Adler F R, Clay C A, Lehmer E M
Department of Biology and Department of Mathematics, University of Utah, Salt Lake City, Utah 84112, USA.
Am Nat. 2008 Dec;172(6):855-67. doi: 10.1086/592405.
Many diseases persist at a relatively low prevalence, seemingly close to extinction. For a chronic disease in a homogeneous population, reducing the transmission rate by a fraction proportional to the prevalence would be sufficient to eradicate the disease. This study examines how higher prevalence of the Sin Nombre virus in male deer mice (Peromyscus maniculatus) might contribute to disease persistence. Analyzing data from over 2,000 individual mice captured in 19 sites over 4 years, we found prevalences of 18.5% in males and 8.8% in females. By examining recaptures, we determined that males are more likely to contract the infection because of higher susceptibility or higher encounter rates. Comparing across 86 sampling periods, we found a higher proportion of males when population densities were low. A capture-recapture analysis indicates that males live longer than females. A mathematical model based on the measured parameters and population size trajectories suggests that the combined heterogeneity in encounters, susceptibility, and mortality may buffer the disease from extinction by concentrating disease in the subgroup most likely to transmit the disease. This buffering effect is not significantly stronger in a fluctuating population, indicating that these forms of heterogeneity might not be the key for disease persistence through host population bottlenecks.
许多疾病以相对较低的流行率持续存在，看似接近于灭绝。对于同质人群中的一种慢性疾病，将传播率降低一个与流行率成比例的分数就足以根除该疾病。本研究考察了雄性鹿鼠（白足鼠）中辛诺柏病毒较高的流行率可能如何导致疾病的持续存在。通过分析4年内在19个地点捕获的2000多只个体小鼠的数据，我们发现雄性的流行率为18.5%，雌性为8.8%。通过检查重新捕获的情况，我们确定雄性由于易感性较高或接触率较高而更有可能感染。在86个采样期进行比较时，我们发现种群密度低时雄性的比例更高。捕获-再捕获分析表明雄性比雌性寿命更长。基于测量参数和种群数量轨迹的数学模型表明，接触、易感性和死亡率方面的综合异质性可能通过将疾病集中在最有可能传播疾病的亚组中来缓冲疾病的灭绝。在波动的种群中，这种缓冲效应并没有明显更强，这表明这些异质性形式可能不是疾病通过宿主种群瓶颈持续存在的关键。
