Alfredo Martins de Oliveira Filho

Produtos naturais para o controle da transmissão da dengue: atividade larvicida de Myroxylon balsamum (óleo vermelho) e de terpenóides e fenilpropanóides

The bioassay-guided fractionation of the hexane extract obtained from the medicinal plant Myroxylon balsamum (red oil) was conducted in preparative thin layer chromatography on silica gel. The obtained fractions and some terpenoids and phenylpropanoids were assayed as larvicidal on third instar Aedes aegypti larvae, NPPN colony. The results indicate that the sesquiterpene nerolidol was the active constituent in the extract and that the sesquiterpenes were more active than the monoterpenes and phenylpropanoids utilized in this study. Lipophilicity seems to be an important property for the activity since the compounds with hydroxyl, carbonyl and methoxyl groups were less active. The results confirm also that essential oils can be a good tool for the control of dengue.

Resistência do Aedes aegypti ao temefós em Municípios do Estado do Ceará

The susceptibility of Aedes aegypti to temefos was evaluated by means of samples of eggs and larvae from four large counties in the state of Ceara (Fortaleza, Barbalha, Juazeiro do Norte and Crato). The technique standardized by the World Health Organization for tests with larvicides was used. The CL50 of eight samples from populations of Aedes was determined, as were their respective resistance ratios, compared to the CL50 of the susceptible Rockefeller strain. All populations submitted to the experiment showed resistance to temefos, with resistance ratios varying between 8 and 16. Analysis of these results reinforces prior evidence regarding the dissemination of temefos resistance in different locations in the state, subjected to considerable pressure for control in recent decades. The larvicide may lose its effectiveness if an urgent attempt is not made to reestablish the susceptibility of Aedes aegypti in these areas, profoundly affecting control campaigns currently under way.

O aproveitamento do resíduo da indústria do sisal no controle de larvas de mosquitos

The aim of this research was to utilize the waste residues of sisal fiber separation from Agave sisalana leaves to develop a larvicide for the combat of mosquito transmitting tropical diseases. Larvae of Aedes aegypti and Culex quinquefasciatus were exposed to different concentrations of the Agave extract for 24 hours to determine lethal concentrations. The LC50 for A. aegypti was 322 ppm and the LC50 for C. quinquefasciatus was 183 ppm. To detect the active substances, saponins were investigated. It was found that the various components of the extract were effective in eliminating the larvae. Under field conditions, this formulation can probably be used at 100 ppm, which causes 100% mortality of C. quinquefasciatus larvae after 3-4 days. The product is not recommended for use against A. aegypti due to the necessity for high concentrations and to the fact that the larvae of this species live frequently on drinking water. To avoid fermentation, Agave extract should be used in a dehydrated form which also represent a good formulation for practical use.

Potential use of Piper nigrum ethanol extract against pyrethroid-resistant Aedes aegypti larvae

Fractionation of Piper nigrum ethanol extract, biomonitored by assays on pyrethroid-resistant Aedes aegypti larvae yielded isolation of the larvicidal amides piperolein-A and piperine. Comparing LC50 values, the ethanol extract (0.98 ppm) was the most toxic, followed by piperolein-A (1.46 ppm) and piperine (1.53 ppm).

Focal and total residual insecticide spraying to control Triatoma brasiliensis and Triatoma pseudomaculata in Northeast Brazil

To efficiently control the triatomines Triatoma brasiliensis and Triatoma pseudomaculata, a field trial was performed to compare conventional versus focal spraying of deltamethrin 5% SC at 25 mg a. i./m2 and the slow-release organophosphate malathion 8.3% SR at 2g a. i./m2. The assay took place in the county of Boa Viagem, Ceará State, with 1541 households, randomly separated into 4 groups. Two of them received focal spraying: PT, treated with deltamethrin indoors and in the peridomicile, and PL, which received slow-release malathion in the same circumstances. The other groups received conventional, i.e., total application: PT with deltamethrin in the intra- and peridomicile, and PL, which was treated with deltamethrin indoors and slow-release malathion in the peridomicile. Entomological surveys at 6 and 12 months post-treatment showed better results for mixed treatment, the PL group, probably due to good indoor performance for the pyrethroid and better performance of the slow-release formulation under the hostile peridomiciliary conditions. Domestic animal shelters underwent numerous modifications over the course of the year, fostering reduced insecticide performance in the peridomicile.

Vectors control importance on leishmaniasis transmission

We reviewed the control of transmission of leishmaniasis regarding chemotherapy, reservoirs elimination, vaccination and insect control through the use of chemical insecticides. We also discussed complementary measures like monitoring traps, impregnated bednets and curtains, repelents, pheromones, biological control, etc. A cost comparison of insecticide interventions through the use of products belonging to the four main chemical groups was also done, comparing together conventional formulations versus a slow-release insecticide developed by the Núcleo de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro. We finally did recommendations on the situation that would justify an insecticide intervention to control sandflies.