What is maedi visna?
Maedi visna (MV), along with caprine arthritis and encephalitis virus (CAEV), are part of the small ruminant lentivirus (SRLV) group of retroviruses, affecting affect sheep and goats. These viruses cause significant clinical disease in sheep (primarily wasting, lung pathology and mastitis) and goats (primarily arthritis) and are a major source of economic losses.
The clinical disease onset is slow and may be confused with many other pathogens, so the presence of virus in a flock is often missed or under-estimated. Current diagnostics also often miss early-stage infections. At present, there are no vaccines or treatments, so control options rely on testing at a herd level, culling infected animals and biosecurity measures. Eradicating disease from a flock can be expensive and slow.
Our research and its impact
Our research on maedi visna focuses on several key areas, with the aim of better understanding and controlling the virus.
Our recent work has shown that the risk of sexual transmission of the virus is low. In addition, animals that carry the “resistant” allelle of the gene TMEM154 can clear the virus to below detectable levels after infection; this offers a promising avenue for breeding for resistance to the virus in sheep. The virus can be detected from nasal swabs of affected animals and we are exploring whether this is sensitive and specific enough to use a diagnostic test for the virus and whether this allows earlier detection than the current serology tests. This would facilitate earlier and more accurate removal of infected animals from flocks, aiding elimination of the disease from a flock.