Virological and epidemiological patterns of swine influenza A virus infections in France: cumulative data from the RESAVIP surveillance network, 2011–2018

This study reports virological and epidemiological data accumulated through passive surveillance conducted during 1,825 herd visits from 2011 to 2018. Among them, 887 (48.6%) tested swIAV-positive. The proportion of positive cases remained stable year-on-year and year-round. The European avian-like swine H1N1 (H1avN1) virus was the most frequently identified (69.6%), and was widespread across the country. The European human-like reassortant swine H1N2 (H1huN2) virus accounted for 22.1% and was only identified in the north-western quarter and recently in the far north. The 2009 pandemic H1N1 (H1N1pdm) virus (3.6%) was detected throughout the country, without settling in areas of higher pig densities. Its proportion increased in winter, during the seasonal epidemics in humans. The European human-like reassortant swine H3N2 as well as H1avN2 viruses were identified sporadically. In up to 30% of swIAV-positive cases, pigs exhibited clinical signs of high intensity, regardless of the viral subtype and vaccination program. The recurrent pattern of the disease, i.e., an endemic infection at the herd level, was reported in 41% of cases and mainly affected post-weaning piglets (OR = 5.11 [3.36-7.76]). Interestingly, the study also revealed a significant association between the recurrent pattern and sow vaccination (OR = 1.96 [1.37-2.80]). Although restricted to the studied pig population, these results bring new knowledge about swIAV dynamics and infection patterns in pig herd...
Source: Veterinary Microbiology - Category: Veterinary Research Source Type: research