Isolation of Madariaga Virus (MADV) in a Horse Coinfected with Equine Infectious Anemia in Venezuela: A Review of MADV Circulation in the Country

BACKGROUND: family and has been periodically infecting equids in Venezuela since its first identification in 1975. This study reports the isolation and molecular characterization of MADV isolated from a horse in December 2024 in the context of MADV cases reported in Venezuela. METHODS: Antibodies to the rabies virus were detected by indirect immunofluorescence, and to the Equine Infectious Anemia virus (EIAV) by passive immunodiffusion. MADV RNA was detected by qRT-PCR. The sequence of the complete viral genome was obtained by next-generation sequencing. RESULTS: The sequence of this virus was highly similar to that of the only human case of MADV reported in the country in 2016, as well as to a sequence of a virus isolated from a horse in Colombia in 2002. The horse was found to be co-infected with EIAV. CONCLUSIONS: The continuous circulation of MADV in Venezuela warrants reinforcing the preventive measures against these alphaviruses, which ignore borders, and may cause important animal and human health concerns.