Morphologic and histologic effects of Chlamydia trachomatis infection on the reproductive tract of vaccinated and non-vaccinated gilts

Genital Chlamydiosis, caused by Chlamydia trachomatis (Ct), is one of the most widely transmitted sexual diseases in humans worldwide. There are around 131 million accounted new infections per year, with prevalence being higher, as 75 % of infections remain asymptomatic (1). To this end, a vaccine would help stop the infection in its tracks as the current therapy with antibiotics only treats symptoms. To test vaccine efficacy there are a few potential animal models to choose from. One of them being swine, they are among other things anatomically and immunogenetically closely related to humans. To address this data shortfall, eighteen gilts of same origin were divided into three groups: one group was infected within the uterus with Ct, one group was vaccinated and infected and one acted as our control group. Day 5 or 6 of cycle following euthanasia their reproductive tracts were assessed macroscopically as well as histologically, paying attention to different parameters such as weight, length and diameter. The study revealed only minor differences between groups which might also be individual differences. Infected and vaccinated animals showed slight increases in myometrial thickness and uterine horn dimensions, along with some mucosal changes that may stem from mild inflammation. However, glandular and epithelial structures remained largely unaffected. These findings suggest that while swine do exhibit some morphologic and histologic responses to Ct application, they may not replicate the clinical symptoms seen in humans. Nevertheless, in eighteen gilts of same genetics, same age, and same time point of cycle, we performed anatomical and histological baseline measurements focusing on the structures of the reproductive tract. These data are important, as such information is currently not available in textbooks.