Histology and ultrastructure of Aedes albopictus larval midgut infected with Bacillus thuringiensis var. israelensis.

Histological and ultrastrucutural alterations in the midgut of Aedes albopictus larvae infected with Bacillus thuringiensis var. israelensis (Bti) were observed by light and transmission electron microscopy (TEM). Two formulations of Bti were used: granulated and powder, with 0.2% active ingredient in 90 larvae of Ae. albopictus distributed in three containers containing 30 larvae each (one control group and two test groups). The midgut epithelium of the control group presented flattened and elongated cells with mace-shape with a narrow base. Midgut epithelium cells' surface was convex and had a large circular nucleus located in the median-apical portion of the cell. These cells also presented a basal lamina with a small accumulation of extracellular fibrous matrix, thus characterizing a basal membrane, with a muscle layer and a peritoneal membrane more externally. After Bti ingestion, the larvae stopped/slowed their natural movements down in 5 min. After 30 min approximately, the swimming movements stopped completely. Internally, the intestinal cells showed a disorganization of the basal processes, dilatation and fragmentation of the rough endoplasmic reticulum, with intense cytoplasmic vacuolization. There were concentric dense laminas accumulated in the cytoplasm, and these residual membranous bodies were seen greatly increased in size after 60 min. Mitochondria, fragments of rough endoplasmic reticulum and other remainder organelles were surrounded and segregated from the cytoplasm by exocytosis. This article reports the histopathological alterations in the midgut of Ae. albopictus after infection with Bti and contributes to a better understanding of the mode of action of this bacterial strain used as bioinsecticide against mosquito larvae.

[Diversity of oviposition containers and buildings where Aedes albopictus and Aedes aegypti can be found]. / Diversidade de criadouros e tipos de imóveis freqüentados por Aedes albopictus e Aedes aegypti.

OBJECTIVE: To assess the diversity of oviposition containers and buildings where females of Aedes albopictus and Aedes aegypti can be found. METHODS: A study was carried out in the city of Rio de Janeiro, Southern Brazil, between 2002 and 2003. Larvae in different types of buildings were investigated, and immature forms found were then sent to the laboratory for identification. The larval frequency for both mosquitoes was estimated in the oviposition containers available. The Breteau index and the building infestation index were calculated and differences were tested using the Chi-square test. RESULTS: The types of buildings that were positive for Aedes albopictus and Aedes aegypti were: dwellings (83.9%); churches, schools, clubs (6.8%); vacant land (6.4%); and businesses (2.8%). Of 9,153 larvae collected, 12.0% were Aedes albopictus and 88.0% were Aedes aegypti. Aedes albopictus were mostly found in drains (25.4%); cans, bottles, empty bottles (23.9%); and plant vases (16.2%). Aedes aegypti was much more frequently found than Aedes albopictus (chi(2)=145.067; p<0.001). Both species were significantly more frequent in artificial than in natural oviposition containers (chi(2)=31.46; p<0.001). The building infestation index and Breteau index for Aedes albopictus were 0.3% and 0.28% in 2002 and 0.4% and 0.5 in 2003, respectively. For Aedes aegypti, they were 1.0%, 1.16 in 2002 and 3.5% and 4.35 in 2003, respectively. CONCLUSIONS: The present study assessed the frequencies of Aedes albopictus and Aedes aegypti females in various types of oviposition containers and types of buildings. The abundant availability of artificial containers in dwellings, associated with the capacity of Ae. albopictus to be also found in natural oviposition containers, has greatly contributed for their gradual adaptation to human environment.

Diversidade de criadouros e tipos de imóveis freqüentados por Aedes albopictus e Aedes aegypti / Diversity of oviposition containers and buildings where Aedes albopictus and Aedes aegypti can be found

OBJETIVOS: Verificar a diversidade de criadouros e tipos de imóveis freqüentados por fêmeas de Aedes albopictus e Aedes aegypti. MÉTODOS: O estudo foi realizado nos anos de 2002 e 2003 no bairro de Campo Grande, Rio de Janeiro, RJ. Realizou-se pesquisa larvária em diferentes tipos de imóveis. As larvas encontradas foram identificadas em laboratório. A freqüência de larvas dessas duas espécies foi computada nos diversos criadouros disponíveis. Foram calculados os índices de infestação predial e de Breteau, as diferenças foram testadas pelo qui-quadrado. RESULTADOS: Os tipos de imóveis positivos para os aedinos foram: residências (83,9 por cento do total); igrejas, escolas, clubes (6,8 por cento); terrenos baldios (6,4 por cento); e comércios (2,8 por cento). Das 9.153 larvas, 12,0 por cento eram de Aedes albopictus e 88,0 por cento de Aedes aegypti. Para aquela espécie, os recipientes onde foram mais encontradas foram ralos (25,4 por cento), latas, garrafas, vasilhames (23,9 por cento) e vasos com plantas (16,2 por cento). Aedes aegypti mostrou-se mais freqüente nos criadouros que Aedes albopictus (chi2=145,067, p<0,001). Também ocorreu diferença significante na freqüência dessas espécies em criadouros artificiais do que em naturais (chi2=31,46; p<0,001). O índice de infestação predial e índice de Breteau para Aedes albopictus foram respectivamente em 2002 (0,3 por cento; 0,28), em 2003 (0,4 por cento; 0,5); para Aedes aegypti, em 2002 (1,0 por cento;1,16) e 2003 (3,5 por cento; 4,35). CONCLUSÕES: Verificou-se a freqüência das fêmeas de Aedes albopictus e Ae. aegypti em variados tipos de criadouros e tipos de imóveis para postura. A oferta abundante de recipientes artificiais inservíveis nas residências, associada à capacidade de Ae. albopictus de freqüentar também os criadouros naturais, contribui sobremaneira para sua adaptação gradativa ao meio antrópico.

OBJECTIVE: To assess the diversity of oviposition containers and buildings where females of Aedes albopictus and Aedes aegypti can be found. METHODS: A study was carried out in the city of Rio de Janeiro, Southern Brazil, between 2002 and 2003. Larvae in different types of buildings were investigated, and immature forms found were then sent to the laboratory for identification. The larval frequency for both mosquitoes was estimated in the oviposition containers available. The Breteau index and the building infestation index were calculated and differences were tested using the Chi-square test. RESULTS: The types of buildings that were positive for Aedes albopictus and Aedes aegypti were: dwellings (83.9 percent); churches, schools, clubs (6.8 percent); vacant land (6.4 percent); and businesses (2.8 percent). Of 9,153 larvae collected, 12.0 percent were Aedes albopictus and 88.0 percent were Aedes aegypti. Aedes albopictus were mostly found in drains (25.4 percent); cans, bottles, empty bottles (23.9 percent); and plant vases (16.2 percent). Aedes aegypti was much more frequently found than Aedes albopictus (chi2=145.067; p<0.001). Both species were significantly more frequent in artificial than in natural oviposition containers (chi2=31.46; p<0.001). The building infestation index and Breteau index for Aedes albopictus were 0.3 percent and 0.28 percent in 2002 and 0.4 percent and 0.5 in 2003, respectively. For Aedes aegypti, they were 1.0 percent, 1.16 in 2002 and 3.5 percent and 4.35 in 2003, respectively. CONCLUSIONS: The present study assessed the frequencies of Aedes albopictus and Aedes aegypti females in various types of oviposition containers and types of buildings. The abundant availability of artificial containers in dwellings, associated with the capacity of Ae. albopictus to be also found in natural oviposition containers, has greatly contributed for their gradual adaptation to human environment.