Veterinary Epidemiology, Economics and Public Health Group, Royal Veterinary College, Hatfield, Hertfordshire, UK.
The Pirbright Institute, Pirbright, Surrey, UK.
Transbound Emerg Dis. 2018 Apr;65(2):e264-e271. doi: 10.1111/tbed.12748. Epub 2017 Nov 9.
Mortality data are routinely collected for many livestock and poultry species, and they are often used for epidemiological purposes, including estimating transmission parameters. In this study, we infer transmission rates for African swine fever virus (ASFV), an important transboundary disease of swine, using mortality data collected from nine pig herds in the Russian Federation with confirmed outbreaks of ASFV. Parameters in a stochastic model for the transmission of ASFV within a herd were estimated using approximate Bayesian computation. Estimates for the basic reproduction number varied amongst herds, ranging from 4.4 to 17.3. This was primarily a consequence of differences in transmission rate (range: 0.7-2.2), but also differences in the mean infectious period (range: 4.5-8.3 days). We also found differences amongst herds in the mean latent period (range: 5.8-9.7 days). Furthermore, our results suggest that ASFV could be circulating in a herd for several weeks before a substantial increase in mortality is observed in a herd, limiting the usefulness of mortality data as a means of early detection of an outbreak. However, our results also show that mortality data are a potential source of data from which to infer transmission parameters, at least for diseases which cause high mortality.
死亡率数据通常被收集用于许多牲畜和家禽物种，并且经常用于流行病学目的，包括估计传播参数。在这项研究中，我们使用从俄罗斯联邦的九个确诊爆发非洲猪瘟病毒（ASF）的猪群中收集的死亡率数据，推断了非洲猪瘟病毒的传播率。使用近似贝叶斯计算，对群内 ASF 传播的随机模型中的参数进行了估计。估计的基本繁殖数在各个畜群之间有所不同，范围从 4.4 到 17.3。这主要是由于传播率（范围：0.7-2.2）的差异，以及平均感染期（范围：4.5-8.3 天）的差异所致。我们还发现，各个畜群之间的平均潜伏期（范围：5.8-9.7 天）也存在差异。此外，我们的结果表明，在畜群中死亡率显著增加之前，ASF 可能已经在畜群中传播了数周，这限制了死亡率数据作为早期发现疫情手段的有用性。然而，我们的结果还表明，死亡率数据是推断传播参数的潜在数据来源，至少对于导致高死亡率的疾病而言是如此。
