Avian Influenza virus serological study among poultry workers in Iran

Objective: Since the mid-1990s, H9N2 subtype influenza A viruses have caused infections in the poultry population around the globe, including several countries in Asia, Europe, North Africa and America. H9N2 influenza viruses are currently circulating in the Middle and Far East, as well as in European poultry, and the infection seems to be endemic in most developing countries. A significant proportion of recent H9N2 isolates contains the L-226 mutation in their hemagglutinin (HA) receptor- binding site and shows preferential binding to analogs of receptors with α2,6-linked sialic acid (SA), which are traits typical of human viruses. Thus, these avian viruses might possess one of the key elements for infection in humans. The H9N2 virus was isolated for the first time from humans in Hong Kong in 1999 and until now different human cases of AI H9N2 have been reported in different countries. The wide circulation of H9N2 viruses throughout Europe and Asia, along with their ability to cause direct infection in mammals and humans, raises public health concerns about their potential to become candidates for the next influenza pandemic (Li KS et al.2003) in addition to the H5N1 virus. Since 1998 H9N2 AI has been reported in Iran (Nili H. 2003) and at present is endemic in the poultry industry; despite the control measures, which include mass vaccination of poultry, this virus has spread rapidly and is currently circulating in the country (Vasfi Marandi M.2013). This study was carried out to reveal the potential exposure to H9N2 AI viruses among Iranian poultry workers. Methods: A total of 200 subjects took part in this study, including 100 poultry workers and 100 healthy residents. Serum samples were collected and tested for the presence of antibodies against two different H9N2 avian influenza viruses by haemagglutination inhibition (HI) and microneutralization (MN) assays, the analyses were repeated at least three times. Two Iranian H9N2 strains were isolated in 1998 and 2008, which showed different phylogenetic and important molecular differences at aa 226 (Q/L) (H3 numbering), (A/chicken/Iran/12VIR/9630/1998)/Q, (A/chicken/Iran/10VIR/854-5/2008)/L. The viruses were replicated in SPF chicken eggs and used in the serological study as antigens. In addition, all samples were tested for the presence of seasonal H3N2, H1N1 2009 pandemic human influenza viruses to verify the presence of cross positivity with the previously listed influenza viruses. Results: Serological results showed that 16% of the exposed poultry workers were positive for the A/chicken/Iran/10VIR/854-5/2008 virus in MN test and 12.33% in HI test using the titer > 40 as positive cut-off value. Only 2% of the exposed staff was positive for the A/chicken/Iran/12VIR/9630/1998 virus. Seroprevalence of control subjects for both H9N2 strains was very low in both tests (1-2%). Conclusion: The results of this study have demonstrated that exposure to avian H9N2 viruses had occurred among poultry workers in the Shiraz region – Iran, with a higher percentage than that recorded in the control population of the same geographic area. Continuous surveillance programmes should be implemented to monitor the presence of avian influenza infections in humans and to evaluate their potential threat to public health and poultry workers.