Indiscriminate feeding of commercial entomopathogenic nematodes caused death of Aedes aegypti larvae: potential for vector control of chikungunya, dengue and yellow fever
2020
Ansari, Minshad A. | Hussain, M Abid
Aedes aegypti, is a major vector of several human diseases such as dengue, yellow fever, chikungunya and Zika virus. Multiple strategies are adopted for its control including eradication of mosquito breeding sites by improving water storage and solid waste disposal as well as treating breeding sites with chemical insecticides. However, continuous use of insecticides has resulted in development of insecticide resistance in Ae. aegypti. This study explores the potential biocontrol of Ae. aegypti by the use of commercial entomopathogenic nematodes, namely Heterorhabditis bacteriophora, H. downesi, H. megidis, Steinernema carpocapsae, S. feltiae and S. kraussei. The pathogenic effect of nematodes (concentrations 10, 250, 500 and 1,000 infective juveniles (IJs)) was assessed against third instar Ae. aegypti in multi-well culture plates for 3 days. The evaluated nematode species were pathogenic to Ae. aegypti, however, their virulence varied significantly. Heterorhabditis bacteriophora and S. carpocapsae were most virulent causing 90-100% mortality at 100 IJs per larva, whereas H. megidis and S. kraussei showed least virulence causing 40-60% mortality. Heterorhabditis downesi and S. feltiae had intermediate virulence. Third instar Ae. aegypti indiscriminately overfeed nematodes triggering melanisation but ingested nematodes overcome the defence system resulting in killing the larvae and reproduced within them. Some of the nematodes were melanised, suggesting a strong humoral defence response by Aedes, nevertheless, with variable degree of melanisation. The melanisation did not stop nematode from multiplying and killing Aedes larvae and thus, they have potential to be developed into a novel strategy for Ae. aegypti control.
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