RESUMO

Dengue virus infections are a serious public health problem worldwide. Aedes aegypti is the primary vector of dengue in Cuba. As there is no vaccine or specific treatment, the control efforts are directed to the reduction of mosquito populations. The indiscriminate use of insecticides can lead to adverse effects on ecosystems, including human health. The sterile insect technique is a species-specific and environment-friendly method of insect population control based on the release of large numbers of sterile insects, ideally males only. The success of this technique for the sustainable management of agricultural pests has encouraged its evaluation for the population suppression of mosquito vector species. Here, we describe an open field trial to evaluate the effect of the release of irradiated male Ae. aegypti on a wild population. The pilot trial was carried out in a suburb of Havana and compared the mosquito population density before and after the intervention, in both untreated control and release areas. The wild population was monitored by an ovitrap network, recording frequency and density of eggs as well as their hatch rate. A significant amount of sterility was induced in the field population of the release area, as compared with the untreated control area. The ovitrap index and the mean number of eggs/trap declined dramatically after 12 and 5 weeks of releases, respectively. For the last 3 weeks, no eggs were collected in the treatment area, clearly indicating a significant suppression of the wild target population. We conclude that the sterile males released competed successfully and induced enough sterility to suppress the local Ae. aegypti population.

RESUMO

BACKGROUND: The efficacy of biolarvicides may be influenced by species of mosquito, larval age and density, temperature, water quality, bacterial formulation, and others. The aim of this study was to evaluate the influence of temperature and chlorine on larvicidal activity of Bacillus thuringiensis Cuban isolates against Aedes aegypti. METHODS: The influence of temperature (25, 30, 35 °C) and chlorine (2.25mg/L) on the larvicidal activity of eleven B. thuringiensis Cuban isolates (collected between 2007 and 2009) were tested under laboratory conditions following WHO protocols. Bioassay data were analyzed by Probit program. The effect of chlorine and temperature (25, 30, 35 and 40 °C) on the Cry and Cyt proteins of these isolates was determined by SDS-PAGE polyacrylamide gel electrophoresis. RESULTS: The pathogenicity of the isolates U81, X48 was affected at 35 °C. However, A21, A51, L910, and R89 isolates increase their entomopathogen activity at 35 °C. No differences were observed in toxicity of M29, R84, R85 and R87 isolates at different temperatures. The Cry 4, Cry 10 and Cry 11 proteins were reduced in A21, X48, R85 isolates at 35 and 40 °C. The Cyt proteins were reduced at 35 and 40 °C in A21, X48, R85, and A51 isolates. In L910 and R84 isolates, the Cyt toxin was degraded only at 40 °C. In chlorinated water, the lethal concentrations 50 and 90 in A21, A51, M29, R84, U81, and X48 isolates were increase. CONCLUSION: A21, A51, L910, R85, and X48 isolates have a strong larvicidal activity for the treatment of Ae. aegypti breeding's sites exposed to high temperature and chlorine.

RESUMO

The sterile insect technique (SIT) is a promising pest control method in terms of efficacy and environmental compatibility. In this study, we determined the efficacy of thiotepa-sterilised males in reducing the target Aedes aegypti populations. Treated male pupae were released weekly into large laboratory cages at a constant ratio of either 5:1 or 2:1 sterile-to-fertile males. A two-to-one release ratio reduced the hatch rate of eggs laid in the cage by approximately a third and reduced the adult catch rate by approximately a quarter, but a 5:1 release drove the population to elimination after 15 weeks of release. These results indicate that thiotepa exposure is an effective means of sterilising Ae. aegypti and males thus treated are able to reduce the reproductive capacity of a stable population under laboratory conditions. Further testing of the method in semi-field enclosures is required to evaluate the mating competitiveness of sterile males when exposed to natural environmental conditions. If proven effective, SIT using thiotepa-sterilised males may be incorporated into an integrated programme of vector control to combat dengue in Cuba.

Assuntos

RESUMO

The sterile insect technique (SIT) is a promising pest control method in terms of efficacy and environmental compatibility. In this study, we determined the efficacy of thiotepa-sterilised males in reducing the target Aedes aegypti populations. Treated male pupae were released weekly into large laboratory cages at a constant ratio of either 5:1 or 2:1 sterile-to-fertile males. A two-to-one release ratio reduced the hatch rate of eggs laid in the cage by approximately a third and reduced the adult catch rate by approximately a quarter, but a 5:1 release drove the population to elimination after 15 weeks of release. These results indicate that thiotepa exposure is an effective means of sterilising Ae. aegypti and males thus treated are able to reduce the reproductive capacity of a stable population under laboratory conditions. Further testing of the method in semi-field enclosures is required to evaluate the mating competitiveness of sterile males when exposed to natural environmental conditions. If proven effective, SIT using thiotepa-sterilised males may be incorporated into an integrated programme of vector control to combat dengue in Cuba.

