Seroconversion and seroreversion rates of anti-Strongyloides IgG in rural areas of the Amazon: a population-based panel study.

Using a panel study design, we aimed to estimate the seroconversion and seroreversion rates of anti-Strongyloides IgG antibodies from surveys carried out 11 months apart in a rural community in the Amazon Basin in Brazil. We used enzyme immunoassays to measure anti-Strongyloides IgG antibodies in 325 baseline plasma samples and 224 others that were collected 11 months later from residents in the agricultural settlement of Granada, Acre State. We observed anti-Strongyloides IgG antibodies in 21.

Dynamics of IgM and IgG Antibody Response Profile against Linear B-Cell Epitopes from Exoerythrocytic (CelTOS and TRAP) and Erythrocytic (CyRPA) Phases of : Follow-Up Study.

Malaria is a serious health problem worldwide affecting mainly children and socially vulnerable people. The biological particularities of , such as the ability to generate dormant liver stages, the rapid maturation of gametocytes, and the emergence of drug resistance, have contributed to difficulties in disease control. In this context, developing an effective vaccine has been considered a fundamental tool for the efficient control and/or elimination of vivax malaria.

Adolescent pregnancy in Cruzeiro do Sul, Acre, Brazil: socioeconomic characteristics, prenatal and obstetric care.

The present study aimed to investigate the socioeconomic and obstetric characteristics of adolescent mothers and the complications they cause to maternal and neonatal health. This baseline data analysis of the MINA-Brazil birth cohort was conducted in the municipality of Cruzeiro do Sul, state of Acre, Brazil. The chi-square test was used to compare characteristics of adolescent and adult postpartum women, and multiple Poisson regression models with robust variance were used to assess associated factors.

Reduced polymorphism of Plasmodium vivax early transcribed membrane protein (PvETRAMP) 11.2.

Background: ETRAMP11.2 (PVX_003565) is a well-characterized protein with antigenic potential. It is considered to be a serological marker for diagnostic tools, and it has been suggested as a potential vaccine candidate.

Clinically silent Plasmodium vivax infections in native Amazonians of northwestern Brazil: acquired immunity or low parasite virulence?

Background: Malaria remains common among native Amazonians, challenging Brazil's elimination efforts.

Objectives: We examined the epidemiology of malaria in riverine populations of the country's main hotspot - the upper Juruá Valley in Acre state, close to the Brazil-Peru border, where Plasmodium vivax accounts for > 80% of cases.

Methods: Participants (n = 262) from 10 villages along the Azul River were screened for malaria parasites by microscopy and genus-specific, cytochrome b (cytb) gene-based polymerase chain reaction.

An open dataset of genome variation in 1,895 worldwide samples.

This report describes the MalariaGEN Pv4 dataset, a new release of curated genome variation data on 1,895 samples of collected at 88 worldwide locations between 2001 and 2017. It includes 1,370 new samples contributed by MalariaGEN and VivaxGEN partner studies in addition to previously published samples from these and other sources. We provide genotype calls at over 4.

An update on pharmacogenetic factors influencing the metabolism and toxicity of artemisinin-based combination therapy in the treatment of malaria.

Introduction: Artemisinin-based combination therapies (ACTs) are recommended first-line antimalarials for uncomplicated malaria. Pharmacokinetic/pharmacodynamic variation associated with ACT drugs and their effect is documented. It is accepted to an extent that inter-individual variation is genetically driven, and should be explored for optimized antimalarial use.

A Retrospective Survey of Rodent-borne Viruses in Rural Populations of Brazilian Amazon.

Introduction: The Amazon tropical rainforest has the most dense and diverse ecosystem worldwide. A few studies have addressed rodent-borne diseases as potential hazards to humans in this region.

Methods: A retrospective survey was conducted using enzyme-linked immunosorbent assay for detecting mammarenavirus and orthohantavirus antibodies in 206 samples collected from rural settlers of the Brazilian Western Amazonian region.

Apical membrane protein 1-specific antibody profile and temporal changes in peripheral blood B-cell populations in Plasmodium vivax malaria.

Plasmodium falciparum-specific antibodies tend to be short-lived, but their cognate memory B cells (MBCs) circulate in the peripheral blood of exposed subjects for several months or years after the last infection. However, the time course of antigen-specific antibodies and B-cell responses to the relatively neglected parasite Plasmodium vivax remains largely unexplored. Here, we showed that uncomplicated vivax malaria elicits short-lived antibodies but long-lived MBC responses to a major blood-stage P vivax antigen, apical membrane protein 1 (PvAMA-1), in subjects exposed to declining malaria transmission in the Amazon Basin of Brazil.

Complement Receptor 1 availability on red blood cell surface modulates Plasmodium vivax invasion of human reticulocytes.

Plasmodium vivax parasites preferentially invade reticulocyte cells in a multistep process that is still poorly understood. In this study, we used ex vivo invasion assays and population genetic analyses to investigate the involvement of complement receptor 1 (CR1) in P. vivax invasion.

Emerging Plasmodium vivax resistance to chloroquine in South America: an overview.

The global emergence of Plasmodium vivax strains resistant to chloroquine (CQ) since the late 1980s is complicating the current international efforts for malaria control and elimination. Furthermore, CQ-resistant vivax malaria has already reached an alarming prevalence in Indonesia, East Timor and Papua New Guinea. More recently, in vivo studies have documented CQ-resistant P.

