Review of the onset and duration of avian influenza viruses shedding in different birds species

Avian influenza is a highly contagious disease with economic and public health importance, which is the cause of many economic losses in poultry industry worldwide. Influenza viruses naturally infected a large number of wild and domestic birds. Migratory wild birds (ducks, geese, and swans) and shore birds are the main reservoirs of influenza viruses. Influenza viruses are excreted through the respiratory secretions and feces. Highly pathogenic avian influenza viruses can be found in the poultry meat and the eggs. HPAI viruses can be found in meat and eggs one day and three days after inoculation, respectively. In experimental studies, the shedding of HPAI and LPAI viruses in the feces and respiratory secretions begins one or two days after inoculation and continue up to several days, which are different in different bird species. The infectious period of disease in poultry affected with LPAI viruses is longer than the HPAI viruses, and the rate of shedding is higher.Based on the conducted studies on the amount and method of the virus shedding in different birds, there are different opinions about the efficacy of cloacal and tracheal swab specimens for the detection of the LPAI and HPAI viruses. Higher shedding of the virus in the feces than respiratory secretion can be due to the proliferation of the virus in the kidneys and the bursa as a result of general infection. Both types of these specimens should be taken in influenza surveillance programs.