Epidemiology and control of frontier malaria in Brazil: lessons from community-based studies in rural Amazonia

We describe the epidemiology of malaria in a frontier agricultural settlement in Brazilian Amazonia. We analysed the incidence of slide-confirmed symptomatic infections diagnosed between 2001 and 2006 in a cohort of 531 individuals (2281.53 person-years of follow-up) and parasite prevalence data derived from four cross-sectional surveys. Overall, the incidence rates of Plasmodium vivax and P. falciparaum were 20.6/100 and 6.8/100 person-years at risk, respectively, with a marked decline in the incidence of both species (81.4 and 56.8%, respectively) observed between 2001 and 2006. PCR revealed 5.4-fold more infections than conventional microscopy in population-wide cross-sectional surveys carried out between 2004 and 2006 (average prevalence, 11.3 vs. 2.0%). Only 27.2% of PCR-positive (but 73.3% of slide-positive) individuals had symptoms when enrolled, indicating that asymptomatic carriage of low-grade parasitaemias is a common phenomenon in frontier settlements. A circular cluster comprising 22.3% of the households, all situated in the area of most recent occupation, comprised 69.1% of all malaria infections diagnosed during the follow-up, with malaria incidence decreasing exponentially with distance from the cluster centre. By targeting one-quarter of the households, with selective indoor spraying or other house-protection measures, malaria incidence could be reduced by more than two-thirds in this community. (C) 2010 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.

Recurrent Parasitemias and Population Dynamics of Plasmodium vivax Polymorphisms in Rural Amazonia

Clinical trials documented alarming post-treatment Plasmodium vivax recurrence rates caused by recrudescence of surviving asexual blood stages, relapse from hypnozoites, or new infections. Here we describe high rates of P vivax recurrence (26-40% 180 days after treatment) in two cohorts of rural Amazonians exposed to low levels of malaria transmission after a vivax malaria episode treated with chloroquine-primaquine. Microsatellite analysis of 28 paired acute infection and recurrence parasites showed only two pairs of identical haplotypes (consistent with recrudescences or reactivation of homologous hypnozoites) and four pairs of related haplotypes (sharing alleles at 11-13 of 14 microsatellites analyzed). Local isolates of P vivax were extraordinarily diverse and rarely shared the same haplotype, indicating that frequent recurrences did not favor the persistence or reappearance of clonal lineages of parasites in the Population. This fast haplotype replacement rate may represent the typical population dynamics Of neutral polymorphisms in parasites from low-endemicity areas.

Population dynamics of genetically diverse Plasmodium falciparum lineages: community-based prospective study in rural Amazonia

Temporal changes in the prevalence of antigenic variants in Plasmodium falciparum populations have been interpreted as evidence of immune-mediated frequency-dependent selection, but evolutively neutral processes may generate similar patterns of serotype replacement. Over 4 years, we investigated the population dynamics of P. falciparum polymorphisms the community level by using 11 putatively neutral microsatellite markers. Plasmodium falciparum Populations were less diverse than sympatric P. vivax isolates, with less multiple-clone infections, lower number of alleles per locus and lower Virtual heterozygosity, but both species showed significant multilocus linkage disequilibrium. Evolutively neutral P. falciparum polymorphisms showed a high turnover rate, with few lineages persisting for several months in the population. Similar results had previously been obtained, in the same community, for sympatric P. vivax isolates. In contrast, the prevalence of the 2 dimorphic types of a major antigen, MSP-2, remained remarkably stable throughout the Study period. We Suggest that the relatively fast turnover of parasite lineages represents the typical population dynamics of neutral polymorphisms in small populations, with clear implications for the detection of frequency-dependent selection of polymorphisms.

