Carla A Sousa

New University of Lisbon, Lisboa, Lisbon, Portugal

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Publications (46)91.23 Total impact

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    ABSTRACT: http://www.ihmt.unl.pt/images/uploaded/news/Resumo_GoncaloSeixas.pdf
    5as Jornadas Científicas do IHMT, Lisboa, Portugal; 12/2014
  • Ricardo Parreira, Carla A Sousa
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    ABSTRACT: Dengue virus (DENV) is the arbovirus with the widest impact on human health. Although its dispersal is partially conditioned by environmental constraints that limit the distribution of its main vector (Aedes aegypti), DENV has been spreading geographically in recent times, but mostly afflicting tropical and subtropical regions. With no prophylactic vaccine or specific therapeutics available, vector control remains the best alternative to restrain its circulation. Moreover, the establishment of thriving vector populations in peri urban environments brings humans and viruses together, opening the possibility for the occurrence of unexpected outbreaks. Europe is no exception: such was the case of Madeira in 2012. In addition to its impact on the health of the local population, health services, and economy, this outbreak revealed how difficult it may be to control the circulation of pathogenic arboviruses, especially taking into consideration that Europe is already partially colonized by another DENV vector, Aedes albopictus.
    Expert Review of Anti-infective Therapy 11/2014; · 3.06 Impact Factor
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    ABSTRACT: The malaria vector Anopheles arabiensis exhibits greater behavioural and ecological plasticity than the other major vectors of the Anopheles gambiae complex, which presents challenges for major control methods. This study reports for the first time the presence of An. arabiensis in Antula, a suburb of Bissau city, the capital of Guinea Bissau, where high levels of hybridization between Anopheles coluzzii and An. gambiae have been reported. Given that previous surveys in the area, based on indoor collections, did not sample An. arabiensis, the possibility of a recently introduced exophilic population was investigated.
    Malaria Journal 11/2014; 13(1):423. · 3.49 Impact Factor
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    ABSTRACT: Dengue is a vector-borne disease and 40% of world population is at risk. Dengue transcends international borders and can be found in tropical and subtropical regions around the world, predominantly in urban and semi-urban areas. A model for dengue disease transmission, composed by mutually-exclusive compartments representing the human and vector dynamics, is presented in this study. The data is from Madeira, a Portuguese island, where an unprecedented outbreak was detected on October 2012. The aim of this work is to simulate the repercussions of the control measures in the fight of the disease.
    09/2014;
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    ABSTRACT: In 2005, The Institute of Hygiene and Tropical Medicine received from the Natural History Museum of Madeira a sample of mosquitoes collected in the island, following complaints of the local inhabitants about a highly nuisance mosquito. These mosquitoes were identified as Aedes aegypti, the first report of this important arbovirus vector in the island. After this report, it took less than 8 years until a Dengue epidemic occurred in the island. The first cases were detected in October 2012 and the epidemic lasted for 20 weeks counting over 2,000 reported cases with no fatalities. Since 2009, IHMT has been participating in the monitoring of A. aegypti in Madeira. Studies involve monitoring of mosquito dispersal and abundance, bioecological characterizations, insecticide resistance profiling and genetic analyses. Here we present an update of the ongoing studies, with emphasis on the levels of insecticide resistance and its mechanisms, and molecular genetic analysis aiming at establishing the origin of this mosquito population. Insecticide susceptibility assays have shown a highly resistant A. aegypti population with mortality rates below 80% for pyrethroid and organochlorine (DDT) insecticides. Genetic analysis of the voltage-gated sodium channel gene revealed a high frequency of the knockdown resistance (kdr) associated mutation F1534C. An additional mutation, V1016I, was also detected at frequencies up to 23%. Phylogenetic analysis based on mtDNA genes suggest a South American origin for this vector population, possibly from Brazil or Venezuela, two countries with important migrant flows with Madeira island.
