The effectiveness of mass vaccination on Marek's disease virus (MDV) outbreaks and detection within a broiler barn: A modeling study
The effectiveness of mass vaccination on Marek's disease virus (MDV) outbreaks and detection within a broiler barn: A modeling study
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DOI：
10.1016/j.epidem.2013.10.001
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发表时间：
2013-12-01
期刊：
影响因子：
3.8
通讯作者：
Woolhouse, Mark E. J.
中科院分区：
文献类型：
--
作者：
Atkins, Katherine E.;Read, Andrew F.;Woolhouse, Mark E. J.
马立克氏病病毒（MDV）是一种家禽病原体，自二十世纪中叶以来毒力不断增强。由于多种疫苗的开发和广泛应用，MDV造成的损失已经减少。然而，过去曾发生过疫苗失败的情况，疫苗突破仍然是一个问题。当前疫苗无法控制疾病将产生重大的经济和福利后果。然而，农场爆发期间该疾病的流行病学尚不清楚。在这里，我们提出了一个数学模型来预测疫苗在降低谷仓内爆发概率和疾病负担方面的有效性。我们发现，畜舍内爆发疫情的机会随着 MDV 毒株的毒力而增加，而当鸡群接种疫苗时，尤其是当污染毒株毒力较低时，鸡群内爆发疫情的机会就会显着降低。由于污染粉尘量较少，疫苗对减少 MDV 爆发的效果几乎是 100%。然而，随着中等毒力 MDV 毒株污染量的增加，疫苗有效性降至零。我们预测，鸡舍越大，MDV 毒株的毒性越强，屠宰羊群时产生的病毒就越多。由于此处研究的菌株毒力为低至中度，因此无论鸟类的疫苗接种情况如何，与全因死亡率相比，MDV 导致的死亡人数都非常低。然而，未接种疫苗的人群的累积 MD 发病率可达 100%，而接种疫苗的人群则为 35%。这些结果表明，无论疫苗状态如何，MDV 导致的死亡不足以评估 MDV 肉鸡舍的流行情况，因此需要积极监测才能成功评估 MDV 爆发的可能性，并限制连续肉鸡群之间 MDV 的传播。 (C) 2013 作者。由 Elsevier B.V 出版。保留所有权利。
Marek's disease virus (MDV), a poultry pathogen, has been increasing in virulence since the mid twentieth century. Since multiple vaccines have been developed and widely implemented, losses due to MDV have decreased. However, vaccine failure has occurred in the past and vaccine breakthroughs remain a problem. Failure of disease control with current vaccines would have significant economic and welfare consequences. Nevertheless, the epidemiology of the disease during a farm outbreak is not well understood. Here we present a mathematical model to predict the effectiveness of vaccines to reduce the outbreak probability and disease burden within a barn. We find that the chance of an outbreak within a barn increases with the virulence of an MDV strain, and is significantly reduced when the flock is vaccinated, especially when there the contaminant strain is of low virulence. With low quantities of contaminated dust, there is nearly a 100% effectiveness of vaccines to reduce MDV outbreaks. However, the vaccine effectiveness drops to zero with an increased amount of contamination with a middle virulence MDV strain. We predict that the larger the barn, and the more virulent the MDV strain is, the more virus is produced by the time the flock is slaughtered. With the low-to-moderate virulence of the strains studied here, the number of deaths due to MDV is very low compared to all-cause mortality regardless of the vaccination status of the birds. However, the cumulative MD incidence can reach 100% for unvaccinated cohorts, and 35% for vaccinated cohorts. These results suggest that death due to MDV is an insufficient metric to assess the prevalence of MDV broiler barns regardless of vaccine status, such that active surveillance is required to successfully assess the probability of MDV outbreaks, and to limit transmission of MDV between successive cohorts of broiler chickens. (C) 2013 The Authors. Published by Elsevier B. V. All rights reserved.