IFST Information Statement on Foodborne Campylobacteriosis – and How to Safeguard Against It

Campylobacters occur widely as part of the intestinal flora of many warm-blooded animals and birds, particularly chickens and turkeys, and can be carried in animals that are used for food production and in domestic pets. In addition, they also occur in untreated water and raw milk. Evidence indicates that the most important risk factors for food-borne infection are consumption of undercooked poultry (particularly chicken), and other meat, unpasteurised or inadequately pasteurised milk and food that has been cross-contaminated.

Symptoms of infection in humans consist of diarrhoea, sometimes with bloodstained stools, which may last from 2-10 days. The illness is usually self-limiting, but can be severe.

Campylobacters do not grow in food at temperatures below 30OC so control measures should focus on the prevention of contamination and cross-contamination. Thus, experts around the world recognise that the application of HACCP to production, processing and distribution of poultry and other food products is important.

Consumers should be aware of the risk associated with consuming raw or undercooked food of animal origin. This risk can be avoided by consuming only thoroughly cooked meat/poultry, and only pasteurised milk; by obtaining water from approved sources; and by good hygiene in the kitchen. There is a low risk of human infection from close contact with companion dogs or cats, particularly if they suffer from diarrhoea.

The Problem
Campylobacters have been known to be the cause of diseases in animals since 1909, but they have been generally recognised only since about 1980 as a cause of human disease. In countries where there is surveillance of infection, campylobacters are the most frequently reported cause of bacterial diarrhoea in humans.
The increase in reports in the developed world may in part be attributed to increased awareness, plus improved laboratory diagnosis and surveillance. Campylobacteriosis is a very widespread diarrhoeal disease in the developing world commonly affecting infants and children, with adults mostly being immune.
Campylobacters, especially Campylobacter jejuni, frequently colonise the intestinal tract of poultry and other birds and animals consumed by people. Numbers of campylobacters in the intestines of infected poultry can be particularly high, up to 107 to 109 per g. During slaughter and processing of campylobacter-infected birds, the poultry carcasses will become contaminated with low numbers of campylobacters from the intestinal tract. A survey in 2001 of UK chicken on retail sale in the UK showed that about 50% of chilled, and 30% of frozen chicken was contaminated with Campylobacter (FSA, 2003).

Consequently, undercooked poultry, and to a lesser extent red meat and offal, are potential sources of campylobacter infections. Raw milk and poorly or untreated water supplies are also important potential sources of campylobacter infection. The main known facts about campylobacters, the disease and the preventive measures are given below.

Campylobacteriosis in Humans
The illness is a gastrointestinal infection caused by the bacterium Campylobacter jejuni or less commonly C. coli. The minimum infectious dose required to cause foodborne disease is known to be quite low and is probably fewer than 500 organisms ingested. Babies, young children and the immuno-compromised are most susceptible, although young adults in developed countries also have an increased incidence of the disease. Symptoms vary from mild to severe with diarrhoea which may be bloody, fever, nausea, abdominal cramps and pain and (seldom) vomiting. In previously healthy adults, illness usually lasts 2-10 days, but minor relapses may occur in up to 25% of patients (Skirrow & Blaser, 2000). The faeces often remain culture-positive for 2-7 weeks after acute infection, unless the illness has been treated with antibiotics, but long-term carriage is rare.

The disease is usually self-limiting, so antibiotic treatment is only indicated in severe cases (Engberg et al, 2001, Guerrant et al, 2001). Complications such as septicaemia, reactive arthritis and Guillain-Barré syndrome (an ascending paralysis) may occur in a low proportion of cases.

In humans, transmission is predominantly via ingestion of contaminated food or water. The main route is thought to be eating undercooked poultry or food cross-contaminated by raw, infected food. Person to person transmission is known but thought to be rare. Household pets with diarrhoea have occasionally been shown to be the source of infection for humans.

The Disease in Animals
C. jejuni causes abortion in sheep, goats and cattle. Dogs and cats can also suffer from campylobacter diarrhoea and they transmit it to humans by direct contact or if hygiene is poor.
Reservoirs of Infection
Chickens, turkeys and raw milk and untreated water are the main sources of infection. Healthy pigs, cattle, dogs, cats and wild birds are also sources. Surface waters such as rivers, lakes, etc. are often contaminated by animal and bird faeces and inadequately chlorinated water supplies have been shown as secondary causes of large outbreaks of campylobacteriosis.
Raw Food Material Likely to be Contaminated
Chicken, turkey and other poultry are likely to be contaminated; less commonly pork, beef and lamb. Raw milk (or inadequately pasteurised milk) have caused a number of outbreaks involving large numbers of people, although outbreaks of campylobacteriosis are relatively rare, with most cases seeming to be sporadic.

