Exposure of wild boar to Influenza A viruses in Bavaria: Analysis of seroprevalences and antibody subtype specificity before and after the panzootic of highly pathogenic avian influenza viruses A (H5N8)

Abstract

Swine influenza A viruses (S-IAV) circulate in wild boar populations worldwide.Subtypes primarily reflect those actually present within the respective pig industry. Accordingly, infections with swine H1N1, H1N2 and H3N2 have been reported for several regions of Germany. As pigs are susceptible not only to S-IAV but also to avian and human influenza A viruses, it is necessary to consider the possibility that new reassortant viruses with pandemic potential may arise in these new hosts. Therefore, in this study the impact of recent IAV epidemics on antibody prevalences in Bavarian wild boar was assessed. Important events considered were the H1N1pdm09 pandemic, which affected humans and swine, and the highly pathogenic avian influenza (HPAI) H5N8 panzootic in 2016 and 2017, affecting wild and domestic birds. IAV seroprevalences were determined analysing 1,396 samples from before and after the H5N8 panzootic, from various regions in Bavaria, a large administrative region in the South of Germany. Taken together, seroprevalences varied markedly from 1.44% to 12.59%, relative to region and time. However, no discrete correlation was found to population density either in wild boar or in pigs. Antibodies against H1N1 were the most prevalent. In addition, antibodies were detected reacting against H1N2 and against H1pdmNx reassortant viruses, already known to circulate in domestic pigs in Bavaria and notably also against the avian influenza A virus H5N8; the latter in samples taken in 2017. These results confirm the exposure of wild boar to IAV of diverse origin and the increasing variability of S-IAV present in the field. The necessity for continuous IAV surveillance not only of domestic swine but also of wildlife is emphasized.

Influenza A in Wild Boars: Viral Circulation in the Emilia-Romagna Region (Northern Italy) between 2017 and 2022

“…Even though wild boars and feral pigs both belong to the Sus scrofa species and can be infected with both avian and swine IAVs in the same way as domestic pigs [ 19 , 27 ], these hosts and their role in the SwIAVs’ ecology are underinvestigated. To date, several reports about SwIAV seroprevalence in European countries are available [ 3 , 19 , 20 , 21 , 24 , 25 , 26 , 41 , 42 ], but only a few of them are about virological circulation [ 19 , 20 , 21 ] and the genotyping of the viral isolates [ 20 ].…”

“…Although the knowledge of IAV infection dynamics in pig hosts is constantly evolving worldwide, viral circulation in wild boars and feral pigs is poorly investigated, despite the fact that the three of them belong to the Sus scrofa species [ 19 ], and only a few reports are available about the Italian situation [ 20 , 21 ]. European epidemiological surveys on IAV circulation in the Eurasian wild boar population demonstrated a seroprevalence ranging between 1.4% and 25.9% [ 3 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ] and a virological prevalence between 0.8% and 3.4% [ 3 , 20 , 21 ]. In addition, the wild boar ecological niche enables the possibility of IAV spillover events from wild birds to wild Sus scrofa species [ 19 ], as has been reported with serological evidence in the US feral swine population [ 27 ].…”

Outbreak of Highly Pathogenic Avian Influenza H5N1 in New England Seals

“…Since October 2020, H5N1 HPAI belonging to the goose/Guangdong H5 2.3.4.4b clade has been responsible for over 70 million poultry deaths across Africa, Asia, Europe, and North America (9). As of July 2022, the World Organisation for Animal Health (WOAH) has reported more than 100 wild mammal infections with (H5) clade 2.3.4.4b in many mesocarnivore species including seals and foxes (9)(10)(11)(12)(13)(14). Rare human infections with H5 clade 2.3.4.4b viruses have been reported (15)(16)(17).…”

Primary harbour seal ( Phoca vitulina ) airway epithelial cells show high susceptibility to infection by a seal‐derived influenza A virus (H5N8)

“…Theoretically, swine can serve as an intermediate host and function as a mixing vessel for avian and mammalian influenza viruses to adapt, reassort, and infect humans (Ma et al., 2009). However, during the last H5Nx HPAI outbreak, an avian—swine–human transmission interface was not involved (Herve et al., 2021; Schulein et al., 2021; Verhagen et al., 2021). One may assume that H5Nx virus reassortment in the swine population is a minor risk.…”