Estimating the incidence of equine viral arteritis and the sensitivity of its surveillance in the French breeding stock.

The research article is about a study that developed and applied a specific set of criteria to estimate both the occurrence of equine viral arteritis outbreaks in French horse breeding stock and the effectiveness of the country’s surveillance system over a period of years.

Objective of the Study

• The study aimed to shine light on equine viral arteritis (EVA), a disease that could majorly impact the economy of the equine industry, specifically in the French breeding stock between 2006 and 2013. Another objective was to estimate the sensitivity of the surveillance process dedicated to monitoring the disease.

Approach and Methodology

• To accomplish its goals, the study established specific criteria to identify the presence of antibodies created in response to EVA in horses, known as seroconversion. This set of criteria was developed through a consensus of multidisciplinary experts. They chose to define seroconversion as either a change in the antibody titer from negative to at least 32 or an eight-fold or greater increase in the level of antibodies.
• With these established criteria, they identified 239 cases and 177 outbreaks of EVA.
• The research also attempted to calculate the effectiveness of the breeding stock surveillance component (BSSC) through a ‘capture-recapture’ model. This model is typically used in ecological studies to estimate the total number of outbreaks, including those that go unreported.

Results and Findings

• The total number of outbreaks was estimated at 215 with the credible interval of 95% ranging from 195-249. This indicates that the range within which the true number of outbreaks lies with 95% certainty, is between 195 and 249.
• The surveillance system’s sensitivity was calculated at 82%, with a 95% credible interval of 71-91%. This suggests that the surveillance system is effective and relevant for preventing the spread of EVA.
• The study confirmed EVA circulation in French breeding stock and identified a notable persistence of neutralizing antibodies for up to eight years in naturally infected mares. It also indicated that some mares may have been reinfected.

Implications of the Study

• The findings of this study substantiate the utility and effectiveness of the BSSC in detecting EVA outbreaks. It also helps understand the longevity of antibodies and potential for reinfection in mares. These insights can guide future surveillance and control measures for EVA in not only France, but potentially other equine industries globally.