Fetal pneumonia and polyarthritis associated with Ureaplasma diversum infection in an aborted beef cattle fetus in Brazil.

Ureaplasma diversum is an opportunistic bovine pathogen associated with reproductive disorders, including infertility, granular vulvovaginitis, placentitis, and abortion; however, detailed descriptions of fetal osteoarticular lesions remain exceptionally uncommon. This report describes the gross, histopathological, and molecular findings of a bovine abortion associated with U. diversum infection presenting with concurrent pulmonary and articular lesions, representing an uncommon manifestation in bovine fetuses in Brazil. An approximately six-month-old Angus fetus was submitted for complete postmortem examination following abortion. Tissue samples were collected for histopathology and molecular investigation of major infectious agents associated with bovine reproductive failure. Gross examination revealed bilateral coxofemoral joint lesions characterized by articular cartilage irregularity and erosions. Histologically, the lungs exhibited moderate multifocal pyogranulomatous pneumonia with prominent bronchus-associated lymphoid tissue (BALT) hyperplasia. The coxofemoral joints showed severe multifocal subacute erosive fibrinonecrotizing arthritis with proliferative lymphoplasmacytic synovitis and secondary osteonecrosis. Histologically, fibrovascular pannus formation, cartilage necrosis, and extension of the lesion into the subchondral bone were observed. Quantitative PCR detected U. diversum DNA in brain, spleen, thymus, liver, and kidney, whereas the paraffin-embedded coxofemoral joint sample tested negative. Molecular assays for other major abortifacient pathogens, including bovine viral diarrhea virus (types 1, 2, and 3), bovine herpesvirus 1 and 6, Leptospira spp., Brucella abortus, Mycoplasma bovis, and Neospora caninum were negative. The exclusion of other common infectious causes, combined with the molecular confirmation of U. diversum and the characteristic inflammatory lesions, support an etiological association between U. diversum infection and the abortion. These findings expand the pathological spectrum of U. diversum infection in bovine fetuses, particularly regarding osteoarticular involvement, and emphasize the diagnostic value of systematic joint evaluation combined with molecular testing in bovine abortion investigations.