Prevalence of Chlamydial Infections in Fattening Pigs and Their Influencing Factors

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.

Selective Pressure Promotes Tetracycline Resistance of Chlamydia Suis in Fattening Pigs

“…Each pig was sampled at the beginning (first sampling) and end (second sampling) of the fattening period (total fattening period of around 3 months). Two conjunctival (both eyes, pooled) and two fecal swabs (FLOQSwabs ® , Copan Italia, Brescia, Italy) were collected per sampling (two timepoints), of which one swab per anatomical site was used for DNA extraction and the other was stored at—80°C in sucrose phosphate transport medium, resulting in a total of eight flocked swabs per pig [9]. …”

“…suis is not considered a primary pathogen for pigs, but it has been associated with several disease complexes including conjunctivitis as well as reproductive disorders, and cases of diarrhea within the herd related to a high C . suis prevalence [9, 10]. The tetracycline resistance found in C .…”

“…In this study, we used 158 swab samples from a vast collection of over 2000 fecal and conjunctival swabs originating from 29 farms [9]. We found that 1) the estimated number of gene copies in a clinical sample by real-time PCR is a good predictor to assess successful isolation, and 2) isolation from conjunctival swabs is far less successful compared to fecal samples suggesting that fecal contamination rather than actual conjunctival infection occurred.…”

Water-filtered infrared A reduces chlamydial infectivity in vitro without causing ex vivo eye damage in pig and mouse models

“…C. suis is primarily known to inapparently infect the porcine gastrointestinal tract with a prevalence of up to 90 % in fattening pigs (12). Together with C. trachomatis, C. suis belongs to the obligate intracellular and Gram-negative bacterial family Chlamydiaceae, which is characterized by a unique biphasic lifecycle consisting of infectious elementary bodies (EBs) and intracellular, dividing reticulate bodies (RBs) (12,13).…”

“…C. suis is primarily known to inapparently infect the porcine gastrointestinal tract with a prevalence of up to 90 % in fattening pigs (12). Together with C. trachomatis, C. suis belongs to the obligate intracellular and Gram-negative bacterial family Chlamydiaceae, which is characterized by a unique biphasic lifecycle consisting of infectious elementary bodies (EBs) and intracellular, dividing reticulate bodies (RBs) (12,13). Alarmingly, mixed infections with C. trachomatis and C. suis have been reported in Nepalese trachoma patients, while co-infection of the two closely related species generated tetracycline resistant C. trachomatis strains in vitro (14,15).…”