Fetoplacental pathology of equine abortion, premature birth, and neonatal loss due to Chlamydia psittaci

Abstract

This report describes the fetoplacental pathology of Chlamydia psittaci-associated abortion, premature birth, and neonatal loss in 46 of 442 equine abortion investigations between 2015 and 2019. Seven abortions, 26 premature births, and 13 neonatal deaths with positive C. psittaci polymerase chain reaction (PCR) were evaluated. In 83% of cases (38/46), C. psittaci infection was considered as the primary cause of loss based on quantitative PCR (qPCR) confirmation, pathological findings, and exclusion of other causes, and was supported by Chlamydia spp immunolabeling in fetoplacental lesions. Lymphohistiocytic placentitis with vasculitis (36/38) affected the amnion, umbilical cord, and chorioallantois at the umbilical vessel insertion and/or cervical pole. Lymphohistiocytic chorionitis in the subvillous stroma extended to the allantois mostly without villous destruction. Lymphohistiocytic amnionitis and funisitis occurred at the amniotic cord attachment. Lymphohistiocytic hepatitis was observed in 19/38 cases and pneumonia was identified in 26 cases. Chlamydia spp immunolabeled in placenta, lung, liver, or splenic tissue in the cases that were tested (14/38). C. psittaci infection was not the cause of loss in 2 cases with other diseases and of uncertain significance in 6 cases with no conclusive cause of loss. immunohistochemistry (IHC) was negative for 6 of these cases (6/8). The highest Chlamydia load was detected in pooled placental tissues by qPCR. qPCR and IHC had 83% congruence at a qPCR cut-off of 1 gene copy. IHC limits of detection corresponded to infections with 2 × 102 gene copies identified by qPCR. This study confirms the etiological role of C. psittaci as a cause of naturally occurring equine reproductive loss.

Detection of Chlamydia abortus in aborted chorioallantoises of horses from Western Canada

“…24 Both studies also reported PCR-positive cases with suppurative placentitis. 6,24 We identified 6 cases of placentitis in the PCRpositive group; 5 cases were identified as suppurative placentitis, and 1 was identified as mild lymphoplasmacytic placentitis. Suppurative placentitis was more common in our cases than in the reported equine studies of C. psittaci; however, suppurative placentitis is common in sheep with C. abortus abortion.…”

“…26 The combined effects of these outcomes reduce fetoplacental exchange and ultimately cause abortion. 26 Placentitis, vasculitis, and rare thrombosis, similar to ovine cases of C. abortus, were reported in cases of C. psittaci equine abortions in Australia 6 ; the authors identified a characteristic lymphohistiocytic placentitis. 6 Similar findings were reported in C. psittaci abortions in Hungary in 2005.…”

“…26 Placentitis, vasculitis, and rare thrombosis, similar to ovine cases of C. abortus, were reported in cases of C. psittaci equine abortions in Australia 6 ; the authors identified a characteristic lymphohistiocytic placentitis. 6 Similar findings were reported in C. psittaci abortions in Hungary in 2005. 24 Both studies also reported PCR-positive cases with suppurative placentitis.…”

Sporadic bovine encephalopathy caused by Chlamydia pecorum secondary to bovine viral diarrhoea virus infection in calves in South Australia

“…In this case, a monoclonal antibody targeting the chlamydial lipopolysaccharide was used to confirm that Chlamydia was associated with brain lesions using previously established methods. 8,15 IHC involves the specific immunolabelling of bacterial antigens within affected tissues followed by colorimetric detection of those antibodies using a chemical substrate. IHC has the advantage of co-localising an organism of interest within histological lesions and, therefore, is a powerful diagnostic tool for confirmation that the agent is responsible for the observed pathology.…”

“…IHC is another method that can be used for the diagnosis of chlamydial infections. In this case, a monoclonal antibody targeting the chlamydial lipopolysaccharide was used to confirm that Chlamydia was associated with brain lesions using previously established methods 8,15 . IHC involves the specific immunolabelling of bacterial antigens within affected tissues followed by colorimetric detection of those antibodies using a chemical substrate.…”