Scholte Ernst-Jan, Knols Bart G J, Takken Willem
Laboratory of Entomology, Wageningen University Research Centre, Binnenhaven 7, P,O, Box 8031, Wageningen, the Netherlands.
Malar J. 2004 Nov 28;3:45. doi: 10.1186/1475-2875-3-45.
The entomopathogenic fungus Metarhizium anisopliae is being considered as a biocontrol agent for adult African malaria vectors. In the laboratory, work was carried out to assess whether horizontal transmission of the pathogen can take place during copulation, as this would enhance the impact of the fungus on target populations when compared with insecticides.
Virgin female Anopheles gambiae sensu stricto were exposed to conidia whilst resting on fungus-impregnated paper. These females were then placed together for one hour with uncontaminated males in proportions of either 1:1 or 1:10 shortly before the onset of mating activity.
Males that had acquired fungal infection after mating indicate that passive transfer of the pathogen from infected females does occur, with mean male infection rates between 10.7 +/- 3.2% and 33.3 +/- 3.8%. The infections caused by horizontal transmission did not result in overall differences in survival between males from test and control groups, but in one of the three experiments the infected males had significantly shorter life spans than uninfected males (P < 0.05).
This study shows that autodissemination of fungal inoculum between An. gambiae s.s. mosquitoes during mating activity is possible under laboratory conditions. Field studies are required next, to assess the extent to which this phenomenon may augment the primary contamination pathway (i.e. direct contact with fungus-impregnated targets) of vector populations in the field.
昆虫病原真菌绿僵菌正被视为成年非洲疟疾传播媒介的生物防治剂。在实验室中，开展了相关工作以评估病原体是否能在交配过程中发生水平传播，因为与杀虫剂相比，这将增强真菌对目标种群的影响。
将未交配过的冈比亚按蚊雌蚊置于浸有真菌的纸片上休息时接触分生孢子。然后在交配活动开始前不久，将这些雌蚊与未受污染的雄蚊按1:1或1:10的比例放在一起一小时。
交配后感染真菌的雄蚊表明病原体确实会从受感染雌蚊处发生被动传播，雄蚊的平均感染率在10.7±3.2%至33.3±3.8%之间。水平传播引起的感染并未导致试验组和对照组雄蚊的总体存活率存在差异，但在三个实验中的一个实验里，受感染雄蚊的寿命明显短于未受感染雄蚊（P<0.05）。
本研究表明，在实验室条件下，冈比亚按蚊在交配活动期间真菌接种物的自动传播是可能的。接下来需要进行实地研究，以评估这种现象在多大程度上可能增加野外病媒种群的主要污染途径（即直接接触浸有真菌的目标物）。
