Yeast-encapsulated essential oils: a new perspective as an environmentally friendly larvicide.
Michael J Workman, Bruno Gomes, Ju-Lin Weng, Linnea K Ista, Camila P Jesus, Mariana R David, Marcelo Ramalho-Ortigao, Fernando A Genta, Scott K Matthews, Ravi Durvasula, Ivy Hurwitz
Author Information
Michael J Workman: Center for Global Health, University of New Mexico Health Sciences Center, Albuquerque, NM, USA. ORCID
Bruno Gomes: Laboratório de Bioquímica e Fisiologia de Insetos, Instituto Oswaldo Cruz (IOC-Fiocruz), Rio de Janeiro, Brazil. ORCID
Ju-Lin Weng: Department of Preventive Medicine and Biostatistics, Uniformed Services University, Bethesda, MD, USA. ORCID
Linnea K Ista: Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM, USA. ORCID
Camila P Jesus: Laboratório de Bioquímica e Fisiologia de Insetos, Instituto Oswaldo Cruz (IOC-Fiocruz), Rio de Janeiro, Brazil.
Mariana R David: Laboratório de Mosquitos Transmissores de Hematozoários, Instituto Oswaldo Cruz (IOC-Fiocruz), Rio de Janeiro, Brazil.
Marcelo Ramalho-Ortigao: Department of Preventive Medicine and Biostatistics, Uniformed Services University, Bethesda, MD, USA. ORCID
Fernando A Genta: Laboratório de Bioquímica e Fisiologia de Insetos, Instituto Oswaldo Cruz (IOC-Fiocruz), Rio de Janeiro, Brazil.
Scott K Matthews: Department of General Preventive Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, NY, USA.
Ravi Durvasula: Loyola University Stritch School of Medicine, Maywood, IL, USA.
Ivy Hurwitz: Center for Global Health, University of New Mexico Health Sciences Center, Albuquerque, NM, USA. ihurwitz@salud.unm.edu.
BACKGROUND: Effective mosquito control approaches incorporate both adult and larval stages. For the latter, physical, biological, and chemical control have been used with varying results. Successful control of larvae has been demonstrated using larvicides including insect growth regulators, e.g. the organophosphate temephos, as well as various entomopathogenic microbial species. However, a variety of health and environmental issues are associated with some of these. Laboratory trials of essential oils (EO) have established the larvicidal activity of these substances, but there are currently no commercially available EO-based larvicides. Here we report on the development of a new approach to mosquito larval control using a novel, yeast-based delivery system for EO. METHODS: Food-grade orange oil (OO) was encapsulated into yeast cells following an established protocol. To prevent environmental contamination, a proprietary washing strategy was developed to remove excess EO that is adsorbed to the cell exterior during the encapsulation process. The OO-loaded yeast particles were then characterized for OO loading, and tested for efficacy against Aedes aegypti larvae. RESULTS: The composition of encapsulated OO extracted from the yeast microparticles was demonstrated not to differ from that of un-encapsulated EO when analyzed by high performance liquid chromatography. After lyophilization, the oil in the larvicide comprised 26-30 percentage weight (wt%), and is consistent with the 60-65% reduction in weight observed after the drying process. Quantitative bioassays carried with Liverpool and Rockefeller Ae. aegypti strains in three different laboratories presented LD of 5.1 (95% CI: 4.6-5.6) to 27.6 (95% CI: 26.4-28.8) mg/l, for L1 and L3/L4 mosquito larvae, respectively. LD ranged between 18.9 (95% CI: 16.4-21.7) mg/l (L1 larvae) to 76.7 (95% CI: 69.7-84.3) mg/l (L3/L4 larvae). CONCLUSIONS: The larvicide based on OO encapsulated in yeast was shown to be highly active (LD < 50 mg/l) against all larval stages of Ae. aegypti. These results demonstrate its potential for incorporation in an integrated approach to larval source management of Ae. aegypti. This novel approach can enable development of affordable control strategies that may have significant impact on global health.
