The impact of the initial public health response to COVID-19 on swine health surveillance in Ontario

Abstract

COVID-19 restrictions and the pandemic have affected animal health and food production through the disease's effects on human activities. COVID-19 impact on swine health surveillance can be assessed by investigating submissions and test positivity for pathogens before and after COVID-19 restrictions. PRRSV, Influenza A virus, Mycoplasma hyopneumoniae and PCV-2 are considered important and economically challenging respiratory diseases for the swine populations. By reviewing test results from swine samples submitted for diagnostic testing to a regional diagnostic laboratory, and by assessing total submissions, total positive tests, and the proportion of positive tests at weekly intervals with time series techniques and generalized linear regression models, we evaluated COVID-19's impact on the monitoring of these respiratory pathogens in Ontario, Canada. We classified weeks that fell from week 12 through week 24 in each year as pandemic equivalent weeks and the non-pandemic weeks included all other weeks. The pandemic period in 2020 resulted in a significantly higher number of submissions (p < 0.05) and PRRSV positive submission counts (p < 0.05) when compared to equivalent time periods in previous years; however, no changes could be detected in the odds of weekly PRRSV submission positivity. Weekly positive proportions of PCV-2 tests were higher during the pandemic period in 2020 compared with the pandemic equivalent period in 2018 and 2017. The counts of submissions that requested tests for PRRSV, Influenza A virus and M. hyopneumonia combined, as well as the number of submissions and the proportions of submissions that tested negative for these multiple respiratory pathogens were not significantly different between the pandemic period in 2020 and other periods examined. Our findings indicate that swine producers, in conjunction with various private and public veterinary support services, continued monitoring and performing diagnostic screening on farms for economically important animal diseases despite complications resulting from COVID-19 public health restrictions. PRRSV continues to have a serious impact on swine health. The absence of an increased proportion of negative tests for individual or groups of pathogens, or an accompanying increase in submissions during the 2020 pandemic period suggests that no new undetected pathogens with an impact on respiratory signs in swine were introduced during this time.

Keywords: Influenza A virus; Laboratory data; M. hyopneumoniae; Negative tests; PCV-2; PRRS; Swine health.

Fig. 1

Graphical illustration of extracted data based on unique submissions. Data were obtained from records of samples submitted from swine farms in Ontario, Canada, to the Animal Health Laboratory from May 1, 2015 through June 30, 2020.

Fig. 2

Trends in four respiratory infectious diseases based on submissions to the Animal Health Laboratory from swine farms in Ontario. The trends for Porcine Reproductive and Respiratory Syndrome virus (PRRSV) are shown in black; Influenza A virus, shown in red; Mycoplasma hyopneumoniae bacteria (M. hyo), shown in green; Porcine circovirus type 2 (PCV-2), shown in blue. The trends for three respiratory pathogens combined were extracted after the decomposition of each time series, shown in purple.

Fig. 3

Time series of the number of weekly unique swine submissions tested for the three respiratory infectious diseases combined. A) Number of weekly swine submissions tested for Influenza A virus, Porcine Reproductive and Respiratory Syndrome virus (PRRSV), and M. hyopneumoniae (M.hyo) are shown in black, and the number of weekly swine submissions negative to all three pathogens are shown in red. B) The proportions of weekly swine submissions negative for all three pathogens.