Survival of Campylobacter Campylobacters do not survive well in food processing environments but they do survive for several months in frozen minced meat and poultry, although freezing kills a substantial proportion of the vegetative cells, and has been used to reduce numbers in raw poultry meat.

Campylobacters are heat-sensitive: for example a ten-fold reduction in count takes approximately 45 seconds at 60º C. Campylobacters are also very sensitive to drying. There is some evidence that campylobacters may survive in a viable but non-culturable form, but the role of this form in transmission is not known. Although campylobacters do not multiply in foods stored at temperatures below 30OC, they may survive for long periods. Survival is better at chill temperatures than it is at ambient temperatures. It is therefore vital to keep campylobacters out of all chilled foods. Irradiation readily destroys campylobacters and could provide a control measure for the future.

Growth Characteristics of Campylobacters
The campylobacters that cause enteritis in man will not grow below 30º C and so they will not multiply on chilled food or on ambient-stable foods stored below 30º C. The optimum growth temperature range of these strains is 37-42 ºC and the maximum is 47 ºC. Campylobacters are acid sensitive and will not grow below pH 4.9. C. jejuni grows best at pH 6.5-7.5 and has a pH range of 4.9-9. They are very sensitive to salt; 2% salt is sufficient to inhibit them, even under otherwise optimal growth conditions.
Management of Food Handlers
If a food handler is shown to have campylobacteriosis, then he/she must be excluded from work whilst symptoms persist. Such a person may return to work provided that the bowel habit has returned to normal for 48 hours, either spontaneously or following cessation of treatment with anti-diarrhoeal drugs, that there has been no vomiting for 48 hours once any treatment has ceased, and that good hygiene practice, particularly handwashing, is observed (DH, 1995; Salmon, 2004).
Implications for the Food Industry
C. jejuni and C. coli must be anticipated as transient contaminants on all food contact surfaces and food processing equipment used for raw food materials, especially raw poultry. On present evidence, the risk of transmission by factory heat processed foods is very low. Certainly, it is very much lower than that from salmonellae for the following reasons: campylobacters do not
easily multiply in food and certainly do not grow below 30 ºC; thus the organisms are unlikely to ‘build up’ in a factory processing area.

Campylobacters appear to die rapidly on dry foods; this is in contrast to the prolonged survival of salmonellae in dried materials. The frequency of human carriers is low and long term carriers are uncommon (Milk may contain campylobacters as a consequence of faecal contamination on the farm. The organism will not survive correct pasteurisation procedures, and outbreaks of human infection associated with milk have generally involved consumption of unpasteurised (or inadequately pasteurised) milk or milk contaminated after pasteurisation. Post-pasteurisation contamination of milk has occurred from bird-pecked milk delivered door-to-door, but this is now rare, as this method of delivery diminishes. Other dairy products do not pose a threat because of the organisms’ low resistance to reduced pH or water activity.

Control
Campylobacter jejuni is readily killed by thorough cooking and by pasteurisation, so the main threat is from contaminated ‘high risk’ products particularly raw poultry meat. In this respect, the application of HACCP principles to production, processing and distribution of poultry products is important. In the UK the Food Standards Agency aims to support measures to reduce the incidence of campylobacters on retail poultry.

Hygiene measures and biosecurity can be used to reduce the incidence of the organisms in/on poultry that is reared intensively (but not poultry reared outdoors) on the farm. Controls and decontamination during processing can reduce the numbers of campylobacters on carcasses, but at present raw poultry is likely to be contaminated with these bacteria.

Cross-contamination from raw poultry can occur in household kitchens and in commercial catering, and has been shown to be an important factor in about 30% of outbreaks (ILSI, 2006). Consumers are advised not to wash poultry carcasses or joints, as this process will spread contaminated water droplets in the kitchen. To minimise contamination of the kitchen environment and cross-contamination of foods, separate surfaces should be used for raw poultry and for other foods, work surfaces should be cleaned thoroughly, re-usable dishcloths should not be used, and people should wash utensils etc and wash their hands thoroughly and dry them thoroughly after handling raw meat or poultry.

Consumers should be aware of the risk of eating raw or under-cooked food of animal origin; they should be advised to avoid unpasteurised milk, to cook meat/poultry thoroughly and to obtain water only from approved sources. How to use good hygiene to prevent cross contamination from surfaces and utensils used in the preparation of raw poultry in the kitchen must also be highlighted through better education in safe food handling.

Contact with the faeces of diarrhoeal pets should be avoided and, if possible, animals should be kept out of the kitchen.