Schall Jos J, Smith Thomas C
Department of Biology, University of Vermont, Burlington, Vermont 05405, USA.
J Parasitol. 2006 Apr;92(2):413-5. doi: 10.1645/GE-688R.1.
Two species of sandflies (Lutzomyia) are competent vectors of Plasmodium mexicanum, a malaria parasite of lizards. The very patchy distribution of sites with high P. mexicanum prevalence in the lizards, and often low or even nil sandfly density at such sites, provoked an evaluation of 2 common lizard ectoparasites, the tick Ixodes pacificus and the mite Geckobiella occidentalis, as potential passive vectors. Plasmodium sp.-specific polymerase chain primers were used to amplify a long segment of the mitochondrial cytochrome b gene that is unlikely to survive intact if the parasite cells are killed within a blood-feeding arthropod. The segment was strongly amplified from sandflies (the positive control for the method) from 1 to 96 hr postfeeding on an infected lizard. For ticks, the gene fragment was poorly amplified at 0 hr postfeed, and not amplified after 2 hr. In contrast, strong amplification of the parasite DNA was observed from mites from 0 to 20 hr postfeed, and weak amplification even at 96 hr.
两种白蛉（罗蛉属）是墨西哥疟原虫的有效传播媒介，墨西哥疟原虫是一种蜥蜴的疟原虫。蜥蜴体内墨西哥疟原虫高流行率的地点分布非常零散，而且这些地点的白蛉密度往往很低甚至为零，这促使人们对两种常见的蜥蜴体表寄生虫——太平洋硬蜱和西方壁虎螨作为潜在被动传播媒介进行评估。使用疟原虫属特异性聚合酶链反应引物扩增线粒体细胞色素b基因的一个长片段，如果寄生虫细胞在吸血节肢动物体内被杀死，该片段不太可能完整存活。在以感染蜥蜴为食后1至96小时，从白蛉（该方法的阳性对照）中强烈扩增出该片段。对于蜱虫，在进食后0小时基因片段扩增不佳，2小时后未扩增。相比之下，在进食后0至20小时从螨虫中观察到寄生虫DNA的强烈扩增，甚至在96小时时仍有微弱扩增。
