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W P Tadei

Publications and source records attributed to W P Tadei.

11 recordsLinked to original sources
PubMed2005

Amazonian malaria vector anopheline relationships interpreted from ITS2 rDNA sequences.

Species identification of anopheline mosquitoes (Diptera: Culicidae) can be problematic because many of them belong to complexes of morphologically similar species, often with contrasted ecology, behaviour and vectorial importance. The application of DNA-based diagnostics has proved to be useful for distinguishing between such species. We determined ribosomal DNA sequences of the second internal transcribed spacer (ITS2) from samples of 16 species of Anopheles captured in the Amazon Basin, Brazil. Length of the ITS2 varied from 323 to 410 base pairs, with GC content ranging from 50.7% to 66.5% and sequence identity from 25% to 99% between species. Maximum-likelihood paup analysis separated two distinct groups of species conforming with the recognized subgenera Anopheles (represented by eiseni, mattogrossensis, mediopunctatus and peryassui) and Nyssorhynchus (represented by 12 spp.). For the latter group, the neighbour-joining tree generated from rDNA sequence ITS2 relationships is compatible with the morphological taxonomic key established for these Amazonian species: albitarsis, aquasalis, benarrochi, braziliensis, darlingi, deaneorum, dunhami, evansae, nuneztovari, oswaldoi, rangeli and triannulatus. These ITS2 sequence data proved to be a useful tool for species identification and, potentially, to solve taxonomic problems.

Animals↗
PubMed2004

Differentiation and genetic variability in natural populations of Anopheles (N.) triannulatus (Neiva & Pinto, 1922) of Brazilian Amazonia.

Populations of Anopheles triannulatus from Macapá (AP), Aripuanã (MT), Ji-Paraná (RO), and Manaus-Janauari Lake (AM) were studied using 16 enzymatic loci. The results of the isozyme analysis showed that the population of Macapá presented higher polymorphism (56.3%). The lowest variability was observed in the population of Manaus (p = 25.0; Ho = 0.077 +/- 0.046). The results of Wright's F statistics showed unbalance due to excess of homozygotes (F(is) > F(st)), denoting a certain intrapopulational differentiation. Although the populations are genetically very close (D = 0.003-0.052), the dendrogram separates the populations in two groups: Macapá separated from that of Manaus, Ji-Paraná, and Aripuanã. This result may suggest a reduction in the genic flow, which possibly had some influence in the substructuration of the populations.

Alleles↗
PubMed2000

Enzymatic analysis in Anopheles nuneztovari Gabaldón (Diptera, Culicidae).

Enzymatic analysis in Anopheles nuneztovari was made using four populations from the Brazilian Amazon and two from Colombia. The enzymes ME and XDH presented a monomorphic locus in all of the studied populations. EST and LAP presented a higher number of loci. In EST, genetic variation was observed in the five loci; LAP presented four loci, with allec variation in two loci. In IDH, three activity regions were stained, with genetic variation for locus Idh-1 in the Brazilian Amazon populations. A locus for MDH was observed, with genetic variation in the six populations. A region was verified for ACON, with four alleles in Sitronela and three in the other populations. PGM constituted one locus, with a high variability in the Brazilian Amazon populations. A locus was observed for 6-PGD with allelic variation in all of the populations with the exception of Tibú. Enzyme PGI presented two loci, both with genetic variability in the Tucuruí population. The enzyme alpha-GPD showed an activity region with polymorphism in the Tucuruí, Tibú and Sitronela populations. The phenotypic variations detected for these enzymes suggest that four (EST, LAP, ACON and PGM) possess monomeric structures and five (IDH, MDH, 6-PGD, PGI and alpha-GPD) dimeric structures in their proteins. These enzymes constitute in important markers to estimate variability and genetic divergence in natural populations of A. nuneztovari.

Alleles↗
PubMed1999

Population structure and genetic divergence in Anopheles nuneztovari (Diptera: Culicidae) from Brazil and Colombia.

