Laboratory of Entomology, Wageningen University and Research Centre, PO Box 8031, 6700 EH Wageningen, The Netherlands.
Malar J. 2010 Jun 16;9:168. doi: 10.1186/1475-2875-9-168.
Entomopathogenic fungi are being investigated as a new mosquito control tool because insecticide resistance is preventing successful mosquito control in many countries, and new methods are required that can target insecticide-resistant malaria vectors. Although laboratory studies have previously examined the effects of entomopathogenic fungi against adult mosquitoes, most application methods used cannot be readily deployed in the field. Because the fungi are biological organisms it is important to test potential field application methods that will not adversely affect them. The two objectives of this study were to investigate any differences in fungal susceptibility between an insecticide-resistant and insecticide-susceptible strain of Anopheles gambiae sensu stricto, and to test a potential field application method with respect to the viability and virulence of two fungal species
Pieces of white polyester netting were dipped in Metarhizium anisopliae ICIPE-30 or Beauveria bassiana IMI391510 mineral oil suspensions. These were kept at 27 +/- 1 degrees C, 80 +/- 10% RH and the viability of the fungal conidia was recorded at different time points. Tube bioassays were used to infect insecticide-resistant (VKPER) and insecticide-susceptible (SKK) strains of An. gambiae s.s., and survival analysis was used to determine effects of mosquito strain, fungus species or time since fungal treatment of the net.
The resistant VKPER strain was significantly more susceptible to fungal infection than the insecticide-susceptible SKK strain. Furthermore, B. bassiana was significantly more virulent than M. anisopliae for both mosquito strains, although this may be linked to the different viabilities of these fungal species. The viability of both fungal species decreased significantly one day after application onto polyester netting when compared to the viability of conidia remaining in suspension.
The insecticide-resistant mosquito strain was susceptible to both species of fungus indicating that entomopathogenic fungi can be used in resistance management and integrated vector management programmes to target insecticide-resistant mosquitoes. Although fungal viability significantly decreased when applied to the netting, the effectiveness of the fungal treatment at killing mosquitoes did not significantly deteriorate. Field trials over a longer trial period need to be carried out to verify whether polyester netting is a good candidate for operational use, and to see if wild insecticide-resistant mosquitoes are as susceptible to fungal infection as the VKPER strain.
由于杀虫剂抗性正使许多国家的蚊虫控制工作无法取得成功，因此需要新的控制方法，特别是针对抗杀虫剂的疟疾传播媒介。虽然实验室研究先前已经研究了病原真菌对成蚊的影响，但大多数使用的应用方法在现场无法轻易部署。由于真菌是生物有机体，因此测试不会对其产生不利影响的潜在现场应用方法非常重要。本研究的两个目标是研究杀虫剂抗性和杀虫剂敏感的冈比亚按蚊（Anopheles gambiae sensu stricto）菌株之间对病原真菌的敏感性差异，并根据两种真菌的生存力和毒力测试一种潜在的野外应用方法。
将白色聚酯网片浸入绿僵菌（Metarhizium anisopliae）ICIPE-30 或球孢白僵菌（Beauveria bassiana）IMI391510 矿物油悬浮液中。将这些网片保存在 27 ± 1°C，80 ± 10%RH 的环境中，并在不同时间点记录真菌孢子的生存力。管生物测定用于感染抗杀虫剂（VKPER）和杀虫剂敏感（SKK）的冈比亚按蚊（An. gambiae s.s.）品系，并使用生存分析来确定蚊虫品系、真菌种类或网片上真菌处理后的时间对网片的影响。
抗性 VKPER 品系对真菌感染的敏感性明显高于杀虫剂敏感的 SKK 品系。此外，尽管这可能与这两种真菌的不同生存力有关，但与绿僵菌相比，球孢白僵菌对两种蚊株的毒力明显更高。与悬浮液中剩余的分生孢子的生存力相比，将这两种真菌应用于聚酯网片后一天，它们的生存力均显著下降。
抗杀虫剂的蚊子品系对这两种真菌均敏感，这表明病原真菌可用于抗药性管理和综合病媒管理计划，以针对抗杀虫剂的蚊子。尽管将真菌应用于网片时，真菌的生存力显著下降，但真菌处理杀死蚊子的效果并没有明显恶化。需要进行更长试验期的野外试验，以验证聚酯网片是否适合实际使用，以及是否野外的抗杀虫剂蚊子与 VKPER 品系一样容易受到真菌感染。
