Abstracts - Nayana C. S. Santos


Nayana C. S. Santos1*, Francisco A. Marques1, Itamar F. Andreazza1, Mário A. N. Silva1, Beatriz H. L. N. S. Maia1, João A. C. Zequi2 and Washington L. E. Magalhães3

1 Federal University of Parana– UFPR, Curitiba, Parana, Brazil;
2 State University of Londrina- UEL, Londrina, Parana, Brazil;
3 Embrapa Florestas, Colombo, Parana, Brazil;
cristina_nayana@hotmail.com; tic@ufpr.br; itamar@ufpr; mnavarro@ufpr.br; noronha@ufpr.br; joaozequi@gmail.com; washington.magalhaes@embrapa.br
*Correspondence: cristina_nayana@hotmail.com

Currently, dengue is the most important arbovirose transmitted by the mosquito Aedes aegypti and represents a world public health problem. In Brazil the control of larvae of this mosquito uses the organophosphate temephos, but after the detection of the resistance of A. aegypti to the temephos and due to the fact of the high toxicity of this substance, this organophosphate is being replaced by other forms of control, among them stands out the use of proteins produced by Bacillus thuringiensis israelensis (Bti)1,2. The objective of this work was to develop a low toxicity larvicide based on Bti proteins, aiming to contribute to the population control of the A. aegypti mosquito. In view of the photolability of the Bti proteins, larvicidal tablets of 50 mg have been developed which slowly and continuously release the proteins being stabilized with excipients, thus prolonging their action in the field. Protein content was measured by the biuret and UV-vis method. The bioassay test was carried out in buckets containing 10 L of drinking water. One tablet and 20 larvae of the A. aegypti mosquito were placed in each bucket, the activity of the tablet was evaluated every 24 h to determine the persistence of the larvicidal activity. The bioassay was performed in the field at a maximum temperature of 21 ºC for 45 days. The results showed that Bti-based proteins tablets caused 100% control of the larval population. Subsequently, protein stability tests were carried out with excipients in the Climatic Chamber with Photoperiod, simulating field conditions, using a 50 mg tablet in 100 mL of potable water, at a maximum temperature of 39ºC and maximum luminosity (3800 Lux-13 h). Tests lasted 45 days, with the protein remaining stable until the end of the analysis, being evaluated by UV-vis daily. An aliquot of the content of the suspensions used to carried out the protein-stability tests had its larvicidal activity evaluated at a concentration ranging from 1.10-1 to 1.10-9 mg protein / 100 mL of dechlorinated water. The results were effective, with 100% larval mortality at all concentrations. Thus, Bti proteins, in the presence of the excipients, represents an efficient alternative to the control of A. aegypti larvae, with significant advantages such as low toxicity and stability in the field.

1. Zaim, M. et al., Trends in parasitology, v. 18, n. 4, p. 161-163, 2002.
2. Chui, V. W. D. et al., Environment international, v. 21, n. 4, p. 433-440, 1995.