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A novel method for standardized application of fungal spore coatings for mosquito exposure bioassays.

Farenhorst M, Knols BG - Malar. J. (2010)

Bottom Line: Viscous Ondina oil formulations were not suitable and significantly reduced spore infectivity.Manually and mechanically applied spore coatings showed similar and reproducible effects on mosquito survival.Use of this standardized application method will help achieve reliable results that are exchangeable between different laboratories.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Entomology, Wageningen University and Research Centre, PO Box 8031, 6700 EH, Wageningen, The Netherlands. marit.farenhorst@wur.nl

ABSTRACT

Background: Interest in the use of fungal entomopathogens against malaria vectors is growing. Fungal spores infect insects via the cuticle and can be applied directly on the insect to evaluate infectivity. For flying insects such as mosquitoes, however, application of fungal suspensions on resting surfaces is more realistic and representative of field settings. For this type of exposure, it is essential to apply specific amounts of fungal spores homogeneously over a surface for testing the effects of fungal dose and exposure time. Contemporary methods such as spraying or brushing spore suspensions onto substrates do not produce the uniformity and consistency that standardized laboratory assays require. Two novel fungus application methods using equipment developed in the paint industry are presented and compared.

Methods: Wired, stainless steel K-bars were tested and optimized for coating fungal spore suspensions onto paper substrates. Different solvents and substrates were evaluated. Two types of coating techniques were compared, i.e. manual and automated coating. A standardized bioassay set-up was designed for testing coated spores against malaria mosquitoes.

Results: K-bar coating provided consistent applications of spore layers onto paper substrates. Viscous Ondina oil formulations were not suitable and significantly reduced spore infectivity. Evaporative Shellsol T solvent dried quickly and resulted in high spore infectivity to mosquitoes. Smooth proofing papers were the most effective substrate and showed higher infectivity than cardboard substrates. Manually and mechanically applied spore coatings showed similar and reproducible effects on mosquito survival. The standardized mosquito exposure bioassay was effective and consistent in measuring effects of fungal dose and exposure time.

Conclusions: K-bar coating is a simple and consistent method for applying fungal spore suspensions onto paper substrates and can produce coating layers with accurate effective spore concentrations. The mosquito bioassay was suitable for evaluating fungal infectivity and virulence, allowing optimizations of spore dose and exposure time. Use of this standardized application method will help achieve reliable results that are exchangeable between different laboratories.

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Effect of coater type. Cumulative daily proportional survival of An. gambiae s.s exposed for 3 hrs to controls (black) or 1 × 1011 viable B. bassiana spores/m2 coated manually with the K-Hand Coater (red) or mechanically with the K-Control Coater (blue). Data represent average ± SE survival of three replicates of 40 females.
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Figure 4: Effect of coater type. Cumulative daily proportional survival of An. gambiae s.s exposed for 3 hrs to controls (black) or 1 × 1011 viable B. bassiana spores/m2 coated manually with the K-Hand Coater (red) or mechanically with the K-Control Coater (blue). Data represent average ± SE survival of three replicates of 40 females.

Mentions: The efficacy of manually applied spore coatings with the K-Hand Coater was compared with automated applications using the K-Control Coater. For both manually and mechanically applied B. bassiana coatings, significant reductions in mosquito survival compared to controls were obtained (HR = 15.31, P < 0.001 and HR = 14.84, P < 0.001 respectively) (Figure 4). Results were equally consistent and reproducible for both methods and the impact on mosquito survival was not significantly different (HR = 0.97, P = 0.9).


A novel method for standardized application of fungal spore coatings for mosquito exposure bioassays.

Farenhorst M, Knols BG - Malar. J. (2010)

Effect of coater type. Cumulative daily proportional survival of An. gambiae s.s exposed for 3 hrs to controls (black) or 1 × 1011 viable B. bassiana spores/m2 coated manually with the K-Hand Coater (red) or mechanically with the K-Control Coater (blue). Data represent average ± SE survival of three replicates of 40 females.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2820041&req=5

Figure 4: Effect of coater type. Cumulative daily proportional survival of An. gambiae s.s exposed for 3 hrs to controls (black) or 1 × 1011 viable B. bassiana spores/m2 coated manually with the K-Hand Coater (red) or mechanically with the K-Control Coater (blue). Data represent average ± SE survival of three replicates of 40 females.
Mentions: The efficacy of manually applied spore coatings with the K-Hand Coater was compared with automated applications using the K-Control Coater. For both manually and mechanically applied B. bassiana coatings, significant reductions in mosquito survival compared to controls were obtained (HR = 15.31, P < 0.001 and HR = 14.84, P < 0.001 respectively) (Figure 4). Results were equally consistent and reproducible for both methods and the impact on mosquito survival was not significantly different (HR = 0.97, P = 0.9).

Bottom Line: Viscous Ondina oil formulations were not suitable and significantly reduced spore infectivity.Manually and mechanically applied spore coatings showed similar and reproducible effects on mosquito survival.Use of this standardized application method will help achieve reliable results that are exchangeable between different laboratories.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Entomology, Wageningen University and Research Centre, PO Box 8031, 6700 EH, Wageningen, The Netherlands. marit.farenhorst@wur.nl

ABSTRACT

Background: Interest in the use of fungal entomopathogens against malaria vectors is growing. Fungal spores infect insects via the cuticle and can be applied directly on the insect to evaluate infectivity. For flying insects such as mosquitoes, however, application of fungal suspensions on resting surfaces is more realistic and representative of field settings. For this type of exposure, it is essential to apply specific amounts of fungal spores homogeneously over a surface for testing the effects of fungal dose and exposure time. Contemporary methods such as spraying or brushing spore suspensions onto substrates do not produce the uniformity and consistency that standardized laboratory assays require. Two novel fungus application methods using equipment developed in the paint industry are presented and compared.

Methods: Wired, stainless steel K-bars were tested and optimized for coating fungal spore suspensions onto paper substrates. Different solvents and substrates were evaluated. Two types of coating techniques were compared, i.e. manual and automated coating. A standardized bioassay set-up was designed for testing coated spores against malaria mosquitoes.

Results: K-bar coating provided consistent applications of spore layers onto paper substrates. Viscous Ondina oil formulations were not suitable and significantly reduced spore infectivity. Evaporative Shellsol T solvent dried quickly and resulted in high spore infectivity to mosquitoes. Smooth proofing papers were the most effective substrate and showed higher infectivity than cardboard substrates. Manually and mechanically applied spore coatings showed similar and reproducible effects on mosquito survival. The standardized mosquito exposure bioassay was effective and consistent in measuring effects of fungal dose and exposure time.

Conclusions: K-bar coating is a simple and consistent method for applying fungal spore suspensions onto paper substrates and can produce coating layers with accurate effective spore concentrations. The mosquito bioassay was suitable for evaluating fungal infectivity and virulence, allowing optimizations of spore dose and exposure time. Use of this standardized application method will help achieve reliable results that are exchangeable between different laboratories.

Show MeSH
Related in: MedlinePlus