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Food Focus May 2006

Campylobacter:

a costly concern

A rise in reported incidents of campylobacteriosis in New Zealand over the past 15 years may be because Kiwis are eating more poultry, according to a recent report by the Institute of Environmental Science and Research (ESR).

The report, Transmission routes for Campylobacteriosis in New Zealand, states that campylobacteriosis is a major public health problem in New Zealand with reported incidence of the illness high compared with other developed countries.

Since being made a notifiable disease in 1980, reported cases of campylobacteriosis have risen steadily. In 1990 case numbers were 3,850 – that’s 116 cases per 100,000 people. By 2004 that figure had more than trebled to 12,213 – almost 327 cases per 100,000. In 2004 campylobacteriosis reports made up 53% of all gastroenteritis notifications.

No significant difference was found between rates of infection in urban compared with rural consumers.

The report states that the cost of treating the disease is estimated at around $62 million a year – 70% of the total cost of infectious intestinal disease in New Zealand.

The report was commissioned by NZFSA to help develop a computer-based quantitative risk assessment (QRA) model that will evaluate all the steps in the food chain, up to the point of consumption, so that NZFSA risk managers can work out where best to intervene in the food production process to effectively reduce the incidence of the illness.

Animal contact

The report implicates poultry consumption as a key risk factor, along with overseas travel and animal contact, in the epidemiology of human campylobacteriosis. Evidence to support the theory that poultry is a very significant source of the illness in New Zealand is based on:

• the high prevalence of contamination of retail poultry products, compared to other meat types and other foods

• the apparently higher number of bacteria present on contaminated poultry, compared to other meat types

• increased consumption of poultry and an increasing trend towards fresh product as opposed to frozen over the past 10-15 years (freezing will reduce the number of bacteria but does not completely eliminate them).

The report estimates that up to 90% of raw retail poultry, including chicken livers, could be contaminated with Campylobacter (though contaminated cooked poultry is rare), compared with up to 13% of red meat.

Cycling the bacterium

It also states that the presence of Campylobacter in environmental waters (and the environment generally) is likely to play an important role in cycling of the bacterium in animals, causing infection in cows, pigs and sheep, and possibly poultry.

“Based on results from case control studies, surveys of the prevalence and level of contamination, and consumption by a high proportion of the population, poultry products are the most common risk factor and the product most likely to be contaminated,” says the report’s author Dr Rob Lake.

“The prevalence of contamination in foods other than poultry is at least ten-fold lower and although consumption of red meat is approximately four times greater than for poultry, it seems unlikely that this would result in greater exposure.

“While the transmission of Campylobacter in New Zealand is likely to be complex, with a number of risk factors operating at once, I believe effective management of the risk from Campylobacter in poultry will cause an observable reduction in the human incidence of campylobacteriosis.”

Consumer education

Interestingly, the report reveals that in Belgium, studies showed that temporarily removing chicken from the market because of a chemical contamination scare reduced the reported incidence of the disease by 40%. Similarly, a decline in consumption in the Netherlands in 2003 also saw case numbers drop.

Iceland successfully reduced its rate of campylobacteriosis by focusing on farm biosecurity, processing controls and consumer education, including risks posed by unhygienic handling and cooking of poultry in the home.

Recent innovations

In recent years New Zealand’s poultry industry has managed successfully to reduce the prevalence of Salmonella in retail products to among the lowest in the world. However, the measures implemented have not reduced the Campylobacter contamination. Recent innovations to reduce the level of contamination include the introduction of leak-proof packaging for poultry.

NZFSA microbiologist Dr Roger Cook says: “This report provides an up-to-date insight into the various transmission routes for Campylobacter in New Zealand and summarises the available data that is applicable to New Zealand’s unique processing conditions and social activities.

“The next step is to populate the QRA risk model being developed in a joint project by NZFSA, ESR, Massey University and NIWA scientists, and the poultry and dairy industries, under the auspices of the Enteric Zoonotic Disease Research Steering Committee.”

More than 180 scientific references and district health board reports were reviewed for the report, as well as overseas studies.

Papers reviewed included studies on outbreaks; environmental contamination; transmission routes; levels in poultry, red meat and offal at slaughter through to retail (packaged and processed), milk, retail and wholesale shellfish, watercress, hydroponic vegetables and cooked food; levels in live poultry, cattle, sheep and pets; growth conditions under refrigeration; identification methodology and sparrows, possums and rabbits as reservoirs/ carriers that spread disease. Studies from overseas include sources of and rates of campylobacteriosis in Iceland, Denmark, Sweden, Norway, Finland, Netherlands, France, Belgium, Canada, USA, Europe and Australia.

No magic bullet

Dr Cook says the report does not provide an answer to the key question of why the rate of reported campylobacteriosis in New Zealand is high compared with overseas countries.

However, the report does conclude that poultry, as a source of Campylobacter in the kitchen environment, is a risk factor whose management will likely result in a significant drop in illness.

Reducing the prevalence of contamination of the poultry supply by Campylobacter will be difficult, and internationally a magic bullet has yet to be found. However, Dr Cook states that “the New Zealand poultry industry is evaluating several promising interventional strategies designed to reduce the levels of Campylobacter on poultry meat after processing”.