Research seminar 10.3.2009: Campylobacters in cattle and broilers


<div>Campylobacteriosis is the most commonly reported bacterial enteric infection worldwide. The human cases are usually sporadic, and most of them are caused by Campylobacter jejuni. In Finland, about 30% of infections are domestically acquired, but in the summer months the proportion of domestic infections is nearly 70%. The incidence peaks annually in July-August. </div>

Researcher Marjaana Hakkinen 
Microbiology Research Unit, Evira, Helsinki
Evira/Helsinki Viikki, Auditorium C111 Kalevi
Tue 10.3.2009, 3:00 – 4:00 pm

Poultry is considered the most important source of campylobacters in sporadic infections. On the other hand, evidence from recent studies suggests that poultry is less significant than is generally thought, and also other animals can be considered notable reservoirs of campylobacters. Cattle are well-known carriers of campylobacters, but these bacteria are rarely detected in beef. Instead, outbreaks attributed to consumption of unpasteurized milk have been reported from several countries.

The campylobacter monitoring of chicken slaughter batches is compulsory since June 2004 in Finland. All slaughter batches from June to October are sampled, and during the rest of the year, sampling is performed according to a specific sampling plan. The campylobacters isolated by the slaughterhouse laboratories are identified at Evira.

In a project of Evira and the University of Helsinki, we examined the prevalence of campylobacters in chicken slaughter batches, and the genotypes of campylobacters isolated from chicken rearing halls and slaughter batches were compared with PFGE, as well as the genotypes of isolates from breeders and their progeny. The campylobacters in cattle were examined in an extensive slaughterhouse survey, and on three dairy cattle farms. Comparison of genotypes of C. jejuni isolates from chickens, cattle and domestically acquired human cases in summer 2003 was carried out in co-operation with THL (formerly KTL) and the poultry industry.

C. jejuni is the most common campylobacter species in chickens and cattle. During the five-year monitoring, the prevalence of campylobacters in chicken slaughter batches has consistently peaked in July-August, but even then it has been lower than in most other countries. Usually only one campylobacter genotype is detected. Furthermore, a proportion of birds can be campylobacter-negative in a campylobacter-positive slaughter batch. The transmission of campylobacters from breeders to chickens seems unlikely.

The prevalence of campylobacters in Finnish cattle was also lower than in many other countries, and the occurrence of campylobacters in carcasses was rare. The Finnish beef can be considered a minor source of campylobacters. In the dairy cattle study, the same genotypes of C. jejuni persisted in the herds throughout the study, and new types occurred only occasionally. The resistance to campylobacter colonisation seemed to vary among animals. Campylobacters were not detected in milk samples.

More than half of the human C. jejuni isolates in summer 2003 represented identical genotypes with chicken and cattle isolates. Less than one third of the human cases were temporally associated with campylobacter isolates from chickens. Chickens can be considered the most important single source in domestically acquired sporadic infections in Finland. The significance of cattle can be notable especially in rural areas, where the environmental routes may be more important than food in transmission of campylobacters.

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