An equine herpesvirus 1 (EHV1) abortion storm at a riding school.

The research studies an outbreak of equine herpesvirus1 (EHV1) that caused multiple abortions in a riding school in The Netherlands in 1991, investigating the cause and epidemiology of the outbreak.

About the Study

• The study focuses on an outbreak of EHV1 at a riding school in the Netherlands in 1991. EHV1 is a virus that can cause a variety of illnesses in horses, including miscarriages, respiratory disease, and neurologic disease.
• Seven out of twelve pregnant mares at the riding school aborted, with another foal dying at 8 days of age. Six of these abortions happened within a span of 12 days in March following the first abortion on 8th February.
• Virological examinations of four aborted foals indicated an EHV1 infection, underlining the severe impact of the virus on pregnancy.

Findings

• The study’s serological results — which focus on the study of blood serum — suggested that the initial abortion on 8th February was the index case. In epidemiology, an index case is the first documented patient in the onset of an epidemiological investigation, or more generally, the first case of a condition or syndrome to be described in the medical literature.
• The results indicate that this initial case likely caused the subsequent six abortions, indicating a possible chain transmission of the virus.

Suggested Cause

• The researchers suggest that the index case could have been caused by a reactivation of a latent (inactive) virus brought on by transportation stress. This means the virus was already present in the horse, but environmental stress could have triggered it to become active and cause illness.

Implication of the Study

• The findings of the study contribute to the current understanding of the pathogenesis (the manner of development) and epidemiology (the study of the distribution and determinants of health-related states) of EHV1 abortion in horses.
• The results highlight the importance of effective EHV1 management to prevent outbreaks and protect the health of pregnant mares and their foals.