สถาบันวิจัยวิทยาศาสตร์สาธารณสุข

NATIONAL INSTITUTE OF HEALTH OF THAILAND

Laboratory and field evaluation of the potency of Bactimos ® Briquets against Aedes aegypti larvae (Diptera: Culicidae)

Authors : Ratana Sithiprasasna*, Thanyaluk Fansiri*, Usavadee Thavara**, Apiwat Tawatsin**

 

Affiliations:        * Department of Entomology, US Army Medical Component, Armed Forces Research Institute of Medical Sciences, Bangkok 10400, Thailand
** National Institute of Health, Department of Medical Sciences, Ministry of Public Health, 88/7 Tiwanon Road, Nonthaburi 11000, Thailand
 
Source:             Presented in the 4th International Conference on Biopesticides, Chiang Mai, Thailand, 13 – 18 February 2005
 
Language:         English
 
Abstract:
 
Bacillus thuringiensis var israelensis is a gram-positive spore-forming bacterium produces a proteinaceous crystal (d-endotoxin) during sporulation. The crystal is cleaved into the toxic polypeptides by specific proteases in the mid-gut of ingesting mosquito larva. The toxic polypeptides bind to the gut epithelium and cause paralysis and death within a short time. This bio-potency study of BactimosÒ Briquets (active ingredient: 7,000 ITU Aedes aegypti International Toxic Units [ITU]/mg Bacillus thuringiensis var israelensis) against late 3rd instar larvae of the arbovirus vector Aedes aegypti has been carried out according to WHO standard protocols. The six concentrations of Bti product were used in each replicated 4 times with 25 mosquito larvae. Probit analysis was then used to determine LC50 which equated to a dosage of 0.54072 mg/L. The potency value of 515.42 ITU/mg (briquets) based on the ratio between the LC50 of International Reference Standard IPS-82 and LC50 of the Bti product was calculated. In field-simulated experiment, the product was evaluated against Ae. aegypti larvae in 4 identical glazed clay water-storage jars (200 L) at the dosage of ¼ dunk/jar and the inhibition of emergence (IE) was employed to assess efficacy. It was found that the BactimosÒ Briquets provided excellent control (IE > 90%) for at least 8 weeks. The potential role of this product will be discussed.