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Influenza A viruses (IAVs) are common causes of respiratory infection in pigs. The objective of this study was to characterize the circulation of IAVs between weaning and market age on the basis of development of antibody response and molecular epidemiology of detected viruses. Two batches of weaned pigs were followed in the nursery and finisher barns with a sample of 81 and 75 pigs. Nasal swabs and blood samples were collected from individual pigs for virological and serological analyses. A H3N2 subtype virus, of cluster IV, was detected in Study 1, with a maximum of 97.9% identity to HA gene of viruses previously isolated in Ontario. In Study 2, a H1N1 subtype virus, of 2009 H1N1 pandemic lineage, was detected, with a maximum of 97.8% identity to HA gene of viruses previously isolated in Ontario. On the basis of HA gene, it was observed that pigs were being detected with the same virus over time. The existence of antibody titers for IAV other than the isolated one confirmed that more than one subtype can circulate in the same population. In Study 1, pigs with higher numbers of IAV detection had lower serological titers for the same virus that was confirmed to circulate in the nursery (P < 0.01). Thorough knowledge of all endemic viral strains is fundamental for development of infection and disease control, particularly in complex production systems. This may include consideration of sampling and testing strategies which could detect circulation of all IAV variants, even if they have low prevalence. [ABSTRACT FROM AUTHOR]

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., (Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.)