Serologic evidence of occupational risk for avian influenza virus transmission at wildfowl-poultry-human interface

Low pathogenic (LP) avian influenza viruses (AIVs) can cause human infections, as the result of direct transmission from infected birds. Human cases are related to mild or subclinical disease, although severe outcomes have been recently reported in subjects infected by H7N9 LPAIVs. Some farming practises are modelled to house birds outdoor, thus exposing them to AIVs harboured in wild avian reservoir. These relatively low bio-security conditions enable the emergence of AIVs in captive-reared birds, increasing the potential zoonotic risk to occupationally exposed workers. Main purpose of this study is to provide serological evidence of LPAIV infection in workers operating in farms located in the Emilia-Romagna Region (Italy). In April 2005-July 2006 period, sera were collected from 57 bird-exposed workers and 7 non bird-exposed controls, planning three blood sample collections from each individual to assess seroconversion against AIVs. Study population included: 46 poultry workers (PWs) and 4 veterinarians operating in 14 farms housing birds under outdoor conditions; 2 veterinarians and 4 technicians involved in AIV laboratory diagnostics; a wildlife professional exposed to wild waterfowl. Haemagglutination inhibition (HI) assay and microneutralization-ELISA (MN) were used as screening and confirmatory tests, respectively. Sera were tested for specific antibodies against twenty LPAIVs belonging to antigenic subtypes from H1 to H14 and including twelve reference strains and eight avian isolates from farms under study. MN results showed serologic evidence of exposures to AIV in 3/46 PWs, showing antibodies against H3, H6, H8 and H9 AIVs. In addition, the wildlife professional was seropositive against H11 AIV subtype.