    Amazonian Conference on Emerging and Infectious Diseases (ACEID) - STRONGER Project, Cayenne, French Guiana; 09/2014
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    ABSTRACT: Background: Aedes aegypti is the mosquito vector of dengue, the most significant mosquito-borne viral diseases in the world. Due to the lack of antiviral therapy or vaccination, reducing dengue transmission depends only on mosquito control. In the archipelago of Cape Verde (West Africa) in November 2009 a dengue epidemic was declared with more than 20000 people affected and six deaths. The presence of A. aegypti in the archipelago was reported since 1931. Objectives: To evaluate the genetic variability and effective population size of A. aegypti populations from Cape Verde before and after the dengue outbreak. Methods: We analysed two mosquito samples from Santiago island collected before and after the dengue outbreak (N=47 in 2007 and N=24 in 2010, respectively) and genotyped them for 14 microsatellites. Parameters of genetic diversity and population differentiation were assessed with the softwares Genepop and Arlequin 3.5. NeEstimator and Bottleneck softwares were used to estimate effective population size (Ne) and detect population changes, respectively. We also used a Bayesian clustering method (software Structure) to evaluate patterns of population structure. Results: Mean over loci allelic richness and expected heterozygosity was 5 and 0.7, respectively in both temporal samples. Ne was smaller in 2010 (Ne=16) than in 2007 (Ne=8), and we detected a bottleneck effect in 2010. The two samples were significantly differentiated, and Bayesian clustering analysis detected two clusters (k=2) corresponding to each temporal sample. Conclusion: We have found comparable levels of genetic diversity between collection years, within the range of values for other African populations. However, there was significant inter-temporal genetic differentiation associated with a signal of population bottleneck and a reduction in effective population size. Results will be discussed with respect to the epidemiology of dengue and control efforts in the archipelago.
    Amazonian Conference on Emerging and Infectious Diseases (ACEID) - STRONGER Project, Cayenne, French Guiana; 09/2014
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    ABSTRACT: Aedes aegypti is the most important mosquito vector of dengue and yellow fever, two of the most significant mosquito-borne viral diseases in the world. Due to the lack of antiviral therapy or vaccination, reducing dengue transmission depends only on mosquito control. In the archipelago of Cape Verde (West Africa) in November 2009 a dengue epidemic was declared with more than 20,000 people affected, 174 hemorrhagic fever cases and six deaths. The presence of Ae. aegypti in the archipelago was reported since 1931. In this study we aim to clarify the origins and population history of Ae. aegypti in Cape Verde by analyzing the variability of the mitochondrial gene NADH dehydrogenase subunit 4 (ND4). We analyzed 42 mosquitoes from three islands (Santiago, Brava and Fogo) collected before and after the dengue outbreak (2007/2010). ND4 sequences of 360bp revealed seven haplotypes, three of which are Cape Verde specific (haplotype diversity =0.637 and nucleotide diversity =0.002). All haplotypes were closely related and formed a star-like structure typical of expanded populations. In a comparison with 194 published haplotypes (including 6 African Aedes sp. outgroups), sequences from Cape Verde occurred in a basal clade mainly associated with West African mosquito populations. Our results suggest a high genetic diversity and a West African origin for this insular mosquito population. We found no evidence of new recent founder events that could be associated with the unique dengue outbreak in 2009.
    19th International BioInformatics Workshop on Virus Evolution and Molecular Epidemiology, National Institute for Infectious Diseases L: Spallanzani, Rome, Italy; 09/2014
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    César Capinha, Jorge Rocha, Carla A Sousa
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    ABSTRACT: Aedes aegypti is the main vector of dengue and a number of other diseases worldwide. Because of the domestic nature of this mosquito, the relative importance of macroclimate in shaping its distribution has been a controversial issue. We have captured here the worldwide macroclimatic conditions occupied by A. aegypti in the last century. We assessed the ability of this information to predict the species' observed distribution using supra-continental spatially-uncorrelated data. We further projected the distribution of the colonized climates in the near future (2010-2039) under two climate-change scenarios. Our results indicate that the macroclimate is largely responsible for setting the maximum range limit of A. aegypti worldwide and that in the near future, relatively wide areas beyond this limit will receive macroclimates previously occupied by the species. By comparing our projections, with those from a previous model based strictly on species-climate relationships (i.e., excluding human influence), we also found support for the hypothesis that much of the species' range in temperate and subtropical regions is being sustained by artificial environments. Altogether, these findings suggest that, if the domestic environments commonly exploited by this species are available in the newly suitable areas, its distribution may expand considerably in the near future.
