Small ruminant lentiviruses - analysis of disease prevalence and distribution of SRLV genotypes in sheep and goat farms in the Czech Republic

Maedi-visna in sheep, and arthritis and encephalitis in goats, are globally widespread and progressive inflammatory diseases caused by retroviruses belonging to the small ruminant lentivirus (SRLV) group. They cause lifelong infections in affected animals, characterised by slow progression to overt disease and are always fatal. The aim of this study was to determine the prevalence of SRLV disease in the Czech Republic, to map the genotypic representation of SRLV using phylogenetic analysis, and to analyse TMEM154 as a selected candidate marker of SRLV resistance in sheep and goats. A total of 3 410 sheep and goat blood samples were collected from 21 flocks. The seroprevalence of maedi-visna in sheep was found to be 19.9% (556/2801), and the seroprevalence of arthritis and encephalitis in goats was 14.1% (86/609). All seropositive animals were tested by nested polymerase chain reaction (nPCR) for the presence of proviral DNA. Phylogenetic analysis identified the SRLV genotype in 77 sequences, of which 60 sheep and goat samples were genotype A and 17 sheep samples were genotype B. While all genotype B sequences were classified as subtype B2, the group of genotype A isolates showed higher variability and were related to subtypes A2 and A3. In addition, 40 seropositive and 50 seronegative sheep and goat samples were randomly selected to design a methodology for LAMP (loop-mediated isothermal amplification) diagnosis of SRLV in sheep and goats. Seronegativity was clearly confirmed by the LAMP method in all samples, and seropositivity was confirmed in 31 out of 40 cases in both sheep and goats. 605 sheep and 60 goat samples were randomly selected for TMEM154 genotyping. Most seropositive animals were heterozygous EK (61%), 58% were homozygous EE, and 45% were homozygous KK. In sheep, all 3 genotypes were identified, while all goats were homozygous EE