Impact of piperaquine resistance in Plasmodium falciparum on malaria treatment effectiveness in The Guianas: a descriptive epidemiological study.

BACKGROUND: Plasmodium falciparum is an apicomplexan parasite responsible for lethal cases of malaria. According to WHO recommendations, P falciparum cases are treated with artemisinin-based combination therapy including dihydroartemisinin-piperaquine. However, the emergence of resistant parasites against dihydroartemisinin-piperaquine was reported in southeast Asia in 2008 and, a few years later, suspected in South America. METHODS: To characterise resistance emergence, a treatment efficacy study was performed on the reported patients infected with P falciparum and treated with dihydroartemisinin-piperaquine in French Guiana (n=6, 2016-18). Contemporary isolates collected in French Guiana were genotyped for P falciparum chloroquine resistance transporter (pfCRT; n=845) and pfpm2 and pfpm3 copy number (n=231), phenotyped using the in vitro piperaquine survival assay (n=86), and analysed through genomic studies (n=50). Additional samples from five Amazonian countries and one outside the region were genotyped (n=1440). FINDINGS: In field isolates, 40 (47%) of 86 (95% CI 35·9-57·1) were resistant to piperaquine in vitro; these phenotypes were more associated with pfCRTC350R (ie, Cys350Arg) and pfpm2 and pfpm3 amplifications (Dunn test, p<0·001). Those markers were also associated with dihydroartemisinin-piperaquine treatment failure (n=3 [50%] of 6). A high prevalence of piperaquine resistance markers was observed in Suriname in 19 (83%) of 35 isolates and in Guyana in 579 (73%) of 791 isolates. The pfCRTC350R mutation emerged before pfpm2 and pfpm3 amplification in a temporal sequence different from southeast Asia, and in the absence of artemisinin partial resistance, suggesting a geographically distinctive epistatic relationship between these genetic markers. INTERPRETATION: The high prevalence of piperaquine resistance markers in parasite populations of the Guianas, and the risk of associated therapeutic failures calls for caution on dihydroartemisinin-piperaquine use in the region. Furthermore, greater attention should be given to potential differences in genotype to phenotype mapping across genetically distinct parasite populations from different continents. FUNDING: Pan American Health Organization and WHO, French Ministry for Research, European Commission, Santé publique France, Agence Nationale de la Recherche, Fundação de Amparo à Pesquisa do Estado do Amazonas, Ministry of Health of Brazil, Oswaldo Cruz Foundation, and National Institutes of Health. TRANSLATIONS: For the French and Portuguese translations of the abstract see Supplementary Materials section.

Trachoma Rapid Assessments in Venezuela, an Example of the Integration of Data Gathering with Service Delivery in Hard-to-reach Populations.

A) PURPOSE: The objective of the study was to assess the presence of trachoma in high priority districts in the Amazon state of Venezuela (the Bolivarian Republic of), and use trachoma data gathering platform to offer integrated primary health care services to underserved hard-to-reach populations living in the border with Colombia. B) METHODS: Trachoma Rapid Assessments (TRA) were conducted in indigenous communities of three municipalities of the Amazonas State of Venezuela from June 2018 to April 2019 using the World Health Organization (WHO) guidelines. Integrated health services were delivered based on the identified needs of the population of the assessed communities. C) RESULTS: 1,185 children aged 1-9 years were examined for trachoma in the three municipalities, of which 6.92% had active trachoma; 994 people 15 years and above were examined for trachomatous trichiasis (TT) finding two cases (0.2%). 1,635 people were examined for other health-related problems and the most common diagnoses were intestinal parasites (54.74%), eye diseases (16.81%), cavities (7.34%), scabies (5.56%), headache (4.40%), and malaria (2.81%); additionally, 2,233 vaccine doses were provided to children and adults to complete vaccination series. D) CONCLUSION: The results of the TRA in the Amazon state of Venezuela suggest that trachoma could be a public health problem and standardized population-based surveys to establish the prevalence and determine the interventions to implement are needed.

Kelch13 mutations in Plasmodium falciparum and risk of spreading in Amazon basin countries.

