INRAE, Oniris, BIOEPAR, 44300, Nantes, France; UMR ASTRE, CIRAD, Montpellier, France; ASTRE, Montpellier University, CIRAD, INRAE, Montpellier, France.
Inserm, Sorbonne Université, Institut Pierre Louis d'Epidémiologie et de Santé Publique (IPLESP), F-75012, Paris, France.
Epidemics. 2020 Dec;33:100409. doi: 10.1016/j.epidem.2020.100409. Epub 2020 Oct 21.
Estimating the epidemic potential of vector-borne diseases, along with the relative contribution of underlying mechanisms, is crucial for animal and human health worldwide. In West African Sahel, several outbreaks of Rift Valley fever (RVF) have occurred over the last decades, but uncertainty remains about the conditions necessary to trigger these outbreaks. We use the basic reproduction number (R) as a measure of RVF epidemic potential in northern Senegal, and map its value in two distinct ecosystems, namely the Ferlo and the Senegal River delta and valley. We consider three consecutive rainy seasons (July-November 2014, 2015 and 2016) and account for several vector and animal species. We parametrize our model with estimates of Aedes vexans arabiensis, Culex poicilipes, Culex tritaeniorhynchus, cattle, sheep and goat abundances. The impact of RVF virus introduction is assessed every week over northern Senegal. We highlight September as the period of highest epidemic potential in northern Senegal, resulting from distinct dynamics in the two study areas. Spatially, in the seasonal environment of the Ferlo, we observe that high-risk locations vary between years. We show that decreased vector densities do not greatly reduce R and that cattle immunity has a greater impact on reducing transmission than small ruminant immunity. The host preferences of vectors and the temperature-dependent time interval between their blood meals are crucial parameters needing further biological investigations.
评估媒介传播疾病的流行潜力，以及潜在机制的相对贡献，对全球动物和人类健康至关重要。在西非萨赫勒地区，过去几十年里发生了几次裂谷热（RVF）疫情，但仍不确定触发这些疫情所需的条件。我们使用基本繁殖数（R）作为衡量塞内加尔北部裂谷热流行潜力的指标，并在两个不同的生态系统中对其进行了映射，即费罗和塞内加尔河三角洲和河谷。我们考虑了三个连续的雨季（2014 年 7 月至 11 月、2015 年和 2016 年），并考虑了几种媒介和动物物种。我们使用 Aedes vexans arabiensis、Culex poicilipes、Culex tritaeniorhynchus、牛、绵羊和山羊丰度的估计值来参数化我们的模型。每周在塞内加尔北部评估 RVF 病毒引入的影响。我们强调 9 月是塞内加尔北部流行潜力最高的时期，这是两个研究区域不同动态的结果。从空间上看，在 Ferlo 的季节性环境中，我们发现高风险地点因年份而异。我们表明，降低媒介密度并不会大大降低 R，并且牛的免疫力对降低传播的影响大于小反刍动物的免疫力。媒介的宿主偏好和它们之间血液餐之间的温度依赖性时间间隔是需要进一步进行生物学研究的关键参数。