    EcoHealth 03/2014; · 2.27 Impact Factor
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    ABSTRACT: Malaria was endemic in Europe for more than two millennia until its eradication inthe1970s. Recent autochthonous cases registered in Greece have increased the awareness regarding the threat of malaria re-emergence in Southern Europe. Currently, the presence of competent vectors, suitable environmental conditions and the evidences of a changing climate may increase the widespread re-emergence of malaria in Southern Europe. This work focused on determining the current relationships between environmental factors and the density of the former malaria vector Anopheles atroparvus in Portugal, a previously endemic country. Adult females were sampled and vector density was estimated in 22 sites in Southern Portugal between 2001 and 2010 and related with land cover and satellite-derived air temperature and vegetation indices. The relationship between vector density and local larval habitat, temperature and, in a broader sense, to environmental suitability, was assessed using a statistical modelling approach. Results showed that present environmental conditions are suitable for vector development at high densities and the spatial and temporal patterns closely resemble the ones registered in the past endemic period. The use of satellite-derived data, together with statistical models, allowed the extrapolation of suitable environmental conditions for vector development from site-level to the Portuguese main land territory.This work also improved the baseline knowledge needed to understand the potential impacts of future environmental changes on vector density and, indirectly, on the risk of malaria re-emergence.
    Remote Sensing of Environment 02/2014; 145:116-130. · 4.77 Impact Factor
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    ABSTRACT: Community participation is mandatory in the prevention of Dengue outbreaks. Taking public views into account is crucial to guide more effective planning and quicker community participation in preventing campaigns. This study aims to assess community perceptions of Madeira population in order to explore their involvement in the A. aegypti's control and reinforce health-educational planning. Due to the lack of accurate methodologies for measuring perception, a new tool to assess the community's perceptions was built. A cross-sectional survey was performed in the Island's aegypti-infested area, exploring residents' perceptions regarding most critical community behaviour: aegypti-source reduction and their domestic aegypti-breeding sites. A novel tool defining five essential topics which underlie the source reduction's awareness and accession was built, herein called Essential-Perception (EP) analysis. Of 1276 individuals, 1182 completed the questionnaire (92 . 6%). EP-Score analysis revealed that community's perceptions were scarce, inconsistent and possibly incorrect. Most of the population (99 . 6%) did not completely understood the five essential topics explored. An average of 54 . 2% of residents only partially understood each essential topic, revealing inconsistencies in their understanding. Each resident apparently believed in an average of four false assumptions/myths. Significant association (p[modifier letter left arrowhead]0.001) was found between both the EP-Score level and the domestic presence of breeding sites, supporting the validity of this EP-analysis. Aedes aegypti's breeding sites, consisting of decor/leisure containers, presented an atypical pattern of infestation comparing with dengue prone regions. The studied population was not prepared for being fully engaged in dengue prevention. Evidences suggest that EP-methodology was efficient and accurate in assessing the community perception and its compliance to practices. Moreover, it suggested a list of myths that could persist in the community. This is the first study reporting an aegypti-entomological pattern and community's perception in a developed dengue-prone region. Tailored messages considering findings of this study are recommended to be used in future campaigns in order to more effectively impact the community perception and behaviour.
    BMC Public Health 01/2014; 14(1):39. · 2.32 Impact Factor
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    ABSTRACT: Malaria was endemic in Europe for more than two millennia until its eradication in the 1970s. Recent autochthonous cases registered in Greece have increased the awareness regarding the threat of malaria re-emergence in Southern Europe. Currently, the presence of competent vectors, suitable environmental conditions and the evidences of a changing climate may increase the widespread re-emergence of malaria in Southern Europe. This work focused on determining the current relationships between environmental factors and the density of the former malaria vector Anopheles atroparvus in Portugal, a previously endemic country. Adult females were sampled and vector density was estimated in 22 sites in Southern Portugal between 2001 and 2010 and related with land cover and satellite-derived air temperature and vegetation indices. The relationship between vector density and local larval habitat, temperature and, in a broader sense, to environmental suitability, was assessed using a statistical modelling approach. Results showed that present environmental conditions are suitable for vector development at high densities and the spatial and temporal patterns closely resemble the ones registered in the past endemic period. The use of satellite-derived data, together with statistical models, allowed the extrapolation of suitable environmental conditions for vector development from site-level to the Portuguese mainland territory. This work also improved the baseline knowledge needed to understand the potential impacts of future environmental changes on vector density and, indirectly, on the risk of malaria re-emergence.
