Clinical features of the 1992 outbreak of equine viral arteritis in Spain.

The research paper reports on an outbreak of Equine viral arteritis (EVA) that occurred among a horse population in Spain in 1992 and investigates its clinical features, severity, and diagnostic methods.

Study Context

• The study centers on a significant outbreak of Equine viral arteritis (EVA) that occurred in 1992 in a riding establishment near Barcelona, Spain.
• The virus affected 31 of the 186 horses, presenting varying levels of severity.

Clinical Features of EVA Observed

• The affected horses exhibited several clinical signs, including fever, depression, minor swelling in the lower abdominal area and limbs, and vesicular-erosive stomatitis, characterized by symptoms such as excessive salivation, petechiae (small pin-point haemorrhages), and small ulcerations.
• The severity of the disease varied among the affected horses, severe forms were only observed in a few, and no deaths were reported.

Hematological Observations

• Blood tests revealed several hematological changes in the most severely affected horses. The changes included thrombocytopenia (a low platelet count), mild leukocytosis (an increase in white blood cells), neutrophilia (an increase in a type of white blood cells called neutrophils), lymphopenia (reduced lymphocyte levels), and eosinopenia (reduced eosinophil levels).
• Additionally, these horses showed an increase in plasma fibrinogen (a blood protein that aids in clotting), a small rise in serum proteins and indirect bilirubin values.

Diagnosis and Virus Isolation Attempts

• The diagnosis of EVA was confirmed by demonstrating seroconversion – a change in the detectable levels of specific antibodies due to infection and subsequent immune response – to equine arteritis virus in the acute and convalescent phases of the disease. This is a widely recognized method for diagnosing viral infections.
• Despite efforts, the researchers were unable to isolate the virus from blood samples collected in citrate tubes, suggesting the need for more effective virus detection methods in such outbreak situations.