Viral zooanthroponoses from turkeys to humans

The research described in this dissertation sought to estimate the seroprevalence of antibodies against avian influenza viruses (AI), avian pneumovirus (aMPV), and avian hemorrhagic enteritis virus (HEV) among individuals with occupational exposure to turkeys. It also sought to determine potential risk factors that may be associated with infection. A controlled, cross-sectional seroprevalence study that included collecting blood specimens and questionnaire data was designed and conducted to investigate these aims. Results from the AI study suggest that farmers who grow small flocks of turkeys are at an increased risk for infection with several strains of low pathogenicity AI viruses. Among these farmers, the adjusted odds ratios (OR) for elevated titers against avian H4, H5, H6, H9, and H10 influenza strains ranged between 3.9(1.2-12.8) and 15.3(2.0-115.2) when compared to non-exposed controls. The measured ORs were adjusted for antibody titers against human influenza and other exposure variables. In Chapter 3, evidence for previous infection with aMPV was investigated among the study population. Results demonstrated that meat processing plant workers had an adjusted OR of 4.1(1.3-13.1) of elevated antibody titer against aMPV as compared to non-exposed controls. This OR was adjusted for antibody titers against the very similar human metapneumovirus. In Chapter 4, evidence of previous infection with HEV, an avian adenovirus, was investigated. There was no statistical difference in optical densities obtained by HEV enzyme immunosorbent assay between the different exposure groups. This may be explained by genetic differences between avian adenoviruses and human adenoviruses that make it difficult for these viruses to cross species barriers. This research provided evidence of zoonotic transmission of avian viruses from turkeys to people who are occupationally exposed to turkeys. The evidence was noted in farmers as well as meat processing plant workers demonstrating that zoonotic transmission occurs in the various sectors of poultry production. Increasing surveillance efforts among such occupational groups is needed in order to better understand the dynamics of zoonotic infections, to determine associated risk and protective factors, to discover pathogens that have the potential of becoming more virulent and cause larger outbreaks among humans, and to develop better public health preparedness plans.