Assuntos

RESUMO

The use of insect pathogens is a viable alternative for insect control because of their relative specificity and lower environmental impact. The search for wild strains against dipterans could have an impact on mosquito control programs. We have made an extensive screening of soil in western Cuba to find bacteria with larvicidal activity against mosquitoes. A total of 150 soil samples were collected and isolates were identifying using the API 50 CHB gallery. Phenotypic characteristics were analyzed by hierarchical ascending classification. Quantitative bioassays were conducted under laboratory conditions following the World Health Organization protocol in order to ascertain the toxicity and efficacy of isolates. The protein profiles of the crystal components were determined by SDS-PAGE. Eight hundred and eighty-one bacterial isolates were obtained, and 13 isolates with entomopathogenic activity were isolated from nine samples. Nine isolates displayed higher entomopathogenic activity against both Cx. quinquefasciatus and Ae. aegypti compared with the reference strain 266/2. All toxic isolates showed higher biological potency than the 266/2 strain. These isolates with high entomopathogenic activity displayed a protein pattern similar to the B. thuringiensis var. israelensis IPS-82 and 266/2 strains. These results are a valuable tool for the control of Diptera of medical importance.

Assuntos

RESUMO

Chemical insecticides may be toxic and cause environmental degradation. Consequently, biological control for insects represents an alternative with low ecological impact. In this work, three soil isolates (A21, A51 and C17) from different regions of the Cuban archipelago were identified, characterized and evaluated against Aedes aegypti and Culex quinquefasciatus. The new isolates were compared with reference IPS82 strain and two strains isolated from biolarvicides Bactivec and Bactoculicida, respectively. The differentiation was done by morphological, biochemical, bioassays activity and molecular methods (SDS-PAGE, plasmid profile and random amplified polymorphic analysis). All isolates were identified as Bacillus thuringiensis. The A21, A51 and C17 isolates showed higher larvicide activity than Bactivec's isolated reference strain, against both A. aegypti and C. quinquefasciatus. A21 isolate had a protein profile similar to IPS82 and Bactivec strain. A51 and C17 isolates produced a characteristic proteins pattern. A21 and A51 isolates had plasmid patterns similar to IPS82 standard strain, while C17 isolate had different both plasmid profile and protein bands. All the studied isolates showed a diverse RAPD patterns and were different from the strains previously used in biological control in Cuba.

Assuntos

RESUMO

Chemical insecticides may be toxic and cause environmental degradation. Consequently, biological control for insects represents an alternative with low ecological impact. In this work, three soil isolates (A21, A51 and C17) from different regions of the Cuban archipelago were identified, characterized and evaluated against Aedes aegypti and Culex quinquefasciatus. The new isolates were compared with reference IPS82 strain and two strains isolated from biolarvicides Bactivec and Bactoculicida, respectively. The differentiation was done by morphological, biochemical, bioassays activity and molecular methods (SDS-PAGE, plasmid profile and random amplified polymorphic analysis). All isolates were identified as Bacillus thuringiensis. The A21, A51 and C17 isolates showed higher larvicide activity than Bactivec’s isolated reference strain, against both A. aegypti and C. quinquefasciatus. A21 isolate had a protein profile similar to IPS82 and Bactivec strain. A51 and C17 isolates produced a characteristic proteins pattern. A21 and A51 isolates had plasmid patterns similar to IPS82 standard strain, while C17 isolate had different both plasmid profile and protein bands. All the studied isolates showed a diverse RAPD patterns and were different from the strains previously used in biological control in Cuba. Rev. Biol. Trop. 59 (3): 1007-1016. Epub 2011 September 01.

El uso prolongado de insecticidas ha conducido al desarrollo de resistencia en diferentes especies de mosquitos y al incremento de la degradación del ambiente. El control biológico de insectos ha devenido como una alternativa útil y de bajo impacto ambiental. En nuestro estudio fueron identificados, caracterizados tres aislamientos de suelos procedentes de diferentes regiones del archipiélago cubano y comparados con cepas de referencia: aisladas de los biolarvicidas Bactivec y Bactoculicida, además de IPS82. La diferenciación de los mismos se llevó a cabo mediante métodos morfológicos, bioquímicos y moleculares (SDSPAGE, perfil plasmídico, RAPD). Los aislamientos fueron identificados como Bacillus thuringiensis; A21, A51 y C17 mostraron una mayor actividad contra larvas de Aedes aegypti and Culex quinquefasciatus que la cepa aislada del biolarvicida Bactivec, utilizada como referencia en este estudio. Dos de los aislamientos poseían perfiles proteicos y plasmídicos similares al de la cepa control IPS82, pero el restante difería de ellos. Los tres mostraron patrones de RAPD diferentes lo que nos permitió su diferenciación. Estos patrones de RAPD también diferían del observado para las cepas utilizadas comúnmente en el control biológico en nuestro país.

Assuntos