Assessing the excretion time of Iranian endemic influenza virus (H9N2 subtype) from laying chicken breeds

The H9N2 subtype of the influenza virus, which is endemic in many regions of Iran, is considered as a candidate for future pandemics. In the present study, excretion time of the Iranian endemic influenza virus (H9N2 subtype) from the feces and pharyngeal secretions of laying chicken breeds was evaluated.

This experimental study conducted at the Diagnostic Laboratory Sciences and Technology Research Center of Shiraz University of Medical Sciences, and the Department of Clinical Science in School of Veterinary Medicine of Shahid Bahonar University of Kerman, from June 2017 to September 2017. At first, the influenza virus A/Chicken/Iran/SH-110/99 (H9N2) was cultured in the allantoic fluid of the embryonated egg and the EID50 for virus was determined by Reed and Muench method. Afterward, the Hy-Line chicks were inoculated intranasally with 106 EID50/ml of influenza virus (H9N2 subtype) and samples were collected from the oropharynx and feces of the birds on days 2, 5, 10 and 17 after inoculation. The presence of the virus in the samples of challenged birds was assessed using the real-time polymerase chain reaction (PCR) method.

The influenza virus was shed from the oro-pharyngeal secretion and feces of the birds 2 days post-infection, and continued until days 10 and 17, respectively. In comparison to the oro-pharynx, the virus was recovered in the feces for a longer time. The influenza virus was detected in 100% and 57.1% of oro-pharyngeal and feces samples of the infected birds on day 2, 85.7% and 100% on day 5, 28.6% and 71.4% on day 10, and 0% and 28.6% on day 17 post-inoculation, respectively. The maximum risk of infected chicken for humans is seen from 2 to 5 days post-infection.

Detection of virus in the samples of birds that challenged with the H9N2 influenza virus showed that the virus could shed from the feces to the surrounding environment longer than the pharyngeal secretions and could be hazardous to humans in contact.