Campylobacter jejuni and C. coli are the most frequent causes of bacterial gastroenteritis in Finland (www.ktl.fi/ttr). The number of laboratory-confirmed cases has nearly doubled over a 10-year period (2,197 cases in 1995 to 4,002 cases in 2005). Campylobacter species are frequently isolated from a wide variety of sources, including poultry, cattle, pigs, sheep, cats, dogs, wild birds, and water. Most Campylobacter infections are sporadic, and the relative contributions of different sources of infection remain unknown. Risk factors for Campylobacter infection, as identified by case-control studies, include eating or preparing raw or undercooked meat, especially chicken meat, drinking unpasteurized milk or untreated water, contact with domestic animals and pets, and foreign travel (14,18,26). A recent case-control study (19) revealed swimming in natural bodies of water to be a novel risk factor. In addition, eating undercooked meat and drinking from dug wells were independent risk factors for domestically acquired Campylobacter infections in Finland (19).Discriminatory typing methods for use in the study of the molecular epidemiology and population genetics of Campylobacter isolates are crucial to better understand the epidemiology and ecology of the organism. Once such information is obtained, it could be used to develop intervention strategies to limit the numbers of human infections. Dingle et al. (6) developed a multilocus sequence typing (MLST) scheme for C. jejuni, which has been shown to be a valuable tool for studying the diversity and population genetics of Campylobacter isolates.

A matched case-control study was conducted to study risk factors for domestically acquired sporadic Campylobacter infections in Finland. Swimming in natural sources of water was a novel risk factor. Eating undercooked meat and drinking dug-well water were also independent risk factors for Campylobacter infection.

This study aimed to investigate the occurrence of complications, especially musculoskeletal symptoms, after sporadic Campylobacter jejuni enteritis of domestic origin in Finland. This multi-centre cross-sectional study was conducted during a seasonal peak in 2002. Questionnaires were sent to Campylobacter-positive patients, representing different geographical areas, 2 months after collection of positive stool samples. Medical records were viewed in several cases. Besides antimicrobial susceptibility testing C. jejuni isolates were serotyped. A total of 235 patients (58%) returned the questionnaire and 201 C. jejuni-positive patients were finally included in the study. Musculoskeletal symptoms associated with C. jejuni enteritis were frequent (39%); joint pain was most commonly reported (81%). The incidence of reactive arthritis was 4% and that of Achilles enthesopathy and/or heel pain was 9%. Stomach ache during enteritis was associated with the later development of joint pain. Antimicrobial treatment was common but did not prevent complications.

The relative importance of different risk-factors for Campylobacter infections and the role of bacterial strain and host characteristics are uncertain. Swimming in natural sources of water was recently described as a novel independent risk-factor for domestically-acquired Campylobacter infections. The present study investigated exposure factors and demographical characteristics (collected in a questionnaire), and determined whether Campylobacter jejuni serotypes could be linked to each other or to the severity of the disease in domestically-acquired sporadic C. jejuni infections during a seasonal peak in Finland. Swimming was associated positively with an age of