Concomitant circulation of lentiviruses and Mycoplasma spp. in dairy goats: a clinical and multi-sample diagnostic approach.

The health of dairy goat herds may be compromised by infections caused by small ruminant lentiviruses (SRLV) and Mycoplasma agalactiae, particularly under coinfection conditions. This study investigated a dairy goat herd composed of 38 animals with a history of joint enlargement and reduced milk production in Northeastern Brazil. Clinical, serological, molecular, and phylogenetic analyses were performed using blood, milk, synovial fluid, and ocular swab samples. Clinically, arthritis was observed in 28.9% (11/38) of the animals, keratoconjunctivitis in 28.9% (11/38), and mastitis or agalactia in 19.4% (6/31) of the lactating females. For SRLV diagnosis, positivity rates were 31.6% (12/38) by agar gel immunodiffusion (AGID) and 65.8% (25/38) by indirect ELISA, with moderate agreement between tests (K = 0.387; P = 0.002). Indirect ELISA for Mycoplasma spp. detected antibodies in 34.2% (13/38) of the animals, while PCR identified M. agalactiae in 83.3% (5/6) of synovial fluid samples, 66.7% (2/3) of ocular swabs, and 79.3% (23/29) of milk samples. Concomitant clinical manifestations were observed exclusively in coinfected animals. Phylogenetic analysis based on the 16 S rRNA gene supported the molecular identification of M. agalactiae. These findings demonstrate the concomitant circulation of SRLV and M. agalactiae in the investigated herd and reinforce the importance of combining clinical evaluation with serological and molecular methods applied to different biological samples for the diagnosis of coinfections in goats.