RE-CURRENT HIGHLY PATHOGENIC AVIAN INFLUENZA (HPAI) H5N1

Avian Influenza (AI) is a One Health, national and global priority disease of economic and public health importance and may manifest as highly pathogenic (HP) or low pathogenic (LP). The LP influenza virus (LPAI) is the precursor of HP influenza virus (HPAI). Both LPAI and HPAI are naturally found in waterfowls including migratory and domestic species. HPAI has been severally introduced into Nigeria since 2006. Nigerian authorities successfully controlled the first incursion by 2018 and the country declared itself free of the disease after series of surveillance for the virus was negative. However, HPAI was again introduced in 2015 but it was a new clade 2.2.3.1c and another H5N8/H5N6 clade 2.3.4.4b from 2016 up till 2019.

Another epidemic wave of HPAI H5N1 clade 2.3.4.4b began in 2021 starting in Kano State in January 2021. Below is a summary of the trend from 2006 to 2025.

Since October 2024, global outbreaks of HPAI especially in Europe is a sign that the virus may be introduced into sub Saharan Africa through migratory birds. Evidence from previous studies showed a connection between wetlands, migratory wild birds, resident waterfowls and trade in these birds at local live bird markets as risk factors for the transmission of HPAI in Nigeria agro-ecological. In December 2024, these interconnection and trade in local birds (live bird market) and backyard poultry farm resulted in the infection that was diagnosed at the NVRI on 31-12- 2024. Independent transmission or spread from the index case may have resulted in 4 more cases in Kano, one case in Katsina and one case in Plateau by January 2025 (7 HPAI cases ). Scientific data suggests that persistent introductions of HPAI into Nigeria is mainly through migratory waterfowls via the shedding of the virus in wetland environment. Contact between migratory and domestic birds or their excretion/secretions are likely source of contamination and transmission of influenza infection to domestic poultry. There appears to be a seasonal pattern in this transmission triad from migratory birds, domestic birds and backyard/commercial poultry in Nigeria. Wild waterfowls migrate from Asia and Europe to warmer climate in Africa every year between September and January. This season coincides with when cases are often detected in Nigeria since 2006. On the other hand, Low Pathogenic Avian influenza (LPAI) subtype H9N2 appears to be endemic and occasionally detected when in combination with other undercurrent infection or unfavourable husbandry may also manifest in morbidity and mortality in poultry.

Recommendation

• - Active seasonal and sentinel surveillance of AI in high risk zones and hot spots including wetlands (e.g., Hadejia-Nguru wetlands) and live bird markets for early detection, early report and control of avian influenza in Nigeria.
•  - Stringent biosecurity measures and monitoring of poultry value chain/trade involving live bird markets and backyard poultry farm.
• - Consideration of HPAI vaccination options