Hepatitis A and E seroprevalence and associated risk factors: a community-based cross-sectional survey in rural Amazonia.

Background: Hepatitis A virus (HAV) and hepatitis E virus (HEV) are both transmitted by the faecal-oral route, and represent common causes of acute hepatitis in developing countries. The endemicity of HAV infection has shifted from high to moderate in Brazil. Human cases of HEV infection seem to be rare, although the virus has been detected in swine livestock and effluents of slaughterhouses.

Parasite virulence, co-infections and cytokine balance in malaria.

Strong early inflammatory responses followed by a timely production of regulatory cytokines are required to control malaria parasite multiplication without inducing major host pathology. Here, we briefly examine the homeostasis of inflammatory responses to malaria parasite species with varying virulence levels and discuss how co-infections with bacteria, viruses, and helminths can modulate inflammation, either aggravating or alleviating malaria-related morbidity.

Molecular markers and genetic diversity of Plasmodium vivax.

Enhanced understanding of the transmission dynamics and population genetics for Plasmodium vivax is crucial in predicting the emergence and spread of novel parasite phenotypes with major public health implications, such as new relapsing patterns, drug resistance and increased virulence. Suitable molecular markers are required for these population genetic studies. Here, we focus on two groups of molecular markers that are commonly used to analyse natural populations of P.

Evidence-based public health and prospects for malaria control in Brazil.

Despite intensive control efforts over the past decades, Brazil still accounts for more than 50% of the malaria burden in the Americas and the Caribbean, with 458,041 slide-confirmed cases reported countrywide in 2007. The reason malaria has proved so difficult to control in this middle-income country with a reasonable health infrastructure remains unclear. Here we examine whether four strategies that were largely successful in other countries (aggressive active case detection, improved anti-relapse therapy for P.

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.

Age-dependent acquisition of protective immunity to malaria in riverine populations of the Amazon Basin of Brazil.

Five community-based cross-sectional surveys of malaria morbidity and associated risk factors in remote riverine populations in northwestern Brazil showed average parasite rates of 4.2% (thick-smear microscopy) and 14.4% (polymerase chain reaction [PCR]) in the overall population, with a spleen rate of 13.

Naturally acquired antibodies to merozoite surface protein (MSP)-1(19) and cumulative exposure to Plasmodium falciparum and Plasmodium vivax in remote populations of the Amazon Basin of Brazil.

To infer recent patterns of malaria transmission, we measured naturally acquired IgG antibodies to the conserved 19-kDa C-terminal region of the merozoite surface protein (MSP)-1 of both Plasmodium vivax (PvMSP-1(19)) and Plasmodium falciparum (PfMSP-1(19)) in remote malaria-exposed populations of the Amazon Basin. Community-based cross-sectional surveys were carried out between 2002 and 2003 in subjects of all age groups living along the margins of the Unini and Jaú rivers, Northwestern Brazil. We found high prevalence rates of IgG antibodies to PvMSP-1(19) (64.

Child health and nutrition in the Western Brazilian Amazon: population-based surveys in two counties in Acre State.

The article presents prevalence rates for malnutrition, intestinal parasitic infections, anemia, and iron deficiency in under-five children in a population-based cross-sectional survey performed in the urban area of two counties in the Western Brazilian Amazon, Assis Brasil (n = 200) and Acrelandia (n = 477). Available data included: (a) weight and height measurements, standardized as z-scores using the 1977 NCHS reference population, (b) diagnosis of current intestinal parasitic infection, (c) blood hemoglobin levels, and (d) plasma ferritin and soluble transferrin receptor levels. Overall prevalence rates of low weight-for-height, low weight-for-age, and low height-for-age were 3.

Prevalence and spatial distribution of intestinal parasitic infections in a rural Amazonian settlement, Acre State, Brazil.

A population-based survey of the prevalence and spatial distribution of intestinal parasitism was carried out in an agricultural settlement in the Amazon Basin of Brazil (Granada, Acre State). More than half (53.4%) of the 429 stool specimens from subjects in all age groups, living in 113 households, had cysts, ova, or larvae of intestinal parasites.

Bottle feeding and exposure to Toxocara as risk factors for wheezing illness among under-five Amazonian children: a population-based cross-sectional study.

We investigated the prevalence and risk factors for wheezing and asthma in young Amazonian children. A population-based cross-sectional survey of 606 children aged 6-59 months was performed in two small towns in Acre State, Northwestern Brazil. Information on outcome variables (recent wheezing and medical diagnosis of asthma) and demographic, socioeconomic, environmental, maternal and nutritional variables was obtained by interviewing children's mothers or guardians.

The Acre Project: the epidemiology of malaria and arthropod-borne virus infections in a rural Amazonian population.

The authors describe the baseline malaria prevalence and arbovirus seroprevalence among 467 subjects in an ongoing cohort study in rural Amazonia. Most subjects (72.2%) reported one or more previous episodes of malaria, and 15.

Polymorphism of the Fcgamma receptor IIA and malaria morbidity.

Fc receptors (FcRs) are expressed on the surface of all types of cells of the immune system. They bind the Fc portion of immunoglobulin (Ig), thereby bridging specific antigen recognition by antibodies with cellular effector mechanisms. FcgammaRIIA, one of the three receptors for human IgG, is a low-affinity receptor for monomeric IgG, but binds IgG immune complexes efficiently.