Serological Evidence of Backyard Pig Exposure to Highly Pathogenic Avian Influenza H5N8 Virus during 2016–2017 Epizootic in France

Abstract

In autumn/winter 2016–2017, HPAI-H5N8 viruses belonging to the A/goose/Guandong/1/1996 (Gs/Gd) lineage, clade 2.3.4.4b, were responsible for outbreaks in domestic poultry in Europe, and veterinarians were requested to reinforce surveillance of pigs bred in HPAI-H5Nx confirmed mixed herds. In this context, ten pig herds were visited in southwestern France from December 2016 to May 2017 and serological analyses for influenza A virus (IAV) infections were carried out by ELISA and hemagglutination inhibition assays. In one herd, one backyard pig was shown to have produced antibodies directed against a virus bearing a H5 from clade 2.3.4.4b, suggesting it would have been infected naturally after close contact with HPAI-H5N8 contaminated domestic ducks. Whereas pigs and other mammals, including humans, may have limited sensitivity to HPAI-H5 clade 2.3.4.4b, this information recalls the importance of implementing appropriate biosecurity measures in pig and poultry farms to avoid IAV interspecies transmission, a prerequisite for co-infections and subsequent emergence of new viral genotypes whose impact on both animal and human health cannot be predicted.

A systematic review of influenza A virus prevalence and transmission dynamics in backyard swine populations globally

“…While the human-origin pandemic A(H1N1)pdm09 virus clade 1A.3.3.2 viruses were more commonly reported in backyard swine, the human H1N1 and H3N2 viruses were also detected in backyard swine in various countries suggesting reverse-zoonotic transmission events from human-to-swine. Intriguingly, the presence of avian-origin highly pathogenic viruses including H5N1 [ 12 ] and H5N8 [ 40 ] suggest the possibilities of avian-to-swine transmission. In particular, the presence of highly pathogenic avian H5N1 viruses in Nigerian backyard swine is of interest because Nigeria falls within the East Africa–West Asia flyway of the migratory birds [ 53 ] used by long-distance migratory wild birds for intercontinental migration for overwintering [ 54 ].…”

“…One highly pathogenic avian influenza H5N8 virus was detected in a backyard swine in France during an H5N8 outbreak among French poultry during 2016–2017. The HI assay confirmed that one backyard swine had antibodies against H5 clade 2.3.4.4b and identified that avian origin H5N8 virus would have been transmitted from domestic ducks raised on the backyard farm to the swine [ 40 ]. No clinical signs of disease were reported from the infected backyard swine.…”

“…10 a). Interestingly, 13 (38.24%) studies reported that swine and poultry regularly interacted in the backyards [ 12 , 20 , 23 , 27 , 28 , 33 , 35 , 37 , 39 , 40 , 47 – 49 ], while seven (20.58%) studies reported interactions among the wild birds, swine, and poultry [ 24 – 26 , 30 , 32 , 36 , 44 ]. Two (5.88%) studies reported interactions among the swine, poultry, and cattle [ 42 , 46 ], while the other remaining studies (n = 12; 35.29%) did not mention any interactions between backyard swine and other animal species [ 18 , 21 , 22 , 29 , 31 , 34 , 38 , 41 , 45 ] (Fig.…”

“…10 b). As far as the reports of interspecies IAV transmission were concerned, numerous studies suggested human-to-swine (reverse zoonotic) transmission of IAV (n = 15; 44.12%) [ 19 , 21 , 22 , 24 , 26 , 27 , 29 , 31 , 33 , 34 , 41 , 42 , 45 , 46 , 50 ] while swine-to-human (n = 2; 5.88%) [ 18 , 23 ], poultry-to-swine (n = 2; 5.88%) [ 36 , 40 ], and wild birds-to-swine (n = 1; 2.94%) [ 47 ] IAV transmissions within the backyards were also suggested. On the other hand, several studies (n = 14; 41.18%), including those that conducted sero-surveillance only [ 29 – 31 , 37 – 41 ], could not determine the epidemiology of IAV transmission in the backyards (Fig.…”

“…10 c). While only a few studies were aimed towards investigating IAV in swine having clinical signs of disease (n = 8; 23.53%) [ 18 – 24 , 41 ], most of the studies included clinically healthy swine (n = 26; 76.47%) [ 12 , 25 – 40 , 42 – 50 ] for the detection of IAV (Fig. 10 d).…”