Risk factors for dengue virus infection in rural Amazonia: Population-based cross-sectional surveys

A comparison of dengue virus (DENV) antibody levels in paired serum samples collected from predominantly DENV-naive residents in an agricultural settlement in Brazilian Amazonia (baseline seroprevalence, 18.3%) showed a seroconversion rate of 3.67 episodes/100 person-years at risk during 12 months of follow-up. Multivariate analysis identified male sex, poverty, and migration from extra-Amazonian states as significant predictors of baseline DENY seropositivity, whereas male sex, a history of clinical diagnosis of dengue fever, and travel to an urban area predicted subsequent seroconversion. The laboratory surveillance of acute febrile illnesses implemented at the study site and in a nearby town between 2004 and 2006 confirmed 11. DENV infections among 102 episodes studied with DENV IgM detection, reverse transcriptase-polymerise chain reaction, and virus isolation; DENV-3 was isolated. Because DENV exposure is associated with migration or travel, personal protection measures when visiting high-risk urban areas may reduce the incidence of DENV infection in this rural population.

A Community-based Survey of Human Toxoplasmosis in Rural Amazonia: Seroprevalence, Seroconversion Rate, and Associated Risk Factors

IgG antibodies to Toxoplasma gondii were detected in, March-April 2004, in 65.8% (95% confidence interval, 60.8-70.8%) of 342 systematically sampled subjects 5-90 years of age (87.5% of the eligible) living in a rural settlement in Amazonia, with a seroconversion rate of 9% over I year of follow-up of 99 seronegative subjects. Multiple logistic regression analysis identified age as the only significant independent predictor of seropositivity at the baseline. Each additional year of age increases the odds of being seropositive by 6%, and 76.8% of the subjects are expected to be seropositive at 30 years of age. A single high-prevalence spatial cluster, comprising 11.9% of the seropositive subjects, was detected in the area; households in the cluster were less likely to have dogs as pets and their heads had a lower education level, when compared with households located outside the cluster. The challenges for preventing human toxoplasmosis in tropical rural settings are discussed.

Evolutionary dynamics of the immunodominant repeats of the Plasmodium vivax malaria-vaccine candidate circumsporozoite protein (CSP)

The circumsporozoite protein (CSP) of Plasmodium vivax, a major target for malaria vaccine development, has immunodominant B-cell epitopes mapped to central nonapeptide repeat arrays. To determine whether rearrangements of repeat motifs during mitotic DNA replication of parasites create significant CSP diversity under conditions of low effective meiotic recombination rates, we examined csp alleles from sympatric P. vivax isolates systematically sampled from an area of low malaria endemicity in Brazil over a period of 14 months. Nine unique csp types, comprising six different nona peptide repeats, were observed in 45 isolates analyzed. Identical or nearly identical repeats predominated in most arrays, consistent with their recent expansion. We found strong linkage disequilibrium at sites across the chromosome 8 segment flanking the csp locus, consistent with rare meiotic recombination in this region. We conclude that CSP repeat diversity may not be severely constrained by rare meiotic recombination in areas of low malaria endemicity. New repeat variants may be readily created by nonhomologous recombination even when meiotic recombination is rare, with potential implications for CSP-based vaccine development. (C) 2010 Elsevier B.V. All rights reserved.

Worldwide sequence conservation of transmission-blocking vaccine candidate Pvs230 in Plasmodium vivax

Pfs230, surface protein of gametocyte/gamete of the human malaria parasite, Plasmodium falciparum, is a prime candidate of malaria transmission-blocking vaccine. Plasmodium vivax has an ortholog of Pfs230 (Pvs230), however, there has been no study in any aspects on Pvs230 to date. To investigate whether Pvs230 can be a vivax malaria transmission-blocking vaccine, we performed evolutionary and population genetic analysis of the Pvs230 gene (pvs230: PVX_003905). Our analysis of Pvs230 and its orthologs in eight Plasmodium species revealed two distinctive parts: an interspecies variable part (IVP) containing species-specific oligopeptide repeats at the N-terminus and a 7.5 kb interspecies conserved part (ICP) containing 14 cysteine-rich domains. Pvs230 was closely related to its orthologs, Pks230 and Pcys230, in monkey malaria parasites. Analysis of 113 pvs230 sequences obtained from worldwide, showed that nucleotide diversity is remarkably low in the non-repeat 8-kb region of pvs230 (theta pi = 0.00118) with 77 polymorphic nucleotide sites, 40 of which results in amino acid replacements. A signature of purifying selection but not of balancing selection was seen on pvs230. Functional and/or structural constraints may limit the level of polymorphism in pvs230. The observed limited polymorphism in pvs230 should ground for utilization of Pvs230 as an effective transmission-blocking vaccine. (C) 2011 Elsevier Ltd. All rights reserved.

