Abstract
Chlamydia suis is an important, highly prevalent, and diverse obligate intracellular pathogen infecting pigs. In order to investigate the prevalence and diversity of C. suis in the U.S., 276 whole blood samples from feral swine were collected as well as 109 fecal swabs and 60 whole blood samples from domestic pigs. C. suis-specific peptide ELISA identified anti-C. suis antibodies in 13.0% of the blood of feral swine (26/276) and 80.0% of the domestic pigs (48/60). FRET-qPCR and DNA sequencing found C. suis DNA in 99.1% of the fecal swabs (108/109) and 21.7% of the whole blood (13/60) of the domestic pigs, but not in any of the assayed blood samples (0/267) in feral swine. Phylogenetic comparison of partial C. suis ompA gene sequences and C. suis-specific multilocus sequencing typing (MLST) revealed significant genetic diversity of the C. suis identified in this study. Highly genetically diverse C. suis strains are prevalent in domestic pigs in the USA. As crowding strongly enhances the frequency and intensity of highly prevalent Chlamydia infections in animals, less population density in feral swine than in domestic pigs may explain the significantly lower C. suis prevalence in feral swine. A future study is warranted to obtain C. suis DNA from feral swine to perform genetic diversity of C. suis between commercial and feral pigs.
Highlights
Obligate intracellular bacteria of genus Chlamydia contains 13 recognized species (C. abortus, C. avium, C. caviae, C. felis, C. gallinacea, C. muridarum, C. pecorum, C. pneumoniae, C. poikilotermis, C. psittaci, C. serpentis, C. suis, and C. trachomatis) [1,2]
The pig is the only known natural host of C. suis, and C. suis infections in pigs have been reported to be associated with a variety of clinical signs including conjunctivitis, rhinitis, pneumonia, enteritis, and reproductive disorders [4,5,6,7]
In the state of infections in pigs have been reported to be associated with a variety of clinical signs including conjunctivitis, rhinitis, pneumonia, enteritis, and reproductive disorders [4,5,6,7]
Summary
Obligate intracellular bacteria of genus Chlamydia contains 13 recognized species (C. abortus, C. avium, C. caviae, C. felis, C. gallinacea, C. muridarum, C. pecorum, C. pneumoniae, C. poikilotermis, C. psittaci, C. serpentis, C. suis, and C. trachomatis) [1,2]. In a similar trend as indicated by peptide-ELISA, C. suis DNA was found in 21.7% (13/60) of the whole blo3oodf 1o0 f domestic pigs, but not in any of the whole blood samples from feral swine (0/276) (Figure 1B). While fecal swabs from feral pigs were not available for FRET-qPCR in this study, peptide ELISA showed a positive but much lower anti-C. suis antibody in feral swine than in domestic pigs (13.0% vs 80.0%, respectively; p < 10−4; Figure 1A). The prevalence of C. suis DNA in fecal swabs was significantly higher when compared to those taken from whole blood samples (Figure 1) This result is most likely due to the gastrointestinal tract being the primary site of infection and chlamydial replication. Molecular typing of detected strains suggests that C. suis in the USA. are genetically diverse as the global diversity of this pathogen reported in other countries
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