Chlamydia pecorum–Induced Arthritis in Experimentally and Naturally Infected Sheep

Abstract

Chlamydia pecorum is an obligate intracellular pathogen with a wide host range including livestock such as sheep, cattle, goats, and pigs as well as wildlife species such as koalas. Chlamydial polyarthritis is an economically important disease resulting in swollen joints, lameness, stiffness, and weight loss in young sheep. In the present study, tissues from sheep experimentally or naturally infected with Chlamydia pecorum were assessed by histopathology and immunohistochemistry. Carpal, hock, and stifle joints as well as spleen, liver, kidney, lymph nodes, lung, and brain of 35 sheep from different inoculation groups were available. Two different C. pecorum strains (IPA and E58), different routes of administration (intraarticular or intravenous), UVA-irradiated IPA strain, and corresponding noninfected control groups were investigated. Similar investigations on tissues from 5 naturally infected sheep were performed. The most obvious inflammatory lesions were observed in synovial tissues and, notably, in the renal pelvis from the experimentally infected group and naturally infected animals. This resulted in chronic or chronic-active arthritis and pyelitis. Intralesional chlamydial inclusions could be demonstrated by immunohistochemistry in both tissues. Immunohistochemical evaluation of the presence and distribution of macrophages, T and B cells in synovial tissues revealed macrophages as the most prevalent inflammatory cell population. Previous observations indicated that C. pecorum isolates can infect circulating monocytes. Together with the finding of the histological lesions in synovial tissues and internal organs alongside the presence of C. pecorum DNA, these observations suggest chlamydial arthritis in lambs is the result of hematogeneous spread of C. pecorum.

Chlamydia pecorum detection in aborted and stillborn lambs from Western Australia

“…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 ]. 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 ].…”

“…The detection of C. pecorum in aborted and stillborn lambs from primiparous ewes from multiple farms was the most striking observation in this study. 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.…”

“…Incidence of abortion, conjunctivitis and lameness are typically not reported for flocks included epidemiological studies because these conditions are challenging to detect in extensively managed sheep and may not be evident at the time of sampling. The incidence of conjunctivitis and arthritis was not able to be determined for flocks in our study, however polyarthritis associated with C. pecorum was detected in sheep from Farm F [ 56 ].…”

Real-Time Fluorometric Isothermal LAMP Assay for Detection of Chlamydia pecorum in Rapidly Processed Ovine Abortion Samples: A Veterinary Practitioner’s Perspective

“…Chlamydia pecorum , an obligate intracellular bacterium and a member of Chlamydiacae , is a significant global livestock and marsupial pathogen. In sheep, C. pecorum is a common cause of polyarthritis and conjunctivitis [ 1 , 2 , 3 , 4 , 5 ]. However, this organism is also frequently detected in the faeces of apparently healthy sheep [ 6 , 7 ].…”

Toxoplasma gondii is not an important contributor to poor reproductive performance of primiparous ewes from southern Australia: a prospective cohort study

“…An unclear association between timing of T. gondii seroconversion and abortion in some ewes was also consistent with observation that other factors were likely to be contributing to abortion or perinatal lamb deaths in these ocks. Abortions, stillbirths and polyarthritis associated with Chlamydia pecorum were detected in primiparous ewe ocks from Western Australia, and non-infectious causes of death (including dystocia and starvation-mismothering) were important contributors to cause of lamb death identi ed at necropsy [3,35]. There was no evidence neosporosis was contributing to foetal or lamb mortality in these ocks [24].…”