Urban heat islands are characterized by high land surface temperature, low humidity, and poor vegetation, and considered to favor the transmission of the mosquito-borne dengue fever that is transmitted by the Aedes aegypti mosquito. We analyzed the recorded dengue incidence in Sao Paulo city, Brazil, in 2010-2011, in terms of multiple environmental and socioeconomic variables. Geographical information systems, thermal remote sensing images, and census data were used to classify city areas according to land surface temperature, vegetation cover, population density, socioeconomic status, and housing standards. Of the 7415 dengue cases, a majority (93.1%) mapped to areas with land surface temperature >28°C. The dengue incidence rate (cases per 100,000 inhabitants) was low (3.2 cases) in high vegetation cover areas, but high (72.3 cases) in low vegetation cover areas where the land surface temperature was 29±2°C. Interestingly, a multiple cluster analysis phenogram showed more dengue cases clustered in areas of land surface temperature >32°C, than in areas characterized as low socioeconomic zones, high population density areas, or slum-like areas. In laboratory experiments, A. aegypti mosquito larval development, blood feeding, and oviposition associated positively with temperatures of 28-32°C, indicating these temperatures to be favorable for dengue transmission. Thus, among all the variables studied, dengue incidence was most affected by the temperature.

BackgroundThe ability to successfully identify and incriminate pathogen vectors is fundamental to effective pathogen control and management. This task is confounded by the existence of cryptic species complexes. Molecular markers can offer a highly effective means of species identification in such complexes and are routinely employed in the study of medical entomology. Here we evaluate a multi-locus system for the identification of potential malaria vectors in the Anopheles strodei subgroup.MethodsLarvae, pupae and adult mosquitoes (n = 61) from the An. strodei subgroup were collected from 21 localities in nine Brazilian states and sequenced for the COI, ITS2 and white gene. A Bayesian phylogenetic approach was used to describe the relationships in the Strodei Subgroup and the utility of COI and ITS2 barcodes was assessed using the neighbor joining tree and “best close match” approaches.ResultsBayesian phylogenetic analysis of the COI, ITS2 and white gene found support for seven clades in the An. strodei subgroup. The COI and ITS2 barcodes were individually unsuccessful at resolving and identifying some species in the Subgroup. The COI barcode failed to resolve An. albertoi and An. strodei but successfully identified approximately 92% of all species queries, while the ITS2 barcode failed to resolve An. arthuri and successfully identified approximately 60% of all species queries. A multi-locus COI-ITS2 barcode, however, resolved all species in a neighbor joining tree and successfully identified all species queries using the “best close match” approach.ConclusionsOur study corroborates the existence of An. albertoi, An. CP Form and An. strodei in the An. strodei subgroup and identifies four species under An. arthuri informally named A-D herein. The use of a multi-locus barcode is proposed for species identification, which has potentially important utility for vector incrimination. Individuals previously found naturally infected with Plasmodium vivax in the southern Amazon basin and reported as An. strodei are likely to have been from An. arthuri C identified in this study.

The field of morphometrics is developing quickly. Recent advances have enabled geometric techniques to be applied to many zoological problems, particularly those involving epidemiologically-relevant mosquitoes. Herein, we briefly introduce geometric morphometric (GM) techniques and then review selected groups of mosquitoes (Culicidae) to which those techniques have been applied. In most of the reviewed cases, GM was capable of satisfactorily discriminating among the tested groups primarily when the studies considered differences within and among species, sexual dimorphism, treatments and the separation of laboratory strains. Although GM approaches have developed quite rapidly, some caution must be taken during data processing for a reliable biometrical approach, such as allometry and asymmetry analyses, scale removal and wing clarification staining for landmark digitization. We also critically forecast directions in this field and discuss how the creation of image databases should enhance species identification in culicids.

