A Large Scale Biorational Approach Using Bacillus thuringiensis israeliensis (Strain AM65-52) for Managing Aedes aegypti Populations to Prevent Dengue, Chikungunya and Zika Transmission

PLoS One. 2017 Feb 15;12(2):e0170079. doi: 10.1371/journal.pone.0170079. eCollection 2017.

Abstract

Background: Aedes aegypti is a container-inhabiting mosquito and a vector of dengue, chikungunya, and Zika viruses. In 2009 several cases of autochthonous dengue transmission were reported in Key West, Florida, USA prompting a comprehensive response to control A. aegypti. In Key West, larvae of this mosquito develop in containers around human habitations which can be numerous and labor intensive to find and treat. Aerial applications of larvicide covering large areas in a short time can be an efficient and economical method to control A. aegypti. Bacillus thuringiensis israelensis (Bti) is a bacterial larvicide which is highly target specific and appropriate for wide area spraying over urban areas, but to date, there are no studies that evaluate aerial spraying of Bti to control container mosquitoes like A. aegypti.

Methodology: This paper examines the effectiveness of aerial larvicide applications using VectoBac® WG, a commercially available Bti formulation, for A. aegypti control in an urban setting in the USA. Droplet characteristics and spray drop deposition were evaluated in Key West, Florida, USA. The mortality of A. aegypti in containers placed under canopy in an urban environment was also evaluated. Efficacy of multiple larvicide applications on adult female A. aegypti population reduction was compared between an untreated control and treatment site.

Conclusions: Droplet characteristics showed that small droplets can penetrate through dense canopy to reach small containers. VectoBac WG droplets reached small containers under heavy canopy in sufficient amounts to cause > 55% mortality on all application days and >90% mortality on 3 of 5 application days while controls had <5% mortality. Aerial applications of VectoBac WG caused significant decrease in adult female populations throughout the summer and during the 38th week (last application) the difference in adult female numbers between untreated and treated sites was >50%. Aerial larvicide applications using VectoBac WG can cover wide areas in a short period of time and can be effective in controlling A. aegypti and reducing A. aegypti-borne transmission in urban areas similar to Key West, Florida, USA.

MeSH terms

  • Aedes / growth & development*
  • Aedes / virology
  • Animals
  • Bacillus thuringiensis*
  • Chikungunya Fever / prevention & control*
  • Chikungunya Fever / transmission
  • Dengue / prevention & control*
  • Dengue / transmission
  • Florida
  • Larva / growth & development
  • Larva / virology
  • Pest Control, Biological / methods*
  • RNA Viruses*
  • Zika Virus Infection / prevention & control*
  • Zika Virus Infection / transmission

Grants and funding

The authors received no specific funding for this work. Author Robert Mickle is the owner of the commercial company “REMSpC Spray Consulting” and was paid a consulting fee by the government agency, Florida Keys Mosquito Control District, for his evaluation of the droplet analysis evaluated for this experiment. The Florida Keys Mosquito Control District is an independent taxing district in Monroe County, Florida. The FKMCD budget is funded by a percentage of Monroe County property taxes. The funders (tax-payers of Monroe Co.) did not play a role in the study design, collection and analysis, decision to publish, or preparation of the manuscript and only provided financial support in the form of authors’ salaries and research materials.