Regional Laboratory for Animal Influenza and Transboundary Diseases, National Veterinary Research Institute, vom plateau, Nigeria.
Department of Veterinary Public Health and Preventive Medicine, Faculty of Veterinary Medicine, University of Jos, Jos, Nigeria.
Arch Virol. 2023 Sep 29;168(10):263. doi: 10.1007/s00705-023-05888-2.
Since 2006, highly pathogenic avian influenza (HPAI) subtypes H5Nx have adversely affected poultry production in Nigeria. Successive waves of infections in the last two decades have raised concerns about the ability to contain infections by biosecurity alone, and evidence of recurrent outbreaks suggests a need for adoption of additional control measures such as vaccination. Although vaccination can be used to control virus spread and reduce the morbidity and mortality caused by HPAI, no country using vaccination alone as a control measure against HPAI has been able to eliminate or prevent re-infection. To inform policy in Nigeria, we examined the intricacies of HPAI vaccination, government regulations, and scientific data regarding what kind of vaccines can be used based on subtype, whether inactivated or live attenuated should be used, when to deliver vaccine either proactively or reactively, where to apply vaccination either in disease control zones, regionally, or nationally, and how to vaccinate the targeted poultry population for optimum success. A resurgence of HPAI outbreaks in Nigeria since 2018, after the country was declared free of the epidemic following the first outbreak in 2006, has led to enhanced intervention. Controlled vaccination entails monitoring the application of vaccines, the capacity to differentiate vaccinated from infected (DIVA) flocks, and assessing seroconversion or other immune correlates of protection. Concurrent surveillance for circulating avian influenza virus (AIV) and analyzing AIV isolates obtained via surveillance efforts for genetic and/or antigenic mismatch with vaccine strains are also important. Countries with high investment in commercial poultry farms like Nigeria may identify and zone territories where vaccines can be applied. This may include ring vaccination to control HPAI in areas or production systems at risk of infection. Before adoption of vaccination as an additional control measure on commercial poultry farms, two outcomes must be considered. First, vaccination is an admission of endemicity. Secondly, vaccinated flocks may no longer be made accessible to international poultry markets in accordance with WOAH trade regulations. Vaccination must therefore be approached with utmost caution and be guided by science-based evidence throughout the implementation strategy after thorough risk assessment. Influenza vaccine research, development, and controlled application in addition to biosecurity may be a precautionary measure in the evolving HPAI scenario in Nigeria.
自 2006 年以来，高致病性禽流感（HPAI）亚型 H5Nx 对尼日利亚的家禽生产造成了不利影响。在过去的二十年中，连续几波感染引起了人们对仅通过生物安全来控制感染的能力的担忧，并且反复爆发的证据表明需要采取其他控制措施，如接种疫苗。虽然疫苗接种可用于控制病毒传播并降低 HPAI 引起的发病率和死亡率，但没有一个仅使用疫苗接种作为控制 HPAI 措施的国家能够消除或防止再次感染。为了为尼日利亚的政策提供信息，我们研究了 HPAI 疫苗接种的复杂性、政府法规以及有关可以根据亚型使用哪种疫苗的科学数据，无论是使用灭活疫苗还是减毒活疫苗，是主动接种还是反应性接种，在疾病控制区、区域还是全国范围内接种疫苗，以及如何对目标家禽群体进行疫苗接种以获得最佳效果。自 2018 年尼日利亚宣布 2006 年首次爆发禽流感以来，该国已摆脱疫情以来，HPAI 爆发再次出现，这导致了强化干预措施的出现。受控疫苗接种需要监测疫苗的应用、区分接种和感染（DIVA）鸡群的能力，以及评估血清转化率或其他免疫保护相关因素。同时进行循环禽流感病毒（AIV）监测，并分析通过监测获得的 AIV 分离株的遗传和/或抗原与疫苗株的不匹配情况也很重要。像尼日利亚这样在商业家禽养殖场投资较高的国家可能会确定和划定可以应用疫苗的领土。这可能包括环疫苗接种，以控制有感染风险的地区或生产系统中的 HPAI。在将疫苗接种作为商业家禽养殖场的附加控制措施采用之前，必须考虑两个结果。首先，疫苗接种是对地方性的承认。其次，根据世界动物卫生组织（WOAH）贸易法规，接种疫苗的禽类可能不再对国际家禽市场开放。因此，在全面风险评估后，在实施疫苗接种策略时，必须非常谨慎地对待疫苗接种，并以基于科学的证据为指导。除了生物安全措施外，流感疫苗的研究、开发和控制应用可能是尼日利亚不断发展的 HPAI 情况下的预防措施。
