A Novel Method for Standardized Application of Fungal Spore Coatings for Mosquito Exposure Bioassays

Overview

Journal Malar J

Publisher Biomed Central

Specialty Tropical Medicine

Date 2010 Jan 22

PMID 20089180

Citations 19

Authors

Marit Farenhorst

Bart G J Knols

Affiliations

Soon will be listed here.

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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References

Akbar W, Lord J, Nechols J, Loughin T . Efficacy of Bauveria bassiana for red flour beetle when applied with plant essential oils or in mineral oil and organosilicone carriers. J Econ Entomol. 2005; 98(3):683-8. DOI: 10.1603/0022-0493-98.3.683. View

Bell A, Blanford S, Jenkins N, Thomas M, Read A . Real-time quantitative PCR for analysis of candidate fungal biopesticides against malaria: technique validation and first applications. J Invertebr Pathol. 2009; 100(3):160-8. PMC: 2666797. DOI: 10.1016/j.jip.2009.01.006. View

Nauen R . Insecticide resistance in disease vectors of public health importance. Pest Manag Sci. 2007; 63(7):628-33. DOI: 10.1002/ps.1406. View

Ansari M, Vestergaard S, Tirry L, Moens M . Selection of a highly virulent fungal isolate, Metarhizium anisopliae CLO 53, for controlling Hoplia philanthus. J Invertebr Pathol. 2004; 85(2):89-96. DOI: 10.1016/j.jip.2004.01.003. View

Scholte E, Nghabi K, Kihonda J, Takken W, Paaijmans K, Abdulla S . An entomopathogenic fungus for control of adult African malaria mosquitoes. Science. 2005; 308(5728):1641-2. DOI: 10.1126/science.1108639. View

Scholte E, Takken W, Knols B . Infection of adult Aedes aegypti and Ae. albopictus mosquitoes with the entomopathogenic fungus Metarhizium anisopliae. Acta Trop. 2007; 102(3):151-8. DOI: 10.1016/j.actatropica.2007.04.011. View

Lomer C, Bateman R, Johnson D, Langewald J, Thomas M . Biological control of locusts and grasshoppers. Annu Rev Entomol. 2000; 46:667-702. DOI: 10.1146/annurev.ento.46.1.667. View

Scholte E, Njiru B, Smallegange R, Takken W, Knols B . Infection of malaria (Anopheles gambiae s.s.) and filariasis (Culex quinquefasciatus) vectors with the entomopathogenic fungus Metarhizium anisopliae. Malar J. 2003; 2:29. PMC: 222926. DOI: 10.1186/1475-2875-2-29. View

DAOUST R, Ward M, Roberts D . Effect of formulation on the viability of Metarhizium anisopliae conidia. J Invertebr Pathol. 1983; 41(2):151-60. DOI: 10.1016/0022-2011(83)90214-8. View

10.

Scholte E, Knols B, Takken W . Infection of the malaria mosquito Anopheles gambiae with the entomopathogenic fungus Metarhizium anisopliae reduces blood feeding and fecundity. J Invertebr Pathol. 2005; 91(1):43-9. DOI: 10.1016/j.jip.2005.10.006. View

11.

Darbro J, Thomas M . Spore persistence and likelihood of aeroallergenicity of entomopathogenic fungi used for mosquito control. Am J Trop Med Hyg. 2009; 80(6):992-7. View

12.

Hemingway J, Field L, Vontas J . An overview of insecticide resistance. Science. 2002; 298(5591):96-7. DOI: 10.1126/science.1078052. View

13.

Farenhorst M, Farina D, Scholte E, Takken W, Hunt R, Coetzee M . African water storage pots for the delivery of the entomopathogenic fungus Metarhizium anisopliae to the malaria vectors Anopheles gambiae s.s. and Anopheles funestus. Am J Trop Med Hyg. 2008; 78(6):910-6. View

14.

Blanford S, Chan B, Jenkins N, Sim D, Turner R, Read A . Fungal pathogen reduces potential for malaria transmission. Science. 2005; 308(5728):1638-41. DOI: 10.1126/science.1108423. View

15.

Read A, Lynch P, Thomas M . How to make evolution-proof insecticides for malaria control. PLoS Biol. 2009; 7(4):e1000058. PMC: 3279047. DOI: 10.1371/journal.pbio.1000058. View

16.

Sosa-Gomez D, Boucias D, Nation J . Attachment of Metarhizium anisopliae to the southern green stink bug Nezara viridula cuticle and fungistatic effect of cuticular lipids and aldehydes. J Invertebr Pathol. 1997; 69(1):31-9. DOI: 10.1006/jipa.1996.4619. View

17.

Thomas M, Read A . Can fungal biopesticides control malaria?. Nat Rev Microbiol. 2007; 5(5):377-83. DOI: 10.1038/nrmicro1638. View

18.

Blanford S, Read A, Thomas M . Thermal behaviour of Anopheles stephensi in response to infection with malaria and fungal entomopathogens. Malar J. 2009; 8:72. PMC: 2683858. DOI: 10.1186/1475-2875-8-72. View

19.

Pedrini N, Crespo R, Juarez M . Biochemistry of insect epicuticle degradation by entomopathogenic fungi. Comp Biochem Physiol C Toxicol Pharmacol. 2006; 146(1-2):124-137. DOI: 10.1016/j.cbpc.2006.08.003. View

20.

Boucias D, Pendland J, Latge J . Nonspecific factors involved in attachment of entomopathogenic deuteromycetes to host insect cuticle. Appl Environ Microbiol. 1988; 54(7):1795-805. PMC: 202748. DOI: 10.1128/aem.54.7.1795-1805.1988. View