Anopheles nuneztovari is considered an important vector of human malaria in several localities in Venezuela and Colombia. Its status as a vector of human malaria is still unresolved in areas of the Brazilian Amazon, in spite of have been found infected with Plasmodium sp.. For a better understanding of the genetic differentiation of populations of A. nuneztovari, electrophoretic analysis using 11 enzymes was performed on four populations from Brazil and two from Colombia. The results showed a strong differentiation for two loci: alpha-glycerophosphate dehydrogenase (alpha-Gpd) and malate dehydrogenase (Mdh) from 16 loci analyzed. Diagnostic loci were not detected. The populations of A. nuneztovari from the Brazilian Amazon showed little genetic structure and low geographic differentiation, based on the F(IS) (0.029), F(ST) (0.070), and genetic distance (0.001-0.032) values. The results of the isozyme analysis do not coincide with the indication of two lineages in the Amazon Basin by analysis of mitochondrial DNA, suggesting that this evolutionary event is recent. The mean F(ST) value (0.324) suggests that there is considerable genetic divergence among populations from the Brazilian Amazon and Colombia. The genetic distance among populations from the Brazilian Amazon and Colombia is ranges from 0.047 to 0.148, with the highest values between the Brazilian Amazon and Sitronela (SIT) (0.125-0.148). These results are consistent with those observed among members of anopheline species complexes. It is suggested that geographic isolation has reduced the gene flow, resulting in the genetic divergence of the SIT population. Dendrogram analysis showed three large groups: one Amazonian and two Colombia, indicating some genetic structuring. The present study is important because it attempted to clarify the taxonomic status of A. nuneztovari and provide a better understanding of the role of this mosquito in transmission of human malaria in northern South America.

Aconitate Hydratase↗
PubMed1998

Ecologic observations on anopheline vectors of malaria in the Brazilian Amazon.

Human intervention in the Brazilian Amazon region promotes contacts between humans and vectors that may favor the propagation of anopheline mosquitoes and the spread of malaria in the absence of planning and infrastructure to control this disease. Vector ecology studies were carried out to determine the risk areas. These data should help in designing appropriate malaria control measures. Data from 14 different regions are reported. Vectors are able to adapt to different environments, which made it necessary to study each area. The parameters studied were Anopheles breeding sites, species distribution, incidence, feeding preferences, hours of maximum activity of adult mosquitoes, seasonality, resting places, and the presence of Plasmodium. Species complexes were also studied. Anopheles darlingi may be responsible for maintaining malaria in human populations in this region. A reduction in the population density of A. darlingi in a particular geographic area can sometimes cause the disappearance of malaria. This species feeds at night but has a peak of activity at the beginning of the evening and another at dawn. Other species are mainly crepuscular and all anophelines demonstrated pronounced exophilia. The timing of feeding activities was found to vary in areas altered by human intervention and also depended on the time of the year and climatic conditions. The larvae were more abundant in the rivers with a less acidic pH and rural areas showed the highest larval index.

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PubMed1996

Biology of Amazonian anopheline. XX. Ontogeny of esterases, leucine aminopeptidase and alpha-glycerophosphate dehydrogenase in Anopheles (Nyssorhynchus) darlingi Root, 1926 (Diptera, Culicidae).

The esterases, leucine aminopeptidase and alpha-glycerophosphate dehydrogenase revealed modifications in gene expressions during the development of Anopheles darlingi. The esterases showed five activity bands, 1 and 2 being more deeply stained during the larval stages than in pupae or adults, esterases 3 and 4 more deeply stained in pupae and adults whereas esterase 5 was present throughout development. Leucine aminopeptidase showed five activity bands: LAP2 and LAP5 were characteristic of larvae, LAP3 was specific for pupae and adults, LAP4 was detected only in pupae, and LAP1 and LAP6 were detected in all stages. alpha-Glycerophosphate dehydrogenase presented one activity band on starch gel whose intensity increased with development. Two activity bands were detected on polyacrylamide gel (alpha-GPDH1 and alpha-GPDH2) in 4th-instar larvae (old pigmented larvae) and this activity increased with development.

