A Reassortant Virus of A Thai Swine Influenza Virus (SIV) and The Pandemic H1N1 of Pig Origin Did Not Induce Severe Disease in Experimental Ducks

Abstract

Currently, the pandemic H1N1 (pH1N1) 2009 influenza A virus and its reassortant pandemic H1N1 influenza (rH1N1) viruses have been circulating in pigs population in many countries around the world including Thailand. Many organizations and researchers have raised some concerns about interspecies transmission, particularly in aquatic avian species including domestic ducks commingling in backyard farming. In order to elucidate the pathogenesis of those viruses in domestic ducks, the study on pH1N1and rH1N1 recently isolated from pigs was conducted to understand the susceptibility, clinical signs, viral shedding and lesions in experimental ducks.  Twenty-one 6-week-old influenza A virus negative ducks were divided into 3 groups (2 challenged groups and 1 control group). In the challenged groups, the ducks in each group were individually inoculated with pH1N1 or rH1N1 as mentioned previously. All experimental ducks were observed for clinical signs and oropharyngeal and cloacal swabs were collected to investigate the viral shedding using a modified real time RT-PCR. Tissues samples were collected for pathological and immunohistochemistry examination. Results demonstrated that neither pH1N1 nor rH1N1 induced significant flu-like clinical signs. However, both viruses could infect the experimental ducks as varied gross and microscopic lesions as well as duration of virus shedding were observed. Interestingly, the detectable lesions and the extended shedding period were found in the group of rH1N1-infected ducks. In conclusion, inter-species transmission should be considered when commingling different animal species.