Enzootic bovine leukosis is a chronic lymphoproliferative disorder in cattle caused by the exogenous retrovirus, bovine leukemia virus (BLV). There are numerous molecular protocols for the detection of bovine leukosis provirus in blood and semen. The aim of this study was to investigate the serology status of BLV infection in bulls in Tabriz, Iran and polymerase chain reaction (PCR) detection of viral genome of BLV in seminal cellular fraction and blood samples in sero-positive and sero-negative bulls. In this study, 45 serum samples from bulls from 18 different herds referred to the Artificial Insemination Centre were used to evaluate the serology infection of BLV by enzyme-linked immunosorbent assay. In addition, blood and semen samples of related bulls were used for the detection of BLV DNA. Antibodies against BLV were detected in five of 45 blood samples (4.4%), and PCR demonstrated that semen and blood samples of five seropositive and one sero-negative bull were infected by BLV. Our findings support the power of a PCR test for BLV detection in bovine semen and blood samples and could be easily used for routine diagnosis. This data strongly suggest that semen from sero-positive bulls could result positive by PCR.

Maedi-Visna is an important slow viral disease of sheep leading to progressive pneumonia, encephalitis and mastitis. Udder is one of the organs affected by MVV. Despite the fact that in Iran Maedi-Visna is known since 2000, to the authors' knowledge correlation of subclinical mastitis and infection with MVV has not been assayed. In this study 50 milk samples from 10 flocks in East Azerbaijan Province of Iran were tested. None of the animals exhibited any clinical signs of the disease. Forty samples were collected from CMT positive ewes and ten were taken from CMT negative ewes. Milk samples were analyzed using PCR targeting gag sequence. Presence of provirus DNA was detected in one sample from CMT negative and seven samples from CMT positive ewes. These data demonstrate that 16.5 % of sheep with subclinical mastitis were infected to MVV. Thus this virus can be considered one of the main pathogenic agents of mastitis and can be dramatically transmitted to lambs by milk.

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