Detection of bovine leukaemia virus (BLV) in tissue samples of naturally and experimentally infected cattle

Enzootic bovine leukaemia (EBL) which is caused by the bovine leukaemia virus (BLV) still plays a remarkable role despite a significant success in sanitation programmes. In the Federal Republic of Germany it was not possible to eradicate the disease until today. Sporadically during slaughter or necropsy of cattle neoplastic lesions of the lymphatic tissues are observed that need to be clarified with regard to BLV as etiological agent. Due to the fact that in most instances no serological data are available from the respective animals and blood drawings from the original holdings are not easy to obtain the polymerase chain reaction (PCR) opens new avenues as supplementary diagnostic tool to test unfixed lymphatic tissues for the presence of BLV proviral DNA. Lymph node tissues from 10 naturally or experimentally BLV-infected cattle, which have been monitored virologically and serologically, and tissues from 4 negative animals were processed, DNA was extracted and subjected to PCR to amplify BLV env gene specific sequences. The results show that in cattle with BLV-induced leukosis as well as in cattle, which were clinically healthy and unsuspicious at slaughter or at post-mortem, either with persistent lymphocytosis (PL) or without, BLV proviral DNA could be detected easily in samples of lymphatic tissues and in high concordance with serological data. In this article data from the National and OIE reference laboratory for EBL at the Friedrich-Loeffler-Institut (FLI, Germany) are presented. Elaborated laboratory protocols for processing of tissue samples and performing of BLV-PCR are recommended.