    Remote Sensing of Environment 01/2014; 145:116–130. · 4.77 Impact Factor
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    ABSTRACT: BACKGROUND: Two biological forms of the mosquito Culex pipiens s.s., denoted pipiens and molestus, display behavioural differences that may affect their role as vectors of arboviruses. In this study, the feeding patterns of molestus and pipiens forms were investigated in Comporta (Portugal), where high levels of inter-form admixture have been recorded. METHODS: Indoor and outdoor mosquito collections were performed in the summer of 2010. Collected Cx. pipiens s.l. females were molecularly identified to species and form by PCR and genotyped for six microsatellites. The source of the blood meal in post-fed females was determined by ELISA and mitochondrial DNA sequencing. RESULTS: The distribution of the forms differed according to the collection method. The molestus form was present only in indoor collections, whereas pipiens and admixed individuals were sampled both indoors and outdoors. In both forms, over 90% of blood meals were made on avian hosts. These included blood meals taken from Passeriformes (Passer domesticus and Turdus merula) by females caught resting inside domestic shelters. CONCLUSION: Genetic structure and blood meal analyses suggest the presence of a bird biting molestus population in the study area. Both forms were found to rest indoors, mainly in avian shelters, but at least a proportion of females of the pipiens form may bite outdoors in sylvan habitats and then search for anthropogenic resting sites to complete their gonotrophic cycle. This behaviour may potentiate the accidental transmission of arboviruses to humans in the region.
    Parasites & Vectors 04/2013; 6(1):93. · 3.25 Impact Factor
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    ABSTRACT: http://congressomedtrop.ihmt.unl.pt/files/Livro_Resumos/index.html#/2/zoomed
    2º Congresso Nacional de Medicina Tropical, IHMT, Lisboa, Portugal; 04/2013
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    ABSTRACT: The increasing population of Aedes aegypti mosquitoes on Madeira Island (Portugal) resulted in the first autochthonous dengue outbreak, which occurred in October 2012. Our study establishes the first genetic evaluation based on the mitochondrial DNA (mtDNA) genes [cytochrome oxidase subunit I (COI) and NADH dehydrogenase subunit 4 (ND4)] and knockdown resistance ( kdr ) mutations exploring the colonisation history and the genetic diversity of this insular vector population. We included mosquito populations from Brazil and Venezuela in the analysis as putative geographic sources. The Ae. aegypti population from Madeira showed extremely low mtDNA genetic variability, with a single haplotype for COI and ND4. We also detected the presence of two important kdr mutations and the quasi-fixation of one of these mutations (F1534C). These results are consistent with a unique recent founder event that occurred on the island of Ae. aegypti mosquitoes that carry kdr mutations associated with insecticide resistance. Finally, we also report the presence of the F1534C kdr mutation in the Brazil and Venezuela populations. To our knowledge, this is the first time this mutation has been found in South American Ae. aegypti mosquitoes. Given the present risk of Ae. aegypti re-invading continental Europe from Madeira and the recent dengue outbreaks on the island, this information is important to plan surveillance and control measures.
    Memórias do Instituto Oswaldo Cruz 01/2013; 108 Suppl 1:3-10. · 1.36 Impact Factor
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    ABSTRACT: Following the identification of two autochthonous cases of dengue type 1 on 3 October 2012, an outbreak of dengue fever has been reported in Madeira, Portugal. As of 25 November, 1,891 cases have been detected on the island where the vector Aedes aegypti had been established in some areas since 2005. This event represents the first epidemic of dengue fever in Europe since 1928 and concerted control measures have been initiated by local health authorities. On 3 October 2012, two autochthonous cases of dengue fever were laboratory confirmed in the Autonomous Region of Madeira (RAM), Portugal, following clinical suspicion of dengue, i.e. sudden onset of fever and influenza-like symptoms in patients without travel history to dengue-endemic regions. Laboratory tests performed by the National Institute of Health in Lisbon identified dengue virus serotype 1 (DENV-1) as causing agent. As of 25 November, the Institute of Health and Social Affairs (Instituto de Administração da Saúde e Assuntos Sociais, IASAUDE, RAM) in Madeira reported 1,891 cases of dengue fever. In this preliminary report we highlight the main features of the outbreak and the control measures taken.
    Euro surveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin 12/2012; · 4.66 Impact Factor
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    ABSTRACT: Portugal is a southern European country that displays favorable ecological conditions for the establishment of West Nile virus (WNV) transmission cycles. Competent mosquito vector species are present throughout the country. Among the species with reported cases of WNV isolation in Portugal, Culex pipiens is the most ubiquitous and abundant mosquito. This species exhibits two biological forms with differences in host preferences. The molestus form has a greater tendency to feed upon humans and other mammals whereas the pipiens form prefers avian hosts. In northern latitudes, both forms are physically separated, with molestus occupying underground habitats and pipiens being found aboveground. However, the warmer climatic conditions of southern regions such as Portugal may favor the sympatric occurrence of both forms hence promoting interform hybridization. Genetic introgression between molestus and pipiens forms may result in a higher propensity for admixed populations to serve as bridge-vectors of WNV between humans and birds. Here we revise our present knowledge on the distribution, role in WNV transmission and genetic structure of the Cx. pipiens complex in continental Portugal. We focus on recent findings of sympatric molestus and pipiens populations that display considerable levels of hybridization and discuss the epidemiological repercussions of this occurrence.
