Outbreak of Western Equine Encephalitis Virus Infection Associated with Neurological Disease in Horses Following a Nearly 40-Year Intermission Period in Argentina
María Aldana Vissani,
Florencia Alamos,
María Silvia Tordoya,
Leonardo Minatel,
Juan Manuel Schammas,
María José Dus Santos,
Karina Trono,
María E. Barrandeguy,
Udeni B. R. Balasuriya,
Mariano Carossino
Affiliations
María Aldana Vissani
Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires B1686, Argentina
Florencia Alamos
Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires B1686, Argentina
María Silvia Tordoya
Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires B1686, Argentina
Leonardo Minatel
Facultad de Ciencias Veterinarias, Universidad de Buenos Aires, Ciudad de Buenos Aires C1427CWN, Argentina
Juan Manuel Schammas
Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires B1686, Argentina
María José Dus Santos
Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires B1686, Argentina
Karina Trono
Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires B1686, Argentina
María E. Barrandeguy
Instituto Nacional de Investigación Agropecuaria (INIA), Plataforma de Investigación en Salud Animal, Estación Experimental La Estanzuela, Colonia, Uruguay
Udeni B. R. Balasuriya
Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
Mariano Carossino
Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
Western equine encephalitis virus (WEEV) is a mosquito-borne arbovirus (genus Alphavirus, family Togaviridae) that has re-emerged in South America in late 2023, causing severe disease in both horses and humans after a nearly 40-year intermission period. We here describe the virological, serological, pathological, and molecular features of WEEV infection in horses during the 2023–2024 outbreak in Argentina. WEEV-infected horses developed neurological signs with mild to severe encephalitis associated with minimal to abundant WEEV-infected cells, as demonstrated by WEEV-specific in situ hybridization. The distribution of viral RNA was multifocal, with predominance within neuronal bodies, neuronal processes, and glial cells in the medulla oblongata and thalamic regions. Phylogenetic analysis of partial nsP4 sequences from three viral isolates obtained from three different provinces of Argentina support grouping with other temporally current WEEV strains from Uruguay and Brazil under a recently proposed novel lineage.
