Testicular ultrasound patterns, sperm quality, seminal microbiota, caprine arthritis encephalitis virus and Coxiella burnetii infection in bucks

This study assesses the frequency and severity of ultrasound-detected testicular alterations across age groups (young and adult) in 219 bucks. Sperm quality and testicular echotexture were evaluated, and their associations with reproductive pathogens (Coxiella (C.) burnetii, caprine arthritis encephalitis virus (CAEV), Chlamydia (C.) abortus and Mycoplasma (M.) agalactiae) were analyzed. Additionally, qPCR was also performed on ejaculates from seropositive bucks. Seminal microbiota was characterized in three groups: 1 (seronegative without lithiasis), 2 (seropositive with lithiasis), and 3 (qPCR-CAEV-positive). A 68.5% of bucks showed testicular microlithiasis (50.2% bilateral and 18.2% unilateral). Moreover, frequency of bilateral lesions differed according to age, being higher in adults, who also showed larger microlithiasis area (P < 0.05). Age was negatively correlated with sperm concentration (P < 0.05). Seropositivity was 35.8% for C. burnetii and 58.8% for CAEV. Adults showed higher CAEV seropositivity (P < 0.001), and 4.2% of ejaculates tested qPCR positive for this pathogen. Bacterial richness was greater (P < 0.001) in group 2 than in group 1. Firmicutes dominated groups 1 and 2, whereas Fusobacteriota prevailed in group 3. The most frequent genus in all three experimental groups was Oceanivirga, with higher abundance in group 1 than in group 2 (P < 0.05). These findings suggest that ejaculate microbiota may be influenced by ultrasound abnormalities and exposure to CAEV and C. burnetii, supporting the use of testicular ultrasound to detect bucks prone to reproductive problems and associated health risks, while also highlighting the need to include males in CAE and Q fever control programs.