Background Mosquito larvae feed on organic detritus from the environment, particularly microorganisms comprising bacteria, protozoa, and algae as well as crustaceans, plant debris, and insect exuviae. Little attention has been paid to nutritional studies in Aedes aegypti larvae. Objectives We investigated the effects of yeast, bacteria and microalgae diets on larval development, pupation time, adult size, emergence, survivorship, lifespan, and wing morphology. Materials and Methods Microorganisms (or Tetramin ® as control) were offered as the only source of food to recently hatched first instar larvae and their development was followed until the adult stage. Protein, carbohydrate, glycogen, and lipid were analyzed in single larvae to correlate energetic reserve accumulation by larva with the developmental rates and nutritional content observed. FITC-labeled microorganisms were offered to fourth instar larvae, and its ingestion was recorded by fluorescence microscopy and quantitation. Results and Discussion Immature stages developed in all diets, however, larvae fed with bacteria and microalgae showed a severe delay in development rates, pupation time, adult emergence and low survivorship. Adult males emerged earlier as expected and had longer survival than females. Diets with better nutritional quality resulted in adults with bigger wings. Asaia sp. and Escherichia coli resulted in better nutrition and developmental parameters and seemed to be the best bacterial candidates to future studies using symbiont-based control. The diet quality was measured and presented different protein and carbohydrate amounts. Bacteria had the lowest protein and carbohydrate rates, yeasts had the highest carbohydrate amount and microalgae showed the highest protein content. Larvae fed with microalgae seem not to be able to process and store these diets properly. Larvae were shown to be able to process yeast cells and store their energetic components efficiently. Conclusion Together, our results point that Ae. aegypti larvae show high plasticity to feed, being able to develop under different microorganism-based diets. The important role of Ae. aegypti in the spread of infectious diseases requires further biological studies in order to understand the vector physiology and thus to manage the larval natural breeding sites aiming a better mosquito control.

BackgroundSexual dimorphism in animals has been studied from different perspectives for decades. In 1874 Darwin hypothesized that it was related to sexual selection, and even after nearly 140 years, when additional empirical data has become available and the subject has been investigated from a contemporary viewpoint, this idea is still supported. Although mosquito (Culicidae) wings are of great importance as they play a sex-specific role, little is known about wing sexual dimorphism in these pathogen-vector insects. Detection and characterization of wing sexual dimorphism in culicids may indirectly enhance our knowledge of their epidemiology or reveal sex-linked genes, aspects that have been discussed by vector control initiatives and developers of genetically modified mosquitoes.MethodsUsing geometric morphometrics, we carried out a comparative assessment of wing sexual dimorphism in ten culicid species of medical/veterinary importance from genera Culex, Aedes, Anopheles and Ochlerotatus collected in Brazil.ResultsDiscriminant analysis revealed significant sexual dimorphism in all the species studied, indicating that phenotypic expression of wing shape in mosquitoes is indeed sex-specific. A cross-validated test performed to reclassify the sexes with and without allometry yielded very similar results. Mahalanobis distances among the ten species showed that the species had different patterns of shape sexual dimorphism and that females are larger than males in some species.ConclusionWing morphology differed significantly between species. The finding of sexual dimorphism in all the species would suggest that the wing geometry of Culicidae is canalized. Although sexual dimorphism is prevalent, species-specific patterns occur. Allometry was not the main determinant of sexual dimorphism, which suggests that sexual selection or other evolutionary mechanisms underlie wing sexual dimorphism in these insects.

BackgroundAnopheles (Kerteszia) cruzii is a primary vector of Plasmodium parasites in Brazil’s Atlantic Forest. Adult females of An. cruzii and An. homunculus, which is a secondary malaria vector, are morphologically similar and difficult to distinguish when using external morphological characteristics only. These two species may occur syntopically with An. bellator, which is also a potential vector of Plasmodium species and is morphologically similar to An. cruzii and An. homunculus. Identification of these species based on female specimens is often jeopardised by polymorphisms, overlapping morphological characteristics and damage caused to specimens during collection. Wing geometric morphometrics has been used to distinguish several insect species; however, this economical and powerful tool has not been applied to Kerteszia species. Our objective was to assess wing geometry to distinguish An. cruzii, An. homunculus and An. bellator.MethodsSpecimens were collected in an area in the Serra do Mar hotspot biodiversity corridor of the Atlantic Forest biome (Cananeia municipality, State of Sao Paulo, Brazil). The right wings of females of An. cruzii (n= 40), An. homunculus (n= 50) and An. bellator (n= 27) were photographed. For each individual, 18 wing landmarks were subjected to standard geometric morphometrics. Discriminant analysis of Procrustean coordinates was performed to quantify wing shape variation.ResultsIndividuals clustered into three distinct groups according to species with a slight overlap between representatives of An. cruzii and An. homunculus. The Mahalanobis distance between An. cruzii and An. homunculus was consistently lower (3.50) than that between An. cruzii and An. bellator (4.58) or An. homunculus and An. bellator (4.32). Pairwise cross-validated reclassification showed that geometric morphometrics is an effective analytical method to distinguish between An. bellator, An. cruzii and An. homunculus with a reliability rate varying between 78-88%. Shape analysis revealed that the wings of An. homunculus are narrower than those of An. cruzii and that An. bellator is different from both of the congeneric species.ConclusionIt is possible to distinguish among the vectors An. cruzii, An. homunculus and An. bellator based on female wing characteristics.

