Campylobacter jejuni in black-headed gulls (Larus ridibundus): prevalence, genotypes, and influence on C. jejuni epidemiology

Abstract

Campylobacteriosis is a zoonotic disease in which birds have been suggested to play an important role as a reservoir. We investigated the prevalence of Campylobacter jejuni subsp. jejuni in black-headed gulls (Larus ridibundus) in southern Sweden with the aim of examining the nature of C. jejuni infection in this bird species. Birds were sampled in four sampling series each year during 1999 (n = 419) and 2000 (n = 365). Longitudinally sampled C. jejuni isolates from individual gulls were subjected to macrorestriction profiling (MRP) by pulsed-field gel electrophoresis to investigate the genotypical stability during the natural course of infection. Furthermore, a subset (n = 76) of black-headed gull isolates was compared to isolates from broiler chickens (n = 38) and humans (n = 56) originating from the same geographic area. We found a pronounced seasonal variation in C. jejuni carriage, with the highest rates found in late autumn. MRP similarities were higher between isolates of human and broiler chicken origin, than between those of wild bird origin and either of the other two hosts. However, identical MRPs were found in two gull isolates and one human isolate after digestion with two restriction enzymes, strongly indicating that they may have been colonized by the same clone of C. jejuni. The MRPs most prevalent in gull isolates did not occur among isolates from humans and broiler chickens, suggesting the existence of a subpopulation of C. jejuni adapted to species-specific colonization or environmental survival.

FIG. 1.

Prevalence of C. jejuni at different sampling series. N, total number of samples from adult birds; n, total number of samples from juvenile birds.

FIG. 2.

Examples of SmaI MRPs of C. jejuni isolates from resampled black-headed gulls. Sampling dates and bird numbers (above braces) corresponding to numbers in Table 2 are given above the gel. Superscripts indicate number of colonies from each sample with the corresponding MRP. M, molecular mass marker (λ ladder).

FIG. 3.

Dendrogram of SmaI MRPs of C. jejuni from black-headed gulls (G), broiler chickens (B), and humans (H). Cluster analysis was performed by using GelCompare version 4.0 with the unweighted pair group method with arithmetic mean (UPGMA). Gray boxes behind MRPs indicate host origin of isolates and a black bar at the bottom indicates a C. coli isolate used as the out-group. A dashed line indicates the demarcation between clusters A and B. For definition of a1, a2, b1, and b2, see the text.