In Leishmania parasites, paradoxically, viruses are present in the RNAi-proficient lineage, in which they trigger induction of host toll-like receptor 3 (TLR3) (dsRNA) and toll-like receptor 7 (TLR7) (single-stranded RNA [ssRNA]) responses during infection, resulting in more severe mucocutaneous infections instead of the typical cutaneous infections [7]. This evidence concerns the gene TLR3 and infection.