Gabriel Zorello Laporta

Biodiversity Can Help Prevent Malaria Outbreaks in Tropical Forests

Background Plasmodium vivax is a widely distributed, neglected parasite that can cause malaria and death in tropical areas. It is associated with an estimated 80–300 million cases of malaria worldwide. Brazilian tropical rain forests encompass host- and vector-rich communities, in which two hypothetical mechanisms could play a role in the dynamics of malaria transmission. The first mechanism is the dilution effect caused by presence of wild warm-blooded animals, which can act as dead-end hosts to Plasmodium parasites. The second is diffuse mosquito vector competition, in which vector and non-vector mosquito species compete for blood feeding upon a defensive host. Considering that the World Health Organization Malaria Eradication Research Agenda calls for novel strategies to eliminate malaria transmission locally, we used mathematical modeling to assess those two mechanisms in a pristine tropical rain forest, where the primary vector is present but malaria is absent. Methodology/Principal Findings The Ross–Macdonald model and a biodiversity-oriented model were parameterized using newly collected data and data from the literature. The basic reproduction number () estimated employing Ross–Macdonald model indicated that malaria cases occur in the study location. However, no malaria cases have been reported since 1980. In contrast, the biodiversity-oriented model corroborated the absence of malaria transmission. In addition, the diffuse competition mechanism was negatively correlated with the risk of malaria transmission, which suggests a protective effect provided by the forest ecosystem. There is a non-linear, unimodal correlation between the mechanism of dead-end transmission of parasites and the risk of malaria transmission, suggesting a protective effect only under certain circumstances (e.g., a high abundance of wild warm-blooded animals). Conclusions/Significance To achieve biological conservation and to eliminate Plasmodium parasites in human populations, the World Health Organization Malaria Eradication Research Agenda should take biodiversity issues into consideration.

Habitat suitability of Anopheles vector species and association with human malaria in the Atlantic Forest in south-eastern Brazil

Every year, autochthonous cases of Plasmodium vivax malaria occur in low-endemicity areas of Vale do Ribeira in the south-eastern part of the Atlantic Forest, state of São Paulo, where Anopheles cruzii and Anopheles bellator are considered the primary vectors. However, other species in the subgenus Nyssorhynchus of Anopheles (e.g., Anopheles marajoara) are abundant and may participate in the dynamics of malarial transmission in that region. The objectives of the present study were to assess the spatial distribution of An. cruzii, An. bellator and An. marajoara and to associate the presence of these species with malaria cases in the municipalities of the Vale do Ribeira. Potential habitat suitability modelling was applied to determine both the spatial distribution of An. cruzii, An. bellator and An. marajoara and to establish the density of each species. Poisson regression was utilized to associate malaria cases with estimated vector densities. As a result, An. cruzii was correlated with the forested slopes of the Serra do Mar, An. bellator with the coastal plain and An. marajoara with the deforested areas. Moreover, both An. marajoara and An. cruzii were positively associated with malaria cases. Considering that An. marajoara was demonstrated to be a primary vector of human Plasmodium in the rural areas of the state of Amapá, more attention should be given to the species in the deforested areas of the Atlantic Forest, where it might be a secondary vector.

Insight into Anopheles (Nyssorhynchus) (Diptera: Culicidae) Species from Brazil

Abstract Anopheles (Nyssorhynchus) benarrochi s.l., Anopheles (Nyssorhynchus) oswaldoi s.l., and Anopheles (Nyssorhynchus) konderi s.l. collected in Acrelândia, state of Acre, Brazil, were identified based on morphological characters of the male genitalia, fourth-instar larvae, and pupae. Morphological variation was observed in the male genitalia of these species in comparison with specimens from other localities in Brazil. DNA sequence from the nuclear ribosomal second internal transcribed spacer of individuals identified as An. benarrochi s.l. by using male genitalia characteristics showed that the various morphological forms are conspecific but are distinct from An. benarrochi B from Colombia. Anopheles konderi s.l. and An. oswaldoi s.l. both misidentified as An. oswaldoi s.s. (Peryassú) throughout Brazil, may actually comprise at least two undescribed species. Diagnostic morphological characteristics of the male genitalia are provided to distinguish Anopheles benarrochi s.l., Anopheles oswaldoi s.l., and Anopheles konderi s.l. from morphologically similar species. Incrimination of An. oswaldoi s.s. in malaria transmission in Brazil needs further investigation because other undescribed species from Acre may have been confounded with this taxon.

