Discussion

Unsegmented dsRNA viruses of the family Todiviridae are known from such divers hosts as fungi, arthropods, and parasites. In some plant-pathogenic fungi, the viruses reduce the virulence of the fungal host, while in mammalian parasites like Leishmania and Trichomonas; the viruses are associated with an increase in virulence. The impact of the viruses on the virulence of Giardia and Eimeria species is still unresolved.  With the exception of Giardia and a few mycoviruses, the viruses are assumed to be only transmitted vertically without ever leaving the host cell, meaning they are not infectious.  Leishmaniaviruses from the New World like, L. (Viannia) brazilliensis and L. (Viannia) guyanensis are known as Leishmania RNA virus 1, viruses from the Old World like L. major and L. aethiopica as Leishmania RNA virus 2. Here we report the molecular detection of a new Leishmania RNA virus 2 in an isolate of L. (Leishmania) infantum from a dog with leishmaniasis in Portugal. The genome codes for two major proteins, a capsid protein and an RNA-dependent RNA polymerase. Within the species Leishmania RNA virus 2, the RNA-dependent RNA polymerase evolves so fast that it is only conserved for 60 % at the amino acid level, making it very difficult to find long-enough regions on the nucleotide level to design (degenerate) primers for screening purposes.