Pathological, microbiological, and molecular characterization of uterine samples in culled sows from farms with a history of reproductive failure in Brazil

Abstract

Reproductive failure in swine herds is an important cause of production losses and increased sow culling. While many diagnostic efforts focus on abortion-derived samples, the evaluation of reproductive tracts from culled sows may provide additional insights. This study aimed to characterize the histopathological, microbiological, and molecular alterations focused on uterine samples of sows from three Brazilian farms with a history of reproductive failures. A total of 207 reproductive tracts from culled sows were collected at slaughter and examined for gross, histological lesions, and bacteriological analysis. Uterine samples were also analyzed via PCR for key pathogens linked to reproductive failure, including viruses (PCV-2, PCV-3, PPV), bacteria ( Brucella suis , Leptospira spp., Listeria spp., Mycoplasma suis , Erysipelothrix rhusiopathiae ), and protozoa ( Toxoplasma gondii ). Twenty-four out of 207 samples (11.6%) were positive for Erysipelothrix rhusiopathiae , 21/207 (10.1%) for PCV-2, 14/207 (6.8%) for porcine parvovirus (PPV), 13/207 (6.3%) for PCV-3, and 10/207 (4.8%) for Leptospira interrogans . Fifteen samples were concurrently positive for two (12/15) or three (3/15) of these infectious agents. Endometritis was observed in 21.74% (45/207) of the samples. The predominant histological patterns of endometritis were mixed (44.5%; 20/45), followed by chronic (26.7%; 12/45), mononuclear (22.2%; 10/45), suppurative/fibrinosuppurative (4.4%; 2/45), and pyogranulomatous (2.2%; 1/45). Findings of chronic endometritis resembling those described in mares with reproductive failures included mainly peri-glandular fibrosis and glandular ectasia. Bacterial culture yielded positive results in 57.7% (26/45) exclusively from endometritis cases, with Escherichia coli , Staphylococcus aureus , and Streptococcus suis being the most frequently isolated pathogens. Ovarian pathology accounted for twenty-four cases (24/207; 11.6%), including stage of anestrus (13/24) and ovarian follicular cysts (11/24). As individual reproductive histories and culling reasons of the sows were unavailable, these findings should be interpreted descriptively rather than as causal evidence of reproductive failure. In this context, the results represent a herd-level screening of circulating pathogens and may guide future farm-specific investigations.

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