Involvement of multiple Chlamydia suis genotypes in porcine conjunctivitis

Area of Science:

• Veterinary Microbiology
• Animal Ophthalmology
• Molecular Epidemiology

Background:

• Chlamydia suis is frequently implicated in pig diseases, especially ocular infections.
• Conjunctivitis is a common ailment in commercial pig farming, impacting animal health and productivity.

Purpose of the Study:

• To investigate the genetic diversity and prevalence of Chlamydia suis in pig conjunctivitis cases in Japan.
• To identify the co-occurrence of multiple Chlamydia suis strains within individual infections and farms.

Main Methods:

• Ocular swabs from conjunctivitis cases on five Japanese pig farms were analyzed.
• Chlamydia positivity was determined using direct fluorescent antibody tests and PCR targeting 16S-23S rRNA ISR and ompA genes.
• Genetic analysis of PCR amplicons identified sequence variants and phylogenetic relationships.

Main Results:

• Chlamydia suis was detected in 40.5% of cases by DFA and 59.5% by PCR.
• Significant genetic diversity was observed, with nine 16S-23S rRNA ISR variants and 20 ompA variants identified.
• Concurrent infections with multiple C. suis ompA (36.4%) and 16S-23S rRNA ISR (9.1%) sequence types were common.
• Multiple genotypes circulated in four of five farms, with Japanese strains showing close relation to international isolates.

Conclusions:

• This study is the first to demonstrate the association of multiple and genetically diverse Chlamydia suis strains in pig conjunctivitis.
• The findings highlight the complex epidemiology of C. suis infections in pigs and suggest widespread circulation of genetically varied strains globally.