Occurrence of porcine reproductive and respiratory syndrome clinical outbreaks in Ontario sow herds, 2017 to 2019.

Abstract

Background: Porcine reproductive and respiratory syndrome (PRRS) is one of the important endemic diseases in swine populations. Monitoring PRRS frequency in commercial herd populations has often been based on laboratory submissions. However, a limitation of this approach is that new clinical outbreaks of PRRS are challenging to identify if epidemiological information is not provided. This hinders the estimation of basic measures such as incidence.

Objectives: The objectives of this study were to describe a system to monitor new clinical outbreaks in Ontario sow herds and to report the incidence of clinical PRRS outbreaks in a subset of Ontario sow herds.

Procedure: We compared herd-level outbreak data from January 1, 2017 to December 31, 2019. Cases were confirmed as positive based on observation of sow herds with typical clinical signs suggestive of PRRS, followed by laboratory confirmation of the PRRS virus.

Results and conclusion: The incidences from year to year were similar (P = 0.058) and were lower compared to estimates in the United States. Descriptively, the highest cumulative incidence was during 2018 (annual incidence risk = 0.067 cases per 100 sow herds, 95% CI = 0.050 to 0.090). This was characterized by an unusually high number of cases reported in the summer.