Emerging Influenza D virus infection in European livestock as determined in serology studies: Are we underestimating its spread over the continent?

Abstract

Influenza D virus (IDV) is a novel orthomyxovirus that was first isolated in 2011 in the United States from a swine exhibiting influenza-like disease. To date, its detection is extended to all continents and in a broad host range: IDV is circulating in cattle, swine, feral swine, camelids, small ruminants and horses. Evidence also suggests a possible species jump to humans, underlining the issue of zoonotic potential. In Europe, serological investigations in cattle have partially allowed the understanding of the virus diffusion in different countries such as Italy, France, Luxembourg and Ireland. The infection is widespread in cattle but limited in other investigated species, consolidating the assumption of cattle as IDV primary host. We hypothesize that commercial livestock trade could play a role in the observed differences in IDV seroprevalence among these areas. Indeed, the overall level of exposure in cattle and swine in destination countries (e.g. Italy) is higher than in origin countries (e.g. France), leading to the hypothesis of a viral shedding following the transportation of young cattle abroad and thus contributing to larger diffusion at countries of destination.IDV large geographic circulation in cattle from Northern to more Southern European countries also supports the hypothesis of a viral spread through livestock trade. This review summarizes available data on IDV seroprevalence in Europe collected so far and integrates unpublished data from IDV European surveillance framework of the last decade. In addition, the possible role of livestock trade and biosecurity measures in this pathogen's spread is discussed.

Serological Surveillance of Influenza D Virus in Ruminants and Swine in West and East Africa, 2017–2020

“…Our data indicated a higher IDV seropositivity rate in cattle compared to the other animal species. These results are in line with data reported in European countries [ 8 ]. Indeed, cattle are considered as the main host for IDV, contributing to its spread.…”

“…Seropositivity rates of IDV in domestic ruminants and swine and HI titers in Africa are much lower than those observed in other continents [8,14,19]. Antigenically different IDV strains were isolated in many regions of the world [5].…”

“…Influenza D Virus (IDV) was first isolated in 2011 in Oklahoma, USA from pigs presenting with flu-like symptoms [ 3 ]. After its first isolation, IDV has been detected in other countries in America [ 4 ], Europe [ 5 , 6 , 7 , 8 ] and Asia [ 9 , 10 ]. Serological studies showed the circulation of IDV in many countries in Africa [ 11 , 12 , 13 ], suggesting a worldwide geographic distribution of the virus.…”

First expert elicitation of knowledge on drivers of emergence of influenza D in Europe

“…is not yet completely elucidated, IDV seems to have a broad host range and has been described almost on all continents, suggesting an intercontinental transmission (Gaudino et al, 2020).…”

“…This paragraph highlights some discrepancies in the literature concerning the genetic diversity, immunity and clinical signs. So far, a couple of major circulating IDV lineages have been described in North America, Europe and Japan (Gaudino et al, 2020;Hayakawa et al, 2020;Murakami et al, 2016Murakami et al, , 2020 and reassortment events between these lineages were reported (Chiapponi et al 2019;Collin et al 2015). Furthermore, the haemagglutinin-esterase fusion (HEF) surface protein is antigenically stable suggesting that antibody escape mutants may not occur frequently (Wan et al, 2020).…”