Outbreak of Western Equine Encephalitis Virus Infection Associated with Neurological Disease in Horses Following a Nearly 40-Year Intermission Period in Argentina

• Published in: Viruses Vol. 16; no. 10; p. 1594
• Main Authors: Vissani, María Aldana, Alamos, Florencia, Tordoya, María Silvia, Minatel, Leonardo, Schammas, Juan Manuel, Dus Santos, María José, Trono, Karina, Barrandeguy, María E, Balasuriya, Udeni B R, Carossino, Mariano
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 10-10-2024; MDPI
• Subjects: Analysis; Animals; Argentina - epidemiology; Care and treatment; Diagnosis; Disease Outbreaks - veterinary; Encephalitis; Encephalitis Virus, Western Equine - genetics; Encephalomyelitis; Encephalomyelitis, Equine - epidemiology; Encephalomyelitis, Equine - veterinary; Encephalomyelitis, Equine - virology; Encephalomyelitis, Western Equine - epidemiology; Encephalomyelitis, Western Equine - virology; Epidemics; Equine encephalomyelitis; Genomes; Glial cells; horse; Horse Diseases - epidemiology; Horse Diseases - virology; Horses; Hybridization; Immunization; Medulla oblongata; Mosquitoes; Nervous System Diseases - epidemiology; Nervous System Diseases - veterinary; Nervous System Diseases - virology; Neurological diseases; Neuronal-glial interactions; outbreak; Outbreaks; Phylogenetics; Phylogeny; Polymerase chain reaction; RNA, Viral - genetics; Serology; Surveillance; Thalamus; Vaccines; Virology; Viruses; WEE; WEEV; West Nile virus; Western equine encephalitis; Western equine encephalitis virus; Argentina; United States > US; North America; horse; Argentina; viral tropism; Western equine encephalitis virus; encephalitis; WEE; WEEV; outbreak; in situ hybridization
• ISSN: 1999-4915; 1999-4915
• DOI: 10.3390/v16101594

Western equine encephalitis virus (WEEV) is a mosquito-borne arbovirus (genus
, family
) 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.