BACKGROUND: The first potential focus for artemisinin resistance in South America was recently confirmed with the presence of the C580Y mutation in the Plasmodium falciparum kelch 13 gene (pfk13) in Guyana. OBJECTIVES: This study aimed to strengthen pfk13 monitoring in the Amazon basin countries, to compile the available data and to evaluate the risk of spreading of mutations. METHODS: Sanger sequencing was done on 862 samples collected between 1998 and 2019, and a global map of pfk13 genotypes available for this region was constructed. Then, the risk of spreading of mutations based on P. falciparum case importation between 2015 and 2018 within countries of the Amazon basin was evaluated. RESULTS: No additional pfk13 C580Y foci were identified. Few mutations (0.5%, 95% CI = 0.3%-0.8%) in the propeller domain were observed in the general parasite population of this region despite a high proportion of K189T mutations (49.1%, 95% CI = 46.2%-52.0%) in the non-propeller domain. Case information revealed two patterns of intense human migration: Venezuela, Guyana and the Roraima State in Brazil; and French Guiana, Suriname and the Amapá State in Brazil. CONCLUSIONS: There are few pfk13 mutant foci, but a high risk of dispersion in the Amazon basin, mainly from the Guiana Shield, proportionate to mining activities. Therefore, access to prompt diagnosis and treatment, and continuous molecular monitoring is essential in these geographical areas.

High Rate of Infection by Only Oncogenic Human Papillomavirus in Amerindians.

Human papillomavirus (HPV), an etiological agent of cervical cancer (CC), has infected humans since ancient times. Amerindians are the furthest migrants out of Africa, and they reached the Americas more than 14,000 years ago. Some groups still remain isolated, and some migrate to towns, forming a gradient spanning urbanization. We hypothesized that, by virtue of their history, lifestyle, and isolation from the global society, remote Amerindian women have lower HPV diversity than do urban women (Amerindian or mestizo). Here we determined the diversity of the 25 most relevant cervical HPV types in 82 Amerindians spanning urbanization (low, medium, and high, consistent with the exposure to urban lifestyles of the town of Puerto Ayacucho in the Venezuelan Amazonas State), and in 29 urban mestizos from the town. Cervical, anal, oral, and introitus samples were taken, and HPVs were typed using reverse DNA hybridization. A total of 23 HPV types were detected, including 11 oncogenic or high-risk types, most associated with CC. Cervical HPV prevalence was 75%, with no differences by group, but Amerindians from low and medium urbanization level had significantly lower HPV diversity than mestizos did. In Amerindians, but not in mestizos, infections by only high-risk HPVs were higher than coinfections or by exclusively low-risk HPVs. Cervical abnormalities only were observed in Amerindians (9/82), consistent with their high HPV infection. The lower cervical HPV diversity in more isolated Amerindians is consistent with their lower exposure to the global pool, and transculturation to urban lifestyles could have implications on HPV ecology, infection, and virulence.IMPORTANCE The role of HPV type distribution on the disparity of cervical cancer (CC) incidence between human populations remains unknown. The incidence of CC in the Amazonas State of Venezuela is higher than the national average. In this study, we determined the diversity of known HPV types (the viral agent of CC) in Amerindian and mestizo women living in the Venezuelan Amazonas State. Understanding the ecological diversity of HPV in populations undergoing lifestyle transformations has important implication on public health measures for CC prevention.

Natural infection of Plasmodium brasilianum in humans: Man and monkey share quartan malaria parasites in the Venezuelan Amazon.

BACKGROUND: The quartan malaria parasite Plasmodium malariae is the widest spread and best adapted human malaria parasite. The simian Plasmodium brasilianum causes quartan fever in New World monkeys and resembles P. malariae morphologically. Since the genetics of the two parasites are nearly identical, differing only in a range of mutations expected within a species, it has long been speculated that the two are the same. However, no naturally acquired infection with parasites termed as P. brasilianum has been found in humans until now. METHODS: We investigated malaria cases from remote Yanomami indigenous communities of the Venezuelan Amazon and analyzed the genes coding for the circumsporozoite protein (CSP) and the small subunit of ribosomes (18S) by species-specific PCR and capillary based-DNA sequencing. FINDINGS: Based on 18S rRNA gene sequencing, we identified 12 patients harboring malaria parasites which were 100% identical with P. brasilianum isolated from the monkey, Alouatta seniculus. Translated amino acid sequences of the CS protein gene showed identical immunodominant repeat units between quartan malaria parasites isolated from both humans and monkeys. INTERPRETATION: This study reports, for the first time, naturally acquired infections in humans with parasites termed as P. brasilianum. We conclude that quartan malaria parasites are easily exchanged between humans and monkeys in Latin America. We hypothesize a lack of host specificity in mammalian hosts and consider quartan malaria to be a true anthropozoonosis. Since the name P. brasilianum suggests a malaria species distinct from P. malariae, we propose that P. brasilianum should have a nomenclatorial revision in case further research confirms our findings. The expansive reservoir of mammalian hosts discriminates quartan malaria from other Plasmodium spp. and requires particular research efforts.

