RESUMO
BACKGROUND: Deforestation is an important driver of malaria dynamics, with a relevant impact on mosquito ecology, including larval habitat availability, blood-feeding behaviour, and peak biting time. The latter is one of several entomological metrics to evaluate vectorial capacity and effectiveness of disease control. This study aimed to test the effect of forest cover percentage on the peak biting time of Plasmodium-uninfected and infected Nyssorhynchus darlingi females. METHODS: Mosquitoes were captured utilizing human landing catch (HLC) in the peridomestic habitat in field collections carried out in the wet, wet-dry transition, and dry seasons from 2014 to 2017 in areas with active malaria transmission in Amazonian Brazil. The study locations were in rural settlements in areas with the mean annual malaria parasite incidence (Annual Parasite Incidence, API ≥ 30). All Ny. darlingi females were tested for Plasmodium spp. infection using real time PCR technique. Forest cover percentage was calculated for each collection site using QGIS v. 2.8 and was categorized in three distinct deforestation scenarios: (1) degraded, < 30% forest cover, (2) intermediate, 30-70% forest cover, and (3) preserved, > 70% forest cover. RESULTS: The highest number of uninfected female Ny. darlingi was found in degraded landscape-sites with forest cover < 30% in any peak biting time between 18:00 and 0:00. Partially degraded landscape-sites, with (30-70%) forest cover, showed the highest number of vivax-infected females, with a peak biting time of 21:00-23:00. The number of P. falciparum-infected mosquitoes was highest in preserved sites with > 70% forest cover, a peak biting at 19:00-20:00, and in sites with 30-70% forest cover at 22:00-23:00. CONCLUSIONS: Results of this study show empirically that degraded landscapes favour uninfected Ny. darlingi with a peak biting time at dusk (18:00-19:00), whereas partially degraded landscapes affect the behaviour of Plasmodium-infected Ny. darlingi by shifting its peak biting time towards hours after dark (21:00-23:00). In preserved sites, Plasmodium-infected Ny. darlingi bite around dusk (18:00-19:00) and shortly after (19:00-20:00).
Assuntos
Comportamento Alimentar , Florestas , Mosquitos Vetores , Animais , Brasil , Feminino , Mosquitos Vetores/fisiologia , Mosquitos Vetores/parasitologia , Conservação dos Recursos Naturais , Mordeduras e Picadas de Insetos/epidemiologia , Estações do Ano , Malária/transmissãoRESUMO
BACKGROUND: Environmental disturbance, deforestation and socioeconomic factors all affect malaria incidence in tropical and subtropical endemic areas. Deforestation is the major driver of habitat loss and fragmentation, which frequently leads to shifts in the composition, abundance and spatial distribution of vector species. The goals of the present study were to: (i) identify anophelines found naturally infected with Plasmodium; (ii) measure the effects of landscape on the number of Nyssorhynchus darlingi, presence of Plasmodium-infected Anophelinae, human biting rate (HBR) and malaria cases; and (iii) determine the frequency and peak biting time of Plasmodium-infected mosquitoes and Ny. darlingi. METHODS: Anopheline mosquitoes were collected in peridomestic and forest edge habitats in seven municipalities in four Amazon Brazilian states. Females were identified to species and tested for Plasmodium by real-time PCR. Negative binomial regression was used to measure any association between deforestation and number of Ny. darlingi, number of Plasmodium-infected Anophelinae, HBR and malaria. Peak biting time of Ny. darlingi and Plasmodium-infected Anophelinae were determined in the 12-h collections. Binomial logistic regression measured the association between presence of Plasmodium-infected Anophelinae and landscape metrics and malaria cases. RESULTS: Ninety-one females of Ny. darlingi, Ny. rangeli, Ny. benarrochi B and Ny. konderi B were found to be infected with Plasmodium. Analysis showed that the number of malaria cases and the number of Plasmodium-infected Anophelinae were more prevalent in sites with higher edge density and intermediate forest cover (30-70%). The distance of the drainage network to a dwelling was inversely correlated to malaria risk. The peak biting time of Plasmodium-infected Anophelinae was 00:00-03:00 h. The presence of Plasmodium-infected mosquitoes was higher in landscapes with > 13 malaria cases. CONCLUSIONS: Nyssorhynchus darlingi, Ny. rangeli, Ny. benarrochi B and Ny. konderi B can be involved in malaria transmission in rural settlements. The highest fraction of Plasmodium-infected Anophelinae was caught from midnight to 03:00 h. In some Amazonian localities, the highest exposure to infectious bites occurs when residents are sleeping, but transmission can occur throughout the night. Forest fragmentation favors increases in both malaria and the occurrence of Plasmodium-infected mosquitoes in peridomestic habitat. The use of insecticide-impregnated mosquito nets can decrease human exposure to infectious Anophelinae and malaria transmission.
