Detection and control of lentiviral infections in sheep and goats

Abstract

The quality of the laboratory diagnosis for Small Ruminant Lentivirus (SRLV) infections, particularly their early detection in sheep and goats is of utmost importance to their control in the host animal population. However, the reliability of serological as well as molecular biological assays is seriously hampered by the immense heterogeneity of the viral genomes. Consequences of sub-optimal laboratory diagnosis include unnoticed transmission of the disease - complicating international trade- and decreasing support for voluntary control programs. This thesis-based review focuses on technically improving the laboratory detection of SRLV and on reducing its costs, starting with an overview relevant to the biology and control of SRLV infections. The quality of antibody testing was thoroughly evaluated and secured, and subsequent efforts to reduce costs proved successful. In addition, a molecular biological tool for the detection of the viral genome was developed in view of the intrinsic limitation of antibody detection, i.e. slow or no antibody formation. Because the collection of the usual sample for testing, blood, which is legally restricted to veterinarians, adds considerably to the testing costs, the possibilities for using less costly samples were evaluated. After some adaptation of the testing protocols, milk (and plasma) was shown to be a reliable substitute of serum. Moreover, the feasibility of testing bulk milk was studied, since this could offer a new and very cost effective way of monitoring for infection at the flock level.