The microbiome of uncontacted Amerindians.

Most studies of the human microbiome have focused on westernized people with life-style practices that decrease microbial survival and transmission, or on traditional societies that are currently in transition to westernization. We characterize the fecal, oral, and skin bacterial microbiome and resistome of members of an isolated Yanomami Amerindian village with no documented previous contact with Western people. These Yanomami harbor a microbiome with the highest diversity of bacteria and genetic functions ever reported in a human group. Despite their isolation, presumably for >11,000 years since their ancestors arrived in South America, and no known exposure to antibiotics, they harbor bacteria that carry functional antibiotic resistance (AR) genes, including those that confer resistance to synthetic antibiotics and are syntenic with mobilization elements. These results suggest that westernization significantly affects human microbiome diversity and that functional AR genes appear to be a feature of the human microbiome even in the absence of exposure to commercial antibiotics. AR genes are likely poised for mobilization and enrichment upon exposure to pharmacological levels of antibiotics. Our findings emphasize the need for extensive characterization of the function of the microbiome and resistome in remote nonwesternized populations before globalization of modern practices affects potentially beneficial bacteria harbored in the human body.

Effect of influenza-induced fever on human bioimpedance values.

BACKGROUND AND AIMS: Bioelectrical impedance analysis (BIA) is a widely used technique to assess body composition and nutritional status. While bioelectrical values are affected by diverse variables, there has been little research on validation of BIA in acute illness, especially to understand prognostic significance. Here we report the use of BIA in acute febrile states induced by influenza. METHODS: Bioimpedance studies were conducted during an H1N1 influenza A outbreak in Venezuelan Amerindian villages from the Amazonas. Measurements were performed on 52 subjects between 1 and 40 years of age, and 7 children were re-examined after starting Oseltamivir treatment. Bioelectrical Impedance Vector Analysis (BIVA) and permutation tests were applied. RESULTS: For the entire sample, febrile individuals showed a tendency toward greater reactance (p=0.058) and phase angle (p=0.037) than afebrile individuals, while resistance and impedance were similar in the two groups. Individuals with repeated measurements showed significant differences in bioimpedance values associated with fever, including increased reactance (p<0.001) and phase angle (p=0.007), and decreased resistance (p=0.007) and impedance (p<0.001). CONCLUSIONS: There are bioelectrical variations induced by influenza that can be related to dehydration, with lower extracellular to intracellular water ratio in febrile individuals, or a direct thermal effect. Caution is recommended when interpreting bioimpedance results in febrile states.

Tetracycline resistance genes acquired at birth.

Newborns acquire their first microbiota at birth. Maternal vaginal or skin bacteria colonize newborns delivered vaginally or by C-section, respectively (Dominguez-Bello et al. 2010 #884). We aimed to determine differences in the presence of four tetracycline (tet) resistance genes, in the microbes of ten newborns and in the mouth and vagina of their mothers, at the time of birth. DNA was amplified by PCR with primers specific for [tet(M), tet(O), tet(Q), and tet(W)]. Maternal vaginas harbored all four tet resistance genes, but most commonly tet(M) and tet(O) (63 and 38 %, respectively). Genes coding for tet resistance differed by birth mode, with 50 % of vaginally delivered babies had tet(M) and tet(O) and 16 and 13 % of infants born by C-section had tet(O) and tet(W), respectively. Newborns acquire antibiotic resistance genes at birth, and the resistance gene profile varies by mode of delivery.

Distinct cutaneous bacterial assemblages in a sampling of South American Amerindians and US residents.

