Caprine arthritis-encephalitis virus (CAEV) and ovine
Maedi-visna virus (MVV) are members of the small ruminant lentiviruses (SRLVs) group in the
retroviridae family infecting goats and sheep worldwide [
1,
2]. Lentiviruses from different animal species have in common their genomic organization, the induction of slowly progressive diseases, the large spectrum of targeted organs and symptoms and the ability to persist in their hosts despite a strong immunological response. Transmission of SRLVs is thought to occur predominantly through ingestion of infected milk but, at least in sheep, horizontal transmission may also play a prominent role [
3,
4]. Common clinical signs caused by SRLV infections include neurological disorders, dyspnoea, emaciation, mastitis and arthritis [
2,
5,
6]. The genomic organization of SRLVs is typical of lentiviruses: positive sense RNA dimmers of approximately 9 kb in size which consist of long terminal repeats (
LTRs),
gag (group specific antigens),
pol (polymerase)
env (envelope) genes in addition to a number of regulatory genes. The
gag and
pol genes are relatively well conserved among SRLVs, which makes them ideal targets for PCR primer design [
2]. Originally, MVV and CAEV prototypical strains such as strain K1514 [
7], EV-1 [
8], SA-OMVV [
9] and Cork-CAEV [
10] were viewed as distinct viral species restricted to their respective hosts. Viruses isolated from sheep were closely related and referred to as MVV, and those isolated from goats were referred to as CAEV. Over the last two decades however, as more SRLV sequences became available for phylogenetic analyses, it became evident that SRLVs can cross the species barrier since some ovine and caprine strains appear on shared branches in family trees [
11‐
13]. Additionally, molecular-epidemiological evidence suggest that SRLVs can transmit between sheep and goats under favourable conditions (Shah et al 2004; Pisoni et al 2005). In Canada, SRLV infections are widespread in small ruminants and have been associated principally with lung and mammary lesions in sheep and arthritis and emaciation in goats [
14,
15]. National surveys revealed that 63% of sheep flocks and 52.9% of goat flocks had at least one infected animal ([
15];Simard C., unpublished observations). In addition, SRLV were detected in 31.3% of Quebec sheep and 82.5% of milking goats ([
16] and unpublished). Despite the fact that SRLVs have been known to circulate and cause disease in Canadian sheep and goats for more than three decades, molecular characterization of SRLV strains had never been carried out in either species [
17]. In this study, we report for the first time, genomic sequences and phylogenetic analyses of Canadian SRLVs from a small geographic area. Nearly complete
gag sequences from both sheep and goats were obtained from animals belonging to single species flocks.