Finnish cattle as reservoir of Campylobacter spp

Marjaana Hakkinen

Tutkimustuotos: OpinnäyteVäitöskirjaArtikkelikokoelma

Abstrakti

The reported incidence of human campylobacteriosis in Finland is higher than in most other European countries. A high annual percentage of sporadic infections is of foreign origin, although a notable proportion of summer infections is domestically acquired. While chickens appear to be a major source of campylobacters for humans in most countries, the prevalence of campylobacters is very low in chicken slaughter batches in Finland. Data on other potential animal reservoirs of human pathogenic campylobacters in Finland are scarce. Consequently, this study aimed to investigate the status of Finnish cattle as a potential source of thermophilic Campylobacter spp. and antibiotic-resistant Campylobacter jejuni for human sporadic campylobacter infections of domestic origin.

A survey of the prevalence of thermophilic Campylobacter spp. in Finnish cattle at twelve Finnish slaughterhouses from January to December 2003 yielded total campylobacter prevalences of 31.1% in faecal samples and 3.5% in carcass samples. Campylobacter jejuni was the most common species present in bovine samples. The prevalence of campylobacters was higher among beef cattle than among dairy cattle. Two predominant serotypes of faecal C. jejuni covered 52% of the samples. Genotyping with pulsed-field gel electrophoresis (PFGE) restriction yielded a high diversity of C. jejuni subtypes in cattle. Determining MICs of six antimicrobials among C. jejuni isolates yielded 9% of isolates resistant to at least one of the antimicrobials examined. No multiresistant isolates were found among the bovine C. jejuni strains.

In the one-year study of the occurrence of Campylobacter spp. among three Finnish dairy cattle herds diverse shedding patterns occurred among both cattle herds and individual animals. The level of excretion was usually low. The same few subtypes of C. jejuni were able to persist in a herd over the sampling period. The faecal colonisation of water troughs can maintain the colonisation during indoor housing, whereas at pasture, preventing access to natural waters can limit colonisation.

Comparison of C. jejuni isolates from humans, chickens and cattle included the design of primers for four new genetic markers, and the PCR examination of domestic human isolates from southern Finland in 1996, 2002 and 2003, chicken isolates from 2003, 2006 and 2007, and bovine isolates from 2003. The results revealed that bovine isolates differed significantly from human and chicken isolates.

The PFGE genotyping of C. jejuni isolates included a geographically representative collection of isolates from domestic sporadic human infections, chicken slaughter batches, and cattle during the seasonal peak of campylobacteriosis in the summer of 2003. The study determined that 55.4% of human isolates were indistinguishable from those of chickens and cattle. Temporal association between isolates from humans and chickens was possible in 31.4% of human infections. Approximately 19% of the human infections may have been associated with cattle. However, isolates from bovine carcasses and human cases represented different PFGE subtypes.

In conclusion, this study suggests that Finnish cattle is a constant reservoir of C. jejuni, the most important Campylobacter spp. in human enteric infections. Although the concentration of these organisms in bovine faeces appeared to be low, excretion can be persistent. The genetic diversity and presence or absence of marker genes support previous suggestions of host-adapted C. jejuni strains, and may indicate variations in virulence between strains from different hosts. In addition to chickens, Finnish cattle appeared to be an important reservoir and possible source of C. jejuni in domestic sporadic human infections. However, sources of campylobacters may differ between rural and urban areas in Finland, and in general, the transmission of C. jejuni of bovine origin probably occurs via other routes than food.
Alkuperäiskielienglanti
JulkaisupaikkaHelsinki
Kustantaja
Painoksen ISBN978-952-225-076-6
Sähköinen ISBN978-952-225-077-3
TilaJulkaistu - 2010
OKM-julkaisutyyppiG5 Tohtorinväitöskirja (artikkeli)

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