Outbreak of equine herpesvirus type 1 myeloencephalitis: new insights from virus identification by PCR and the application of an EHV-1-specific antibody detection ELISA.

This research deals with an outbreak of equine herpesvirus type 1 (EHV-1) that led to neurological disease in five out of ten pregnant mares. Among the affected mares, one lost their fetus while another gave birth but remained sick. The study used polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) tests to diagnose and monitor the EHV-1 infections.

Understanding the Outbreak Situation

• The paper begins by shedding light on an outbreak of equine herpesvirus type 1 myeloencephalitis, a neurological disease, that affected half of the ten pregnant, lactating mares being studied. Among these, three developed severe complications requiring euthanasia for their welfare.
• Of the mares that survived, one unfortunately miscarried her EHV-1-positive fetus 68 days after the initial signs were observed. Meanwhile, another mare gave birth to a healthy foal on day 283 of the study, but she remained ill with persistent neurological symptoms.

Techniques for Identification and Monitoring the Virus

• To diagnose this neurological disease, the researchers utilized a combination of postmortem findings, PCR for virus identification, and serological tests with an EHV-1-specific ELISA.
• The 10 foals born at the beginning of the study all developed a thick mucopurulent nasal discharge, a notable symptom of EHV-1 infection. The investigators amplified the viral genetic material using PCR and monitored the infection using an ELISA.
• The study also involved a similar investigation of the EHV-1 infection status in the five mares that were in close contact but not affected by the outbreak.

Understanding the Immune Response

• Seven days after the index case (the first case identified), three of the affected mares showed either no or only marginal EHV-1-specific antibody levels. Over time, however, their antibody titres increased, indicating an immune response to the infection.
• On the other hand, serum samples from the five unaffected mares showed positive EHV-1 antibodies when first tested seven or thirteen days after the index case, suggesting a previous exposure to the virus without developing the disease.