The potential role of quail as a mixing vessel for reassortant influenza a virus

Abstract

Quail has been proposed as an intermediate host for the generation of reassortant influenza A viruses with pandemic potential. However, the reassortment between avian and mammalian strains in quails has never been studied under experimental conditions. To better understand the role of quail as an intermediate host of influenza A viruses (IAVs), quails were either co-infected with swine-origin pandemic H1N1 2009 (pH1N1) and LPAI duck H3N2 (dkH3N2) viruses or co-infected with endemic Thai swine H1N1 (swH1N1) and dkH3N2 viruses. The presence of reassortant viruses and genetic features of such reassortants generated in quails from both co-infected groups were determined and compared. This study showed that novel reassortant viruses could be readily generated in quails from both co-infected groups. The finding confirmed that quails can be intermediate hosts of IAVs and generate new reassortant viruses. It was shown that, the reassortant viruses could be generated with significantly higher frequency in the respiratory tract of pH1N1 and dkH3N2 co-infected quails (21.4%) than those of swH1N1 and dkH3N2 co-infected quails (0.8%), indicating that pH1N1 have higher potential to reassort with dkH3N2 when compared to swH1N1. In addition, this study found that co-infecting viruses showed higher oropharyngeal shedding titers and more severe pathogenic in quails compared to single viruses. Furthermore, due to little available information on the pathogenicity of pH1N1 in quails, the pathogenicity, viral replication and transmission characteristics of pH1N1 in quails were also investigated and directly compared with swH1N1 and dkH3N2 viruses. Quails were inoculated intranasally and orally with each virus and evaluated for clinical signs, virus shedding and transmission to contact birds, pathological changes and antibody response to infection. All of the infected and contact quails did not develop any clinical signs. In contrast to swH1N1, quails infected pH1N1 and dkH3N2 shed relatively high virus titers predominantly from the oropharynx until 7 and 5 DPI, respectively, and transmitted to naive contact quails via direct contact. Gross and histopathological lesions were observed mainly in respiratory and intestinal tracts of infected quails which pH1N1 and dkH3N2 were more pathogenic than swH1N1. Seroconversions were detected only in some pH1N1 infected quails at 7 DPI and in most of swH1N1 infected and contact quails from 3 DPI onwards and at 7 DPI, respectively. Thus, these results demonstrated that quails were more susceptible to infection with the pH1N1 and dkH3N2 compared to swH1N1. Overall, the results from this study indicated that quails were susceptible to infection with the pH1N1, swH1N1 and dkH3N2 and could serve as an intermediate host of IAVs for the generation new reassortant viruses. Therefore, quails should be closely monitored to prevent the risk of generating reassortant viruses with pandemic potential.