Glenda Lewis.
is food-borne. About 6000-7000 cases are reported each year, compared to just over 1000 cases of salmonella, and it is estimated that a further 25,000 cases go unreported. Typically, victims suffer about a week of debilitating gastroenteritis, and need a week off work or school. For some, this is a week with no income. This all adds to a significant economic deficit nationally.
Rates of infection started to rise markedly in the early 1990s, tracking the rise in consumption of fresh chilled, not frozen, chicken. The rate peaked in 2006, when New Zealand was wryly referred to by international food safety experts as ‘‘campylobacter capital of the world’’.
Director of the NZ Food Safety Science & Research Centre (NZFSSRC), Professor Nigel French, and his lab team at Massey University, worked with the Institute of Environmental Sciences and Research (ESR) and the New Zealand Food Safety Authority (now MPI), to trace the origin of infections using new genetic forensic technologies.
They confirmed that poultry was by far the most common source of infection. After regulatory controls developed by MPI and voluntary industry controls were implemented, reported cases immediately reduced by more than half (from a peak of over 380 per 100,000 of population to 161 per 100,000).
But the average level has not reduced further since then, and poultry is still estimated to be a major contributor to campylobacter infections in New Zealand, particularly in urban areas.
Like E coli, campylobacter bacteria are common in the gut and faeces of many animals. Humans can be exposed to campylobacter from contaminated water (including rivers), raw meat, raw milk and contaminated surfaces . Heating above 75 degrees Celsius will kill these pathogens in poultry, red meat and milk. Physical contact with animals is also a significant pathway for infection.
Eliminating campylobacter from the poultry processing chain has proven very difficult in many countries, including New Zealand. Even though chickens are processed in a way that eliminates most campylobacter by the end of processing, the bacteria are still commonly found on the surface of raw chicken meat and the juices around it, and in numbers sufficient to cause illness. Campylobacter is a survivor! At a recent meeting of food scientists in Nelson, Professor Arnoud van Vliet of the University of Surrey, called campylobacter ‘‘Europe’s new superbug’’.
He reported high levels of campylobacter in fresh chicken packs sold in reputable British supermarkets. Campylobacter was present in between 64 per cent and 78 per cent of the sample surveyed.
Genetic sequencing has made it possible to track the evolution of fast-changing bacteria, and identify the sources of infection with precision. The attribution of the Havelock North outbreak to sheep faeces was incontrovertible. Knowing the source after the event is not much comfort to the afflicted, however. As always, prevention is better than cure.
A new concern with campylobacter is the emergence in 2014 of a strain that is resistant to two antibiotics – tetracycline and fluoroquinolone. A survey conducted in 2015 found that this strain was prevalent in poultry in the North Island and had become the most common in human campylobacter infections.
This is unusual for NZ, where we have historically experienced very low levels of antibiotic resistance in campylobacter. Fortunately, antibiotic treatment is not usually required for campylobacter infection but if it is, erythromycin is usually the drug of choice. To date, there is no evidence of widespread resistance to this antibiotic in New Zealand.
The NZ Food Safety Science & Research Centre advises you to follow the rules if you want to continue enjoying your roast and butter chicken. We strongly advise against eating raw chicken as sashimi.
Meanwhile, NZFSSRC scientists around New Zealand will continue to work with government, industry, and colleagues here and overseas, to monitor and reduce contamination levels. We’re also keeping a close watch on the evolution of this persistent bacterium and the resistance of some to antibiotics. For more information, visit mpi.govt.nz/ food-safety/food-safety-forconsumers/tips-for-food-safety/
Professor Nigel French is director of the NZ Food Safety Science & Research Centre and Glenda Lewis is a communications adviser to the centre.