Prevalence of Nonpathogenic Avibacterium paragallinarum in Naïve-Healthy Layer Flocks Across Multiple States in the United States

IF 3.5 2区农林科学 Q2 INFECTIOUS DISEASES

Transboundary and Emerging Diseases Pub Date : 2025-05-18 DOI:10.1155/tbed/9994679

Mostafa M. S. Shelkamy, Amro Hashish, Mariela E. Srednik, Maria Chaves, Nubia R. Macedo, Eman Gadu, Stephan Schmitz-Esser, Qijing Zhang, Chong Wang, Yuko Sato, Mohamed El-Gazzar

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Abstract

Infectious coryza (IC) caused by Avibacterium paragallinarum (AP) is an emerging infectious respiratory disease in the commercial chicken layer industry in the Midwestern US states. Outbreak investigations around positive index cases led to the discovery of nonpathogenic AP (npAP), which caused quantitative real-time PCR (qPCR) positive results in naïve-healthy layer (NHL) flocks. Therefore, the reliability of positive qPCR as confirmed diagnosis of IC became questionable and the poultry industry was deprived from an essential diagnostic tool in the face of an actively spreading outbreak. However, the prevalence of npAP in NHL flocks and the magnitude of this diagnostic challenge remained unclear. This pilot surveillance study aims to provide an initial estimate of npAP prevalence in the US commercial layer industry. Two differential qPCR assays were recently developed to differentiate pathogenic AP (pAP) and npAP. A total of 710 oropharyngeal (OP) swab pools (5 swabs/pool) were collected from 80 NHL sites across 13 US states and tested using qPCR assay targeting the recN gene as a screening test. Two hundred thirty-one out of 710 total pools were positive for npAP (32.5%) representing 28 positive sites out of the 80 total sites (35%). All positive qPCR samples from NHL flocks were confirmed to be due npAP. The differential qPCR was capable of confirming 85.71% of the npAP cases, while the remaining cases required further isolation and whole-genome sequencing (WGS). In conclusion, this pilot study indicates that the prevalence of npAP in NHL flocks in the United States is above 30%. Therefore, in flocks with no clinical signs, qPCR assays cannot be relied upon for IC diagnostic confirmation. Currently, isolation combined with WGS is the only diagnostic tool capable of completely differentiating between these two AP populations, which indicates the immediate need for improvements in the available diagnostic assays.

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在美国多个州Naïve-Healthy蛋鸡群中非致病性副allinarum的患病率

传染性鼻炎（IC）是由副allinarum Avibacterium （AP）引起的一种新兴的呼吸道传染病，在美国中西部各州的商业鸡蛋鸡业中流行。围绕阳性指标病例的暴发调查导致非致病性AP （npAP）的发现，这导致naïve-healthy蛋鸡（NHL）群的实时荧光定量PCR （qPCR）结果呈阳性。因此，qPCR阳性作为IC确诊诊断的可靠性受到质疑，家禽业在面对积极蔓延的疫情时失去了一种必要的诊断工具。然而，npAP在NHL禽群中的流行程度和这一诊断挑战的程度仍不清楚。这项试点监测研究的目的是提供美国商业蛋鸡行业npAP流行率的初步估计。最近开发了两种差异qPCR方法来区分致病性AP （pAP）和npAP。从美国13个州的80个NHL位点共收集710个口咽拭子（5个拭子/池），并使用靶向recN基因的qPCR检测作为筛查试验进行检测。710个总池中有231个npAP阳性（32.5%），代表80个总站点中的28个阳性位点（35%）。所有来自NHL禽群的qPCR阳性样本均被证实为npAP所致。差异qPCR能确诊85.71%的npAP病例，其余病例需要进一步分离和全基因组测序（WGS）。总之，这项初步研究表明，npAP在美国NHL禽群中的患病率超过30%。因此，在没有临床症状的禽群中，qPCR检测不能作为IC诊断的依据。目前，分离结合WGS是唯一能够完全区分这两种AP群体的诊断工具，这表明现有诊断方法急需改进。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Transboundary and Emerging Diseases 农林科学-传染病学

CiteScore

8.90

自引率

9.30%

发文量

350

审稿时长

1 months

期刊介绍： Transboundary and Emerging Diseases brings together in one place the latest research on infectious diseases considered to hold the greatest economic threat to animals and humans worldwide. The journal provides a venue for global research on their diagnosis, prevention and management, and for papers on public health, pathogenesis, epidemiology, statistical modeling, diagnostics, biosecurity issues, genomics, vaccine development and rapid communication of new outbreaks. Papers should include timely research approaches using state-of-the-art technologies. The editors encourage papers adopting a science-based approach on socio-economic and environmental factors influencing the management of the bio-security threat posed by these diseases, including risk analysis and disease spread modeling. Preference will be given to communications focusing on novel science-based approaches to controlling transboundary and emerging diseases. The following topics are generally considered out-of-scope, but decisions are made on a case-by-case basis (for example, studies on cryptic wildlife populations, and those on potential species extinctions): Pathogen discovery: a common pathogen newly recognised in a specific country, or a new pathogen or genetic sequence for which there is little context about — or insights regarding — its emergence or spread. Prevalence estimation surveys and risk factor studies based on survey (rather than longitudinal) methodology, except when such studies are unique. Surveys of knowledge, attitudes and practices are within scope. Diagnostic test development if not accompanied by robust sensitivity and specificity estimation from field studies. Studies focused only on laboratory methods in which relevance to disease emergence and spread is not obvious or can not be inferred (“pure research” type studies). Narrative literature reviews which do not generate new knowledge. Systematic and scoping reviews, and meta-analyses are within scope.