Peer-reviewed veterinary case report
Equine herpes myeloencephalopathy outbreak in Chile
By Durán MC et al.·2025·Unidad Medicina y Cirugía Equina·View original on Europe PMC →
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Original publication title: First Equine Herpes Myeloencephalopathy (EHM) Outbreak in Chile.
- Species:
- horse
Plain-English summary
Equine herpes myeloencephalopathy (EHM) is a serious neurological disease in horses caused by a virus known as Equine herpesvirus type 1 (EHV-1). In Chile, there was a first outbreak involving 567 polo horses, mostly mares and geldings, with an average age of about 10 years. Out of these horses, 13 showed signs of the virus, with 11 developing EHM and two horses unfortunately dying from the disease. Testing revealed that a small percentage of horses tested positive for the virus, and while most of the infected horses showed symptoms, some that tested negative also had signs of illness. Overall, the outbreak had low rates of illness and death, and quick action to enforce quarantine and safety measures helped prevent further spread of the disease.
Abstract
Equine herpes myeloencephalopathy (EHM) is a neurological disease in horses caused by Equine herpesvirus type 1 (EHV-1). It is a serious condition, often resulting in severe neurological deficits, and can be fatal. In this report, we discuss the first outbreak of EHM in Chile (clinical signs, epidemiology, diagnosis, and control measures). A total of 567 polo horses were kept at the facility: 58.4% mares, 41.6% geldings, and stallions. Mean age was 9.7 ± 0.132 years. Thirteen horses showed clinical signs of EHV-1, eight had fevers (1.4%), and eleven developed EHM (1.9%). Only six of the eleven EHM cases had high fevers (>39.5 °C). Mortality was 0.35% (index case and one additional case) and morbidity reached 3.35% (19/567). PCR testing was performed on 214 horses (37.7%); 13 tested positive (6.1%) and 201 negative (93.9%). Of PCR-positive horses, 53.8% showed clinical signs. Notably, 2.9% of PCR-negative horses also presented signs compatible with EHV-1. CT values among positive cases ranged from 30 to 39. This first EHM outbreak in Chile showed low morbidity and mortality. Rapid implementation of strict quarantine and biosecurity effectively limited spread. Further data on viral prevalence and types are needed to improve preparedness.
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Search related cases →Original publication on Europe PMC: https://europepmc.org/article/MED/40867672