Davies C R, Jones L D, Nuttall P A
NERC, Institute of Virology and Environmental Microbiology, Oxford, England.
Am J Trop Med Hyg. 1990 Jul;43(1):99-103. doi: 10.4269/ajtmh.1990.43.99.
Infection thresholds of Thogoto virus in 2 ixodid tick species, Rhipicephalus appendiculatus and Amblyomma variegatum, were compared. Thogoto virus has been isolated from naturally infected R. appendiculatus and A. variegatum in Central Africa, where both commonly parasitize the same hosts. No significant difference was found between the infection thresholds of Thogoto virus in the 2 species. The percentage of nymphs of both species infected by feeding on viremic hamsters was directly correlated with the time between host inoculation and tick engorgement. The blood titers in infected hamsters increased each day during the 3-4 day viremia until the hamsters died. The percentage of nymphs infected correlated with the viremic titer on the final day of engorgement (the time of maximum blood uptake). The 5% infection threshold for nymphs of R. appendiculatus and A. variegatum was estimated as 10(2.8) and 10(2.7) plaque forming units (PFU)/ml viremia, respectively. The prevalence of infection approached 100% for blood titers greater than 10(6.3) PFU/ml and greater than 10(7) PFU/ml, respectively. The apparent bloodmeal size of the 2 species differed by 8-fold and suggested that, in terms of the number of PFU ingested, R. appendiculatus was more susceptible than A. variegatum to per os infection by Thogoto virus.
比较了图戈托病毒在2种硬蜱（微小牛蜱和变异革蜱）中的感染阈值。在中非，图戈托病毒已从自然感染的微小牛蜱和变异革蜱中分离出来，这两种蜱通常寄生于同一宿主。未发现图戈托病毒在这2种蜱中的感染阈值有显著差异。通过吸食病毒血症仓鼠血液而感染的两种蜱若虫百分比与宿主接种病毒至蜱饱血之间的时间直接相关。在3 - 4天的病毒血症期间，感染仓鼠的血液滴度每天都在增加，直至仓鼠死亡。感染的若虫百分比与饱血最后一天（最大吸血量时）的病毒血症滴度相关。微小牛蜱和变异革蜱若虫的5%感染阈值估计分别为10(2.8)和10(2.7) 蚀斑形成单位（PFU）/毫升病毒血症。当血液滴度分别大于10(6.3) PFU/毫升和大于10(7) PFU/毫升时，感染率接近100%。这两种蜱的表观血餐大小相差8倍，这表明就摄入的PFU数量而言，微小牛蜱比变异革蜱对图戈托病毒经口感染更易感。
