Ngumbi Philip M, Irungu Lucy W, Ndegwa Paul N, Maniania Nguya K
Kenya Medical Research Institute, University of Nairobi, Nairobi, Kenya.
J Vector Borne Dis. 2011 Mar;48(1):37-40.
BACKGROUND & OBJECTIVES: Biological control of sandflies using entomopathogenic fungi is a possible alternative to the expensive synthetic chemical control. It is potentially sustainable, less hazardous, and relatively inexpensive and merits further investigations. The objective of this study was to identify the most pathogenic fungal isolate(s) to sandflies in the laboratory.
Isolates of entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were screened for their pathogenicity against Phlebotomus duboscqi. Adult flies were contaminated using the technique described by Migiro et al (2010). Briefly, flies were exposed to 0.1 g of dry conidia evenly spread on a cotton velvet cloth covering the inner side of a cylindrical plastic tube (95 mm long × 48 mm diam). In all 25 sandflies were transferred into the cylindrical tube and allowed to walk on the velvet for one minute, after which they were transferred from the velvet into the cages in Perplex. Insects in the control treatments were exposed to fungusfree velvet cloth before being transferred into similar cages. The treatments were maintained at 25 ± 2°C, 60-70% RH and 12L: 12D photoperiod. The experiment was replicated 5 times. The most pathogenic isolates were selected for further studies.
A total of 19 isolates were screened against adult sandflies in the laboratory. Mortality in the controls was approximately 16.8 ± 1.7 %. All the isolates were found to be pathogenic to P. duboscqi. Mortality ranged between 76.8 and 100% on all the fungal isolates tested. The lethal time taken to 50% (LT50) and 90% (LT90) mortality ranged from 3.0-7.8 days and from 5.3-16.2 days, respectively. The virulent isolates, causing mortalities of 97.5-100%, were selected for further studies.
INTERPRETATION & CONCLUSION: The high susceptibility of sandflies to entomopathogenic fungi suggests that fungi are potential alternatives to chemical control methods. We conclude that application of entomopathogenic fungi could result in acute mortalities of sandflies and reduction of parasite transmission and subsequently, reduction of leishmaniasis risk. This method of biological control has great potential as a new strategy for leishmaniasis control.
利用昆虫病原真菌对白蛉进行生物防治是一种替代昂贵合成化学防治方法的可能选择。它具有潜在的可持续性、危害较小且相对成本较低，值得进一步研究。本研究的目的是在实验室中确定对白蛉致病性最强的真菌分离株。
对昆虫病原真菌绿僵菌和球孢白僵菌的分离株进行了针对杜氏白蛉的致病性筛选。成年白蛉采用Migiro等人（2010年）描述的技术进行感染。简要来说，将白蛉暴露于均匀铺在覆盖圆柱形塑料管（95毫米长×48毫米直径）内侧的棉绒布上的0.1克干燥分生孢子中。总共25只白蛉被转移到圆柱形管中，让它们在绒布上行走一分钟，之后从绒布转移到Perplex中的笼子里。对照处理中的昆虫在转移到类似笼子之前先暴露于无菌绒布。处理条件维持在25±2°C、60 - 70%相对湿度和12小时光照：12小时黑暗的光周期。实验重复5次。选择致病性最强的分离株进行进一步研究。
在实验室中总共对19个分离株针对成年白蛉进行了筛选。对照中的死亡率约为16.8±1.7%。所有分离株均被发现对杜氏白蛉具有致病性。在所有测试的真菌分离株上，死亡率在76.8%至100%之间。导致50%（LT50）和90%（LT90）死亡率的致死时间分别为3.0 - 7.8天和5.3 - 16.2天。选择导致死亡率为97.5 - 100%的强毒株进行进一步研究。
白蛉对昆虫病原真菌的高易感性表明真菌是化学防治方法的潜在替代物。我们得出结论，应用昆虫病原真菌可导致白蛉急性死亡并减少寄生虫传播，进而降低利什曼病风险。这种生物防治方法作为利什曼病控制的新策略具有巨大潜力。