Malaria on the Amazonian frontier: Transmission dynamics, risk factors, spatial distribution, and prospects for control

Little follow-up data on malaria transmission in communities originating from frontier settlements in Amazonia are available. Here we describe a cohort study in a frontier settlement in Acre, Brazil, where 509 subjects contributed 489.7 person-years of follow-up. The association between malaria morbidity during the follow-up and individual, household, and spatial covariates was explored with mixed-effects logistic regression models and spatial analysis. Incidence rates for Plasmodium vivax and Plasmodium falciparum malaria were 30.0/100 and 16.3/100 person-years at risk, respectively. Malaria morbidity was strongly associated with land clearing and farming, and decreased after five years of residence in the area, suggesting that clinical immunity develops among subjects exposed to low malaria endemicity. Significant spatial clustering of malaria was observed in the areas of most recent occupation, indicating that the continuous influx of nonimmune settlers to forest-fringe areas perpetuates the cycle of environmental change and colonization that favors malaria transmission in rural Amazonia.

Single-Nucleotide Polymorphism and Copy Number Variation of the Multidrug Resistance-1 Locus of Plasmodium vivax: Local and Global Patterns

Emerging resistance to chloroquine (CQ) poses a major challenge for Plasmodium vivax malaria control, and nucleotide substitutions and copy number variation in the P. vivax multidrug resistance 1 (pvmdr-1) locus, which encodes a digestive vacuole membrane transporter, may modulate this phenotype. We describe patterns of genetic variation in pvmdr-1 alleles from Acre and Amazonas in northwestern Brazil, and compare then with those reported in other malaria-endemic regions. The pvmdr-1 mutation Y976F, which is associated with CQ resistance in Southeast Asia and Oceania, remains rare in northwestern Brazil (1.8%) and its prevalence mirrors that of CO resistance worldwide. Gene amplification of pvmdr-1, which is associated with mefloquine resistance but increased susceptibility to CO, remains relatively rare in northwestern Brazil (0.9%) and globally (< 4%), but became common (> 10%) in Tak Province, Thailand, possibly because of drug-mediated selection. The global database we have assembled provides a baseline for further studies of genetic variation in pvmdr-1 and drug resistance in P. vivax malaria.

Human toxocariasis in rural Brazilian Amazonia: Seroprevalence, risk factors, and spatial distribution

This population-based cross-sectional study of 403 rural settlers in Brazilian Amazonia revealed an overall rate of IgG seropositivity to Toxocara canis excretory-secretory larval antigen of 26.8% (95% confidence interval [CI], 22.5-31.4%). Multilevel logistic regression analysis identified current infection with hookworm (odds ratio [OR], 2.32; 95% CI, 1.11-4.86) and residence in the most recently occupied sectors of the settlement (OR, 1.81.; 95%CI, 1.3-2.52) as significant risk factors for Toxocara seropositivity; age > 14 years (OR, 0.46; 95% CI, 0.28-0.73) and the presence of cats in the household (OR, 0.57; 95% CI, 0.32-1.02) appeared to be protective. Two significant high-prevalence clusters were detected in the area, together comprising 38.9% of the seropositive subjects; households in the clusters had slightly lower socioeconomic status and were less likely to have cats as pets. The obstacles for controlling human toxocariasis in this and other tropical rural settings are discussed.

EXPANSIÓN URBANA Y ESPACIALIDADE RURAL-URBANA EN LA AMAZONIA BRASILEÑA: EL CASO DE UNA PERIFERIA URBANA EN SANTARÉM-PA, BRASIL

