Maedi-Visna resistance genotyping (TMEM154)

Successfully Maedi-Visna-sanitised herds are still at risk of reinfection. Increasing the proportion of less susceptible animals in the herd would in any case promote animal health in the longer term. Studies at German and international universities have shown that individual variants of certain cell surface protein molecules significantly reduce susceptibility to infection with the virus that causes Maedi-Visna by up to threefold. The genetic information determining these molecules can be genotyped in accustomed tissue sample types (resistance markers) and thus support breeding decisions. In addition, clear breed differences indicate a genetic component. However, this does not mean that sheep with an optimal genetic make-up for these proteins are completely protected. This is because the susceptibility of the individual animal is a complex trait and is probably influenced by other, currently unknown, genetic factors. In addition, it is advisable to consider as many traits as possible both of the individual and within the herd and to scrutinise husbandry management when making decisions about individual use for breeding or additional animal purchases in order to achieve comprehensive breeding success.
The gene variant with the greatest potential to date is an exchange at position 35 of the transmembrane protein 154 (TMEM154 E35K). Another promising, albeit rarer, gene variant is a gap (deletion) in the chemokine receptor 5 (CCR5) gene. It is emphasised that investigations in this regard have not yet been completed and, in particular, the transferability of these preliminary results to local breeds is still pending. In this context, the testing of animals for these gene variants is recommended, but their utilisation for breeding purposes must be carefully considered!