    Journal of the American Mosquito Control Association 12/2012; 28(4 Suppl):75-80. · 0.83 Impact Factor
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    ABSTRACT: The Culex pipiens complex includes two widespread mosquito vector species, Cx. pipiens and Cx. quinquefasciatus. The distribution of these species varies in latitude, with the former being present in temperate regions and the latter in tropical and subtropical regions. However, their distribution range overlaps in certain areas and interspecific hybridization has been documented. Genetic introgression between these species may have epidemiological repercussions for West Nile virus (WNV) transmission. Bayesian clustering analysis based on multilocus genotypes of 12 microsatellites was used to determine levels of hybridization between these two species in Macaronesian islands, the only contact zone described in West Africa. The distribution of the two species reflects both the islands' biogeography and historical aspects of human colonization. Madeira Island displayed a homogenous population of Cx. pipiens, whereas Cape Verde showed a more intriguing scenario with extensive hybridization. In the islands of Brava and Santiago, only Cx. quinquefasciatus was found, while in Fogo and Maio high hybrid rates (∼40%) between the two species were detected. Within the admixed populations, second-generation hybrids (∼50%) were identified suggesting a lack of isolation mechanisms. The observed levels of hybridization may locally potentiate the transmission to humans of zoonotic arboviruses such as WNV.
    Ecology and Evolution 08/2012; 2(8):1889-902. · 1.66 Impact Factor
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    ABSTRACT: Malaria is dependent on environmental factors and considered as potentially re-emerging in temperate regions. Remote sensing data have been used successfully for monitoring environmental conditions that influence the patterns of such arthropod vector-borne diseases. Anopheles atroparvus density data were collected from 2002 to 2005, on a bimonthly basis, at three sites in a former malarial area in Southern Portugal. The development of the Remote Vector Model (RVM) was based upon two main variables: temperature and the Normalized Differential Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra satellite. Temperature influences the mosquito life cycle and affects its intra-annual prevalence, and MODIS NDVI was used as a proxy for suitable habitat conditions. Mosquito data were used for calibration and validation of the model. For areas with high mosquito density, the model validation demonstrated a Pearson correlation of 0.68 (p<0.05) and a modelling efficiency/Nash-Sutcliffe of 0.44 representing the model's ability to predict intra- and inter-annual vector density trends. RVM estimates the density of the former malarial vector An. atroparvus as a function of temperature and of MODIS NDVI. RVM is a satellite data-based assimilation algorithm that uses temperature fields to predict the intra- and inter-annual densities of this mosquito species using MODIS NDVI. RVM is a relevant tool for vector density estimation, contributing to the risk assessment of transmission of mosquito-borne diseases and can be part of the early warning system and contingency plans providing support to the decision making process of relevant authorities.
    Journal of Vector Ecology 12/2011; 36(2):279-91. · 1.44 Impact Factor
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    ABSTRACT: There is a growing concern that global climate change will affect the potential for pathogen transmission by insect species that are vectors of human diseases. One of these species is the former European malaria vector, Anopheles atroparvus. Levels of population differentiation of An. atroparvus from southern Europe were characterized as a first attempt to elucidate patterns of population structure of this former malaria vector. Results are discussed in light of a hypothetical situation of re-establishment of malaria transmission. Genetic and phenotypic variation was analysed in nine mosquito samples collected from five European countries, using eight microsatellite loci and geometric morphometrics on 21 wing landmarks. Levels of genetic diversity were comparable to those reported for tropical malaria vectors. Low levels of genetic (0.004 <FST <0.086) and phenotypic differentiation were detected among An. atroparvus populations spanning over 3,000 km distance. Genetic differentiation (0.202 <FST <0.299) was higher between the sibling species An. atroparvus and Anopheles maculipennis s.s. Differentiation between sibling species was not so evident at the phenotype level. Levels of population differentiation within An. atroparvus were low and not correlated with geographic distance or with putative physical barriers to gene flow (Alps and Pyrenées). While these results may suggest considerable levels of gene flow, other explanations such as the effect of historical population perturbations can also be hypothesized.
    Malaria Journal 01/2011; 10:5. · 3.49 Impact Factor