Potential breeding containers of Aedes aegypti (Linnaeus, 1762) and Aedes albopictus (Skuse, 1894) at strategic points in a city in the eastern region of Maranhão.

Potential breeding containers for Aedes aegypti and Aedes albopictus mosquitoes are found in different environments, these places are considered by the National Dengue Control Program in Brazil as strategic points (SP), which have favorable conditions for the development of those insects. The aim of this study is to identify potential breeding containers for A. aegypti and A. albopictus at strategic points in the city of Codó, Maranhão. This study was conducted in five districts, one in each administrative area of the city. A survey of the types and quantity of existing strategic points in each neighborhood was carried out, and surveys of these properties were carried out to inspect the potential breeding containers, with the collection of the vectors' number of immatures found at them. 125 properties were inspected of which 76.91% and 81.25% were vacant lots in the dry and rainy seasons, respectively. There was a difference between the median of the different strategic points (H = 21.96; p < 0.0001), For A. aegypti, there was no difference between the medians of number of immatures regarding the strategic points (H = 3.71; p = 0.28). The total number of immature A. albopictus was higher in vacant lots than in workshops (H = 9.41; p = 0.02, p < 0.05). 4,356 and 4,911 potential breeding containers were found in the dry and rainy seasons, respectively. Regarding the potential breeding containers, 7 (0.16%) and 47 (0.96%) were found with immature vectors, in the dry and rainy seasons, respectively. There were more positive containers in the rainy season for which there was a difference between the median of the number of mosquitoes per positive container (H = 15.66; p = 0.01), the number of immatures for the tires group was greater than Vases and Fixed groups (p < 0.05); the same result was observed in the analyses of the species in the separate form. The impressive number of potential breeding containers found in the SP in both seasons highlights the importance of developing control strategies for these vectors, with emphasis on places such as vacant lots, workshops, tire shops and junkyards, which are serving as dispersal urban sites of vectors.

Strain of Bacillus thuringiensis from Restinga, toxic to Aedes (Stegomyia) aegypti (Linnaeus) (Diptera, Culicidae) / Estirpe de Bacillus thuringiensis da restinga, tóxico ao Aedes (Stegomyia) aegypti (Linnaeus) (Diptera, Culicidae)

Abstract Bacillus thuringiensis is the most commonly used entomopathogen in the control of Aedes aegypti, which is a vector for different etiological agents that cause serious infections in humans. Several studies aim to isolate strains of this bacterium from different environments, with the perspective of selecting isolates with larvicidal activity for mosquitoes. Aiming at the insecticidal action of B. thuringiensis, the present study aimed to prospect B. thuringiensis of restinga and mangrove soils from the state of Maranhão, Brazil, with toxic potential for use in the biological control of Ae. aegypti. Bioassays were performed to determine the entomopathogenic activity of the bacilli against Ae. aegypti and lethal concentrations (LC50 and CL90) were estimated after the tests. Polymerase Chain Reaction and SDS-PAGE techniques were performed to verify the gene and protein content of the isolates, respectively. The soil of the mangrove and restinga ecosystems showed potential for obtaining B. thuringiensis. This isolate, in addition to having proteins with molecular mass similar to the toxins Cry and Cyt, also presented several diptera-specific genes cry and cyt, demonstrating that it has high potential to be used in the biological control of Ae. aegypti.

