Jordaan L C, van Ark H
Veterinary Research Institute, Onderstepoort.
Onderstepoort J Vet Res. 1990 Sep;57(3):189-95.
A survey by means of questionnaires was conducted along the Orange River to determine the extent of blackfly annoyance to livestock during 1984-1988. Severe annoyance reached peaks during September-November and increased over the years. Annoyance levels decreased with distance from the river with occasional severe annoyance as far away as 76 km. Annoyance levels increased with distance downstream from the P. K. le Roux dam to Augrabies (750 km). Greater water releases for increased irrigation and electricity generation may be an important reason for the higher annoyance levels. Present day high and increasing irrigation water requirements and the great length of the river probably render control by water level fluctuations impractical. Loss of condition of especially small livestock is the main consequence of annoyance by female blackflies. Decreased percentage lambing and occasional deaths were also reported.
通过问卷调查的方式，沿着奥兰治河开展了一项调查，以确定1984年至1988年期间蚋对牲畜造成滋扰的程度。严重滋扰在9月至11月达到高峰，且多年来呈上升趋势。滋扰程度随着与河流距离的增加而降低，在距离河流76公里处偶尔也会出现严重滋扰情况。从PK勒鲁克斯大坝到奥赫拉比斯（750公里），滋扰程度随着下游距离的增加而上升。为增加灌溉和发电而加大的水量排放可能是滋扰程度较高的一个重要原因。当前灌溉用水需求居高不下且不断增加，以及河流长度很长，这可能使得通过水位波动进行控制不切实际。雌性蚋的滋扰主要造成了特别是小牲畜的身体状况下降。还报告了产羔率降低和偶尔出现死亡的情况。
