Transmission dynamics of avian influenza viruses in Egyptian poultry markets

Abstract

Live bird markets (LBMs) are considered hotspots for Avian Influenza Viruses (AIVs). In such markets, AIVs pose threats to both poultry and public health. Within LBMs, AIVs spread through various routes, including direct contact, environmental contamination, and aerosol transmission. Unique factors in Egyptian LBMs, such as the coexistence of wild and domestic birds, increase transmission risks between birds as well as spill-overs into exposed humans. Understanding the transmission dynamics of AIVs is vital for implementing effective control measures. We conducted a study in four Egyptian LBMs located in Mediterranean coast cities from November 2021 to March 2023. In this study we tested 3,971 samples from poultry, wild birds, and the environment, out of which 692 (17.4%) were positive for AIV. Poultry exhibited a higher prevalence (42.2%) than wild birds (34.4%). Environmental samples, including water (30.8%), surfaces (17.2%), and air (18.2%), also tested positive for AIV. Diverse AIV subtypes, including H5N1, H9N2, H5/H9 co-infection, and H5N8, were detected among avian species and the environment. Temporal analysis revealed fluctuating IAV positivity rates from November 2021 to March 2023. These results emphasize the importance of continuous surveillance, resource allocation, and multisectoral collaboration to protect poultry and human health, and prevent novel influenza strains' emergence in Egyptian LBMs.

Fig. 1. Positivity rate of IAV in poultry, wild birds, and environment by month during active AIV surveillance from November 2021 to March 2023 in Egyptian LBM.

IAV-positive wild bird samples are represented in pink, IAV-positive poultry samples are represented in green, IAV-positive environment samples are represented in blue, and IAV-negative samples are represented in white.

Fig. 2. Percentage of AIV positive non-subtyped and subtyped (H5N1, H5N8, and H9N2) in avian and environmental samples by month during surveillance from November 2021 to March 2023.

A IAV subtyped and non-subtyped in avian samples, in poultry and wild birds; B IAV subtyped and non-subtyped in environmental samples: surface, water, and air. IAV positive non-subtyped samples are represented in light red, H5N1 subtyped samples are represented in light green, H5N8 subtyped samples are represented in light blue, H9N2 subtyped samples are represented in light yellow, and H5/H9 subtyped samples are represented in grey.

Fig. 3. Transmission pathways of avian influenza viruses among poultry and wild birds in shared environments, and human interactions in LBM.

Avian influenza viruses in wild birds are represented in green circles and avian influenza viruses in domestic birds are represented in red circles.