Evidence for avian influenza A infections among Iowa’s agricultural workers

Abstract

Background Identifying risk factors for zoonotic influenza transmission may aid public health officials in pandemic influenza planning. Objectives We sought to evaluate rural Iowan agriculture workers exposed to poultry for previous evidence of avian influenza virus infection. Methods In 2004, we enrolled 803 rural adult Iowans in a 2‐year prospective study of zoonotic influenza transmission. Their enrollment data and sera were compared with those of 66 adult controls enrolled at the University of Iowa in 2006 by using proportional odds modeling. Results Of the 803 participants 58·8% were male with a mean age of 55·6 years. Forty‐eight percent reported previous poultry exposure. Sera were studied by microneutralization techniques for antibodies against avian H4, H5, H6, H7 and H9 viruses. Touching live birds was associated (OR 1·2; 95% CI 1·02–1·8) with increased antibody titer against H5 virus. Similarly, participants who reported hunting wild birds had increased antibody titers against H7 virus (OR 2·8; 95%CI 1·2–6·5) and subjects who reported recent exposure to poultry had increased antibody titers against H6 (OR 3·4; 95% CI 1·4–8·5) and H7 viruses (OR 2·5, 95% CI 1·1–5·7). There was no evidence of elevated antibody against avian H4 or H9 viruses. Conclusions These data suggest that hunting and exposure to poultry may be important risk factors for avian influenza virus infection among rural US populations. Agriculture workers should be included in influenza pandemic plans.

Serological comparison of antibodies to avian influenza viruses, subtypes H5N2, H6N1, H7N3 and H7N9 between poultry workers and non-poultry workers in Taiwan in 2012

“…Third, because there were no reliable or referenced cut-off values of seropositivity for different subtypes in previous studies, cut-off values of seropositivity were set at an HI titre of 40 for H6N1, H7N3 and H7N9 subtypes and at 1:80 for H5N2. In conclusion, this study indicates that poultry workers have a higher risk of exposure to AIVs during occupational activities and consistently supports the results reported previously by other studies [10,[21][22][23][24]. Therefore, active surveillance for the early detection and intervention of viral infections in live poultry should be conducted continuously.…”

Antigenic Characterization of H3 Subtypes of Avian Influenza A Viruses from North America

“…Among these birds, those living in wetland and aquatic environments (e.g., Anseriformes spp., particularly ducks, geese, and swans, and Charadriiformes spp., particularly gulls, terns, and waders) are by far the major source of these isolates and are generally accepted as major natural IAV reservoirs (25, 50). Infected wild birds, especially migratory waterfowl, are believed to serve as a vector facilitating the spread of avian IAVs among wild bird species and different geographic locations, and are one source for viral transmission into domestic poultry (34, 50), swine (19), and humans (16). …”

Weighing serological evidence of human exposure to animal influenza viruses − a literature review

“…Gray et al also found neutralising antibodies to H6N2 and H7N2 influenza virus in the same study, but the prevalences were not significantly different between the exposed group and non-exposed controls (1.4 vs 4.0% and 5.5 vs 0%) [63]. Five other studies failed to find serological evidence of H6 or H7 exposure [18,63,80,102,117]. Only one-cross sectional study looked at H7N9 exposure, finding a seroprevalence of 6.3% in poultry workers in Guangdong, China, and a significantly lower percentage in non-exposed controls (0%) [110].…”

“…Moreover, two studies executed in Romania and Vietnam found no antibodies in either group [18,91]. Gray et al also found neutralising antibodies to H6N2 and H7N2 influenza virus in the same study, but the prevalences were not significantly different between the exposed group and non-exposed controls (1.4 vs 4.0% and 5.5 vs 0%) [63]. Five other studies failed to find serological evidence of H6 or H7 exposure [18,63,80,102,117].…”

“…Gray et al found a significant difference in the seroprevalence of H5N2 antibodies in a swine- and poultry-exposed rural population from Iowa, United States, vs unexposed controls from the same region (8.8 vs 0%) [63]. Okoye et al found H5N2 antibodies in poultry-exposed and -unexposed groups from Nigeria (0.3 vs 1.8%), however, this difference was not significant [63,102]. Moreover, two studies executed in Romania and Vietnam found no antibodies in either group [18,91].…”