Influence of enzootic bovine leukosis virus upon the incidence of subclinical mastitis in cows at a different stage of infection

Studies were performed on 26 cows, divided into 3 groups on the basis of serological (by immunodiffusion test) and haematological analyses for bovine leukosis: Group I seropositive without changes in haemogram; group II seropositive with changes in haemogram and group III (control) BLV negative. A statistically significant difference was observed in the incidence of subclinical mastitis in cows from group II (P<0.05) compared to healthy animals. The most commonly isolated microorganism was S. agalactiae (46.80%), followed by Staphylococcus spp. (36.06%). The results of our studies, as well as data from other investigators evidenced that the incidence of subclinical mastitis was higher in cows with changes in the white blood cell picture due to the immunosuppressive effect of the enzootic bovine leukosis virus.