Plasmodium falciparum infections in low-transmission settings are often asymptomatic with low parasite densities despite low herd immunity. Based on studies in Zanzibar, this may be due to parasitic (nonvirulence) rather than host (immunity) factors. In high-transmission settings, high replication rate and virulence represents a competitive advantage, whereas in low-transmission settings nonvirulent parasites escape both competition and treatment. Such parasites also survive longer in low-transmission settings due to lower host immunity response and less frequent indirect drug exposure. This has major implications for optimal malaria control and elimination strategies.

尽管牛群免疫力较低，但低传播环境中的恶性疟原虫感染通常无症状，寄生虫密度低。根据桑给巴尔的研究，这可能是由于寄生（非毒力）而不是宿主（免疫）因素引起的。在高传播环境中，高复制率和高毒力代表了竞争优势，而在低传播环境中，无毒寄生虫则逃脱了竞争和治疗。由于较低的宿主免疫反应和较少的间接药物暴露，此类寄生虫在低传播环境中也可以存活更长的时间。这对最佳的疟疾控制和消除策略具有重要意义。