The activity of methylene blue against asexual and sexual stages of Plasmodium vivax.

Methylene blue (MB) is an alternative for combating drug-resistant malaria parasites. Its transmission-blocking potential has been demonstrated in vivo in murine models, in vitro, and in clinical trials. MB shows high efficacy against Plasmodium vivax asexual stages; however, its efficacy in sexual stages is unknown. In this study, we evaluated the potential of MB against asexual and sexual forms of P. vivax isolated from the blood of patients residing in the Brazilian Amazon. An ex vivo schizont maturation assay, zygote to ookinete transformation assay, direct membrane feed assay (DMFA), and standard membrane feed assay (SMFA) using P. vivax gametocytes with MB exposure were performed. A cytotoxicity assay was also performed on freshly collected peripheral blood mononuclear cells (PBMCs) and the hepatocyte carcinoma cell line HepG2. MB inhibited the P. vivax schizont maturation and demonstrated an IC50 lower than that of chloroquine (control drug). In the sexual forms, the MB demonstrated a high level of inhibition in the transformation of the zygotes into ookinetes. In the DMFA, MB did not considerably affect the infection rate and showed low inhibition, but it demonstrated a slight decrease in the infection intensity in all tested concentrations. In contrast, in the SMFA, MB was able to completely block the transmission at the highest concentration (20 µM). MB demonstrated low cytotoxicity to fresh PBMCs but demonstrated higher cytotoxicity to the hepatocyte carcinoma cell line HepG2. These results show that MB may be a potential drug for vivax malaria treatment.

Rattlesnakes bites in the Brazilian Amazon: Clinical epidemiology, spatial distribution and ecological determinants.

Crotalus bites are considered a public health problem especially in Latin America. This study was performed to describe the epidemiology, spatial distribution and environmental determinants of Crotalus durissus bites in the Brazilian Amazon. Crotalus durissus envenomings official database included cases reported from 2010 to 2015. A total of 70,816 snakebites were recorded in the Amazon Region, 3058 (4.3%) cases being classified as crotalid, with a mean incidence rate of 11.1/100,000 inhabitants/year. The highest mean incidence rates were reported in Roraima, Tocantins and Maranhão. Area covered by water bodies, precipitation and soil humidity were negatively associated to rattlesnake encountering. Rattlesnake bites incidence was positively associated to tree canopy loss and altitude. In the Amazon, severe manifestations at admission, delayed medical assistance, lack of antivenom administration and ages ≥61 and 0-15 years were predictors of death in C. durissus snakebites. Spatial distribution of rattlesnake bites across the Brazilian Amazon showed higher incidence in areas of transition from the equatorial forest to the savanna, and in the savanna itself. Such results may aid focused policy-making in order to mitigate the burden, clinical complications and death as well as to manage Crotalus rattlesnake populations in the Brazilian Amazon.

Mother-to-child Transmission of HIV From 1999 to 2011 in the Amazonas, Brazil: Risk Factors and Remaining Gaps in Prevention Strategies.

BACKGROUND: The purpose of the study was to estimate rates of mother-to-child transmission (MTCT) of HIV in the Amazonas, Brazil, and to identify the associated factors. METHODS: This was a retrospective cohort study of 1210 children born to HIV-infected women between 1999 and 2011 and enrolled before age of 18 months in a reference HIV/AIDS pediatrics service in Manaus. We used multivariable logistic regression to assess the effect of maternal, obstetric and prophylactic interventions on MTCT of HIV. RESULTS: Ten children were excluded because of undocumented maternal HIV status. Among 1200 children, 163 (13.6%) were lost to follow-up. We included in the analysis 1037 children with known HIV status. Of those, 68 children were HIV infected, resulting in a MTCT rate of 6.6% [95% confidence interval (CI): 5.3-8.3]. Among mothers, 76.1% had received antiretroviral therapy during pregnancy, 59.3% elective caesarean, and 9.7% were breastfed. Factors associated with lower odds of MTCT of HIV were antiretroviral therapy during pregnancy [odds ratio (OR): 0.26; 95% CI: 0.12-0.58], elective caesarean (OR: 0.48; 95% CI: 0.23-0.98) and with MTCT: being breastfed (OR: 4.56; 95% CI: 2.19-9.50). Transmission decreased from 7.5% in 2007-2008 to 3.2% in 2011, while breastfeeding decreased from 30.8% in 1999-2000 to 3.9% in 2011-2012. CONCLUSIONS: The HIV rate of MTCT is still high in the Amazonas and challenges for its prevention prevail including lost to follow-up and gaps in critical strategies such as antiretroviral use during pregnancy. More efforts are needed to increase the number of women and babies who successfully complete the prevention of MTCT cascade and work toward elimination of MTCT of HIV.