Table_1_Evaluating Disease Threats to Sustainable Poultry Production in Africa: Newcastle Disease, Infectious Bursal Disease, and Avian Infectious Bronchitis in Commercial Poultry Flocks in Kano and Oyo States, Nigeria.XLSX

The growth of the poultry industry in Nigeria is constrained by major poultry diseases, despite the implementation of vaccination programs. This study aimed to assess the level of protection against Newcastle disease (ND), infectious bursal disease (IBD), and avian infectious bronchitis (IB) afforded by current vaccination schedules and characterize the circulating virus strains in commercial poultry flocks in Nigeria. A cross-sectional study was conducted on 44 commercial poultry farms in Oyo and Kano states of Nigeria. Serum and tissue samples and data on flock, clinical and vaccination records were collected on each farm. Farms were classified as being protected or not protected against ND, IBD and IB based on a defined criterion. Real-time reverse transcription polymerase chain reaction (rRT-PCR) testing was performed for each target virus on tissue samples and positive samples were sequenced. A total of 15/44 (34.1%), 35/44 (79.5%), and 1/44 (2.3%) farms were considered to be protected against ND, IBD, and IB, respectively, at the time of sampling. NDV RNA was detected on 7/44 (15.9%) farms and sequences obtained from 3/7 farms were characterized as the lentogenic strain. Infectious bursal disease virus (IBDV) RNA was detected on 16/44 (36.4%) farms tested; very virulent (vv) IBDV and non-virulent (nv) IBDV strains were both detected in 3/16 (18.8%) positive samples. Sequences of IBDV isolates were either clustered with a group of genotype 3 virulent IBDV strains or were related to vaccine strains MB and D78 strains. IBV RNA was detected on 36/44 (81.8%) farms, with variant02, Massachusetts, 4/91, and Q1 variants detected. Sequences of IBV isolates were either clustered with the vaccines strains Massachusetts M41 and H120 or were most closely related to the D274-like strains or a clade of sequences reported in Nigeria and Niger in 2006 and 2007. This study revealed that most study farms in Oyo and Kano states did not have adequate protective antibody titers against IBV and NDV and were therefore at risk of field challenge. Infectious bursal disease virus and IBV RNA were detected on farms with a history of vaccination suggesting potential vaccination failure, or that the vaccine strains used mismatch with the circulating strains and are therefore not protective.

尽管已推行疫苗接种计划，但尼日利亚家禽养殖业的发展仍受主要家禽疫病的制约。本研究旨在评估现行疫苗接种方案对新城疫（Newcastle disease, ND）、传染性法氏囊病（infectious bursal disease, IBD）及禽传染性支气管炎（avian infectious bronchitis, IB）的保护效力，并对尼日利亚商业家禽群中流行的病毒毒株进行分型鉴定。研究于尼日利亚奥约州和卡诺州的44家商业家禽养殖场开展横断面研究，采集各养殖场的血清与组织样本，以及禽群、临床症状和疫苗接种记录相关数据。根据既定判定标准，将养殖场分为针对ND、IBD及IB具有保护力或无保护力两类。对组织样本中的各目标病毒开展实时逆转录聚合酶链式反应（real-time reverse transcription polymerase chain reaction, rRT-PCR）检测，并对阳性样本进行测序。采样时，分别有15/44（34.1%）、35/44（79.5%）及1/44（2.3%）的养殖场被认为对ND、IBD和IB具有保护力。在7/44（15.9%）的养殖场中检测到新城疫病毒（NDV）RNA，其中3/7养殖场的测序毒株被鉴定为弱毒株（lentogenic strain）。在16/44（36.4%）的受检养殖场中检测到传染性法氏囊病病毒（IBDV）RNA，其中3/16（18.8%）的阳性样本同时检出超强毒（very virulent, vv）IBDV与无毒力（non-virulent, nv）IBDV毒株。IBDV分离株的序列要么与基因型3的强毒IBDV毒株聚类，要么与MB株和D78疫苗株相关。在36/44（81.8%）的养殖场中检测到禽传染性支气管炎病毒（IBV）RNA，检出的亚型包括variant02、马萨诸塞（Massachusetts）、4/91及Q1亚型。IBV分离株的序列要么与马萨诸塞M41和H120疫苗株聚类，要么与D274样毒株高度相似，或属于2006年及2007年在尼日利亚和尼日尔报道的序列进化分支。本研究显示，奥约州和卡诺州的大部分受试养殖场未产生针对IBV和NDV的足够保护性抗体滴度，因此面临野外毒株攻击的风险。在有疫苗接种史的养殖场中检测到IBDV和IBV RNA，这提示可能存在疫苗接种失败，或所用疫苗株与流行毒株不匹配，因而无法提供保护。