Experimental Infection of Pregnant Ewes with Chlamydia pecorum

Pregnant ewes were infected in midpregnancy with three isolates of Chlamydia pecorum derived from the feces of healthy lambs from three different farms. Oral infection, alone or together with Fasciola hepatica, did not result in tissue invasion, since all placental and fecal samples were negative for chlamydiae. Intravenous infection resulted in placental infection in 16 of 18 ewes in that chlamydiae were cultured from placentas or vaginal swabs. Two ewes bore dead lambs after a shortened gestation time. The chlamydiae isolated were all C. pecorum. There were no significant differences between the weights of the lambs from the infected groups and those from uninfected control ewes. Most ewes showed no serological evidence of infection by the complement fixation test; therefore, it is unlikely that the enteric subtype of C. pecorum is responsible for the cross-reactions sometimes seen in flocks being tested for C. psittaci infection.

于妊娠中期，将从3个不同农场健康羔羊粪便中分离得到的3株反刍动物衣原体（Chlamydia pecorum）分离株接种于妊娠母羊。单独经口接种或联合肝片形吸虫（Fasciola hepatica）接种均未引发组织侵袭，所有胎盘与粪便样本的衣原体检测结果均为阴性。经静脉接种组的18只母羊中，有16只发生胎盘感染，可从其胎盘或阴道拭子中分离培养出衣原体。其中2只母羊在妊娠周期缩短后产下死羔。分离所得衣原体均为C. pecorum。感染组羔羊与未感染对照组母羊所产羔羊的体重无显著差异。多数母羊经补体结合试验（complement fixation test）未检测到感染的血清学证据；因此，在针对鹦鹉热衣原体（Chlamydia psittaci）感染开展检测的羊群中偶见的交叉反应，不太可能由反刍动物衣原体的肠道亚型引发。