Spatiotemporal Trends of Pelvic Organ Prolapse Incidence in North American Swine Breeding Herds and Association with Climatic Factors

Kimberly Aguirre Siliezar¹José Pablo Gómez Vázquez²Rebecca Robbins³MARIA JOSE CLAVIJO⁴Beatriz Martínez-López^2*

• ¹Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
• ²Center for Animal Disease Modeling and Surveillance (CADMS), Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
• ³Pig Improvement Company (PIC), Hendersonville, TN, United States
• ⁴Department of Veterinary Diagnostic & Production Animal Medicine (VDPAM), Iowa State University, Ames, IA, United States

Sow mortality in the U.S. has nearly doubled, rising from 5.68% in 1997 to 14.5% in 2022. Recent studies cite sudden death, prolapses, lameness, PRRSV outbreaks, trauma, and infections as key contributors. Among these, pelvic organ prolapse (POP)—including uterine, vaginal, and rectal prolapses—has become a major global cause of sow mortality and morbidity. However, contemporary research on POP in North America is limited. This study addresses this gap by analyzing POP incidence in North American swine farms between 2019 to 2024 to (1) describe the spatiotemporal distribution of POP incidence, (2) identify significant clusters of increased POP incidence in space and time, and (3) evaluate potential associations between climatic factors (e.g., temperature, atmospheric moisture, wind speed, soil moisture) and POP incidence. Descriptive statistics were used to characterize trends, SaTScan was utilized for cluster analysis, and a zero-inflated beta regression model assessed associations between POP incidence and environmental factors. Results revealed a rising trend in POP across over 100 farms in the U.S. and Canada from 2019 to 2024, with consistently higher incidence occurring during colder months. We identified two significant clusters (p = 0.001) where POP incidence was higher within the cluster compared to outside. One cluster spanned five states over nearly four years (mean inside = 0.059 vs. mean outside = 0.029), suggesting widespread system-level risk, while the other was localized to a single farm (mean inside = 0.34 vs. mean outside = 0.032), reflecting potential farm-level drivers. Year and decreased soil moisture were significantly (p < 0.001) associated with increased POP incidence in the beta regression analysis. These findings highlight important patterns of POP in breeding herds, while offering valuable insights to help swine producers and veterinarians assess risk to sows and develop targeted mitigation strategies.