Resumo Bacillus thuringiensis é o entomopatógeno mais utilizado no controle do Aedes aegypti, vetor de diferentes agentes etiológicos que causam infecções graves em humanos. Diversos estudos têm como objetivo isolar cepas dessa bactéria de diferentes ambientes, com a perspectiva de selecionar isolados com atividade larvicida para mosquitos. Visando a ação inseticida de B. thuringiensis, o presente estudo teve como objetivo prospectar B. thuringiensis de solos de restinga e mangue do estado do Maranhão, Brasil, com potencial tóxico para uso no controle biológico de Ae. aegypti. Bioensaios foram realizados para determinar a atividade entomopatogênica do bacilo contra Ae. aegypti e as concentrações letais (CL50 e CL90) foram estimadas após os testes. As técnicas de Reação em Cadeia da Polimerase e SDS-PAGE foram realizadas para verificar o conteúdo de genes e proteínas dos isolados, respectivamente. Os solos dos ecossistemas de mangue e restinga apresentaram potencial para obtenção de B. thuringiensis. O isolado BtMA-750, obtido a partir da amostra de solo da restinga, foi interessantemente distinguido por sua alta toxicidade para Ae. aegypti. Este isolado, além de apresentar proteínas com massa molecular semelhante às toxinas Cry e Cyt, apresentou também diversos genes díptero-específicos cry e cyt, demonstrando que tem alto potencial para ser usado no controle biológico de Ae. aegypti.

Isolates of Bacillus thuringiensis from Maranhão biomes with potential insecticidal action against Aedes aegypti larvae (Diptera, Culicidae) / Isolados de Bacillus thuringiensis de biomas maranhenses com potencial ação inseticida contra larvas de Aedes aegypti (Diptera, Culicidae)

Abstract Entomopathogenic agents are viable and effective options due to their selective action against insects but benign effects on humans and the environment. The most promising entomopathogens include subspecies of Bacillus thuringiensis (Bt), which are widely used for the biological control of insects, including mosquito vectors of human pathogens. The efficacy of B. thuringiensis toxicity has led to the search for new potentially toxic isolates in different regions of the world. Therefore, soil samples from the Amazon, Cerrado and Caatinga biomes of the state of Maranhão were evaluated for their potential larvicidal action against Aedes aegypti. The isolates with high toxicity to mosquito larvae, as detected by bioassays, were subjected to histological evaluation under a light microscope to identify the genes potentially responsible for the toxicity. Additionally, the toxic effects of these isolates on the intestinal epithelium were assessed. In the new B. thuringiensis isolates toxic to A. aegypti larvae, cry and cyt genes were amplified at different frequencies, with cry4, cyt1, cry32, cry10 and cry11 being the most frequent (33-55%) among those investigated. These genes encode specific proteins toxic to dipterans and may explain the severe morphological changes in the intestine of A. aegypti larvae caused by the toxins of the isolates.

Resumo Os agentes entomopatógenos são alternativas viáveis e eficazes, devido à sua ação seletiva para insetos sendo inofensivos ao homem e ao meio ambiente. Dentre os entomopatógenos mais promissores, destacam-se as subespécies de Bacillus thuringiensis (Bt) amplamente utilizadas no controle biológico de insetos incluindo espécies de mosquitos vetores de agentes patogênicos ao homem. A eficiência da toxicidade de Bt incentiva a prospecção de novos isolados em diversas regiões do mundo. Desta forma, em busca de novos isolados de B. thuringiensis potencialmente tóxicos, amostras de solo provenientes dos biomas Amazônia, Cerrado e Caatinga do estado do Maranhão foram avaliadas em relação ao seu potencial larvicida para Aedes aegypti. Os isolados que provocaram elevada toxicidade para larvas do mosquito, detectada por bioensaios, foram avaliados em relação aos potenciais genes responsáveis pela atividade tóxica, além da avaliação de efeitos tóxicos no epitélio intestinal através de análises histológicas em microscopia de luz. Os novos isolados de Bt tóxicos para larva de A. aegypti amplificaram frequências diferentes de genes cry e cyt sendo os mais frequentes (55-33%) os cry4, cyt1, cry32, cry10 e cry11 dentre os investigados. Esses genes codificam para proteínas tóxicas específicas para ordem Diptera, e podem explicar as severas alterações morfológicas provocadas pelas toxinas dos isolados observadas no intestino das larvas de A. aegypti.

Isolates of Bacillus thuringiensis from Maranhão biomes with potential insecticidal action against Aedes aegypti larvae (Diptera, Culicidae).