Assuntos
Culicidae , Animais , Brasil/epidemiologia , Culicidae/parasitologia , Culicidae/fisiologia , Ecossistema , Comportamento Alimentar , Humanos , Mordeduras e Picadas de Insetos , Malária/epidemiologia , Malária/transmissão , Mosquitos Vetores/parasitologia , Mosquitos Vetores/fisiologia , Plasmodium/isolamento & purificação , PrevalênciaRESUMO
Inter-relationships among mosquito vectors, Plasmodium parasites, human ecology, and biotic and abiotic factors, drive malaria risk. Specifically, rural landscapes shaped by human activities have a great potential to increase the abundance of malaria vectors, putting many vulnerable people at risk. Understanding at which point the abundance of vectors increases in the landscape can help to design policies and interventions for effective and sustainable control. Using a dataset of adult female mosquitoes collected at 79 sites in malaria endemic areas in the Brazilian Amazon, this study aimed to (1) verify the association among forest cover percentage (PLAND), forest edge density (ED), and variation in mosquito diversity; and to (2) test the hypothesis of an association between landscape structure (i.e., PLAND and ED) and Nyssorhynchus darlingi (Root) dominance. Mosquito collections were performed employing human landing catch (HLC) (peridomestic habitat) and Shannon trap combined with HLC (forest fringe habitat). Nyssorhynchus darlingi abundance was used as the response variable in a generalized linear mixed model, and the Shannon diversity index (H') of the Culicidae community, PLAND, and the distance house-water drainage were used as predictors. Three ED categories were also used as random effects. A path analysis was used to understand comparative strengths of direct and indirect relationships among Amazon vegetation classes, Culicidae community, and Ny. darlingi abundance. Our results demonstrate that Ny. darlingi is negatively affected by H´ and PLAND of peridomestic habitat, and that increasing these variables (one-unit value at ß0 = 768) leads to a decrease of 226 (P < 0.001) and 533 (P = 0.003) individuals, respectively. At the forest fringe, a similar result was found for H' (ß1 = -218; P < 0.001) and PLAND (ß1 = -337; P = 0.04). Anthropogenic changes in the Amazon vegetation classes decreased mosquito biodiversity, leading to increased Ny. darlingi abundance. Changes in landscape structure, specifically decreases in PLAND and increases in ED, led to Ny. darlingi becoming the dominant species, increasing malaria risk. Ecological mechanisms involving changes in landscape and mosquito species composition can help to understand changes in the epidemiology of malaria.
Assuntos
Biodiversidade , Culicidae/crescimento & desenvolvimento , Atividades Humanas , Insetos Vetores/crescimento & desenvolvimento , Malária/parasitologia , Floresta Úmida , Animais , Brasil , Geografia , Modelos Lineares , Modelos Teóricos , Análise de Componente PrincipalRESUMO
Deforestation can increase the transmission of malaria. Here, we build upon the existing link between malaria risk and deforestation by investigating how the global demand for commodities that increase deforestation can also increase malaria risk. We use a database of trade relationships to link the consumption of deforestation-implicated commodities in developed countries to estimates of country-level malaria risk in developing countries. We estimate that about 20% of the malaria risk in deforestation hotspots is driven by the international trade of deforestation-implicated export commodities, such as timber, wood products, tobacco, cocoa, coffee and cotton. By linking malaria risk to final consumers of commodities, we contribute information to support demand-side policy measures to complement existing malaria control interventions, with co-benefits for reducing deforestation and forest disturbance.