Detection of Plasmodium falciparum and Plasmodium vivax subclinical infection in non-endemic region: implications for blood transfusion and malaria epidemiology

BackgroundIn Brazil, malaria is endemic in the Amazon River basin and non-endemic in the extra-Amazon region, which includes areas of São Paulo state. In this state, a number of autochthonous cases of malaria occur annually, and the prevalence of subclinical infection is unknown. Asymptomatic infections may remain undetected, maintaining transmission of the pathogen, including by blood transfusion. In these report it has been described subclinical Plasmodium infection in blood donors from a blood transfusion centre in São Paulo, Brazil.MethodsIn this cross-sectional study, representative samples of blood were obtained from 1,108 healthy blood donors at the Fundação Pró-Sangue Hemocentro de São Paulo, the main blood transfusion centre in São Paulo. Malaria exposure was defined by the home region (exposed: forest region; non-exposed: non-forest region). Real-time PCR was used to detect Plasmodium falciparum and Plasmodium vivax. Subclinical malaria cases were geo-referenced.ResultsEighty-four (7.41%) blood donors tested positive for Plasmodium; 57 of these were infected by P. falciparum, 25 by P. vivax, and 2 by both. The prevalence of P. falciparum and P. vivax was 5.14 and 2.26, respectively. The overall prevalence ratio (PR) was 3.23 (95% confidence interval (CI) 2.03, 5.13); P. falciparum PR was 16.11 (95% CI 5.87, 44.21) and P. vivax PR was 0.47 (95% CI 0.2, 1.12). Plasmodium falciparum subclinical malaria infection in the Atlantic Forest domain was present in the mountain regions while P. vivax infection was observed in cities from forest-surrounded areas.ConclusionsThe presence of Plasmodium in healthy blood donors from a region known as non-endemic, which is important in the context of transfusion biosafety, was described. Infected recipients may become asymptomatic carriers and a reservoir for parasites, maintaining their transmission. Furthermore, P. falciparum PR was positively associated with the forest environment, and P. vivax was associated with forest fragmentation.

Análise espacial e sazonal da leptospirose no município de São Paulo, SP, 1998 a 2006

OBJECTIVE To analyze the spatial and seasonal distribution of leptospirosis and identify possible ecological and social components of its transmission. METHODS A total of 2,490 cases registered in each district of the municipality of São Paulo, Southeastern Brazil, between 1998 and 2006, were georeferenced. The data were obtained from the Notifiable Diseases Information System. Thematic maps were made, showing the variables of incidence rate, lethality rate, literacy rate, average monthly income, number of residents per household, water supply and sewage system. To identify spatial patterns (dispersed, clustered or random), these variables were analyzed using the global and local Moran indices. Spearmans correlation coefficient was used to test associations between variables with clustered spatial patterns. RESULTS Clustered spatial patterns were observed for the variables of leptospirosis incidence, literacy rate, average monthly income, number of residents per household, water supply and sewage system. There were 773 notified cases in the dry season and 1,717 cases in the rainy season. The incidence and lethality rates correlated with the populations socioeconomic conditions, independently of the period. CONCLUSIONS Leptospirosis is spread throughout the municipality of São Paulo, and its incidence increases during the rainy season. In the dry season, the localities where cases appear coincide with the areas of poorest housing conditions. In the rainy season, it also increases in other districts, probably due to the proximity of rivers and streams.OBJETIVO: Analisar a distribuicao espacial e sazonal da leptospirose, identificando possiveis componentes ecologicos e sociais para a sua transmissao. METODOS: Foram georreferenciados 2.490 casos em cada distrito do municipio de Sao Paulo, SP, registrados de 1998 a 2006. Os dados foram obtidos do Sistema de Informacao de Agravos de Notificacao. Foram realizados mapas tematicos com as variaveis taxa de incidencia, letalidade, taxa de alfabetizacao, renda media mensal, numero de moradores por domicilio, abastecimento de agua e rede de esgoto. Para identificar o padrao espacial (disperso, em aglomerado ou randomico), foram analisadas pelo Indice de Moran global e local. Foi utilizado o coeficiente de correlacao de Spearman para testar associacoes entre as variaveis com padrao espacial em aglomerados. RESULTADOS: O padrao espacial em aglomerados foi observado nas variaveis taxa de incidencia de leptospirose, taxa de alfabetizacao, renda media mensal, numero de moradores por domicilio, abastecimento de agua e rede de esgoto. Foram notificados 773 casos no periodo seco e 1.717 no umido. A incidencia e a letalidade estao correlacionadas com as condicoes socioeconomicas da populacao, independentemente do periodo. CONCLUSOES: A leptospirose esta distribuida por todo o municipio de Sao Paulo e sua incidencia aumenta no periodo das chuvas. No periodo seco, os locais de aparecimento dos casos coincidem com as areas de piores condicoes de moradia e, durante o periodo umido, tambem aumenta em outros distritos, provavelmente devido a proximidade de rios e corregos.

