Matsuyama Ryota, Yamamoto Takehisa, Hayama Yoko, Omori Ryosuke
Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
Epidemiology Research Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan.
Front Vet Sci. 2021 Dec 15;8:772995. doi: 10.3389/fvets.2021.772995. eCollection 2021.
Understanding the morbidity and lethality of diseases is necessary to evaluate the effectiveness of countermeasure against the epidemics (e.g., vaccination). To estimate them, detailed data on host population dynamics are required; however, estimating the population size for wildlife is often difficult. We aimed to elucidate the morbidity and lethality of classical swine fever (CSF) currently highly prevalent in the wild boar population in Japan. To this end, we estimated lethality rate, recovery rate, and case fatality ratio (CFR) of CSF without detailed data on the population estimates of wild boar. A mathematical model was constructed to describe the CSF dynamics and population dynamics of wild boar. We fitted the model to the (i) results of the reverse transcription polymerase chain reaction (RT-PCR) test for the CSFV gene and the (ii) results of the enzyme-linked immunosorbent assay (ELISA) test for the antibody against CSFV in sampled wild boar. In the 280 wild boar sampled from September 2018 to March 2019 in the major CSF-affected area in Japan, the lethality rate and recovery rate of CSF per week were estimated as 0.165 (95% confidence interval: 0.081-0.250) and 0.004 (0-0.009), respectively. While the estimate of lethality rate of CSF was similar with the estimates in previous studies, the recovery rate was lower than those reported previously. CFR was estimated as 0.959 (0.904-0.981) using our estimate of recovery rate. This study is the first to estimate lethality rate of CSF from the dynamics of CSF epidemics in the wild boar population. Since the value of CFR is sensitive to the value of recovery rate, the accuracy in the estimate of recovery rate is a key for the accurate estimation of CFR. A long-term transmission experiment of moderately virulent strains may lead to more accurate estimation of the recovery rate and CFR of CSF.
了解疾病的发病率和致死率对于评估针对流行病的对策（如疫苗接种）的有效性至关重要。为了估算这些数据，需要宿主种群动态的详细数据；然而，估算野生动物的种群数量往往很困难。我们旨在阐明目前在日本野猪种群中高度流行的经典猪瘟（CSF）的发病率和致死率。为此，我们在没有野猪种群数量估算详细数据的情况下，估算了CSF的致死率、恢复率和病死率（CFR）。构建了一个数学模型来描述CSF动态和野猪的种群动态。我们将该模型与（i）针对CSFV基因的逆转录聚合酶链反应（RT-PCR）检测结果以及（ii）在采样野猪中针对抗CSFV抗体的酶联免疫吸附测定（ELISA）检测结果进行拟合。在2018年9月至2019年3月从日本主要CSF疫区采样的280头野猪中，每周CSF的致死率和恢复率分别估计为0.165（95%置信区间：0.081 - 0.250）和0.004（0 - 0.009）。虽然CSF致死率的估计与先前研究的估计相似，但恢复率低于先前报道的水平。使用我们对恢复率的估计，CFR估计为0.959（0.904 - 0.981）。本研究首次从野猪种群中CSF流行病的动态估算了CSF的致死率。由于CFR的值对恢复率的值敏感，恢复率估计的准确性是准确估计CFR的关键。中等毒力菌株的长期传播实验可能会导致对CSF恢复率和CFR的更准确估计。