The human skin harbors complex bacterial communities. Prior studies showing high inter-individual variation focused on subjects from developed countries. We therefore compared cutaneous bacterial communities of Amerindians in the Venezuelan Amazon with subjects in the United States. Forearm skin specimens were studied from healthy Amerindians in Platanillal village in Amazonas State, and from healthy persons in New York and Colorado. All skin sampling used similar swab/buffer techniques. Multiplexed V2-targeted 16S rRNA gene pyrosequencing yielded high quality sequences from 112 samples. The results show 20 phyla, with three (Proteobacteria, Firmicutes, Actinobacteria) predominating. US residents and Venezuelan Amerindians had significantly different forearm skin bacterial community compositions, with United States dominated by Propionibacterium. Among the Amerindians, there was a deep split based on bacterial community membership, with 30 and 42 samples, respectively, falling into each of the two groups, not associated with age, gender, or body mass index. One Amerindian group had diversity similar to the United States, but was dominated by Staphylococcus rather than Propionibacterium. The other Amerindian group was significantly more diverse and even than the US or the other Amerindian group, and featured a broad range of Proteobacteria. The results provide evidence that ethnicity, lifestyle and/or geography are associated with the structure of human cutaneous bacterial communities.

Human gut microbiome viewed across age and geography.

Gut microbial communities represent one source of human genetic and metabolic diversity. To examine how gut microbiomes differ among human populations, here we characterize bacterial species in fecal samples from 531 individuals, plus the gene content of 110 of them. The cohort encompassed healthy children and adults from the Amazonas of Venezuela, rural Malawi and US metropolitan areas and included mono- and dizygotic twins. Shared features of the functional maturation of the gut microbiome were identified during the first three years of life in all three populations, including age-associated changes in the genes involved in vitamin biosynthesis and metabolism. Pronounced differences in bacterial assemblages and functional gene repertoires were noted between US residents and those in the other two countries. These distinctive features are evident in early infancy as well as adulthood. Our findings underscore the need to consider the microbiome when evaluating human development, nutritional needs, physiological variations and the impact of westernization.

Naturally acquired immune responses to malaria vaccine candidate antigens MSP3 and GLURP in Guahibo and Piaroa indigenous communities of the Venezuelan Amazon.

BACKGROUND: Malaria transmission in most of Latin America can be considered as controlled. In such a scenario, parameters of baseline immunity to malaria antigens are of specific interest with respect to future malaria eradication efforts. METHODS: A cross-sectional study was carried out in two indigenous population groups in Amazonas/Venezuela. Data from the regional malaria documentation system were extracted and participants from the ethnic groups of the Guahibo (n = 180) and Piaroa (n = 295) were investigated for the presence of Plasmodium parasites and naturally acquired antibodies to Plasmodium falciparum antigens in serum. The GMZ2 vaccine candidate proteins MSP3 and GLURP were chosen as serological markers. RESULTS: The incidence of P. falciparum in both communities was found to be less than 2%, and none of the participants harboured P. falciparum at the time of the cross-sectional. Nearly a quarter of the participants (111/475; 23,4%) had positive antibody titres to at least one of the antigens. 53/475 participants (11.2%) were positive for MSP3, and 93/475 participants (19.6%) were positive for GLURP. High positive responses were detected in 36/475 participants (7.6%) and 61/475 participants (12.8%) for MSP3 and GLURP, respectively. Guahibo participants had significantly higher antibody titres than Piaroa participants. CONCLUSIONS: Considering the low incidence of P. falciparum, submicroscopical infections may explain the comparatively high anti-P. falciparum antibody concentrations.

Antígenos de Plasmodium falciparum, blancos de la respuesta inmunitaria humoral en pacientes tratados con cloroquina / Antigens of Plasmodium falciparum, target of humoral immune response in patients treated with chloroquine

Se planteó identificar antígenos que pudieran ser reconocidos por los anticuerpos IgG1 e IgG3, descritos como protectores en la infección malárica, en personas con respuesta clínica adecuada (RCA) o falla al tratamiento (FT) antimalárico, provenientes de localidades con diferentes grados de endemicidad. Se evaluaron por Immunoblotting muestras de sueros de individuos provenientes de tres localidades del Edo. Amazonas (Venezuela): Puerto Ayacucho (Atures), San Juan de Manapiare (Manapiare) y Platanal (Alto Orinoco). La reactividad de IgG, IgG1 e IgG3 frente a componentes antigénicos del extracto de P. falciparum (FCB2), permitió identificar un mayor número de moléculas específicas en los pacientes con RCA que en los pacientes con FT. La frecuencia de reconocimiento de polipéptidos fue baja en las tres localidades, algunas moléculas con una frecuencia de reconocimiento igual o mayor al 20% pertenecían a sueros de individuos de las localidades de Puerto Ayacucho y Platanal, ambas con exposición permanente a P. falciparum. Dado el reconocimiento de polipéptidos por IgG, IgG1 e IgG3 en sueros de pacientes con RCA, estos podrían ser considerados como posibles blancos relevantes de la respuesta inmunológica protectora que coadyuven con el tratamiento antimalárico. Esto contribuiría al desarrollo y diseño de vacunas más efectivas, que prevengan la infección malárica y/o potencien la eficacia a la quimioterapia.

