Within the genera Chlamydia, the development of refined diagnostic techniques has allowed the identification of four species that are capable of infecting pigs, according to Stina Englund at Sweden's National Veterinary Institute and co-authors there and at Stavby–Väsby and the Swedish University of Agricultural Sciences in Uppsala.

In a paper published recently in BMC Veterinary Research, they explain that the Chlamydiaceae family, including the genera, Chlamydia, is a well-recognised cause of disease in many animal species including cats, ruminants, birds and humans. Within the genus, nine distinct species have been identified. Of these, four have been described in pigs – C. abortus, C. psittaci, C. pecorum and C. suis – and they have been linked to reproductive disorders, conjunctivitis, enteritis, pneumonia, polyarthritis, pleuritis and polyserositis.

Because the epidemiology, clinical and zoonotic impacts of these species in pigs are not well understood, they set up a study aimed to investigate the presence of Chlamydia spp. in the intestines of growing pigs and in conjunctival swabs from finisher pigs, and relate the findings to clinical signs.

By histology, 20 of 48 pigs had intestinal lesions that may have been consistent with chlamydial infection.

By PCR, 46 of the pigs were positive whereas two samples were inhibited. Sequencing of 19 DNA extracts identified these as Chlamydia suis.

By immunohistochemistry, 32 of 44 samples were positive and a significant relationship was detected between macroscopically visible intestinal lesions and a high degree of infection.

By real-time PCR, a significant difference was detected between pigs with and without conjunctivitis when a Ct value of 36 was employed but not when a Ct value of 38 was employed.

C. suis was demonstrated in most samples but overall, no correlation with clinical signs was detected, according to Englund and co-authors. However, they did note a correlation between samples with a high degree of infection and the presence of clinical signs.

The Swedish group suggest it is possible that the intensive pig production systems studied might predispose for the transmission and maintenance of the infection, thus increasing the infectious load and the risk for disease in the pig.

Reference

Englund S., C.H. af Segerstad, F. Arnlund, E. Westergren and M. Jacobson. 2012. The occurrence of Chlamydia spp. in pigs with and without clinical disease. BMC Veterinary Research, 8:9. doi:10.1186/1746-6148-8-9

Further Reading

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You can view the full report (as a provisional PDF) by clicking here.

Further Reading

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Find out more information on endometritis and vulval discharge syndrome, which have been linked to Chlamydia, by clicking here.

March 2012