Variation among natural populations of Culex (Culex) Key words: Culex pipiens complex -Culex quinquefasciatus -clines -molecular identification -wing morphologyThe Culex (Culex) pipiens complex in the Americas is composed of two main species, Culex (Culex) quinquefasciatus Say, which is adapted to tropical zones and Cx. pipiens L., which is found in temperate zones. In intermediate areas, these two members can mate yielding hybrids and intermediate forms (Barr 1957), through the processes of gene flow and introgression (Humeres et al. 1998, McAbee et al. 2008, Kothera et al. 2009). Mosquitoes of the Cx. pipiens complex are potential vectors of filarid worms in tropical and subtropical areas (Bockarie et al. 2009) and diverse arboviruses, including West Nile virus (Apperson et al. 2004, Cook et al. 2006.Adult females and immature stages of the Cx. pipiens complex are morphologically similar. The differentiation of adult males can be made by analysis of genitalia, which includes measuring the DV/D ratio of the dorsal arms of the aedeagus in the phallosome, as reported by Sundararaman (1949). Because members of the Cx. pipiens complex have a broad geographical distribution, other phenotypical differences beyond those of the male genitalia can be found. For example, some wing characters can also been used for morphologic identification of mosquito species.Financial support: FAPESP (05/50225-2, 06/02622-5) SAM and CM contributed equally to this work (FAPESP 06/57272-9 and 07/1665-5, respectively The taxonomic keys compiled by Forattini (2002) compared wing morphology of adult females. In that report, the subcosta vein (Sc) was reported to bind with the costa vein (C) before the bifurcation of the radial 2+3 vein (R 2+3 ) in Cx. quinquefasciatus, whereas in Cx. pipiens, the Sc vein binds to vein C at the same point or beyond the R 2+3 bifurcation. To our knowledge, these findings have not been investigated in other geographically distant populations. Linam and Nielsen (1962) reported that Bekku (1956), in Northern Japan, also attempted to use wing characteristics [the length of radial cell R 2 (second marginal cell) divided by the length of vein R 3 ] to distinguish adults of the pipiens group. The results of Bekku (1956) were inconclusive, which was later explained when Kamura (1958) found that these particular wing measurements varied with the temperature of the environment. Nielsen and Rees (1961) and Linam and Nielsen (1962) reported that the most reliable method of separating females of Cx. pipiens and Cx. quinquefasciatus was by a wing measurement value obtained by dividing the length of the cell R 2 by the length of the vein R 2+3 (R 2 /R 2+3 ratio). These authors reported the value of this ratio to be about 5.0 in Cx. pipiens and 3.0 or less in Cx. quinquefasciatus, with intermediate values present in the hybrids. However, these studies did not evaluate morphometric data among mosquito populations and climatic/geographic gradients.In insects, the phenotypic variations among members of species complexes have...

BackgroundBrazil is a tropical country that is largely covered by rainforests and other natural ecosystems, which provide ideal conditions for the existence of many arboviruses. However, few analyses have examined the associations between environmental factors and arboviral diseases. Thus, based on the hypothesis of correlation between environment and epidemiology, the proposals of this study were (1) to obtain the probability of occurrence of Oropouche, Mayaro, Saint Louis and Rocio fevers in Brazil based on environmental conditions corresponding to the periods of occurrence of the outbreaks; (2) to describe the macroclimatic scenario in Brazil in the last 50 years, evaluating if there was any detectable tendency to increase temperatures and (3) to model future expansion of those arboviruses in Brazil based on future temperature projections.Methodology/Principal findingsOur model assessed seven environmental factors (annual rainfall, annual temperature, elevation, seasonality of temperature, seasonality of precipitation, thermal amplitude, and daytime temperature variation) for their association with the occurrence of outbreaks in the last 50 years. Our results suggest that various environmental factors distinctly influence the distribution of each arbovirus, with temperature being the central determinant of disease distribution in all high-risk areas. These areas are subject to change, since the average temperature of some areas has increased significantly over the time.Conclusions/SignificanceThis is the first spatio-temporal study of the Oropouche, Mayaro, Saint Louis, and Rocio arboviruses, and our results indicate that they may become increasingly important public health problems in Brazil. Thus, next studies and control programs should include these diseases and also take into consideration key environmental elements.