Department of Epidemiology, Crisis organization and Diagnostics, Central Veterinary Institute (CVI) part of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands.
Prev Vet Med. 2012 Dec 1;107(3-4):253-9. doi: 10.1016/j.prevetmed.2012.06.010. Epub 2012 Jul 20.
Even though low pathogenic avian influenza viruses (LPAIv) affect the poultry industry of several countries in the world, information about their transmission characteristics in poultry is sparse. Outbreak reports of LPAIv in layer chickens have described drops in egg production that appear to be correlated with the virus transmission dynamics. The objective of this study was to use egg production data from LPAIv infected layer flocks to quantify the within-flock transmission parameters of the virus. Egg production data from two commercial layer chicken flocks which were infected with an H7N3 LPAIv were used for this study. In addition, an isolate of the H7N3 LPAIv causing these outbreaks was used in a transmission experiment. The field and experimental estimates showed that this is a virus with high transmission characteristics. Furthermore, with the field method, the day of introduction of the virus into the flock was estimated. The method here presented uses compartmental models that assume homogeneous mixing. This method is, therefore, best suited to study transmission in commercial flocks with a litter (floor-reared) housing system. It would also perform better, when used to study transmission retrospectively, after the outbreak has finished and there is egg production data from recovered chickens. This method cannot be used when a flock was affected with a LPAIv with low transmission characteristics (R(0)<2), since the drop in egg production would be low and likely to be confounded with the expected decrease in production due to aging of the flock. Because only two flocks were used for this analysis, this study is a preliminary basis for a proof of principle that transmission parameters of LPAIv infections in layer chicken flocks could be quantified using the egg production data from affected flocks.
尽管低致病性禽流感病毒（LPAIv）会影响世界上几个国家的家禽业，但有关其在家禽中传播特征的信息却很少。在蛋鸡中爆发的 LPAIv 报告描述了产蛋量下降的情况，这些情况似乎与病毒传播动力学有关。本研究的目的是使用感染 LPAIv 的蛋鸡群的产蛋数据来量化病毒在鸡群内的传播参数。本研究使用了两批感染 H7N3 LPAIv 的商业蛋鸡群的产蛋数据。此外，还使用了导致这些暴发的 H7N3 LPAIv 分离株进行了传播实验。现场和实验估计表明，这是一种具有高传播特性的病毒。此外，通过现场方法，估计了病毒进入鸡群的日期。本研究提出的方法使用了假设同质混合的房室模型。因此，该方法最适合用于研究具有垫料（地面饲养）饲养系统的商业鸡群中的传播。在暴发结束后，使用恢复鸡的产蛋数据进行回溯性研究时，该方法的效果更好。当鸡群感染传播特性较低的 LPAIv（R(0)<2）时，该方法无法使用，因为产蛋量下降幅度较小，可能与鸡群老化导致的预期产蛋量下降相混淆。由于仅使用了两个鸡群进行此分析，因此本研究是一个初步的原理证明，即可以使用受感染鸡群的产蛋数据来量化蛋鸡群中 LPAIv 感染的传播参数。
