Patient-based dengue virus surveillance in Aedes aegypti from Recife, Brazil.

Background & objectives: Dengue is currently one of the most important arthropod-borne diseases and may be caused by four different dengue virus serotypes (DENV-1 to DENV-4), transmitted mainly by Aedes aegypti (Diptera: Culicidae) mosquitoes. With the lack of a dengue vaccine, vector control strategies constitute a crucial mode to prevent or reduce disease transmission. In this context, DENV detection in natural Ae. aegypti populations may serve as a potential additional tool for early prediction systems of dengue outbreaks, leading to an intensification of vector control measures, aimed at reducing disease transmission. In Brazil, this type of surveillance has been performed sporadically by a few groups and has not been incorporated as a routine activity in control programs. This study aimed at detecting DENV in natural Ae. aegypti from Recife, Pernambuco, to check the circulating serotypes and the occurrence of transovarial transmission in local mosquito populations. Methods: From January 2005 to June 2006, mosquitoes (adults and eggs) were collected in houses where people with clinical suspicion of dengue infection lived at. RNA was extracted from pooled mosquitoes and RT-PCR was performed in these samples for detection of the four DENV serotypes. Results & conclusion: Out of 83 pools of adult mosquitoes collected in the field, nine were positive for DENV: five for DENV-1, two for DENV-2 and two for DENV-3. From 139 pools of adult mosquitoes reared from collected eggs, there were 17 positive pools: three for DENV-1, 10 for DENV-2, and four for DENV-3. These results are discussed in the paper in regard to the local dengue epidemiological data. The conclusions clearly point to the informative power and sensitivity of DENV entomological surveillance and to the importance of including mosquito immature forms in this strategy.

Genetic diversity in Brazilian populations of Aedes albopictus

Random amplified polymorphic DNA (RAPD) analysis technique was undertaken in Aedes albopictus populations from three states in Brazil, Rio de Janeiro (RJ), Minas Gerais (MG) and Pernambuco (PE), to estimate the level of genetic variability and levels of genetic exchange between populations. Allele and genotype frequencies were measured on 47 RAPD loci. Average observed heterozigosity (Ho) ranged from 0.282 in MG to 0.355 in Casa Forte (PE) population. Genetic distances estimates indicated that RJ and MG were more genetically similar than populations from PE. Genetic variation observed in local Brazilian populations was attributed to genetic drift associated with restricted gene flow in recently established populations

Natural lectin activity in the haemolymph of Panstrogylus megistus (Heteroptera: Reduvidae)

A hemolinfa de Panstrongylus megistus mostrou uma atividade lectínica natural para eritrócitos de vários vertebrados e näo mostrou especificidade para os diversos tipos de eritrócitos testados (humano ABO, pato, coelho,c amundongo,carneiro, galinha e boi). Com relaçäo aos eritrócitos humanos a atividade lectínica foi similar nos tipos A+, B+ e AB+ enquanto a atividade mais alta foi observada no tipo O+. O título de aglutinaçäo entre eritrócitos animais näo mostrou diferença apreciável, excluindo eritrócitos de boi, que apresentaram o título mmais baixo. A determinaçäo da concentraçäo mínima de inibiçäo foi realizada com eritrócitos humanos O+. A aglutinaçäo foi inibida por vários carboidratos (ramnose, D-dalactose, rafinose, D-lactose e D-fucose). A ramnose foi o inibidor mais potente (0,78 mM). Os resultados sugerem a presença de mais de uma lectina na hemolinfa de P. megistus

Effects of juvenile hormone analogue on ecdysis prevention induced by precocene in Rhodnius prolixus (Hemiptera: Reduviidae).

Adicionado ao sangue alimentar na dose de 25 micros/ml o precoceno II causou um aumento no periodo de intermuda em ninfas de 4o. estadio de Rhodnius prolixus. Este atraso da muda foi relacionado com a diminuicao da area dos nucleos das celulas das glandulas protoracicas e com a queda da atividade mitotica das celulas da epiderme do inseto. Um analogo de hormonio juvenil aplicado topicamente (60 micros/inseto) junto com o tratamento oral com precoceno II preveniu a atrofia das glandulas protoracicas e induziu um aumento no numero de mitoses nas celulas da epiderme, diminuindo o periodo de intermuda nestes insetos.A possivel relacao entre a acao do hormonio juvenil e a producao de ecdisona pelas glandulas protoracicas e discutida