Animals↗
PubMedDate not supplied

The control of anopheline mosquitos by the spraying of Deltamethrin on raffia curtains used in miners' huts in areas endemic for malaria.

The residual potential of an aqueous solution of Deltamethrin (FW 25 mg i.a./m) was evaluated on raffia curtains. These are sheets of synthetic material used in the construction of huts to house miners. Experiments were conducted during 420 days and the curtains were always rolled up in the daytime and unrolled in late afternoon. Data analyzed by logarithmic regression indicated that raffia treated with Deltamethrin had higher mortality indices than that covered with DDT. The residual capacity of Deltamethrin on raffia was high. The mortality percentage was above 85% after 360 days and dropped to about 50% at 420 days. The effect of DDT was reduced after 180 days and reached zero by the end of the experiment. Based or the results of these experiments, it is recommended that Deltamethrin be used to spray raffia curtains in mining regions and other areas that are endemic for malaria.

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PubMedDate not supplied

Larvicidal activity of Bacillus sphaericus 2362 against Anopheles nuneztovari, Anopheles darlingi and Anopheles braziliensis (Diptera, Culicidae).

In this present study, preliminary data was obtained regarding the mortality rate of the Amazonian anophelines, Anopheles nuneztovari, Anopheles darlingi and Anopheles braziliensis when subjected to treatment with Bacillus sphaericus strain 2362, the WHO standard strain. Initially, experiments were conducted to test the mortality rate of the three species of anopheline larvae. The third larval instar of An. nuneztovari and the second and third larval instars of An. darlingi proved to be the least susceptible. In other experiments, the same three mosquito species were tested with the standard strain 2362, An. nuneztovari was the least susceptible to this insect pathogen, while An. braziliensis was the most susceptible. This latter species showed a difference in the level of LC50 concentration, when compared to the former, of 2.4, 2.5 and 1.8 in readings taken 24, 48 and 72 hours after exposure to the bacillus.

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PubMedDate not supplied

Malaria vectors in the Brazilian amazon: Anopheles of the subgenus Nyssorhynchus.

Various species of Anopheles (Nyssorhynchus) were studied in the Amazon with the objective of determining their importance as malaria vectors. Of the 33 known Anopheles species occurring in the Amazon, only 9 were found to be infected with Plasmodium. The different species of this subgenus varied both in diversity and density in the collection areas. The populations showed a tendency towards lower density and diversity in virgin forest than in areas modified by human intervention. The principal vector, An. darlingi, is anthropophilic with a continuous activity cycle lasting the entire night but peaking at sunset and sunrise. These species (Nyssorhynchus) are peridomiciliary, entering houses to feed on blood and immediately leaving to settle on nearby vegetation. Anopheles nuneztovari proved to be zoophilic, crepuscular and peridomiciliary. These habits may change depending on a series of external factors, especially those related to human activity. There is a possibility that sibling species exist in the study area and they are being studied with reference to An. darlingi, An. albitarsis and An. nuneztovari. The present results do not suggest the existence of subpopulations of An. darlingi in the Brazilian Amazon.

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PubMedDate not supplied

Studies on the Bacillus sphaericus larvicidal activity against malarial vector species in Amazonia.

In this work, bioassays were carried out in laboratory conditions (average temperature 26 +/- 2 degrees C) to test ten strains of Bacillus sphaericus, isolated from Brazilian soils against third instar larvae from anopheline species recorded as malaria vectors in Amazonian-Anopheles nuneztovari and An. darlingi. With the former mosquito, three strains--S2, S20 and S46 showed relative activity, in 24 and 48 hr exposure to the B. spahericus strains. With the latter only the S2 and S20 were effective in the 48 hr reading. The studied strains that showed the most adequate response in the Amazonian region were S2 and S20 showing broader and more efficient results. Therefore, S2 was the most effective when the 24 and 48 hr readings were considered, because it showed the greatest relative activity values.

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