Poultry meat remains a major source of Campylobacter infection in New Zealand, according to a study.

Researchers looked at transmission pathways and source attribution for campylobacteriosis in New Zealand. Most patients were infected with strains attributed to a poultry source, and poultry meat consumption was common, while 14 percent were linked to cattle.

The reduction in campylobacteriosis in New Zealand since 2008 has been relatively small. The decline in 2006 to 2008 was linked to interventions in broiler meat processing. In 2020, New Zealand set a public health goal for a 20 percent reduction in foodborne campylobacteriosis by 2025.

Providing updated information
The study’s purpose was to updat evidence on the contributions of different sources of campylobacteriosis to inform a refreshed food safety risk management strategy and action plan. It was funded by the Ministry for Primary Industries and published in the International Journal of Infectious Diseases.

A case-control study involved every second notified case sampled in Auckland and every patient in Manawatū and Whanganui between March 2018 and March 2019. These areas cover almost 40 percent of the population. More than 80 percent of people involved as cases or controls had consumed poultry within the previous seven days.

Source attribution of campylobacteriosis from these two regions was done by testing isolates from fecal samples of notified cases and from sources such as poultry, cattle and sheep and using modelling to assign a probable source for each case.

Members of the New Zealand Health Survey cohort were the control population. This is an annual survey of individuals from 14,000 randomly-seleced households.

The number of cases interviewed, and for which a clinical isolate was obtained, was 666 with 445 in Auckland and 221 from Manawatū and Whanganui. Around 200 isolates each came from cattle, sheep and poultry.

Difference in urban and rural settings
Poultry consumption was not identified as a main risk factor as such. However specific risk factors related to preparation and eating poultry did result in statistically significantly elevated odds ratios such as consumption of undercooked chicken or eating chicken outside the home.

While direct contact with poultry presents a significantly elevated risk, it affects only a small proportion of the poultry attributed cases, according to the study.

Ninety percent of urban campylobacteriosis cases were attributed to poultry sources, compared to almost 75 percent of rural cases with almost all the rest linked to cattle.

The importance of non-poultry pathways was explored using the 93 cattle attributed cases. Results indicate that living or working on a farm is the most important risk for these cases.

While raw milk was a significant risk factor for cattle-attributed urban cases, it was reported by only a small proportion, mostly in the Manawatū or Whanganui region.

The poultry meat chain offers links wher intensified or new control measures can be implemented, said researchers.

“Generation of strong risk-based evidence on the dominant transmission pathway for campylobacteriosis in New Zealand provides a solid platform for continuing efforts by government and industry to mitigate this important public health problem.”