Heinig Rebecca L, Thomas Matthew B
Merkle Laboratory, The Pennsylvania State University, University Park, PA, 16803, USA.
Malar J. 2015 Jan 28;14:22. doi: 10.1186/s12936-014-0526-x.
Mosquitoes are becoming increasingly resistant to the chemical insecticides currently available for malaria vector control, spurring interest in alternative management tools. One promising technology is the use of fungal entomopathogens. Fungi have been shown to impact the potential for mosquitoes to transmit malaria by reducing mosquito longevity and altering behaviour associated with flight and host location. Additionally, fungi could impact the development of malaria parasites within the mosquito via competition for resources or effects on the mosquito immune system. This study evaluated whether co-infection or superinfection with the fungal entomopathogen Beauveria bassiana affected malaria infection progress in Anopheles stephensi mosquitoes.
The study used two parasite species to examine possible effects of fungal infection at different parasite development stages. First, the rodent malaria model Plasmodium yoelii was used to explore interactions at the oocyst stage. Plasmodium yoelii produces high oocyst densities in infected mosquitoes and thus was expected to maximize host immunological and resource demands. Second, fungal interactions with mature sporozoites were evaluated by infecting mosquitoes with the human malaria species Plasmodium falciparum, which is highly efficient at invading mosquito salivary glands.
With P. yoelii, there was no evidence that fungal co-infection (on the same day as the blood meal) or superinfection (during a subsequent gonotrophic cycle after parasite infection) affected the proportion of mosquitoes with oocysts, the number of oocysts per infected mosquito or the number of sporozoites per oocyst. Similarly, for P. falciparum, there was no evidence that fungal infection affected sporozoite prevalence. Furthermore, there was no impact of infection with either malaria species on fungal virulence as measured by mosquito survival time.
These results suggest that the impact of fungus on malaria control potential is limited to the well-established effects on mosquito survival and transmission behaviour. Direct or indirect interactions between fungus and malaria parasites within mosquitoes appear to have little additional influence.
蚊子对目前用于控制疟疾传播媒介的化学杀虫剂的耐药性日益增强，这激发了人们对替代管理工具的兴趣。一种有前景的技术是使用真菌昆虫病原体。研究表明，真菌可通过缩短蚊子寿命以及改变与飞行和宿主定位相关的行为，来影响蚊子传播疟疾的可能性。此外，真菌可能通过资源竞争或对蚊子免疫系统的影响，来影响蚊子体内疟原虫的发育。本研究评估了真菌昆虫病原体球孢白僵菌的共感染或重复感染是否会影响斯氏按蚊体内的疟疾感染进程。
该研究使用了两种疟原虫物种，以检验真菌感染在不同疟原虫发育阶段可能产生的影响。首先，使用啮齿动物疟疾模型约氏疟原虫来探究卵囊阶段的相互作用。约氏疟原虫在受感染的蚊子中会产生高密度的卵囊，因此预计它会使宿主的免疫和资源需求最大化。其次，通过用人类疟原虫物种恶性疟原虫感染蚊子，来评估真菌与成熟子孢子之间的相互作用，恶性疟原虫在侵入蚊子唾液腺方面效率很高。
对于约氏疟原虫，没有证据表明真菌共感染（与血餐在同一天）或重复感染（在寄生虫感染后的后续生殖营养周期内）会影响有卵囊的蚊子比例、每只受感染蚊子的卵囊数量或每个卵囊的子孢子数量。同样，对于恶性疟原虫，也没有证据表明真菌感染会影响子孢子的流行率。此外，用这两种疟原虫中的任何一种进行感染，对以蚊子存活时间衡量的真菌毒力均无影响。
这些结果表明，真菌对疟疾控制潜力的影响仅限于对蚊子存活和传播行为的既定影响。蚊子体内真菌与疟原虫之间的直接或间接相互作用似乎几乎没有额外影响。
