Minimal Susceptibility to Highly Pathogenic Avian Infl uenza H5N1 Viral Infection of Pigeons (Columba livia) and Potential Transmission of the Virus to Comingled Domestic Chickens

In order to elucidate the epidemic dissemination role of pigeons in the outbreak of the highly pathogenic avian infl uenza (HPAI) H5N1 (infl uenza A) virus, this study was conducted by experimental infection of the HPAI H5N1 virus in pigeons. Twenty-eight pigeons, aged 1 yr that were serologically negative for the H5N1-specifi c HI antibodies, were inoculated intranasally with various doses of the HPAI H5N1 virus at infectious doses of 10 to 1 × 10 6 median tissue culture TCID50, this is the amount of dose that will produce pathological change in 50% of the cell cultures inoculated. To evaluate the virus transmission of infected pigeons to the environment, pigeons inoculated with 1 × 10 5 TCID50 of HPAI H5N1 were determined for their transmission ability to sentinel avian infl uenza virus-free chickens. Viral isolation and real-time hydrolysis probe (TaqMan) reverse transcriptase polymerase chain reaction were performed to detect viruses from choanal cleft and cloacal swabs. Antibody responses were detected by hemagglutination inhibition and serum neutralization assay. In this study, the median infective dose (ID50) and the median lethal dose (LD50) of the HPAI H5N1 virus of inoculated pigeons were 1 × 10 5 and 1 × 10 6 TCID50, respectively. The viruses were also consistently isolated from either cloanal or cloacal swabs of the infected groups. The sentinel chickens housed in the same cage were infected with the HPAI H5N1 virus shedding from the experimental pigeons. The sentinel chickens exhibited clinical signs with high morbidity and mortality. The results showed that the pigeons were less susceptible to HPAI H5N1 virus infection than chickens. The pigeons might be play role as distributors of avian infl uenza virus transmission and shedding from the infected pigeons to contacted chickens. Therefore, the good biosafety and biosecurity management in farms should be emphasized for control and prevention of the HPAI H5N1 virus.