Scholte Ernst-Jan, Knols Bart G J, Takken Willem
Laboratory of Entomology, Wageningen University, 6700 EH Wageningen, The Netherlands.
J Invertebr Pathol. 2006 Jan;91(1):43-9. doi: 10.1016/j.jip.2005.10.006. Epub 2005 Dec 22.
The entomopathogenic fungus Metarhizium anisopliae is being considered as a biocontrol agent against adult African malaria vectors. In addition to causing significant mortality, this pathogen is known to cause reductions in feeding and fecundity in a range of insects. In the present study we investigated whether infection with M. anisopliae affected blood feeding and fecundity of adult female malaria vectors Anopheles gambiae Giles sensu stricto. Mosquitoes were contaminated with either a low or a moderately high dose of oil-formulated conidia of M. anisopliae, and offered a single human blood meal 48, 72, or 96 h later to assess feeding propensity and individual blood meal size. In a second experiment, individual fungus-infected females were offered a blood meal every third day (to a total of 8 gonotrophic cycles), and allowed to oviposit after each cycle in order to quantify feeding propensity and fecundity. Infected females took smaller blood meals and displayed reduced feeding propensity. It was found that mosquitoes, inoculated with a moderately high dose of fungal conidia, exhibited reduced appetite related to increasing fungal growth. Of the fungus-infected females, the proportion of mosquitoes taking the second blood meal was reduced with 51%. This was further reduced to 35.3% by the 4th blood meal. During 8 feeding opportunities, the average number of blood meals taken by uninfected females was 4.39, against 3.40 (low dose), and 2.07 (high dose) blood meals for the fungus-infected females. Moreover, infected females produced fewer eggs per gonotrophic cycle and had a lower life-time fecundity. Epidemiological models show that both blood feeding and fecundity are among the most important factors affecting the likelihood of a mosquito transmitting malaria, which suggests that this fungus may have potential as biocontrol agent for vector-borne disease control.
昆虫病原真菌绿僵菌正被视为对抗成年非洲疟疾传播媒介的一种生物防治剂。除了造成显著的死亡率外，这种病原体还会导致一系列昆虫的取食和繁殖力下降。在本研究中，我们调查了感染绿僵菌是否会影响成年雌性疟疾传播媒介冈比亚按蚊（Giles狭义种）的吸血和繁殖力。用低剂量或中等高剂量的绿僵菌油剂分生孢子污染蚊子，并在48、72或96小时后给它们提供一次人血餐，以评估取食倾向和个体血餐量。在第二个实验中，每隔三天给个体感染真菌的雌性蚊子提供一次血餐（总共8个生殖营养周期），并在每个周期后让它们产卵，以量化取食倾向和繁殖力。受感染的雌性蚊子血餐量较小，取食倾向降低。结果发现，接种中等高剂量真菌分生孢子的蚊子，其食欲随着真菌生长的增加而降低。在感染真菌的雌性蚊子中，取食第二次血餐的蚊子比例降低了51%。到第4次血餐时，这一比例进一步降至35.3%。在8次取食机会中，未感染雌性蚊子平均取食血餐的次数为4.39次，而感染真菌的雌性蚊子分别为3.40次（低剂量）和2.07次（高剂量）。此外，受感染的雌性蚊子每个生殖营养周期产卵较少，终生繁殖力较低。流行病学模型表明，吸血和繁殖力都是影响蚊子传播疟疾可能性的最重要因素之一，这表明这种真菌可能具有作为媒介传播疾病控制生物防治剂的潜力。