Mosquito (Diptera: Culicidae) assemblages associated with Nidularium and Vriesea bromeliads in Serra do Mar, Atlantic Forest, Brazil

BackgroundThe most substantial and best preserved area of Atlantic Forest is within the biogeographical sub-region of Serra do Mar. The topographic complexity of the region creates a diverse array of microclimates, which can affect species distribution and diversity inside the forest. Given that Atlantic Forest includes highly heterogeneous environments, a diverse and medically important Culicidae assemblage, and possible species co-occurrence, we evaluated mosquito assemblages from bromeliad phytotelmata in Serra do Mar (southeastern Brazil).MethodsLarvae and pupae were collected monthly from Nidularium and Vriesea bromeliads between July 2008 and June 2009. Collection sites were divided into landscape categories (lowland, hillslope and hilltop) based on elevation and slope. Correlations between bromeliad mosquito assemblage and environmental variables were assessed using multivariate redundancy analysis. Differences in species diversity between bromeliads within each category of elevation were explored using the Renyi diversity index. Univariate binary logistic regression analyses were used to assess species co-occurrence.ResultsA total of 2,024 mosquitoes belonging to 22 species were collected. Landscape categories (pseudo-F value = 1.89, p = 0.04), bromeliad water volume (pseudo-F = 2.99, p = 0.03) and bromeliad fullness (Pseudo-F = 4.47, p < 0.01) influenced mosquito assemblage structure. Renyi diversity index show that lowland possesses the highest diversity indices. The presence of An. homunculus was associated with Cx. ocellatus and the presence of An. cruzii was associated with Cx. neglectus, Cx. inimitabilis fuscatus and Cx. worontzowi. Anopheles cruzii and An. homunculus were taken from the same bromeliad, however, the co-occurrence between those two species was not statistically significant.ConclusionsOne of the main findings of our study was that differences in species among mosquito assemblages were influenced by landscape characteristics. The bromeliad factor that influenced mosquito abundance and assemblage structure was fullness. The findings of the current study raise important questions about the role of An. homunculus in the transmission of Plasmodium in Serra do Mar, southeastern Atlantic Forest.

Spatial and seasonal analysis on leptospirosis in the municipality of São Paulo, Southeastern Brazil, 1998 to 2006

OBJECTIVE To analyze the spatial and seasonal distribution of leptospirosis and identify possible ecological and social components of its transmission. METHODS A total of 2,490 cases registered in each district of the municipality of São Paulo, Southeastern Brazil, between 1998 and 2006, were georeferenced. The data were obtained from the Notifiable Diseases Information System. Thematic maps were made, showing the variables of incidence rate, lethality rate, literacy rate, average monthly income, number of residents per household, water supply and sewage system. To identify spatial patterns (dispersed, clustered or random), these variables were analyzed using the global and local Moran indices. Spearmans correlation coefficient was used to test associations between variables with clustered spatial patterns. RESULTS Clustered spatial patterns were observed for the variables of leptospirosis incidence, literacy rate, average monthly income, number of residents per household, water supply and sewage system. There were 773 notified cases in the dry season and 1,717 cases in the rainy season. The incidence and lethality rates correlated with the populations socioeconomic conditions, independently of the period. CONCLUSIONS Leptospirosis is spread throughout the municipality of São Paulo, and its incidence increases during the rainy season. In the dry season, the localities where cases appear coincide with the areas of poorest housing conditions. In the rainy season, it also increases in other districts, probably due to the proximity of rivers and streams.OBJETIVO: Analisar a distribuicao espacial e sazonal da leptospirose, identificando possiveis componentes ecologicos e sociais para a sua transmissao. METODOS: Foram georreferenciados 2.490 casos em cada distrito do municipio de Sao Paulo, SP, registrados de 1998 a 2006. Os dados foram obtidos do Sistema de Informacao de Agravos de Notificacao. Foram realizados mapas tematicos com as variaveis taxa de incidencia, letalidade, taxa de alfabetizacao, renda media mensal, numero de moradores por domicilio, abastecimento de agua e rede de esgoto. Para identificar o padrao espacial (disperso, em aglomerado ou randomico), foram analisadas pelo Indice de Moran global e local. Foi utilizado o coeficiente de correlacao de Spearman para testar associacoes entre as variaveis com padrao espacial em aglomerados. RESULTADOS: O padrao espacial em aglomerados foi observado nas variaveis taxa de incidencia de leptospirose, taxa de alfabetizacao, renda media mensal, numero de moradores por domicilio, abastecimento de agua e rede de esgoto. Foram notificados 773 casos no periodo seco e 1.717 no umido. A incidencia e a letalidade estao correlacionadas com as condicoes socioeconomicas da populacao, independentemente do periodo. CONCLUSOES: A leptospirose esta distribuida por todo o municipio de Sao Paulo e sua incidencia aumenta no periodo das chuvas. No periodo seco, os locais de aparecimento dos casos coincidem com as areas de piores condicoes de moradia e, durante o periodo umido, tambem aumenta em outros distritos, provavelmente devido a proximidade de rios e corregos.