Assuntos
Comércio , Conservação dos Recursos Naturais , Internacionalidade , Malária/transmissão , Agricultura/estatística & dados numéricos , Agricultura/tendências , Conservação dos Recursos Naturais/estatística & dados numéricos , Conservação dos Recursos Naturais/tendências , Ecologia , Economia , Monitoramento Ambiental , Florestas , Geografia , Humanos , Malária/epidemiologia , Modelos Teóricos , Políticas , Fatores de Risco , Árvores , MadeiraRESUMO
The Malaria Frontier Hypothesis (MFH) is the current model for predicting malaria emergence in the Brazilian Amazon. It has two important dimensions, 'settlement time' and 'malaria incidence', and its prediction are: malaria incidence peaks five years after the initiation of human settlement and declines towards zero after an estimated 10 years. Although MFH is currently accepted, it has been challenged recently. Herein, we described a novel method for estimating settlement timeline by using remote sensing technology integrated in an open-software geographic information system. Surprisingly, we found that of the majority of the rural settlements with high malaria incidence are more than 10 years old.
Assuntos
Conservação dos Recursos Naturais , Florestas , Malária/transmissão , Brasil/epidemiologia , Conservação dos Recursos Naturais/tendências , Sistemas de Informação Geográfica , Humanos , Incidência , Malária/epidemiologia , Malária/parasitologia , Carga Parasitária , População Rural , Fatores de TempoRESUMO
The precise role that deforestation for agricultural settlements and commercial forest products plays in promoting or inhibiting malaria incidence in Amazonian Brazil is controversial. Using publically available databases, we analyzed temporal malaria incidence (2009-2015) in municipalities of nine Amazonian states in relation to ecologically defined variables: (i) deforestation (rate of forest clearing over time); (ii) degraded forest (degree of human disturbance and openness of forest canopy for logging) and (iii) impacted forest (sum of deforested and degraded forest patches). We found that areas affected by one kilometer square of deforestation produced 27 new malaria cases (r² = 0.78; F1,10 = 35.81; P < 0.001). Unexpectedly, we found both a highly significant positive correlation between number of impacted forest patches less than 5 km2 and malaria cases, and that these patch sizes accounted for greater than ~95% of all patches in the study area. There was a significantly negative correlation between extraction forestry economic indices and malaria cases. Our results emphasize not only that deforestation promotes malaria incidence, but also that it directly or indirectly results in a low Human Development Index, and favors environmental conditions that promote malaria vector proliferation.
Assuntos
Florestas , Malária/epidemiologia , Clima Tropical , Brasil/epidemiologia , Conservação dos Recursos Naturais , Ecologia , Geografia Médica , Humanos , Incidência , Malária/parasitologia , Malária/transmissão , Vigilância da População , Fatores de RiscoRESUMO
As alterações das paisagens promovidas pelo homem, em razão das atividades relacionadas ao uso e ocupação do solo, representam um desafio para as atividades de controle da malária na Amazônia brasileira. Desse modo, buscou-se avaliar o sistema ecológico da malária através da construção de três eixos: desmatamento, uso do solo e diversidade de Culicidae. Esses eixos tiveram a paisagem como centro de conexão, modulados por fatores de pressão (hospedeiro humano), de risco (o vetor) e de causa (o agente infeccioso). A transmissão de patógenos, incluindo espécies de Plasmodium, ocorre na intersecção entre os nichos do hospedeiro humano, dos vetores e dos parasitos, em ambiente que permite a interconexão dos mesmos. Nesse sentido, verificou-se que cada quilômetro quadrado de área impactada pelo desmatamento, entre 2009-2015, produziu 27 novos casos de malária (r² = 0,78; F1,10 = 35,81; P <0,001) na Amazônia Legal brasileira, com uma correlação positiva altamente significativa entre o número de áreas de florestas impactadas com menos de 5 km² e a incidência da doença. Em virtude das relações indiretas com o desmatamento, foi possível verificar que o aumento da produção de soja, madeira, gado e óleo de palma no mundo apresentou alta correlação positiva significativa com a incidência de malária em países tropicais. No cenário brasileiro, a abundância de Nyssorhynchus darlingi respondeu positivamente à perda da cobertura florestal de áreas endêmicas de malária. Ao contrário, a diversidade de Culicidae diminuiu, deixando os vetores como espécies dominantes, favorecendo a taxa de picada e a capacidade de transmissão do Plasmodium. Desse modo, foi possível concluir que a incidência da doença, em áreas rurais, está fortemente associada aos padrões de uso e ocupação do solo. A estrutura da paisagem pode ser indicador de risco para a doença, em virtude das dinâmicas ecológicas do Ny. darlingi.
