Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/1998
Publication Date: N/A
Interpretive Summary: Conjunctivitis is commonly seen in pigs of all ages. The disease is usually mild; but may become a clinical problem. The goal of this research was to determine whether a strain of Chlamydia trachomatis recovered from the eyes of growing and finishing pigs could cause conjunctivitis in gnotobiotic piglets. The isolate produced a mild to moderate conjunctivitis by 7 days. Many of the pigs still had histological lesions at 21 days post infection. The pigs in the study were housed under ideal conditions; the disease could be expected to be more severe in dusty or poor conditions often seen on farms. The results prove that chlamydia must be considered in cases of conjunctivitis in pig.
Technical Abstract: The objective of this study was to determine whether a chlamydial strain recovered from growing and finishing swine with conjunctivitis or keratoconjunctivitis could cause the same infections in gnotobiotic pigs. The strain shares biological characteristics with Chlamydia trachomatis. After propagation in Vero cells and preparation of the inoculum (10**7 inclusion-forming units/ml), chlamydial strain H7 was instilled into the ventral conjunctival sac (0.15 ml/sac) of 12 anesthetized 3-day-old gnotobiotic piglets. Four age-matched gnotobiotic piglets were anesthetized and sham=infected with uninfected cell culture lysates. None of the principal piglets developed clinical symptoms of conjunctivitis or keratoconjunctivitis. Pincipal piglets necropsied 7 days post infection (DPI) had histologic lesions of mild to moderate conjunctivitis; immunohistochemistry revealed chlamydial antigen in conjunctival epithelium. A majority of principal piglets necropsied 14-28 DPI had histologic lesions of mild conjunctivitis, but chlamydial antigen was not detected by immunohistochemistry. The results indicated that chlamydial strain H7 can cause mild or occasionally moderate conjunctivitis in gnotobiotic pigs, but conjunctival infection is asymptomatic.