Phylogenesis of Small Ruminant Lentiviruses: a systematic review protocol v2

Small ruminant lentiviruses (SRLV) include the closely related Visna-Maedi virus (VMV) and caprine arthritis encephalitis virus (CAEV), which infect sheep and goats. These viruses cause huge economic losses in the small ruminants industry, affecting production and animal welfare. To date, there are five recognized SRLV genotypes (A, B, C, D, and E), based on nucleotide sequences derived from gag, pol, env, and LTRs regions and several subgenotypes. Thanks to the improvement of molecular studies, the knowledge on genetic characterization and phylogenesis of SRLVs has increased since the 1990s. However, using different protocols among the various studies produced problems concerning the exact placement of subgenotypes in the phylogenetic tree. This systematic review protocol aims to define strict selection criteria and critical appraisal of published studies to perform a critical synthesis of all knowledge on the phylogenesis of SRLVs following the PRISMA-P guidelines. Eligibility criteria, information sources, search strategy, data management, selection process, data collection process, data extraction, outcomes and prioritization, studies quality assessment, and data synthesis will be performed. Thank the systematic review, an updated overview of the phylogenesis of SRLVs will be performed, and the best reliable molecular approach in diagnosis and research may be highlighted.