Larvicidal Activities of Indigenous Bacillus thuringiensis Isolates and Nematode Symbiotic Bacterial Toxins against the Mosquito Vector, Culex pipiens (Diptera: Culicidae)

Ashraf M Ahmed; Hamdy I Hussein; Talat A El-Kersh; Yazeed A Al-Sheikh; Tahany H Ayaad; Hanan A El-Sadawy; Fahd A Al-Mekhlafi; Mohamed S Ibrahim; Jameel Al-Tamimi; Fahd A Nasr

Larvicidal Activities of Indigenous Bacillus thuringiensis Isolates and Nematode Symbiotic Bacterial Toxins against the Mosquito Vector, Culex pipiens (Diptera: Culicidae)

J Arthropod Borne Dis. 2017 May 27;11(2):260-277. eCollection 2017 Jun.

Authors

Ashraf M Ahmed^{1

2}, Hamdy I Hussein³, Talat A El-Kersh⁴, Yazeed A Al-Sheikh⁴, Tahany H Ayaad^{1

5}, Hanan A El-Sadawy⁶, Fahd A Al-Mekhlafi^{7

8}, Mohamed S Ibrahim⁴, Jameel Al-Tamimi¹, Fahd A Nasr⁷

Affiliations

¹ Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia.
² Department of Zoology, College of Science, Minia University, El-Minia, Egypt.
³ Department of Plant Protection, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia.
⁴ Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia.
⁵ Department of Entomology, College of Science, Cairo University, Giza, Egypt.
⁶ Parasitology and Animal Diseases Department, Veterinary Division, National Research Centre, Dokki, Giza, Egypt.
⁷ Bioproducts Research Chair, Department of Zoology, College of Science, King Saud University, Saudi Arabia.
⁸ Department of Agricultural Production, College of Agriculture and Veterinary Medicine, Thamar University, Dhamar, Yemen.

PMID: 29062851
PMCID: PMC5641615

Abstract

Background: The incidence of mosquito-borne diseases and the resistance of mosquitoes to conventional pesticides have recently caused a panic to the authorities in the endemic countries. This study was conducted to identify native larvicidal biopesticides against Culex pipiens for utilization in the battle against mosquito-borne diseases.

Methods: Larvicidal activities of new indigenous Bacillus thuringiensis isolates and crude toxin complexes (TCs) of two nematode bacterial-symbionts, Photorhabdus luminescens akhurstii (HRM1) and Ph. luminescens akhurstii (HS1) that tested against Cx. pipiens. B. thuringiensis isolates were recovered from different environmental samples in Saudi Arabia, and the entomopathogenic nematodes, Heterorhabditis indica (HRM1) and He. sp (HS1) were isolated from Egypt. Larvicidal activities (LC₅₀ and LC₉₅) of the potentially active B. thuringiensis strains or TCs were then evaluated at 24 and 48h post-treatment.

Results: Three B. thuringiensis isolates were almost as active as the reference B. thuringiensis israelensis (Bti-H14), and seven isolates were 1.6-5.4 times more toxic than Bti-H14. On the other hand, the TCs of the bacterial symbionts, HRM1 and HS1, showed promising larvicidal activities. HS1 showed LC₅₀ of 2.54 folds that of HRM1 at 24h post-treatment. Moreover, histopathological examinations of the HS1-treated larvae showed deformations in midgut epithelial cells at 24h post-treatment.

Conclusion: Synergistic activity and molecular characterization of these potentially active biocontrol agents are currently being investigated. These results may lead to the identification of eco-friend mosquito larvicidal product(s) that could contribute to the battle against mosquito-borne diseases.

Keywords: Bacillus thuringiensis; Biopesticide; Culex pipiens; Heterorhabditis nematodes; Photorhabdus bacteria.