Dynamics of Campylobacter colonization of a natural host, Sturnus vulgaris (European starling)

Abstract

Wild European Starlings (Sturnus vulgaris) shed Campylobacter at high rates, suggesting that they may be a source of human and farm animal infection. A survey of Campylobacter shedding of 957 wild starlings was undertaken by culture of faecal specimens and genetic analysis of the campylobacters isolated: shedding rates were 30.6% for Campylobacter jejuni, 0.6% for C. coli and 6.3% for C. lari. Genotyping by multilocus sequence typing (MLST) and antigen sequence typing established that these bacteria were distinct from poultry or human disease isolates with the ST-177 and ST-682 clonal complexes possibly representing starling-adapted genotypes. There was seasonal variation in both shedding rate and genotypic diversity, both exhibiting a maximum during the late spring/early summer. Host age also affected Campylobacter shedding, which was higher in younger birds, and turnover was rapid with no evidence of cross-immunity among Campylobacter species or genotypes. In nestlings, C. jejuni shedding was evident from 9 days of age but siblings were not readily co-infected. The dynamics of Campylobacter infection of starlings differed from that observed in commercial poultry and consequently there was no evidence that wild starlings represent a major source of Campylobacter infections of food animals or humans.

Fig. 1

The isolation rates of C. jejuni, C. coli and C. lari during the course of a year. Samples were collected only in the months that are shown.

Fig. 2

The distinct clustering of C. jejuni isolates from starlings. A. A Clonal Frame analysis demonstrating that the majority of C. jejuni isolates from starlings cluster separately from C. jejuni isolates representative of the diversity isolated from human disease and farm animals. Clusters that can be related to clonal complexes are indicated. B. The probabilistic assignment of the same C. jejuni allelic profiles to host source using Structure. Each allelic profile is represented by a vertical bar, showing the estimated probability that it comes from each of the sources identified. Key: starling (red), ruminant (green), environment (blue), human disease (yellow), poultry (pink).

Fig. 3

The C. jejuni clonal complexes isolated during 2004, by month. ST-574 and ST-283 were isolated in June and accounted for only 0.5% of the isolates each.