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      Influencia de factores bióticos sobre la eficacia de Bacillus thuringiensis var. israelensis contra Aedes aegypti (Diptera: Culicidae) Translated title: Influence of biotic factors on the efficacy of Bacillus thuringiensis var. Israelensis against Aedes aegypti (Diptera: Culicidae)

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          Abstract

          Introducción: Bacillus thuringiensis H-14 ha mostrado alta eficacia sobre las larvas de Aedes aegypti, pero su efectividad puede ser influida por numerosos factores. El conocimiento de estos es de gran importancia porque permite optimizar los parámetros de aplicación en condiciones reales, para garantizar la eficiencia de los tratamientos y reducir el impacto ambiental. Objetivo: evaluar la influencia de los factores bióticos sobre la eficacia de Bacillus thuringiensis H-14 contra las larvas de Aedes aegypti. Métodos: se realizó un estudio experimental mediante bioensayos de laboratorio, siguiendo la metodología de la Organización Mundial de la Salud. Se evaluó la influencia de la disponibilidad de alimento, densidad y estadio larvario sobre la eficacia de Bacillus thuringiensis H-14 para Aedes aegypti. Se utilizó un biolarvicida comercial (Bactivec, Labiofam) y una cepa de referencia de Aedes aegypti (Rockefeller). Resultados: la eficacia de Bacillus thuringiensis H-14 fue menor en la medida en que avanzó la densidad y el estadio de desarrollo larvario, lo que puede estar en relación con la conducta de alimentación y la disponibilidad del principio activo. La presencia abundante de alimento también limita la eficacia por un efecto de competencia. Conclusiones: la eficacia de Bacillus thuringiensis H-14 se afectó por la disponibilidad de alimento, el estadio de desarrollo y la densidad larvaria, por lo que debe tenerse en cuenta esto para las aplicaciones del biolarvicida en el terreno.

          Translated abstract

          Introduction: Bacillus thuringiensis H-14 has shown high efficacy on Aedes aegypti larvae. But a number of factors could affect its effectiveness. Knowing these factors is of vital importance for improving the application parameters in real conditions in order to guarantee the treatment's efficiency and to reduce environmental impact. Objective: to evaluate the influence of some biotic factors on Bacillus thuringiensis H-14 efficacy against Aedes aegypti (Rockefeller). Methods: an experimental study was conducted following the WHO guidelines. The influence of the food availability, the larval density and the larval staging was evaluated on laboratory bioassays. A commercial Bacillus thuringiensis H-14 formulation against a reference Aedes aegypti strain was used. Results: the efficacy of Bacillus thuringiensis H-14 decreased in a linear manner with increasing larval density and development stage. This could be related to food intake and availability of the active principle. Competition in food intake resulted in lower efficacy of Bacillus thuringiensis H-14 applications. Conclusions: the Bacillus thuringiensis H-14 efficacy was affected for the availability of food, the larval development stage and the larval density, so all this should be borne in mind when applying the biolarvicide in situ.

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          Bacillus thuringiensis serovariety israelensis and Bacillus sphaericus for mosquito control.

          L Lacey (2006)
          Since the discovery of Bacillus thuringiensis (Berliner) serovariety israelensis de Barjac (Bti) and efficacious isolates of Bacillus sphaericus Neide, formulations of these bacteria have become the predominant non-chemical means employed for control of mosquito larvae at several locations in the United States and other countries. An overview of developments in the past 20 years is presented in this chapter regarding the toxins of Bti and B. sphaericus, their modes of action, efficacy and factors that affect larvicidal activity, development of resistance, safety, and their roles in integrated mosquito control. The efficacy of Bti formulations has been demonstrated in a variety of habitats against a multitude of species of mosquitoes. B. sphaericus formulations have been utilized predominantly in organically enriched habitats against Culex species, but they are also active in a variety of habitats having low organic enrichment, against numerous species, and across several genera. Stegomyia spp. are not susceptible to practical doses of B. sphaericus formulations. B. sphaericus has been shown to persist longer than Bti in polluted habitats and, under certain circumstances, can recycle in larval cadavers. A disadvantage of B. sphaericus has been the development of resistance in certain populations of Cx. quinquefasciatus Say and Cx. pipiens Linnaeus. Biotic and abiotic factors that influence the larvicidal activity of Bti and B. sphaericus include species of mosquito and their respective feeding strategies, rate of ingestion, age and density of larvae, habitat factors (temperature, solar radiation, depth of water, turbidity, tannin and organic content, presence of vegetation, etc.), formulation factors (type of formulation, toxin content, how effectively the material reaches the target, and settling rate), storage conditions, production factors, means of application and frequency of treatments. Due to their efficacy and relative specificity, both Bti and B. sphaericus can be ideal control agents in integrated programs especially where other biological control agents, environmental management, personal protection and the judicious use of insecticides are combined.
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            BACILLUS THURINGIENSIS SEROVARIETY ISRAELENSIS AND BACILLUS SPHAERICUS FOR MOSQUITO CONTROL

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              Factors influencing the activity of Bacillus thuringiensis var. israelensis treatments.

              Environmental factors influence the effectiveness of microbial control agents in mosquito control programs. Four of these factors (water temperature, larval density, sunlight and the effect of associated filter feeders) were studied with Bacillus thuringiensis var. israelensis under laboratory and semifield conditions in Europe using different instars of Aedes vexans, Ae. aegypti and Culex pipiens. Bioassays conducted at a low temperature (5 degrees C) yielded 10-fold higher LC50 and LC90 values compared with those conducted at a high temperature (25 degrees C). The efficacy of B.t.i. decreased in a linear manner with increasing larval density. Sunlight can reduce the effectiveness of B.t.i. by several times. Competition in food intake by filter feeding Daphnia resulted in lower mortality of mosquito larvae after B.t.i. applications.
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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                mtr
                Revista Cubana de Medicina Tropical
                Rev Cubana Med Trop
                Centro Nacional de Información de Ciencias Médicas (Ciudad de la Habana )
                1561-3054
                September 2012
                : 64
                : 3
                : 235-243
                Affiliations
                [1 ] Grupo Empresarial de Producciones Biofarmaceúticas y Químicas Cuba
                [2 ] Universidade Estadual de Maringá Brazil
                Article
                S0375-07602012000300004
                9c59629b-7ddd-4382-ba2f-ed80835504ed

                http://creativecommons.org/licenses/by/4.0/

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                SciELO Cuba

                Self URI (journal page): http://scielo.sld.cu/scielo.php?script=sci_serial&pid=0375-0760&lng=en
                Categories
                TROPICAL MEDICINE

                Infectious disease & Microbiology
                Bacillus thuringiensis,biolarvicides,biotic factors,bioassays,biolarvicida,factores bióticos,bioensayos

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