Changes in the landscapes caused by humans, due to the activities related to the use and occupation of the soil, represent a challenge for malaria control activities in the Brazilian Amazon. Therefore, we evaluated the ecological system of malaria in relation to the construction of three drivers: deforestation, land use and Culicidae diversity. These drivers had in common the landscape, modulated by factors of pressure (human host), risk (the vector) and necessary cause (the infectious agent). The transmission of pathogens, including species of Plasmodium, occurs at the intersection among niches of the human host, the vectors and the parasites, in an environment that allows the interconnection of these organisms. The data analyzed herein verified that every square kilometer of area impacted by deforestation between 2009-2015 produced 27 new cases of malaria (r² = 0.78, F1.10 = 35.81, P <0.001) in the Brazilian Legal Amazon, with a highly significant positive correlation between the number of forest areas with impacted less than 5 km² and the incidence of the disease. Due to the indirect relationship with deforestation, it was possible to verify that the increase in the production of soybean, wood, cattle and palm oil worldwide showed a significant positive correlation with the incidence of malaria in tropical countries. In the Brazilian scenario, the abundance of Nyssorhynchus darlingi responded positively to the loss of forest cover of endemic areas of malaria. In opposite, the Culicidae diversity decreased, leaving vectors as dominant species, favoring the biting rate and the capacity to Plasmodium transmission. Thus, it was possible to conclude that the incidence of the disease in rural areas is strongly associated with the patterns of land use and occupation. The structure of the landscape can be an indicator of risk for the disease, due to the ecological dynamics of the Ny. darlingi.
Assuntos
Usos do Solo , Ecossistema , Conservação dos Recursos Naturais , Malária/transmissão , Culicidae , Brasil , EcologiaRESUMO
The Malaria Frontier Hypothesis (MFH) is the current model for predicting malaria emergence in the Brazilian Amazon. It has two important dimensions, 'settlement time' and 'malaria incidence', and its prediction are: malaria incidence peaks five years after the initiation of human settlement and declines towards zero after an estimated 10 years. Although MFH is currently accepted, it has been challenged recently. Herein, we described a novel method for estimating settlement timeline by using remote sensing technology integrated in an open-software geographic information system. Surprisingly, we found that of the majority of the rural settlements with high malaria incidence are more than 10 years old.
Assuntos
Humanos , Sistemas de Informação Geográfica/organização & administração , Malária/parasitologia , Malária/transmissão , Malária/epidemiologia , População Rural , Brasil/epidemiologia , Florestas , Conservação dos Recursos Naturais/tendências , Carga Parasitária/estatística & dados numéricosRESUMO
On the ecological scale of an organism, a homogeneous geographical landscape can represent a mosaic of heterogeneous landscapes. The bionomy of Kerteszia mosquitoes can contribute to foundation landscape ecology by virtue of in the role of the configuration and composition of the habitat played in the distribution of mosquito species. Thus, this study aimed: to compare the abundance of Kerteszia in dense tropical rainforest, restinga and rural area, to assess the bioecological characteristics of the main bromeliads hosting Kerteszia, and to associate the bioecological arrangement of the bromeliads with Kerteszia distribution. Field collections were conducted in a monthly schedule from December of 2010 to November 2011. The vegetation of landscapes was characterized on the basis of a digital cartographic database, the manual of the Brazilian vegetation, environmental atlas information, satellite images and visits to the sites. Multivariate generalized linear models were employed using the R-project statistical program. The results were: Anopheles cruzii was the most frequent species in dense tropical rainforest (67.42%), with a positive association (deviance=25.8; P=0.002). Anopheles bellator was more abundant in the Restinga area (78.97%), with a positive association (deviance=10.4, P=0.018). There was a positive aggregation of Restinga with An. bellator (RR=2.42) but a lower level with An. cruzii (RR=0.31). Thus we can conclude that landscape characteristics influence the distribution of Kerteszia mosquitoes. An. bellator has a higher prevalence in Restinga areas, whereas An. cruzii was the most prevalent in the dense tropical rainforest.