Pathological evaluation of reproductive system of porcine reproductive and respiratory syndrome virus-vaccinated and nonvaccinated anestrus sows and gilts.

The purpose of the study was to evaluate pathologically the reproductive system of nonvaccinated and porcine reproductive and respiratory syndrome virus (PRRSV)-vaccinated sows/gilts, as well as the assessment of vaccination impact on their endometrium/myometrium and ovaries. In a farrow-to-finish farm, all sows and gilts were systematically vaccinated with a PRRSV-inactivated vaccine for a period of 18 months. During the last semester before the beginning of the trial, the genital organs (uterus and ovaries) from 50 females (nonvaccinated primiparous and multiparous sows that did not exhibit signs of estrus until 10 days post-weaning) were collected at the slaughterhouse for gross and microscopic examination (parity 1 to >6). Respectively, during the following three semesters after the implementation of the experimental PRRSV vaccination scheme, the genital organs from 75 vaccinated sows-25 samples taken along the period of each semester-were also collected. Gross examinations included measurements of uterine horn (thickness and diameter) and ovaries (diameter). Microscopic examination focused on histopathological examination of ovarian cysts or other cystic formations and evaluation of the endometrium and myometrium. Measurements of uterine horn's thickness/diameter and ovaries' diameter were at normal levels, and no significant differences were found on gross examination between vaccinated and nonvaccinated females. The results of histopathological examinations did not show lesions of endometritis or myometritis, but revealed ovarian cystic formations with a diameter of >2 cm that were luteinizing cysts. The presence of these luteinizing cysts was significantly lower in PRRSV-vaccinated animals, compared to nonvaccinated, three semesters (p=0.017) after the start of vaccinations and for the total trial period (p=0.009).