Chlamydia pecorum–Associated Sporadic Ovine Abortion

Abstract

Despite previous detection of Chlamydia pecorum in sporadic ovine abortions, published descriptions of naturally occurring infections with fetoplacental lesions are lacking. This report provides the first descriptions of severe necrosuppurative chorionitis with vasculitis, and fetal pyelonephritis and enteritis in late-term abortions of maiden ewes. Chlamydial infection was detected using a Chlamydia genus-specific qPCR (quantitative polymerase chain reaction) on tissue extracts from 3 fetuses. C. pecorum was identified using a targeted qPCR assay, which also determined infectious load within fetal tissues. The presence of viable C. pecorum in fetal samples was confirmed by cell culture. Multilocus sequence typing (MLST) data indicated that the C. pecorum strains from each fetus were identical and of sequence type (ST) 23. Chlamydia sp. immunohistochemistry showed strong positive immunolabeling of fetoplacental lesions. Other infectious abortigenic agents were excluded with specific testing. This report confirms C. pecorum as a likely cause of ovine abortion and provides the first descriptions of associated fetoplacental lesions in naturally infected sheep.

Chlamydia pecorum detection in aborted and stillborn lambs from Western Australia

“…Firstly, other endemic and exotic abortigenic agents were not detected. Secondly, histopathological changes for cases where C. pecorum was detected were consistent with those reported for C. abortus and previously described C. pecorum abortion in small ruminants [ 18 , 58 , 59 ]. The high loads of C. pecorum detected in placenta and foetal liver from aborted and stillborn lambs (Table 2 ) was consistent with observations for other clinical diseases associated with C. pecorum [ 44 , 55 , 56 ].…”

“…Chlamydia pecorum has predominantly been associated with polyarthritis [ 54 – 56 ], keratoconjunctivitis [ 43 ] and asymptomatic gastrointestinal carriage and faecal shedding in Australian sheep [ 57 ]. Abortion due to C. pecorum is sporadic and not commonly reported [ 12 , 18 , 20 ], and the role of C. pecorum as an abortigenic agent is not well defined. Thereby, detection of this organism in aborted and stillborn lambs from multiple farms with no epidemiological or geographical relationship is notable, and C. pecorum should be considered as a differential diagnosis for abortion and perinatal mortality in Australian sheep.…”

“…The high loads of C. pecorum detected in placenta and foetal liver from aborted and stillborn lambs (Table 2 ) was consistent with observations for other clinical diseases associated with C. pecorum [ 44 , 55 , 56 ]. Finally, MLST and ompA characterisation of high load C. pecorum DNA from aborted and stillborn lambs identified ST23 type strains that were identical to other globally distributed ST23 strains associated with pathology in sheep and cattle, including abortion [ 18 , 60 ], arthritis [ 61 , 62 ] and conjunctivitis [ 61 , 62 ] in sheep, and sporadic bovine encephalopathy in cattle [ 44 , 61 ]. Emerging evidence of abortigenic potential of C. pecorum is perhaps not surprising given the closely related C. abortus is an important cause of abortion in sheep in other countries, and C. psittaci is a cause of abortion in horses [ 63 , 64 ].…”

“…Infectious disease screening was not conducted for lambs that died from causes other than abortion or stillbirth, including those classified as starvation-mismothering. However, similar to other bacterial infections of the pregnant uterus, it is likely that C. pecorum -associated placentitis results in a spectrum of outcomes, including abortion, stillbirths, lambs that are born alive, but weak and with low birth weights and poor survival, congenital infections or even normal offspring, depending on the severity of placental pathology and colonisation [ 18 , 65 ]. Future investigations should determine whether infection contributes to reduced lamb viability, as well as abortion or stillbirth, and factors that impact outcome for infection.…”

“…This is consistent with older reports describing these as the most common infectious causes of abortion and perinatal mortality in Australian sheep [ 14 – 17 ]. Sporadic abortion associated with Chlamydia pecorum has been reported in sheep from Australia [ 12 , 18 ] and overseas [ 19 , 20 ], but the epidemiology of C. pecorum -associated abortion in sheep remains poorly understood.…”