Santarém es una ciudad de la Amazonia brasileña, que ha desempeñado un papel importante en la ocupación del oeste de Pará. Situado en la confluencia del Tapajós y Amazonas entre Belém y Manaus, se convirtió funciones que históricamente se había solidificado, como el centro comercial. El dinamismo de su área de influencia ha dibujado área urbana grande, reafirmando su primacía en el bajo Amazonas. Su crecimiento urbano ha sido muy desigual, reproduciendo una urbanización extensiva en la zona de expansión urbana. Así, surgen algunas preguntas: ¿Cómo conceptualizar estos espacios, ya que el Plan Director de la adecuación de la ciudad como los barrios de la zona urbana? ¿Cuándo y cómo fue la urbanización extensiva en estas áreas? Vamos a analizar las características de los espacios rurales y urbanas (Perla del Maicá y Zona Verde) con el fin de entender cómo este proceso se fusionen. Para desarrollar esta investigación, las encuestas se llevaron a cabo observaciones bibliográfico y documental, observación sistemática, entrevistas con los residentes del área de estudio, con expertos de las agencias municipales, registros fotográficos, análisis de material cartográfico, sistematización y análisis. La búsqueda está en marcha, habiéndose iniciado en 2009. La relevancia del tema de gran importancia para comprender los procesos complejos, y al mismo tiempo, más actual que la Amazonía.

Sistemas agroflorestais: manejando a biodiversidade e compondo a paisagem rural: palestras.

Sistemas agroflorestais: manejando a biodiversidade e compondo a paisagem rural. Biodiversidade e processos funcionais de sistemas agroflorestais. Applying agroecological concepts tothe development of ecologically pest management strategies. Biodiversidade e dinamica em sistemas agroflorestais. Diversificacao de manejo em sistemas agroflorestais. Certificacao socioambiental de sistemas agroflorestais. Valoracao de servicos ambientais em sistemas agroflorestais: metodos, problemas e perspectivas. Reservas de carbono y emision de gases en diferentes sistemas de uso de la tierra en dos sitios de la Amazonia Peruana. A Amazonia, o Amazonas e o mecanismo de desenvolvimento limpo (MDL) do protocolo de Quioto.

Sistemas agroflorestais: manejando a biodiversidade e compondo a paisagem rural - resumos expandidos.

Manejo e uso da biodiversidade em sistemas agroflorestais. Integracao dos sistemas agroflorestais no planejamento da paisagem rural. Insercao de sistemas agroflorestais em acoes de desenvolvimento, centradas no homem e na comunidade, na Amazonia brasileira.

Rural property size drives patterns of upland and riparian forest retention in a tropical deforestation frontier

Deforestation in Brazilian Amazonia accounts for a disproportionate global scale fraction of both carbon emissions from biomass burning and biodiversity erosion through habitat loss. Here we use field- and remote-sensing data to examine the effects of private landholding size on the amount and type of forest cover retained within economically active rural properties in an aging southern Amazonian deforestation frontier. Data on both upland and riparian forest cover from a survey of 300 rural properties indicated that 49.4% (SD = 29.0%) of the total forest cover was maintained as of 2007. and that property size is a key regional-scale determinant of patterns of deforestation and land-use change. Small properties (<= 150 ha) retained a lower proportion of forest (20.7%, SD = 17.6) than did large properties (>150 ha; 55.6%, SD = 27.2). Generalized linear models showed that property size had a positive effect on remaining areas of both upland and total forest cover. Using a Landsat time-series, the age of first clear-cutting that could be mapped within the boundaries of each property had a negative effect on the proportion of upland, riparian, and total forest cover retained. Based on these data, we show contrasts in land-use strategies between smallholders and largeholders, as well as differences in compliance with legal requirements in relation to minimum forest cover set-asides within private landholdings. This suggests that property size structure must be explicitly considered in landscape-scale conservation planning initiatives guiding agro-pastoral frontier expansion into remaining areas of tropical forest. (C) 2010 Elsevier Ltd. All rights reserved.

Seroprevalence of anti-Leishmania spp. antibodies in rural dogs from the city of Monte Negro, State of Rondonia, Brazil

The present study assessed the prevalence of anti-Leishmania spp antibodies in dogs from the city of Monte Negro, State of Rondonia, Brazil ELISA (NE >= 3) and IFAT (>= 1 40) were used to evaluate 161 serum samples collected from rural dogs from Monte Negro Forty-five (27 9%) dogs were positive by ELISA tests and five (3 1%) were positive by IFAT The present study showed for the first time the frequency of exposure to Leishmania spp in dogs in the State of Rondonia, Amazon Region