Department of Clinical Studies, School of Veterinary Medicine, Shiraz University, Shiraz, Iran,
Clinic for Poultry and Fish Medicine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria.
Avian Dis. 2021 Mar;65(1):177-187. doi: 10.1637/aviandiseases-D-20-00107.
Currently, the poultry industry worldwide is facing an emerging trend of fowl adenovirus (FAdV)-associated diseases with a significant economic impact, especially in meat-type chickens. Vertical transmission is an important feature of all FAdVs; hence, preventive measures mostly revolve around breeding stocks. However, knowledge about temporal development of FAdV infections in modern commercial settings is rare or even nonexistent. In the present study, longitudinal monitoring for FAdV was conducted in broiler breeder flocks located in a confined geographical region with intensive poultry production in Iran. For this, the antibody status of birds from 4 to 32 wk of age was monitored with a commercial FAdV-ELISA and virus neutralization test (VNT). In parallel, fecal shedding of FAdV was determined at the peak of egg production with real-time PCR and virus isolation. Overall, the commercial ELISA showed seroconversion of flocks before onset of production. VNT resolved in detail infection patterns of individual serotypes with a primordial FAdV-D (FAdV-2/-11) infection, frequently followed by FAdV-E (FAdV-8a, -8b) superinfection. FAdV-A (FAdV-1) was traced in half of the investigated flocks, while no evidence of infection with FAdV-C (FAdV-4, -10) was noted. Common serological profiles between different houses of the same farm indicate an overarching biosecurity. Serological profiles coupled with virological findings at the peak of egg production indicated that higher antibody levels, determined by ELISA, correlated with lower amounts of viral DNA in fecal excretion. Simultaneously, the number of isolated FAdVs belonging to distinct serotypes declined in accordance with a rise of neutralizing antibodies in birds, underlining the significance of serotype-specific antibodies in the epidemiology of FAdV in breeders. Investigations in breeders were complemented with screening of FAdV-associated diseases in local broilers over a 3-yr period; 26 cases of inclusion body hepatitis with dominant involvement of FAdV-11/FAdV-8b, one outbreak of adenoviral gizzard erosion related to FAdV-1, and no evidence of hepatitis-hydropericardium syndrome suggest that identical serotypes are maintained in the local poultry industry.
目前，全球家禽业正面临着一种新兴的禽腺病毒（FAdV）相关疾病趋势，这对经济造成了重大影响，尤其是在肉用型鸡中。垂直传播是所有 FAdV 的一个重要特征；因此，预防措施主要围绕种鸡展开。然而，关于现代商业环境中 FAdV 感染的时间发展的知识很少甚至不存在。在本研究中，对伊朗一个密集型家禽生产的封闭地理区域的肉鸡种鸡群进行了 FAdV 的纵向监测。为此，使用商业 FAdV-ELISA 和病毒中和试验（VNT）监测了 4 至 32 周龄鸡的抗体状态。同时，在产蛋高峰期通过实时 PCR 和病毒分离来确定 FAdV 的粪便脱落情况。总体而言，商业 ELISA 显示在生产开始前鸡群发生了血清转化。VNT 详细解析了个别血清型的感染模式，其中存在原发性 FAdV-D（FAdV-2/-11）感染，随后经常发生 FAdV-E（FAdV-8a、-8b）的继发感染。在一半的调查鸡群中追踪到了 FAdV-A（FAdV-1），而没有发现 FAdV-C（FAdV-4、-10）感染的证据。同一农场不同鸡舍之间的常见血清学特征表明存在全面的生物安全措施。在产蛋高峰期的血清学特征和病毒学发现表明，ELISA 确定的较高抗体水平与粪便排泄中病毒 DNA 的量呈负相关。同时，随着鸟类中和抗体数量的增加，属于不同血清型的分离 FAdV 的数量相应减少，这强调了血清型特异性抗体在种鸡 FAdV 流行病学中的重要性。对种鸡的调查补充了 3 年来对当地肉鸡中与 FAdV 相关疾病的筛查；26 例包涵体肝炎，主要涉及 FAdV-11/FAdV-8b，1 例与 FAdV-1 相关的腺胃侵蚀，无肝炎-心包积液综合征的证据表明，相同的血清型在当地家禽业中得以维持。
