Synergistic larvicidal effect and morphological alterations induced by ethanolic extracts of Annona muricata and Piper nigrum against the dengue fever vector Aedes aegypti.

BACKGROUND: Phytopesticide combinations of different botanical sources are seldom reported. Annona muricata seed and Piper nigrum fruit ethanolic extracts enriched in acetogenins and piperamides, respectively, were synergistically used as larvicides against the dengue fever vector Aedes aegypti. RESULTS: Individual bioassays of A. muricata and P. nigrum indicated respective LC50 values of 93.48 and 1.84 µg mL(-1) against third-instar larvae. Five combinations of different proportions of plant extracts pointed to synergism between the extracts. The best A. muricata:P. nigrum extract combination was 90:10, which showed 5.12 times the amount of synergism, as confirmed by statistical equations and total concentration log versus combination proportions. Concerning the morphology, A. muricata caused larvae body elongation, mainly in the abdomen, along with the appearance of a cervix. Conversely, P. nigrum induced abdomen and whole body shortening. The morphological effects of A. muricata were prevalent in all of the combinations tested, irrespective of its proportion in the combination. CONCLUSION: It is suggested that the different mechanisms of action of the larvicidal actives A. muricata acetogenins and P. nigrum piperamides explain the observed synergism. The combination of inexpensive botanicals and a low-cost organosolvent such as ethanol leads to a simple and efficient phytolarvicidal formulation.

The combined action of phytolarvicides for the control of dengue fever vector, Aedes aegypti

Amongst other botanical sources, Annona muricata L., Annonaceae, seeds and Piper nigrum L., Piperaceae, fruits are particularly enriched with acetogenins and piperine-related amides, respectively. These crude ethanolic extracts are potent Aedes aegypti bioactives that can kill Aedes aegypti larvae (dengue fever mosquito). A. muricata displayed a 93.48 µg/mL LC50 and P. nigrum an 1.84 µg/mL LC50. An uncommon pharmacognostical/toxicological approach was used, namely different combinations of both extracts to achieve an improved lethal effect on the larvae. The independence test (χ²) was utilized to evaluate the combination of the two crude extracts. All of the tested combinations behaved synergistically and these novel results were attributed to the completely different biochemical mechanisms of the differentiated chemical substances that were present in the two botanical sources. Besides the two above selected plants, Melia azedarach L., Meliaceae, Origanum vulgare L., Lamiaceae, and Ilex paraguariensis A. St.-Hil., Aquifoliaceae, in order of decreasing toxicity, may also be sought as potential extracts for the sake of synergic combinations.

Genetic variability of a population of Aedes aegypti from Paraná, Brazil, using the mitochondrial ND4 gene / Variabilidade genética de uma população de Aedes aegypti do Paraná, Brasil, usando o gene mitocondrial ND4

Genetic variability of a population of Aedes aegypti from Paraná, Brazil, using the mitochondrial ND4 gene. To analyze the genetic variability of populations of Aedes aegypti, 156 samples were collected from 10 municipalities in the state of Paraná, Brazil. A 311 base pairs (bp) region of the NADH dehydrogenase subunit 4 (ND4) mitochondrial gene was examined. An analysis of this fragment identified eight distinct haplotypes. The mean genetic diversity was high (h = 0.702; p = 0.01556). AMOVA analysis indicated that most of the variation (67%) occurred within populations and the F ST value (0.32996) was highly significant. F ST values were significant in most comparisons among cities. The isolation by distance was not significant (r = -0.1216 and p = 0, 7550), indicating that genetic distance is not related to geographic distance. Neighbor-joining analysis showed two genetically distinct groups within Paraná. The DNA polymorphism and AMOVA data indicate a decreased gene flow in populations from Paraná, which can result in increased vectorial competence.

Variabilidade genética de uma população de Aedes aegypti do Paraná, Brasil, usando o gene mitocondrial ND4. Para analisar a variabilidade genética de populações de Aedes aegypti, 156 amostras foram coletadas em dez cidades do estado do Paraná, Brasil. Foi examinada a distribuição dos 311 pares de base do gene que codifica a subunidade 4 da enzima NADH desidrogenase. Pela amplificação e o sequenciamento deste fragmento foram identificados 8 haplótipos distintos. Os valores de diversidade genética foram altos (h = 0.702; p = 0.01556). A análise de AMOVA indicou que a maior variação ocorreu dentro das populações com um valor de FST de 0.32996 altamente significativo. Valores de FST foram significativos na maior das comparações entre as cidades. O isolamento por distância não foi significativo (r = -0.1216 e p = 0.755), indicando que a distância genética não está relacionada a distância geográfica. A análise de Neighbor-joining mostrou dois grupos genéticos distintos dentro do estado do Paraná, grupo I e grupo II. O polimorfismo de DNA e os dados de AMOVA indicam decréscimo de fluxo gênico no estado do Paraná, o que pode resultar em aumento da competência vetorial da população.

Generic insect repellent detector from the fruit fly Drosophila melanogaster.

BACKGROUND: Insect repellents are prophylactic tools against a number of vector-borne diseases. There is growing demand for repellents outperforming DEET in cost and safety, but with the current technologies R&D of a new product takes almost 10 years, with a prohibitive cost of $30 million dollar in part due to the demand for large-scale synthesis of thousands of test compounds of which only 1 may reach the market. R&D could be expedited and cost dramatically reduced with a molecular/physiological target to streamline putative repellents for final efficacy and toxicological tests. METHODOLOGY: Using olfactory-based choice assay we show here that the fruit fly is repelled by not only DEET, but also IR3535 and picaridin thus suggesting they might have "generic repellent detector(s)," which may be of practical applications in new repellent screenings. We performed single unit recordings from all olfactory sensilla in the antennae and maxillary palps. Although the ab3A neuron in the wild type flies responded to picaridin, it was unresponsive to DEET and IR3535. By contrast, a neuron housed in the palp basiconic sensilla pb1 responded to DEET, IR3535, and picaridin, with apparent sensitivity higher than that of the DEET detectors in the mosquitoes Culex quinquefasciatus and Aedes aegypti. DmOr42a was transplanted from pb1 to the "empty neuron" and showed to be sensitive to the three insect repellents. CONCLUSIONS: For the first time we have demonstrated that the fruit fly avoids not only DEET but also IR3535 and picaridin, and identified an olfactory receptor neuron (ORN), which is sensitive to these three major insect repellents. We have also identified the insect repellent-sensitive receptor, DmOr42a. This generic detector fulfils the requirements for a simplified bioassay for early screening of test insect repellents.