Entomopathogenic agents are viable and effective options due to their selective action against insects but benign effects on humans and the environment. The most promising entomopathogens include subspecies of Bacillus thuringiensis (Bt), which are widely used for the biological control of insects, including mosquito vectors of human pathogens. The efficacy of B. thuringiensis toxicity has led to the search for new potentially toxic isolates in different regions of the world. Therefore, soil samples from the Amazon, Cerrado and Caatinga biomes of the state of Maranhão were evaluated for their potential larvicidal action against Aedes aegypti. The isolates with high toxicity to mosquito larvae, as detected by bioassays, were subjected to histological evaluation under a light microscope to identify the genes potentially responsible for the toxicity. Additionally, the toxic effects of these isolates on the intestinal epithelium were assessed. In the new B. thuringiensis isolates toxic to A. aegypti larvae, cry and cyt genes were amplified at different frequencies, with cry4, cyt1, cry32, cry10 and cry11 being the most frequent (33-55%) among those investigated. These genes encode specific proteins toxic to dipterans and may explain the severe morphological changes in the intestine of A. aegypti larvae caused by the toxins of the isolates.

Strain of Bacillus thuringiensis from Restinga, toxic to Aedes (Stegomyia) aegypti (Linnaeus) (Diptera, Culicidae).

Bacillus thuringiensis is the most commonly used entomopathogen in the control of Aedes aegypti, which is a vector for different etiological agents that cause serious infections in humans. Several studies aim to isolate strains of this bacterium from different environments, with the perspective of selecting isolates with larvicidal activity for mosquitoes. Aiming at the insecticidal action of B. thuringiensis, the present study aimed to prospect B. thuringiensis of restinga and mangrove soils from the state of Maranhão, Brazil, with toxic potential for use in the biological control of Ae. aegypti. Bioassays were performed to determine the entomopathogenic activity of the bacilli against Ae. aegypti and lethal concentrations (LC50 and CL90) were estimated after the tests. Polymerase Chain Reaction and SDS-PAGE techniques were performed to verify the gene and protein content of the isolates, respectively. The soil of the mangrove and restinga ecosystems showed potential for obtaining B. thuringiensis. This isolate, in addition to having proteins with molecular mass similar to the toxins Cry and Cyt, also presented several diptera-specific genes cry and cyt, demonstrating that it has high potential to be used in the biological control of Ae. aegypti.

Isolates of Bacillus thuringiensis from Maranhão biomes with potential insecticidal action against Aedes aegypti larvae (Diptera, Culicidae)

Abstract Entomopathogenic agents are viable and effective options due to their selective action against insects but benign effects on humans and the environment. The most promising entomopathogens include subspecies of Bacillus thuringiensis (Bt), which are widely used for the biological control of insects, including mosquito vectors of human pathogens. The efficacy of B. thuringiensis toxicity has led to the search for new potentially toxic isolates in different regions of the world. Therefore, soil samples from the Amazon, Cerrado and Caatinga biomes of the state of Maranhão were evaluated for their potential larvicidal action against Aedes aegypti. The isolates with high toxicity to mosquito larvae, as detected by bioassays, were subjected to histological evaluation under a light microscope to identify the genes potentially responsible for the toxicity. Additionally, the toxic effects of these isolates on the intestinal epithelium were assessed. In the new B. thuringiensis isolates toxic to A. aegypti larvae, cry and cyt genes were amplified at different frequencies, with cry4, cyt1, cry32, cry10 and cry11 being the most frequent (33-55%) among those investigated. These genes encode specific proteins toxic to dipterans and may explain the severe morphological changes in the intestine of A. aegypti larvae caused by the toxins of the isolates.

