First Equine Herpes Myeloencephalopathy (EHM) Outbreak in Chile

Area of Science:

• Veterinary Neurology
• Equine Infectious Diseases
• Virology

Background:

• Equine herpes myeloencephalopathy (EHM) is a severe neurological condition in horses caused by Equine herpesvirus type 1 (EHV-1).
• This report details the initial EHM outbreak in Chile, encompassing clinical observations, epidemiological factors, diagnostic approaches, and implemented control strategies.

Observation:

• The outbreak involved 567 polo horses, with 13 exhibiting EHV-1 clinical signs, 8 experiencing fever, and 11 developing EHM.
• PCR testing confirmed EHV-1 in 6.1% of tested horses, with a notable percentage of PCR-negative horses also showing compatible clinical signs.
• Low fever was observed in some EHM cases, and mortality and morbidity rates were 0.35% and 3.35%, respectively.

Findings:

• The first EHM outbreak in Chile demonstrated low morbidity and mortality rates.
• Rapid implementation of stringent quarantine and biosecurity protocols was effective in limiting disease transmission.
• PCR results indicated a 6.1% positivity rate, but clinical signs were also present in some PCR-negative horses.

Implications:

• Effective biosecurity and quarantine measures are crucial for controlling EHM outbreaks in equine populations.
• Further research into viral prevalence and specific EHV-1 strains is necessary for enhanced preparedness and disease management strategies.
• Understanding the diagnostic nuances, including PCR-negative cases with clinical signs, is vital for accurate EHM diagnosis and control.