Pathological characterization of the main infectious bovine abortions in Argentina

Infectious abortion is a major cause of reproductive loss in cattle, yet the diagnosis remains challenging. In this study, we evaluated the gross and microscopic lesions of bovine fetuses aborted due to the main infectious agents in Argentina. Clear pathogen-specific patterns were identified. Neospora caninum was strongly associated with central nervous system (CNS) and cardiac inflammation, whereas Campylobacter fetus and Brucella abortus predominantly produced bronchointerstitial pneumonia. Leptospira spp. consistently affected hepatic and renal tissues and was associated with marked portal hepatitis and interstitial nephritis. Bovine viral diarrhea virus (BVDV) infections resulted in mild multisystemic and nonspecific lesions. Lesion severity also differed by fetal age. N. caninum produced more severe CNS and cardiac inflammation in mid-gestation fetuses, and C. fetus induced more severe hepatic lesions during mid-gestation. Statistical analyses confirmed distinct organ tropisms and lesion profiles among pathogens, supporting their diagnostic relevance. Based on these findings, targeted sampling of CNS and heart (for N. caninum); lung (for C. fetus and B. abortus); liver and kidney (for Leptospira spp.); and heart, lung, and CNS (for BVDV) may improve diagnostic accuracy in abortion investigations. These findings provide robust criteria for differentiating major abortifacient agents in routine diagnostic practice.