RESUMEN
Thirteen strains of M. bovoculi, 6 from frozen bull-semen (3.5% of 168), 3 from neat bull-semen (3.0% of 100), one each from heart blood and stomach contents of aborted foetus of 85 (1.18%) bovine-abortions, one each from stomach contents and pooled internal organs of 9 (11.1%) stillborn calves, were isolated. All the isolates were resistant to ampicillin and sensitive to spiramycin, vibramycin, demeclocyclin, oxytetracycline, lincomycin and tylosin. However, variation in resistance to tetracycline, erythromycin, neomycin, kanamycin and streptomycin was observed. The gross lesions like congestion of lungs, liver, kidney and spleen were noted only in stillborn calf. However, significant microscopic lesions were encountered in internal tissues of both the aborted bovine fetuses and stillborn calf. Thickened alveolar wall, congestion of blood vessels, mesenchymal cell proliferation along with infiltration of lymphocytes and macrophages were observed in lungs. The liver showed mild infiltration of lymphocytes, macrophages in hepatic triad and necrosis of hepatic cells. The kidney tissues had focal lymphocytic infiltration in the interstitium. One strain of M. bovoculi (isolate # SBC-7/84,IO) isolated from a stillborn calf was found abortigenic upon experimental inoculation in pregnant guinea pigs.