Abstract
Small mammals are known to carry Campylobacter spp.; however, little is known about the genotypes and their role in human infections. We studied intestinal content from small wild mammals collected in their natural habitats in Finland in 2010–2017, and in close proximity to 40 pig or cattle farms in 2017. The animals were trapped using traditional Finnish metal snap traps. Campylobacter spp. were isolated from the intestinal content using direct plating on mCCDA. A total of 19% of the captured wild animals (n = 577) and 41% of the pooled farm samples (n = 227) were positive for C. jejuni, which was the only Campylobacter species identified. The highest prevalence occurred in yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) which carried Campylobacter spp. in 66.3 and 63.9% of the farm samples and 41.5 and 24.4% of individual animals trapped from natural habitats, respectively. Interestingly, all house mouse (Mus musculus) and shrew (Sorex spp.) samples were negative for Campylobacter spp. C. jejuni isolates (n = 145) were further characterized by whole-genome sequencing. Core genome multilocus sequence typing (cgMLST) clustering showed that mouse and vole strains were separated from the rest of the C. jejuni population (636 and 671 allelic differences, 94 and 99% of core loci, respectively). Very little or no alleles were shared with C. jejuni genomes described earlier from livestock or human isolates. FastANI results further indicated that C. jejuni strains from voles are likely to represent a new previously undescribed species or subspecies of Campylobacter. Core-genome phylogeny showed that there was no difference between isolates originating from the farm and wild captured animals. Instead, the phylogeny followed the host species-association. There was some evidence (one strain each) of livestock-associated C. jejuni occurring in a farm-caught A. flavicollis and a brown rat (Rattus norvegicus), indicating that although small mammals may not be the original reservoir of Campylobacter colonizing livestock, they may sporadically carry C. jejuni strains occurring mainly in livestock and be associated with disease in humans.
Highlights
Campylobacter spp., especially C. jejuni and C. coli, are common causes of gastroenteritis in humans globally, campylobacteriosis being the most frequently reported zoonosis in the EU area (EFSA and ECDC, 2019)
M. glareolus, Sorex araneus, and Microtus agrestis were common among both in-farm caught samples and those collected from natural habitats throughout Finland
Seven out of the 147 C. jejuni isolates from mice, rats, or voles matched a previously defined 7-gene multilocus sequence typing (MLST) profile, most of which were associated with a clonal complex (CC): sequence type (ST) 1304 (n = 3, ST-1304 CC), ST 2219 (n = 1, ST-45 CC), ST 3704 (n = 1), ST 4791 (n = 1, ST-45 CC), or ST 8562 (n = 1) (Supplementary Dataset 1)
Summary
Campylobacter spp., especially C. jejuni and C. coli, are common causes of gastroenteritis in humans globally, campylobacteriosis being the most frequently reported zoonosis in the EU area (EFSA and ECDC, 2019). Previous research has found a possible link between the presence of rodents, or the absence of control thereof, and higher Campylobacter prevalence in chicken flocks (Kapperud et al, 1993; Berndtson et al, 1996; Sommer et al, 2013; Agunos et al, 2014; Allain et al, 2014; Torralbo et al, 2014) Several rodent species such as the bank vole (Myodes glareolus), yellow-necked mouse (Apodemus flavicollis), house mouse (Mus musculus), and brown rat (Rattus norvegicus) have been shown to carry Campylobacter species in their intestinal tracts (Fernie and Healing, 1976; Healing and Greenwood, 1991; Meerburg et al, 2006; Backhans et al, 2013; Lõhmus and Albihn, 2013). In particular, M. musculus and R. norvegicus are species that commonly live in close proximity to human habitation, and M. glareolus and A. flavicollis frequently invade human settlements at the onset of winter
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