Detection of BLV in frozen semen samples by PCR assay

Abstract

Detection of BLV in frozen semen samples by PCR assay Dus Santos Maria Jose; Rodriguez Sabrina; Wigdorovitz Andrés; Trono Karina Instituto de Virología, CICVyA, INTA-Castelar. CC 77. Buenos Aires, Argentina. Detection of BLV in frozen semen samples by PCR assay María José Dus Santos, Sabrina Rodriguez, Andrés Wigdorovitz and Karina Trono. Instituto de Virología, CICVyA, INTA-Castelar. CC 77. Buenos Aires, Argentina [email protected] The sanitary and economic impact of BLV infection is associated with the interference in the international movement of cattle and their germ plasm. Although experimental data support the improbability that semen from BLV-positive bulls could infect recipient cows, restriction for commercialization of semen from infected animals is still present. The objective of this work was to standardize a PCR assay to diagnose the presence of BLV genome and to describe the pattern of BLV detection in frozen semen samples. The developed methodology involves the amplification of an internal fragment of gag gene and posses a limit of detection of 60 viral particles. Additionally, a biological test in susceptible sheep was performed in order to evaluate the transmission of BLV genome by semen from seropositive animals. This data strongly suggest that semen from seropositive bulls that resulted negative by PCR can be used for artificial insemination (AI), accompanied by proper collection protocols. Frozen semen samples from 30 seropositive bulls were analyzed. It was possible to detect proviral DNA in 118 out of 545 samples. It was important to note that BLV genome detection occurred in several collections but in an alternated way with non detection periods. On the other hand, in 4 seropositive bulls, it was not possible to detect BLV genome in all the samples analyzed. The development of this PCR assay constitutes a valuable diagnostic tool to determine the BLV-free status of semen used for AI. Moreover, the results suggest that BLV could present an intermittent pattern of excretion