Wild and domestic birds are the main reservoirs of C. jejuni and C. coli. However, other primary reservoirs have been described: cattle, pigs (essentially C. coli) and small ruminants, as well as pets (cats and dogs).
Although certain species of Campylobacter are pathogenic for animals and are implicated in problems such as infecundity or abortion, C. jejuni and C.coli are considered low- or non-pathogenic for animals.
The main route for transmission of Campylobacter to humans is through food, via contaminated products, including poorly treated drinking water. Direct transmission through another person, an infected animal (especially a pet) or a contaminated carcass is likely to occur more frequently in certain exposed populations (breeders, veterinarians, slaughterhouse workers, sewer workers, etc.).
The most frequently observed manifestation of the disease in humans is severe enteritis (symptoms: diarrhoea in 85% of cases, abdominal pain in 79%, bloody stools in 15%, fever in 50%, headache in 41%, vomiting in 15%) caused by intestinal infection.
The infection can be complicated (in less than 1 case out of 1000) by bacteraemia, secondary localisations and a post-infectious syndrome (less than one case in 1000). Infected individuals do however remain contagious for an average period of 38 days (70 days maximum).
Exceptionally, C. jejuni can cause post-infectious arthritis, hepatic or renal inflammation, and most notably Guillain-Barré syndrome, which brings about temporary paralysis of the peripheral nervous system. This syndrome is considered very serious, and can be fatal in up to 2-3% of cases, with major neurological sequelae in 15-20% of cases.
Anyone can develop campylobacteriosis. However, the propensity for developing the more severe forms of the disease is higher in:
- elderly people;
- people previously having undergone digestive surgery;
- individuals receiving peritoneal dialysis (kidney failure);
- people with a weakened immune system (on immunodepressants or suffering from an auto-immune disease such as HIV infection).
Infection status and frequently contaminated foods
Since the early 2000s, the annual count (incidence) of human campylobacteriosis cases is usually higher than 40 identified cases per 100 000 inhabitants (mostly in summer), in the European Union. In France, the National centre of reference (NCR) reported 6.2 identified cases per 100 000 inhabitants in 2009, due to a very high rate of under-reporting by doctors.
Most of the cases described were isolated from each other (sporadic).
Foodborne illness outbreaks linked to Campylobacter are often correlated with consumption of contaminated water, raw milk, meat or poultry.
Contamination transfer via cutting boards or knives used to handle raw poultry and consumption of insufficiently cooked meat (poultry, beef, pork) appear to be the main risk factors.
Due both to the existence of animal reservoirs and the many possibilities of contamination transfer, many types of foods, including water, can be contaminated, although meat and meat-based products should be considered as the primary source.
Contamination control methods
In general, freezing halts the growth of Campylobacter and most likely destroys a small amount of the bacterial population, especially in liquids. However, these bacteria are able to survive at refrigerator temperatures (0 to 10°C).
Campylobacter are also highly sensitive to heat: treatment at temperatures over 65°C are considered sufficient to destroy them regardless of the medium (liquid or solid).
It should be noted that these bacteria show no particular resistence to salt or acids.
The risks of campylobacteriosis can be greatly reduced by adopting good hygiene practices in the home. It is therefore essential to:
- wash your hands after handling raw meat;
- use one cutting board (wood or plastic) for raw meats and fish, and a separate one for other foods;
- carefully wash all cutting boards, platters and utensils used for preparing and seasoning raw meat before reusing them;
- cook butchery meats and poultry sufficiently (>65°C at the centre), especially when barbecuing. For poultry, the joint between the thigh and the drumstick should not be pink and no blood should be visible;
- follow the rules for proper hygiene when handling meats and during their preparation and consumption;
- never eat raw poultry (i.e. carpaccio-style).
The Ploufragan-Plouzané Laboratory (ANSES) is the official National Reference Laboratory (NRL) for Campylobacter.
The European Union Reference Laboratory (EURL) for Campylobacter (network including the European NRLs, among others) is hosted by the National Veterinary Institute (SVA) in Uppsala, Sweden.
Until now, no specific regulations on the detection of Campylobacter in end-product foodstuffs have been issued, including in the recent EU laws.
The NRL has also published Opinions and Reports on the risks of animal campylobacteriosis (in ruminants and poultry).