Equine Herpesvirus Type 1 Myeloencephalitis in the Brazilian Amazon

SIMPLE SUMMARY: The horse breeding industry has great importance in the state of Pará, contributing to society in economic and cultural ways. For this, it is necessary to know the disorders that affect these animals, especially those caused by worldwide distributed virus, such as equine herpesvirus type 1. In this sense, the clinical and epidemiological investigation of this work about equine herpesvirus myeloencephalopathy show important results to the inclusion of this neurological disorder in the differential diagnosis of neurological diseases most common in horses in the state of Pará, Brazil. The work shows the viral circulation in different farms, clinical signs, epidemiological findings, macroscopic and microscopic findings in that animals submitted to necropsy. ABSTRACT: An investigative and epidemiological study was carried out for equine herpesvirus type 1 (HVE-1) in 10 outbreaks of neurological disease from different farms in the state of Pará, Brazil. 25 horses were studied: six male and 19 females, aged between one and 13 years. A necropsy of six horses was performed, and the others recovered either with or without treatment (T1—vitamin B1 + dexamentasone; T2—vitamin B1 + flunixim meglumine). Animals that received treatment recovered after eight days. The main clinical signs observed were motor incoordination, progressive paresis, thoracic and/or pelvic limbs abducted after induction of clinical examination, knuckling of the hind fetlocks, sagging and swaying of the hindquarters while standing or walking and paresis. All animals were positive: 88% (22/25) in nested PCR and 72% (18/25) in serum neutralization (including three negatives in serology). Focal brownish areas compatible with hemorrhage were found in the white and gray matter of the spinal cord of two animals. On histological analysis, there were perivasculitis and neutrophilic vasculitis in the gray matter of the spinal cord and brain. Based on the evidence, this work proves the circulation of HVE-1 in the Amazon biome, mainly in the state of Pará, Brazil.