Equine Herpesvirus Type 1 Myeloencephalitis in the Brazilian Amazon.
Authors: Barbosa José Diomedes, Lins André de Medeiros Costa, Bomjardim Henrique Dos Anjos, Silveira Natália da Silva E Silva, Barbosa Camila Cordeiro, Beuttemmuller Edsel Alves, Brito Marilene Farias, Salvarani Felipe Masiero
Journal: Animals : an open access journal from MDPI
Summary
# Equine Herpesvirus Type 1 Myeloencephalitis in the Brazilian Amazon Equine herpesvirus type 1 (EHV-1) is a known neurological threat in temperate regions, but its presence and clinical presentation in tropical South America remained poorly characterised until this investigation of 10 disease outbreaks across farms in Pará state, Brazil. Barbosa and colleagues conducted a combined epidemiological and necropsy study of 25 affected horses (aged 1–13 years), using nested PCR and serum neutralisation testing alongside histopathological examination of six fatal cases, whilst comparing two treatment protocols: thiamine plus dexamethasone versus thiamine plus flunixmeglumine. Nested PCR achieved 88% positivity (22/25 horses), substantially higher than the 72% serology result, indicating active viral replication; treated animals recovered within eight days regardless of anti-inflammatory choice, whilst clinical signs included progressive paresis, knuckling of hind fetlocks, hindquarter ataxia and characteristic abduction of limbs during examination. Histological findings revealed perivasculitis and neutrophilic vasculitis in grey matter of spinal cord and brain, with focal haemorrhages visible in white and grey matter in two necropsied cases, confirming myeloencephalitis as the underlying pathology. For equine practitioners in tropical and subtropical regions, this documentation of EHV-1 circulation in the Amazon basin expands the geographic scope of neurological herpesvirus surveillance and suggests that clinical protocols established elsewhere may be applicable, though practitioners should maintain heightened awareness of this pathogen in areas previously considered low-risk.
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Practical Takeaways
- •HVE-1 myeloencephalitis is circulating in the Brazilian Amazon and should be considered in differential diagnosis for equine neurological disease presenting with progressive paresis and incoordination
- •Early treatment with vitamin B1 combined with anti-inflammatory agents (dexamethasone or flunixim meglumine) is associated with recovery within 8 days
- •Practitioners in endemic regions should maintain biosecurity protocols and consider HVE-1 serology/PCR testing for horses with acute onset neurological signs, particularly hind limb dysfunction
Key Findings
- •88% (22/25) of horses tested positive for HVE-1 via nested PCR across 10 outbreaks in Pará, Brazil
- •Clinical signs included motor incoordination, progressive paresis, knuckling of hind fetlocks, and hindquarter sagging/swaying
- •Histopathological examination revealed perivasculitis and neutrophilic vasculitis in gray matter of spinal cord and brain
- •Horses receiving treatment (vitamin B1 with either dexamethasone or flunixim meglumine) recovered within 8 days