Fourie L J, Petney T N, Horak I G, de Jager C
Department of Zoology/Entomology, University of the Orange Free State, Bloemfontein, South Africa.
Vet Parasitol. 1989 Oct;33(3-4):319-28. doi: 10.1016/0304-4017(89)90141-6.
The epidemiology of Karoo paralysis, induced by the tick Ixodes rubicundus, was investigated in a paralysis-enzootic area of the southwestern Orange Free State, Republic of South Africa. Sheep became paralysed during the last week of April and the first week of May during the 1985 and 1986 seasons, respectively. Paralysis cases were recorded up until July, but most paralysis cases occurred during the first week of May with a second but smaller peak occurring during June. Tick numbers on paralysed sheep closely followed peak periods in paralysis. A total of 65 and 50% of the naive sheep became paralysed during the 1985 and 1986 seasons, respectively. The seasonal pattern of tick infestation by female I. rubicundus was similar on both previously exposed and on naive sheep. The results of this study indicate that a certain number of ticks per kilogram host body mass is required before symptoms of paresis of paralysis are observed. In general the tick burden per kilogram host mass was significantly greater in paralysed compared to non-paralysed sheep. The range in the number of ticks per kilogram host mass may, however, overlap between non-paralysed and paralysed groups. Previously exposed or previously paralysed sheep are less susceptible to paralysis in the following year. Differences in susceptibility between individual sheep seems likely.
在南非共和国奥兰治自由邦西南部的一个麻痹性动物病流行区，对由红硬蜱引起的卡鲁麻痹的流行病学进行了调查。在1985年和1986年的季节里，绵羊分别在4月的最后一周和5月的第一周出现麻痹症状。麻痹病例记录一直持续到7月，但大多数麻痹病例发生在5月的第一周，6月出现第二个较小的高峰。麻痹绵羊身上的蜱虫数量与麻痹高峰期密切相关。在1985年和1986年的季节里，分别有65%和50%的未接触过蜱虫的绵羊出现麻痹症状。雌性红硬蜱在先前接触过蜱虫的绵羊和未接触过蜱虫的绵羊身上的季节性寄生模式相似。这项研究的结果表明，在观察到轻瘫或麻痹症状之前，每千克宿主体重需要一定数量的蜱虫。一般来说，与未麻痹的绵羊相比，麻痹绵羊每千克体重的蜱虫负担明显更大。然而，未麻痹组和麻痹组每千克宿主体重的蜱虫数量范围可能会有重叠。先前接触过蜱虫或先前出现过麻痹症状的绵羊在次年对麻痹的易感性较低。个体绵羊之间的易感性差异似乎很可能存在。