Resumo Os agentes entomopatógenos são alternativas viáveis e eficazes, devido à sua ação seletiva para insetos sendo inofensivos ao homem e ao meio ambiente. Dentre os entomopatógenos mais promissores, destacam-se as subespécies de Bacillus thuringiensis (Bt) amplamente utilizadas no controle biológico de insetos incluindo espécies de mosquitos vetores de agentes patogênicos ao homem. A eficiência da toxicidade de Bt incentiva a prospecção de novos isolados em diversas regiões do mundo. Desta forma, em busca de novos isolados de B. thuringiensis potencialmente tóxicos, amostras de solo provenientes dos biomas Amazônia, Cerrado e Caatinga do estado do Maranhão foram avaliadas em relação ao seu potencial larvicida para Aedes aegypti. Os isolados que provocaram elevada toxicidade para larvas do mosquito, detectada por bioensaios, foram avaliados em relação aos potenciais genes responsáveis pela atividade tóxica, além da avaliação de efeitos tóxicos no epitélio intestinal através de análises histológicas em microscopia de luz. Os novos isolados de Bt tóxicos para larva de A. aegypti amplificaram frequências diferentes de genes cry e cyt sendo os mais frequentes (55-33%) os cry4, cyt1, cry32, cry10 e cry11 dentre os investigados. Esses genes codificam para proteínas tóxicas específicas para ordem Diptera, e podem explicar as severas alterações morfológicas provocadas pelas toxinas dos isolados observadas no intestino das larvas de A. aegypti.

Strain of Bacillus thuringiensis from Restinga, toxic to Aedes (Stegomyia) aegypti (Linnaeus) (Diptera, Culicidae)

Abstract Bacillus thuringiensis is the most commonly used entomopathogen in the control of Aedes aegypti, which is a vector for different etiological agents that cause serious infections in humans. Several studies aim to isolate strains of this bacterium from different environments, with the perspective of selecting isolates with larvicidal activity for mosquitoes. Aiming at the insecticidal action of B. thuringiensis, the present study aimed to prospect B. thuringiensis of restinga and mangrove soils from the state of Maranhão, Brazil, with toxic potential for use in the biological control of Ae. aegypti. Bioassays were performed to determine the entomopathogenic activity of the bacilli against Ae. aegypti and lethal concentrations (LC50 and CL90) were estimated after the tests. Polymerase Chain Reaction and SDS-PAGE techniques were performed to verify the gene and protein content of the isolates, respectively. The soil of the mangrove and restinga ecosystems showed potential for obtaining B. thuringiensis. This isolate, in addition to having proteins with molecular mass similar to the toxins Cry and Cyt, also presented several diptera-specific genes cry and cyt, demonstrating that it has high potential to be used in the biological control of Ae. aegypti.

Resumo Bacillus thuringiensis é o entomopatógeno mais utilizado no controle do Aedes aegypti, vetor de diferentes agentes etiológicos que causam infecções graves em humanos. Diversos estudos têm como objetivo isolar cepas dessa bactéria de diferentes ambientes, com a perspectiva de selecionar isolados com atividade larvicida para mosquitos. Visando a ação inseticida de B. thuringiensis, o presente estudo teve como objetivo prospectar B. thuringiensis de solos de restinga e mangue do estado do Maranhão, Brasil, com potencial tóxico para uso no controle biológico de Ae. aegypti. Bioensaios foram realizados para determinar a atividade entomopatogênica do bacilo contra Ae. aegypti e as concentrações letais (CL50 e CL90) foram estimadas após os testes. As técnicas de Reação em Cadeia da Polimerase e SDS-PAGE foram realizadas para verificar o conteúdo de genes e proteínas dos isolados, respectivamente. Os solos dos ecossistemas de mangue e restinga apresentaram potencial para obtenção de B. thuringiensis. O isolado BtMA-750, obtido a partir da amostra de solo da restinga, foi interessantemente distinguido por sua alta toxicidade para Ae. aegypti. Este isolado, além de apresentar proteínas com massa molecular semelhante às toxinas Cry e Cyt, apresentou também diversos genes díptero-específicos cry e cyt, demonstrando que tem alto potencial para ser usado no controle biológico de Ae. aegypti.