Serologic Evidence of H1 Swine Influenza Virus Infection in Swine Farm Residents and Employees

Abstract

We evaluated seropositivity to swine and human H1 influenza viruses in 74 swine farm owners, employees, their family members, and veterinarians in rural south-central Wisconsin, compared with 114 urban Milwaukee, Wisconsin, residents. The number of swine farm participants with positive serum hemagglutination-inhibition (HI) antibody titers >40 to swine influenza viruses (17/74) was significantly higher (p<0.001) than the number of seropositive urban control samples (1/114). The geometric mean serum HI antibody titers to swine influenza viruses were also significantly higher (p<0.001) among the farm participants. Swine virus seropositivity was significantly (p<0.05) associated with being a farm owner or a farm family member, living on a farm, or entering the swine barn >4 days/week. Because pigs can play a role in generating genetically novel influenza viruses, swine farmers may represent an important sentinel population to evaluate the emergence of new pandemic influenza viruses.

Increased risk of A(H1N1)pdm09 influenza infection in UK pig industry workers compared to a general population cohort

“…With regard to other SIV strains other than A(H1N1)pdm09, previous studies found an increased risk of seropositivity to at least one SIV in pig workers, including H1N1,17, 18, 27, 29, 31, 33, 41, 42, 43 H1N218, 28, 31 and H3N228, 29, 30, 44 strains. In our study, we found increased risk of seropositivity both to swine H1N2 and H3N2 Perth.…”

“…Pigs are a particularly important species in this regard as the occurrence of both types of SA receptors permits binding of human and avian influenza viruses making them an efficient ‘mixing vessel' 11, 12, 13, 14. Interspecies transmission (in both directions) of swine and human influenza viruses is well recognised, evidenced by the isolation of human influenza virus in swine15, 16 and evidence of swine influenza virus (SIV) infection in people with close occupational17, 18, 19 and/or residential proximity to pigs20, 21; or prolonged exposure at an agricultural fair22. Transmission between pigs and bird species is exemplified by various reports of isolation of SIV from turkeys 23, 24, 25.…”

Epidemiological update on swine influenza (H1N1) in pigs

“…Because a relatively small number of zoonotic swine infl uenza virus infection have been documented by virus isolation, whether infections with swine infl uenza viruses are clinically different than infections with routine human infl uenza viruses remains unclear. It is therefore important to pursue virus isolation aggressively when swine farming people show infl uenzalike symptoms [65]. The special environment and lifestyle in southern China provide more chances for wild aquatic birds, domestic poultry, pigs and humans to come in contact closely and hence create an opportunity for interspecies transmission and generation of new reassortant infl uenza viruses.…”

The Animal-Human Interface and Infectious Disease in Industrial Food Animal Production: Rethinking Biosecurity and Biocontainment

“…A number of studies also demonstrate that zoonotic viruses can be transmitted across the animal-human interface in the context of food animal production ( Table 2). Studies on seroprevalence of H1 swine influenza virus infections 27,70 and hepatitis E 22 indicate that farmers and farm workers can be infected by viruses from food animals. Myers et al reported that swine farmers had higher titers of H1N1 and H1N2 antibodies and greatly elevated risks of seropositivity to these two influenza A viruses (35.3 and 13.8 odds ratios, respectively, as compared with community referents).…”

“…23 Thus, it is not surprising that increased risks of pathogen exposure and infections, both bacterial and viral, have been reported among farmers, their families, and farm workers at poultry and swine operations. [24][25][26][27][28][29][30][31][32][33] …”