McMahon B H, Manore C A, Hyman J M, LaBute M X, Fair J M
Los Alamos National Laboratory, Theoretical Biology and Biophysics, Los Alamos, NM 87545.
Department of Mathematics, Tulane University, New Orleans, LA 70118 ; Center for Computational Science, Tulane University, New Orleans, LA 70118.
Math Model Nat Phenom. 2014 Jan 1;9(2):161-177. doi: 10.1051/mmnp/20149211.
We present and characterize a multi-host epidemic model of Rift Valley fever (RVF) virus in East Africa with geographic spread on a network, rule-based mitigation measures, and mosquito infection and population dynamics. Susceptible populations are depleted by disease and vaccination and are replenished with the birth of new animals. We observe that the severity of the epidemics is strongly correlated with the duration of the rainy season and that even severe epidemics are abruptly terminated when the rain stops. Because naturally acquired herd immunity is established, total mortality across 25 years is relatively insensitive to many mitigation approaches. Strong reductions in cattle mortality are expected, however, with sufficient reduction in population densities of either vectors or susceptible (ie. unvaccinated) hosts. A better understanding of RVF epidemiology would result from serology surveys to quantify the importance of herd immunity in epidemic control, and sequencing of virus from representative animals to quantify the realative importance of transportation and local reservoirs in nucleating yearly epidemics. Our results suggest that an effective multi-layered mitigation strategy would include vector control, movement control, and vaccination of young animals yearly, even in the absence of expected rainfall.
我们提出并描述了东非裂谷热（RVF）病毒的多宿主流行模型，该模型考虑了网络上的地理传播、基于规则的缓解措施以及蚊子感染和种群动态。易感种群因疾病和疫苗接种而减少，并随着新动物的出生而补充。我们观察到，疫情的严重程度与雨季持续时间密切相关，而且即使是严重的疫情也会在雨停时突然终止。由于建立了自然获得的群体免疫，25年期间的总死亡率对许多缓解方法相对不敏感。然而，如果媒介或易感（即未接种疫苗）宿主的种群密度有足够降低，预计牛的死亡率会大幅下降。通过血清学调查来量化群体免疫在疫情控制中的重要性，以及对代表性动物的病毒进行测序以量化运输和本地宿主库在每年疫情爆发中的相对重要性，将有助于更好地理解RVF流行病学。我们的结果表明，即使在没有预期降雨的情况下，有效的多层缓解策略也应包括媒介控制、移动控制以及每年对幼畜进行疫苗接种。
