Abstract
Chlamydial infections in pigs are associated with respiratory disease, diarrhea, conjunctivitis and other pathologies. The aim of this study was to define the prevalence of Chlamydiaceae in Swiss fattening pigs by applying sensitive and specific detection methods and to correlate prior antibiotic treatment and farm related factors with differences in prevalence. Conjunctival and fecal swabs were collected from 636 pigs in 29 Swiss fattening pig farms with and without antibiotic treatment, at the beginning and the end of the fattening period. The swabs were screened by real-time PCR for Chlamydiaceae. For the chlamydial detection and species-identification, a DNA-microarray analysis was performed. All farms were positive for Chlamydiaceae with 94.3 and 92.0% prevalence in fecal swabs as well as 45.9 and 32.6% in conjunctival swabs at the first and second time points, respectively. Antibiotic treatment could not clear the infection on herd level. Potential contact with wild boars was a significant risk factor, while hygiene criteria did not influence chlamydial prevalence. A correlation of chlamydial positivity to diarrhea, but not to conjunctivitis was evident. Chlamydia suis was the predominant species. Mixed infections with C. suis and C. pecorum were common, with a substantial increase in C. pecorum positivity at the end of the fattening period, and this finding was associated with ruminant contact. C. abortus was detected in one conjunctival swab. In this study, C. suis inhabited the intestinal tract of nearly all examined pigs, implying a long-term infection. C. pecorum was also common and might be transmitted to pigs by ruminants.
Highlights
Members of the Chlamydiaceae are known to cause a broad spectrum of diseases in numerous vertebrate host species worldwide
There are eleven species included in the Genus Chlamydia, four of which have been documented in pigs: Chlamydia suis, Chlamydia pecorum, Chlamydia abortus and Chlamydia psittaci, with C. suis being the most important
94.3% and in the second sampling 92.0% of the fecal swabs were positive for Chlamydiaceae, as well as 45.9 and 32.6% of the conjunctival swabs, respectively
Summary
Members of the Chlamydiaceae are known to cause a broad spectrum of diseases in numerous vertebrate host species worldwide. There are eleven species included in the Genus Chlamydia, four of which have been documented in pigs: Chlamydia suis, Chlamydia pecorum, Chlamydia abortus and Chlamydia psittaci, with C. suis being the most important. Chlamydiaceae in pigs are associated with disorders like conjunctivitis, pneumonia, pericarditis, polyarthritis, polyserositis, enteritis and reproductive problems of sows and boars; infections are often asymptomatic and routine diagnostics usually do not include chlamydiae [1]. In fecal samples from pigs, C. suis is the most frequently found chlamydial species [7,13]. C. suis is most often found in pigs, many other animal species like cattle, horses, frogs and cats can become naturally infected [14,15,16,17]. C. suis DNA was found in conjunctival swabs of employees in a Belgian pig slaughterhouse [19,20]
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