Evidence for Avian Influenza A Infections Among Iowa's Agricultural Workers

1. Evidence for Avian Influenza A Infections Among Iowa's Agricultural Workers Abstract Acknowledgements Conclusion Results Materials & Methods Introduction Discussion Gregory C. Gray, MD, MPH,1 Troy McCarthy,1 Ana W. Capuano, MPS, 1 Mark Lebeck,1 Sharon F. Setterquist, MT(ASCP),1  Christopher W. Olsen, DVM, PhD,2 Charles F. Lynch, MD, PhD,3 Michael C. Alavanja, PhD4 1Center for Emerging Infectious Diseases, Dept. of Epidemiology, University of Iowa College of Public Health, Iowa City, IA; 2Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI;3Department of Epidemiology, University of Iowa College of Public Health, Iowa City, IA; 4National Cancer Institute, Bethesda, MD In 2004 we enrolled 803 Agricultural Health Study (AHS) cohort members in a 2-year prospective study of zoonotic influenza transmission. The study involved the collection of sera and animal exposure data upon enrollment and at 12 and 24 months. In 2006, we also collected similar cross-sectional data and sera from 66 University of Iowa employees and students (university controls) who denied any poultry exposures. Sera were studied with microneutralization assays against H4, H5, H6, H7, and H9 avian influenza viruses and hemagglutinin inhibition assays against 3 human influenza viruses. Participants (n=869) were 56.7% male and had a mean age of 54.6 yrs. Many participants had poultry exposures: 58.2% reported some exposure to birds either through poultry production, hunting, or handling poultry sometime in their lifetimes; 16.1% had worked with poultry since the year 2000; and 15.3% reporting hunting wild game birds. Bivariate and multivariable modeling was used to examine potential risk factors for association with elevated enrollment sera antibody titers against the individual viruses. In multivariable modeling age, gender, receipt of influenza vaccines, and elevated antibodies to human influenza viruses were included when statistically important. By proportional odds modeling, elevated adjusted odds of increased antibody titer were found against avian H7 virus for subjects who self-reported hunting wild birds (OR=2.8, 95%CI 1.2-6.5;) and against both H6 and H7 virus for those recently working with poultry (OR=3.4, 95%Cl 1.4-8.5; OR=2.5, 95%Cl 1.1-5.7).While titers were too sparsely distributed to run proportional odds modeling for H5 virus, a traditional exact logistical regression model for titers ≥ 1:10 revealed that AHS members were at increased odds (OR=9.2, 95%CI=1.6-infinity) of elevated titers compared to university controls. None of the poultry exposures were clearly associated with elevated antibody titers to H4 or H9 viruses. Examining the serial serum samples revealed little evidence of an increase in antibody titer over time for any of the viruses. Hunting and poultry exposure may be important risk factors for avian influenza virus infection among agricultural workers. (Revised) • Although difficult to study, avian influenza virus transmission to humans has been documented. • Myers et. al. found that US poultry-exposed veterinarians had serological evidence of previous infections with avian H5, H6, and H7 influenza viruses (Clin Infect Dis, July 1, 2007 in press). • Following the 2003 Netherlands poultry outbreak, Meijer et al. found that 49% of 508 poultry cullers and 64% of 63 persons exposed to H7N7 infected humans had serological evidence of H7N7 infection (J Virol Methods 2006;132:113-20). • Subjects who have recently worked with poultry (from 2000 on) had elevated adjusted odds of increased antibody titer against H6 and H7 avian influenza viruses (Table 1) . • Subjects who reported frequently touching live poultry or game birds had elevated adjusted odds of increased antibody titer against avian H5 virus. • Subjects who reported hunting wild birds had elevated adjusted odds of increased antibody titer against H7 avian influenza virus. • We used data from the 90,000-person Agricultural Health Study to identify 385adults occupationally exposed to poultry and 418 non-poultry exposed AHS members. 66 non-poultry exposed University of Iowa controls were also compared. • Upon enrollment, and after 12 and 24 months of follow-up, participants completed a questionnaire and donated sera. • During the 2 years of follow-up, if a participant developed signs and symptoms of an influenza-like illness, they completed a questionnaire, provided a gargle sample and nasal swab within 48 hours of symptom development, and shipped the questionnaire and specimens to the investigators. • We studied sera with hemagglutination inhibition (against three human influenza A viruses: A/New Caledonia/20/99 (H1N1), A/Nanchang/933/95 (H3N2), A/Panama/2007/99 (H3N2);and microneutralization (against five avian influenza viruses: A/Duck/Cz/1/56 (H4N8), A/Chucker/MN/14591-7/98 (H5N2), A/Turkey/MA/65 (H6N2), A/Turkey/VA/4529/02 (H7N2), A/Turkey/MN/38391-6/95 (H9N2). • Serologic results were adjusted for antibodies to human influenza virus. • These data suggest that adults exposed to poultry and wild birds are at increased risk of avian influenza virus infections. • Agriculture workers should receive training to reduce their risk of zoonotic influenza virus infections. • Agriculture workers should be included in influenza surveillance strategies and considered for inclusion as priority recipients for annual and pandemic influenza vaccines. Collaborators - Kevin Knudson, PhDCEID Staff - Whitney Baker, Ghazi Kayali Funding – NIH / NIAID- R21 AI059214-01 (Gray)