Laboratorio de Biomedicina Molecular, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Boulevard del Maestro S/N esquina Elías Piña, Col, Narciso Mendoza, 88710, Cd, Reynosa, Tamaulipas, México.
Parasit Vectors. 2011 Sep 9;4:171. doi: 10.1186/1756-3305-4-171.
Dengue is a viral disease transmitted by Aedes mosquitoes. It is a threat for public health worldwide and its primary vector Aedes aegypti is becoming resistant to chemical insecticides. These factors have encouraged studies to evaluate entomopathogenic fungi against the vector. Here we evaluated mortality, infection, insemination and fecundity rates in A. aegypti females after infection by autodissemination with two Mexican strains of Metarhizium anisopliae.
Two M. anisopliae strains were tested: The Ma-CBG-1 least virulent (lv), and the Ma-CBG-2 highly virulent (hv) strain. The lv was tested as non mosquito-passed (NMP), and mosquito-passed (MP), while the hv was examined only as MP version, therefore including the control four treatments were used. In the first bioassay virulence of fungal strains towards female mosquitoes was determined by indirect exposure for 48 hours to conidia-impregnated paper. In the second bioassay autodissemination of fungal conidia from fungus-contaminated males to females was evaluated. Daily mortality allowed computation of survival curves and calculation of the LT50 by the Kaplan-Meier model. All combinations of fungal sporulation and mating insemination across the four treatments were analyzed by χ2. The mean fecundity was analyzed by ANOVA and means contrasted with the Ryan test.
Indirect exposure to conidia allowed a faster rate of mortality, but exposure to a fungal-contaminated male was also an effective method of infecting female mosquitoes. All females confined with the hv strain-contaminated male died in fifteen days with a LT50 of 7.57 (± 0.45) where the control was 24.82 (± 0.92). For the lv strain, it was possible to increase fungal virulence by passing the strain through mosquitoes. 85% of females exposed to hv-contaminated males became infected and of them just 10% were inseminated; control insemination was 46%. The hv strain reduced fecundity by up to 99%, and the lv strain caused a 40% reduction in fecundity.
The hv isolate infringed a high mortality, allowed a low rate of insemination, and reduced fecundity to nearly zero in females confined with a fungus-contaminated male. This pathogenic impact exerted through sexual transmission makes the hv strain of M. anisopliae worthy of further research.
登革热是一种由埃及伊蚊传播的病毒性疾病。它是全球公共卫生的威胁，其主要媒介埃及伊蚊对化学杀虫剂的抵抗力越来越强。这些因素促使人们研究利用昆虫病原真菌来对付这种病媒。在这里，我们评估了通过自体传播感染两种来自墨西哥的绿僵菌对埃及伊蚊雌性的死亡率、感染率、授精率和繁殖力的影响。
测试了两种绿僵菌菌株：最不毒力的 Ma-CBG-1(lv)菌株和高毒力的 Ma-CBG-2(hv)菌株。lv 菌株被测试为非传病（NMP）和传病（MP），而 hv 菌株仅作为 MP 版本进行检测，因此包括对照，共使用了四种处理。在第一个生物测定中，通过间接暴露于 48 小时内的孢子浸渍纸上来确定真菌菌株对雌性蚊子的毒力。在第二个生物测定中，评估了真菌孢子从受污染的雄性传播到雌性的自传播。每日死亡率允许计算存活曲线，并通过 Kaplan-Meier 模型计算 LT50。通过 χ2 分析了四种处理方式下真菌孢子繁殖和交配授精的所有组合。通过 ANOVA 分析平均繁殖力，并通过 Ryan 检验进行均值对比。
间接接触孢子可以更快地导致死亡率，但暴露于受真菌污染的雄性也是感染雌性蚊子的有效方法。所有与 hv 菌株污染的雄性一起饲养的雌性蚊子在 15 天内全部死亡，LT50 为 7.57(±0.45)，而对照组为 24.82(±0.92)。对于 lv 菌株，通过蚊子传播可以提高菌株的真菌毒力。暴露于 hv 污染的雄性的 85%的雌性蚊子受到感染，其中只有 10%被授精；对照组的授精率为 46%。hv 菌株将繁殖力降低了多达 99%，而 lv 菌株则将繁殖力降低了 40%。
hv 分离株造成高死亡率，允许低授精率，并使与受真菌污染的雄性一起饲养的雌性蚊子的繁殖力几乎降为零。这种通过性传播造成的致病性影响使 M. anisopliae 的 hv 菌株值得进一步研究。
