Cross-species Transmission and Host Adaptation of Feline Leukaemia Virus between Domestic Cats and the Wild Felid Leopardus guigna.

2.Feline leukaemia virus (FeLV) is widespread in domestic cats and frequently spills over into wild felid populations, causing severe outbreaks in non-domestic felid populations. Domestic cats carry both endogenous FeLV (enFeLV) and exogenous variants of FeLV (exFeLV), which can recombine to generate novel variants with alternate receptor usage. In contrast, most non-domestic felids, including the guigna are lack enFeLV This study applied amplification of the FeLV envelope gene combined with Illumina sequencing to characterise FeLV envelope gene diversity and transmission dynamics in guignas (Leopardus guigna), a small wild felid native to Chile and Argentina. Seven PCR amplicons from five free ranging guignas were sequenced. Illumina contigs demonstrated that infections originated from Chilean domestic cats; however, a distinct guigna-specific cluster with unique sequence variations was identified, suggesting that FeLV transmission also occurs among guignas independent of domestic cats. Phylogenetic analysis showed that all guigna sequences formed a Chile-specific FeLV clade, closely related to domestic cat viruses but clearly separated from international FeLV-A strains.