HEALTH TOPICS A TO Z

The agent

Campylobacters are bacteria that are a major cause of diarrhoeal illness in humans and are generally regarded as the most common bacterial cause of gastroenteritis worldwide. In developed and developing countries, they cause more cases of diarrhoea than, for example, foodborne Salmonella bacteria. In developing countries, Campylobacter infections in children under the age of two years are especially frequent, sometimes resulting in death. In almost all developed countries, the incidence of human campylobacter infections has been steadily increasing for several years. The reasons for this are unknown.

Campylobacters are mainly spiral-shaped, S-shaped or curved, rod-shaped bacteria. There are 16 species and six subspecies assigned to the genus Campylobacter, of which the most frequently reported in human disease are C. jejuni (subspecies jejuni) and C. coli. C. laridis and C. upsaliensis are also regarded as primary pathogens, but are generally reported far less frequently in cases of human disease. Most species prefer a micro-aerobic (containing 3-10% oxygen) atmosphere for growth. A few species tend to favour an anaerobic environment, although they will grow under micro-aerobic conditions also.

The disease

• Campylobacteriosis is the disease caused by the presence of campylobacters. The onset of disease symptoms usually occurs two to five days after infection, but can range from one to ten days.
• The most common clinical symptoms of campylobacter infections include diarrhoea (frequently with blood in the faeces), abdominal pain, fever, headache, nausea, and/or vomiting. The symptoms typically last three to six days.
• A fatal outcome is rare and is usually confined to very young or elderly patients, or to those already suffering from another serious disease such as AIDS.
• Complications such as bacteremia, hepatitis, pancreatitis (infections of the blood, liver and pancreas respectively), and abortion have all been reported with various degrees of frequency. Post-infection complications may include reactive arthritis (painful inflammation of the joints which can last for several months) and neurological disorders such as Guillain-Barré syndrome, a polio-like form of paralysis that can result in respiratory and severe neurological dysfunction or death in a small, but significant, number of cases.
• The high incidence of campylobacter diarrhoea, as well as its duration and possible sequelae, makes it highly important from a socio-economic perspective.

Sources and transmission

• Campylobacters are widely distributed and occur in most warm-blooded domestic, production and wild animals. They are prevalent in food animals such as poultry, cattle, pigs, sheep, ostriches and shellfish; and in pets, including cats and dogs.
• The main route of transmission is generally believed to be foodborne, via undercooked meats and meat products, as well as raw or contaminated milk. The ingestion of contaminated water or ice is also a recognized source of infection.
• Campylobacteriosis is considered to be a zoonosis, a disease transmitted to humans from animals or animal products. In animals, campylobacters seldom cause disease.
• One of the major gaps in our knowledge at present is the relative contribution of each of the above sources to the overall burden of disease. Since common-source outbreaks account for a rather small proportion of cases, the vast majority of reports are made sporadically, with no easily discernible pattern. Estimation of the importance of all known sources is therefore extremely difficult. In addition, the wide occurrence of campylobacters also hinders the development of strategies to control campylobacters in the food supply "from farm to fork".

Control and prevention methods

• Treatment is not generally indicated, except electrolyte replacement and rehydration. Antimicrobial treatment (erythromycin, tetracycline, quinolones) is indicated in invasive cases or to eliminate the carrier state.
• The prevention of infection requires control measures at all stages of the food chain, from agricultural production on the farm, to processing, manufacturing and preparation of foods in both commercial establishments and the domestic environment.
• Specific intervention methods on the farm have been shown to reduce the incidence of campylobacter in poultry. Measures include enhanced biosecurity to avoid horizontal transmission of campylobacter from the environment to the flock of birds. This control option is feasible only where birds are kept in closed housing conditions.
• There are no proven intervention methods to reduce campylobacter in cattle farms. Prevention of the contamination of raw milk on the farm is not consistently possible; therefore, consumption of raw milk should be avoided.
• Good hygienic slaughtering practices will reduce contamination of carcasses by faeces, but will not guarantee the absence of campylobacter from meat and meat products. Education in hygienic handling of foods for abattoir workers and those involved in the production of raw meat is essential to keep microbiological contamination to a minimum.
• The only effective method of eliminating campylobacter from contaminated foods is to introduce a bactericidal treatment, such as heating (e.g. cooking or pasteurization) or irradiation.
• Preventive measures for campylobacter infection in the household kitchen are similar to those used against other foodborne bacterial diseases.
• In countries without adequate sewage disposal systems, faeces and articles soiled with faeces may need to be disinfected before disposal.

Recommendations for the public and travellers

• Make sure your food is properly cooked and still hot when served.
• Avoid raw milk and products made from raw milk. Drink only pasteurized or boiled milk.
• Avoid ice unless you are sure it is made from safe water.
• When the safety of drinking water is doubtful, boil it or if this is not possible, disinfect it with a reliable, slow-release disinfectant agent. These are usually available at pharmacies.
• Wash hands thoroughly and frequently using soap, in particular after contact with pets or farm animals, or after having been to the toilet.
• Wash fruits and vegetables carefully, particularly if they are eaten raw. If possible, vegetables and fruits should be peeled.
• WHO's brochure A Guide on Safe Food for Travellers gives practical advice for safeguarding health when travelling*.

Recommendations for food handlers

• Both professional and domestic food handlers should be vigilant during the preparation of food and should observe hygienic rules of food preparation.
• Professional food handlers who suffer from fever, diarrhoea, vomiting or visible infected skin lesions should report to their employer immediately.
• More information for food handlers is given in the WHO Guide on Hygiene in Food Service and Mass Catering Establishments (Document code: WHO/FNU/FOS/94.5).