extracted from the Institute of Environmental Science and Research (ESR) Notifiable Diseases Database (EpiSurv) and hospitalization data were extracted from the National Minimum Dataset (NMDS). Pregnant women aged 15 to 45 years and children less than 15 years of age were included. Subgroup analysis was conducted for age and ethnicity. Outcomes of infection were described. RESULTS: In the 20-year period considered, there were 147 pregnancy-associated cases of listeriosis either notified to ESR (n = 106) and/or coded in the NMDS (n = 99), giving a crude incidence rate of 12.3 (95% CI 10.4, 14.4) per 100,000 births. In addition, there were 22 cases in children aged 28 days to < 15 years (incidence =0.12, 95% CI 0.08 to 0.19 per 100,000). There were no trends observed over time in the incidence of pregnancy-associated listeriosis. Incidence rates of pregnancy-associated and childhood listeriosis were highest in people of Pacific and Asian ethnicity. CONCLUSIONS: NZ has a low incidence of listeriosis in pregnant women and children, however, the consequences of infection are frequently severe. Those of Pacific and Asian ethnicity have the highest rates of disease and future messaging around food safety should target these groups. This study provides important insights into the epidemiology of listeriosis in pregnant women and children in NZ.