Department of Environmental Sciences, Section of Conservation Biology, University of Basel, St. Johanns-Vorstadt 10, CH-4056 Basel, Switzerland.
Int J Parasitol. 2010 Aug 1;40(9):1045-50. doi: 10.1016/j.ijpara.2010.02.012. Epub 2010 Mar 23.
Parasite transmission fundamentally affects the epidemiology of host-parasite systems, and is considered to be a key element in the epidemiological modelling of infectious diseases. Recent research has stressed the importance of detailed disease-specific variables involved in the transmission process. Riccardoella limacum is a hematophagous mite living in the mantle cavity of terrestrial gastropods. In this study, we experimentally examined whether the transmission success of R. limacum is affected by the contact frequency, parasite load and/or behaviour of the land snail Arianta arbustorum, a common host of R. limacum. In the experiment the transmission success was mainly affected by physical contacts among snails and slightly influenced by parasite intensity of the infected snail. Using these results we developed two different transmission models based on contact frequencies and transmission probability among host snails. As parameters for the models we used life-history data from three natural A. arbustorum populations with different population densities. Data on contact frequencies of video-recorded snail groups were used to fit the density response of the contact function, assuming either a linear relationship (model 1) or a second-degree polynomial relationship based on the ideal gas model of animal encounter (model 2). We calculated transmission coefficients (beta), basic reproductive ratios (R(0)) and host threshold population densities for parasite persistence in the three A. arbustorum populations. We found higher transmission coefficients (beta) and larger R(0)-values in model 1 than in model 2. Furthermore, the host population with the highest density showed larger R(0)-values (16.47-22.59) compared to populations with intermediate (2.71-7.45) or low population density (0.75-4.10). Host threshold population density for parasite persistence ranged from 0.35 to 2.72 snails per m(2). Our results show that the integration of the disease-relevant biology of the organisms concerned may improve models of host-parasite dynamics.
寄生虫传播从根本上影响宿主-寄生虫系统的流行病学，被认为是传染病流行病学建模的关键要素。最近的研究强调了传染病传播过程中涉及的详细疾病特定变量的重要性。Riccardoella limacum 是一种寄生在陆生腹足纲动物套膜腔中的吸血螨。在本研究中，我们通过实验检验了 Riccardoella limacum 的传播成功率是否受到接触频率、寄生虫负荷和/或陆生蜗牛 Arianta arbustorum 的行为的影响，Arianta arbustorum 是 Riccardoella limacum 的常见宿主。在实验中，传播成功率主要受到蜗牛之间的物理接触影响，而受感染蜗牛的寄生虫强度的影响较小。利用这些结果，我们根据宿主蜗牛之间的接触频率和传播概率开发了两种不同的传播模型。作为模型的参数，我们使用了三个具有不同种群密度的天然 Arianta arbustorum 种群的生活史数据。使用视频记录的蜗牛群体的接触频率数据来拟合接触函数的密度响应，假设基于动物遭遇理想气体模型的线性关系（模型 1）或二次多项式关系（模型 2）。我们为三个 Arianta arbustorum 种群中的寄生虫持久性计算了传播系数（β）、基本繁殖率（R(0)）和宿主阈值种群密度。我们发现模型 1 中的传播系数（β）和 R(0)值大于模型 2。此外，密度最高的宿主种群的 R(0)值（16.47-22.59）大于中等密度（2.71-7.45）或低密度（0.75-4.10）的宿主种群。宿主阈值种群密度为寄生虫持久性范围从 0.35 到 2.72 只蜗牛/平方米。我们的研究结果表明，整合有关生物体的相关疾病生物学知识可能会提高宿主-寄生虫动力学模型的准确性。
