Detection and quantification of 14 Campylobacter species in pet dogs reveals an increase in species richness in feces of diarrheic animals

Abstract

Background: The genus Campylobacter includes many species, some of which are known human and animal pathogens. Even though studies have repeatedly identified domestic dogs as a risk factor for human campylobacteriosis, our understanding of Campylobacter ecology in this reservoir is limited. Work to date has focused primarily on a limited number of species using culture-based methods. To expand our understanding of Campylobacter ecology in dogs, a collection of fecal samples from 70 healthy and 65 diarrheic pet dogs were examined for the presence and levels of 14 Campylobacter species using quantitative PCR.

Results: It was found that 58% of healthy dogs and 97% of diarrheic dogs shed detectable levels of Campylobacter spp., with C. coli, C. concisus, C. fetus, C. gracilis, C. helveticus, C. jejuni, C. lari, C. mucosalis, C. showae, C. sputorum and C. upsaliensis levels significantly higher in the diarrheic population. Levels of individual Campylobacter species detected ranged from 103 to 108 organisms per gram of feces. In addition, many individual samples contained multiple species of Campylobacter, with healthy dogs carrying from 0-7 detectable species while diarrheic dogs carried from 0-12 detectable species.

Conclusions: These findings represent the largest number of Campylobacter species specifically tested for in animals and is the first report to determine quantifiable levels of Campylobacter being shed from dogs. This study demonstrates that domestic dogs can carry a wide range of Campylobacter species naturally and that there is a notable increase in species richness detectable in the diarrheic population. With several of the detected Campylobacter species known or emerging pathogens, these results are relevant to both ecological and public health discussions.

Figure 1

Distribution and levels of Campylobacter detected in feces from healthy and diarrheic dogs. Rows represent a single fecal sample while columns represent individual species of Campylobacter assayed. Coloured boxes indicate the target copies per gram of feces detected. The lower detection limit of the assays is 10³ copies/g of feces [21].

Figure 2

Species richness of Campylobacter detected in healthy and diarrheic dog samples.

Figure 3

Total bacterial 16S rRNA gene copies detected per gram of healthy and diarrheic dog feces (n = 20 for each population). Box plots show the 25^th to 75^th percentile range of the data within the box, with the median indicated with a line in the box. The whiskers represent the remaining quartile ranges, with outliers indicated as dots.