Aspectos ecológicos da população de Culex quinquefasciatus Say (Diptera, Culicidae) em abrigos situados no Parque Ecológico do Tietê, São Paulo, SP

The study aimed to understand ecological aspects of Culex quinquefasciatus adult population in shelters along the year. Sampling of adults were carried out monthly during one year on a riverside vegetation. The insects were captured with a mechanical aspirator. Males and females were sorted and quantified; the degree of ovarian development was identified according to Sellas criterion. Meteorological data were correlated with the seasonal variations in the mosquito population. 8298 Cx. quinquefasciatus mosquitoes were collected. 6313 (76%) were males and 1985 (24%), females. 90,1% of the females had an empty abdomen, 7,4% had blood and 2,5% had mature eggs. The correlation between number of mosquitoes versus temperature and rainfall was weak. The high proportion of males can be explained by female dispersal and by the tendency of males for staying in the shelters. It was observed that the riverside vegetation permits the accumulation of mosquitoes and represents a shelter for them.

Culex nigripalpus Theobald (Diptera, Culicidae) feeding habit at the Parque Ecológico do Tietê, São Paulo, Brazil

The blood feeding of a population of Cx. nigripalpus from Parque Ecologico do Tiete (PET) was investigated using an indirect ELISA protocol. Mosquitoes were captured outside houses. Five hundred sixteen engorged females collected in a reforested area and 25 in an open area were tested. Rodents and dogs were the most common blood sources, accounting for approximately 65.3% of blood meals. Human blood was detected in 10.9%, dog blood in 26.1%, chicken blood in 2.4%, and rodent blood in 39.2% of the 541 insects tested. ELISA failed in identifying the blood sources of 233 engorged females, indicating that the mosquitoes may have fed on a host which was not tested. One hundred six individuals were positive for more than one host. The unweighted human blood index was 0.14 and the rodent/human, human/chicken, and dog/rodent feeding index values were 2.70, 1.51, and 1.33, respectively. Furthermore, rodents are defensive hosts for this haematophagous insect which looks for another host to complete blood-feeding. Considering that rodents are potential reservoirs for Mucambo virus and Saint Louis encephalitis virus and that Cx. nigripalpus feed on the blood of those mammals, we hypothesize that mosquito population in PET could participate in the transmission cycle of those arboviruses. Additionally, this species might be involved in the transmission of Dirofilaria immitis to dogs at this area.

Coexistence mechanisms at multiple scales in mosquito assemblages.

BackgroundSpecies coexistence in mosquito assemblages may depend on mechanisms related to interspecific resource partitioning occurring at multiple scales. In the present work we investigated co-occurrence or spatial segregation in mosquito assemblages sharing resources at micro-habitat, habitat and landscape scales. Environmental characteristics, mosquito fauna as adults and larvae were assessed along vegetation gradient in a natural landscape of tropical rainforest. Huisman-Olff-Fresco (HOF) and Generalized Additive (GAM) models were employed to explore relationships between abundances of potential competitors in mosquito assemblages and vegetation gradient (e.g., scrublands, mixed arboreal vegetation and dense ombrophilous forest). We tested hypotheses concerning mosquito species co-occurrence or spatial segregation employing binomial logistic regression models.ResultsCo-occurrences and spatial segregation of mosquito species showed evidences of three scales of coexistence mechanisms: 1) micro-habitat - scale 1: different behaviors in response to food availability in specific vertical strata within larval container; 2) habitat - scale 2: specialized strategies related to heterogeneity of resource availability among larval containers and 3) landscape - scale 3: asymmetrical competition dependent upon the context of abiotic and biotic variables.ConclusionResults of the present work suggest that coexistence mechanisms can concomitantly work at multiple scales.