Small ruminant lentiviruses cause economic losses in Belgium’s sheep and goat population. They also have a negative impact on animal welfare. With this project, we aim to gain a better insight into the presence of these viruses in the Belgian small ruminant population and how they are transmitted from one animal to the next. We will also optimise the diagnostic tests and gather knowledge on the facility with which these viruses are spread between sheep and goats via direct contact. The optimised tests and the acquired knowledge should, in the medium-term, contribute to reducing the presence of these viruses in Belgium.
Maedi-Visna virus (MVV) and Caprine arthritis encephalitis virus (CAEV) are the prototypes of a group of viruses that infect sheep and goats and were recently grouped together as small ruminant lentiviruses (SRLV). These viruses are characterised by high genetic variability and the induction of a slow and variable humoral immune response. Both aspects make proper diagnosis of these viruses difficult. Infection of sheep and goats with these viruses leads to economic losses (weight loss and lower milk production) and also causes slow but progressive inflammatory disease symptoms, such as mastitis, pneumonia, and arthritis, which have an important impact on the welfare of infected animals.
Although SRLVs are known to be present in the Belgian sheep and goat population, no data are available on their prevalence. First of all, we will therefore examine to what extent these viruses are present in the Belgian population. We will then examine which strains circulate in Belgium (SRLVs are currently divided into 5 genotypes). This is important to allow a substantiated choice to be made when selecting the diagnostic tests used to detect virus-specific antibodies via ELISA and immunodiffusion, on the one hand, and viral genetic material via PCR, on the other hand. In addition, various commercially available ELISA and immunodiffusion tests will be compared with each other, so that the most suitable tests for the Belgian situation can be selected in the future. Furthermore, the added value of a PCR diagnostic will be examined. Finally, we will investigate how efficient genotype A strains (MVV-like) and genotype B strains (CAEV-like) are transmitted via direct contact between sheep and goats and whether also cross-species transmission of these viruses from sheep to goats and vice versa occurs. This will yield useful information for the organisation of sampling at farms that participate in the voluntary certification program and where both sheep and goats are present. It will also make it possible to estimate the risk of virus transmission at competitions where both sheep and goats are displayed.