Baylis M, Bouayoune H, Touti J, El Hasnaoui H
Institute for Animal Health, Pirbright, Surrey, UK.
Med Vet Entomol. 1998 Jul;12(3):255-66. doi: 10.1046/j.1365-2915.1998.00109.x.
African horse sickness (AHS) is a vector-borne, infectious disease of equids caused by African horse sickness virus (AHSV). The only proven field vector of the virus is the biting midge Culicoides imicola. Following a recent epizootic (1989-91) of AHS in Morocco, light traps and automatic weather stations were operated for 2 years at twenty-two sites distributed over much of the country. The annually-averaged mean daily trap catch of C. imicola at these sites was negatively correlated with wind speed, and positively correlated with the average and mean annual minimum NDVI (Normalized Difference Vegetation Index, a remotely sensed measure of vegetation activity). There were no significant correlations between the mean daily trap catch and air temperature, soil temperature, relative humidity, saturation deficit, rainfall, altitude or the mean annual maximum or range of NDVI. The best two-variable model, which combined WindspeedMnAvMn (the average daily minimum wind speed of the least windy month) and NDVImin (the average annual minimum NDVI) as predictors, explained over 50% of the variance in the annually-averaged mean daily trap catch of C. imicola. There was a significant, positive correlation between minimum wind speed at night and the daily mortality rate of adult female C. imicola and it is suggested that the relationship between wind speed and the abundance of C. imicola arises from effects on adult mortality or dispersal. Considering several climatic variables, in North Africa NDVImin was most significantly correlated with total annual rainfall. It is suggested that the relationship between NDVImin and the abundance of C. imicola arises from the impact of soil moisture on both. It is proposed that areas of Morocco with higher levels of soil moisture in late summer or autumn provide more, larger and/or more enduring breeding sites for C. imicola, as well as supporting more photosynthetically active vegetation and hence having higher NDVI.
非洲马瘟（AHS）是由非洲马瘟病毒（AHSV）引起的一种通过媒介传播的马属动物传染病。该病毒唯一经证实的野外传播媒介是吸血蠓库蠓。在摩洛哥近期（1989 - 1991年）发生非洲马瘟 epizootic 之后，在该国大部分地区分布的22个地点设置了诱虫灯和自动气象站，持续运行了2年。这些地点库蠓的年平均每日诱捕量与风速呈负相关，与年平均和年最低归一化植被指数（NDVI，一种遥感测量植被活动的指标）呈正相关。每日诱捕量与气温、土壤温度、相对湿度、饱和差、降雨量、海拔高度或年最大NDVI或NDVI范围之间没有显著相关性。最佳的双变量模型，将风速最小月份的平均每日最低风速（WindspeedMnAvMn）和年最低NDVI（NDVImin）作为预测因子，解释了库蠓年平均每日诱捕量方差的50%以上。夜间最低风速与成年雌性库蠓的每日死亡率之间存在显著的正相关关系，表明风速与库蠓数量之间的关系源于对成虫死亡率或扩散的影响。考虑多个气候变量，在北非，NDVImin与年总降雨量的相关性最为显著。有人认为，NDVImin与库蠓数量之间的关系源于土壤湿度对两者的影响。有人提出，摩洛哥夏末或秋季土壤湿度较高的地区为库蠓提供了更多、更大和/或更持久的繁殖场所，同时支持更多光合活性植被，因此具有更高的NDVI。
