Abstract
This study investigated the pathogenesis of two variant strains (LLG and POS) of Chlamydia abortus, in comparison to a typical wild-type strain (S26/3) which is known to be responsible for late term abortion in small ruminants. Challenge with the three strains at mid-gestation resulted in similar pregnancy outcomes, with abortion occurring in approximately 50–60% of ewes with the mean gestational lengths also being similar. However, differences were observed in the severity of placental pathology, with infection appearing milder for strain LLG, which was reflected in the lower number of organisms shed in vaginal swabs post-partum and less gross pathology and organisms present in placental smears. Results for strain POS were somewhat different than LLG with a more focal restriction of infection observed. Post-abortion antibody responses revealed prominent differences in seropositivity to the major outer membrane protein (MOMP) present in elementary body (EB) preparations under denaturing conditions, most notably with anti-LLG and anti-POS convalescent sera where there was no or reduced detection of MOMP present in EBs derived from the three strains. These results and additional analysis of whole EB and chlamydial outer membrane complex preparations suggest that there are conformational differences in MOMP for the three strains. Overall, the results suggest that gross placental pathology and clinical outcome is not indicative of bacterial colonization and the severity of infection. The results also highlight potential conformational differences in MOMP epitopes that perhaps impact on disease diagnosis and the development of new vaccines.
Highlights
Fetal mortality in sheep and goats caused by the obligate intracellular bacterium Chlamydia abortus (C. abortus) was first described in 1950 [1] and is recognised as an economically important disease affecting the global agricultural industry
The greatest number of abortions occurred in the S26/3-infected ewes, with the six ewes that aborted producing a total of nine dead fetuses and one non-viable lamb
Variant Chlamydia abortus pathogenesis studies on these variant strains have only been conducted in mice [10,15,29], and differences have been observed with regards to virulence and pathogenicity, mouse placentation differs greatly from that of the sheep and it was unknown how these strains would behave in the natural small ruminant host
Summary
Fetal mortality in sheep and goats caused by the obligate intracellular bacterium Chlamydia abortus (C. abortus) (syn. ovine enzootic abortion, OEA; enzootic abortion of ewes, EAE; ovine chlamydial abortion) was first described in 1950 [1] and is recognised as an economically important disease affecting the global agricultural industry. Fetal mortality in sheep and goats caused by the obligate intracellular bacterium Chlamydia abortus (C. abortus) C. abortus causes sporadic reproductive failure in cattle, horses and pigs and the bacterium presents a dangerous zoonotic risk to pregnant women [2,3,4]. The bacterium has a predilection for the trophoblast cells of the placenta where infection becomes established and spreads out into the surrounding chorion. This leads to destruction of the placental tissue which affects nutrient acquisition and hormonal regulation and can result in the premature expulsion of the fetus [5]. Histological changes in the placenta and the appearance of lesions typically occur after 90 days gestation (dg) [6,7], it has been shown that in experimentally-infected sheep, C. abortus can be detected in the placenta as early as 85dg [8]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
