Gouda Mennatallah, Powell Jim, McClure Jen, Walsh Daniel P, Storm Daniel
Department of Mathematics and Statistics, Utah State University, Logan, UT, 84321, USA.
Wildlife Biology Program, Montana Cooperative Wildlife Research Unit, U.S. Geological Survey, University of Montana, Missoula, MT, 59812, USA.
Bull Math Biol. 2025 Mar 13;87(4):52. doi: 10.1007/s11538-024-01394-x.
Chronic wasting disease (CWD) is a fatal neurodegenerative disease infecting cervids. It is highly contagious and caused by misfolded prions that propagate via templated conformational conversion of the cervid's normal prion protein. Prevalence of CWD in free-ranging deer in North America is mostly low, but in some regions local prevalence has reached 80%. CWD prions can be transmitted via direct contact with infected individuals or indirectly through the environment. Infected individuals shed prions through feces, urine, saliva or carcasses, and prions have long environmental persistence. Long-distance dispersal of infected deer poses a significant risk for CWD spread. We propose an integrodifference equation (IDE) model to capture CWD dynamics and the consequences of long-distance dispersal behavior in white-tailed deer (WTD, Odocoileus virginianus). A diffusion-settling model characterizes long-distance dispersal kernels, accommodating hypothetical dispersal behaviors through time-dependent settling rate functions. Three new closed-form dispersal kernels are approximated using Laplace's method and parameterized with GPS location data collected from WTD in Wisconsin, USA. Settling rates reflecting ongoing sensitivity to stimuli which prompt deer to disperse from their natal home range give the most supported long-distance dispersal kernel. Impact of long-distance dispersal on CWD spread is quantified using the IDE model. At high population densities, long-distance dispersal can magnify CWD spread by a factor of four. At lower population densities single infected individuals cannot initiate an outbreak, but CWD may still spread due to the accumulation of environmental hazard from prions behind the wave of invasion, possibly presenting substantial management challenges.
慢性消耗病（CWD）是一种感染鹿科动物的致命神经退行性疾病。它具有高度传染性，由错误折叠的朊病毒引起，这些朊病毒通过鹿正常朊病毒蛋白的模板化构象转换进行传播。在北美的野生鹿中，CWD的流行率大多较低，但在一些地区，当地流行率已达到80%。CWD朊病毒可通过与受感染个体直接接触或通过环境间接传播。受感染个体通过粪便、尿液、唾液或尸体排出朊病毒，并且朊病毒在环境中具有长期持久性。受感染鹿的远距离扩散对CWD的传播构成了重大风险。我们提出了一个积分差分方程（IDE）模型，以捕捉白尾鹿（Odocoileus virginianus）中CWD的动态以及远距离扩散行为的后果。一个扩散沉降模型表征远距离扩散核，通过随时间变化的沉降速率函数来适应假设的扩散行为。使用拉普拉斯方法近似了三个新的封闭形式的扩散核，并根据从美国威斯康星州的白尾鹿收集的GPS位置数据进行参数化。反映对促使鹿从其出生栖息地范围扩散的刺激持续敏感性的沉降速率给出了最受支持的远距离扩散核。使用IDE模型量化了远距离扩散对CWD传播的影响。在高种群密度下，远距离扩散可使CWD的传播扩大四倍。在较低种群密度下，单个受感染个体无法引发疫情，但由于入侵浪潮后朊病毒造成的环境危害积累，CWD仍可能传播，这可能带来重大的管理挑战。