Here we studied the presence of antigens recognized by IgG1 and IgG3 antibodies, thought as protective, in patients with adequate clinical response (RCA) or treatment failure (FT), living in areas of different degrees of endemicity. Immunoblotting was evaluated from serum samples of individuals from three locations in the State Amazonas (Venezuela): Puerto Ayacucho (Atures), San Juan de Manapiare (Manapiare) and Pantanal (Alto Orinoco). The reactivity of IgG, IgG1 and IgG3 against antigenic components of the extract of P. falciparum (FCB2) identified a greater number of specific molecules in patients with RCA in patients with AFT. The frequency of recognition of polypeptides was low in all three locations, with some molecules having a recognition rate of greater than or equal to 20% sera of individuals belonging to the towns of Puerto Ayacucho and Platanal, both with cases of P. falciparum. Given the recognition of polypeptides by IgG, IgG1 and IgG3 in sera of patients with RCA, they could be considered as possible targets for relevant protective immune responses that contribute to malaria treatment. This would contribute to the development and design of more effective vaccines that prevent malaria infection and/or enhance the efficacy of chemotherapy.

Mapa de riesgo de transmisión de malaria en la cuenca del río Caura, Venezuela / Risk map of malaria transmission in the Caura river basin, Venezuela

Los mapas de riesgo de malaria se han usado para apoyar la optimización de recursos humanos, materiales y financieros disponibles para la prevención y control de la enfermedad. En Venezuela, estos mapas se basan en el Índice Parasitario Anual donde se clasifican municipios en diferentes intervalos de riesgo. Los mismos tienen poca resolución espacial, usan intervalos de riesgo muy amplios y no consideran múltiples factores de riesgo tales como comportamiento biológico de parásitos y vectores, condiciones favorables al contacto hombre-vector y para la prevención y control de la enfermedad. El objetivo del trabajo es identificar áreas de riesgo de malaria en la cuenca del río Caura, estado Bolívar, Guayana venezolana, basado en una evaluación multicriterio de variables ambientales y antrópicas favorables para la transmisión de la malaria. Los criterios de riesgo se expresaron en capas de imágenes raster usando reglas de decisión y se normalizaron usando lógica difusa. La combinación de los criterios produjo un mapa síntesis de valores continuos de riesgo de transmisión de malaria basado en índices de: a) conveniencia climática para la viabilidad de Anopheles darlingi y Plasmodium spp.; b) conveniencia geomorfológica y de vegetación para la formación de criaderos; c) preferencias de ocupación humana y, d) vulnerabilidad de las comunidades. El mapa se reclasificó en niveles de riesgo y se evaluó superponiendo sobre éste el número de casos de malaria acumulados por nivel de riesgo entre 2000 y 2010, y se discute su importancia para la vigilancia epidemiológica en la región.

Malaria risk maps have been used to support the optimization of the use of human, material and financial resources for the prevention and control of the disease. In Venezuela, these maps are based on annual parasite index, where municipalities are classified using different risk intervals. These maps have low spatial resolution, use risk intervals too broad and do not consider multiple risk factors and their different spatial and temporal scales (eg. biological behavior of parasites and vectors, conditions conducive to man-vector contact and potentially favorable conditions to the prevention and control of the disease). The aim of this study was to identify risk areas of malaria in the Caura River Basin (Venezuelan Guayana), based in a multi-criteria evaluation of climatic, geographical and anthropogenic variables and their suitability for malaria transmission. The risk criteria were expressed spatially as raster image layers using decision rules and normalized using fuzzy logic. The combination of different criteria produced a synthesis map of continuous values of risk of malaria transmission based on the following indexes: a) climatic suitability for the viability of Anopheles darlingi and Plasmodium spp., b) geomorphologic and vegetation suitability for vector hatcheries; c) human occupation preferences and d) vulnerability of communities. The resultant map was reclassified in levels of risk and it was evaluated overlaying the number of cases accumulated per level of risk between 2000 and 2010, and its epidemiological surveillance importance is discussed for the region.

The bacterial microbiota in the oral mucosa of rural Amerindians.

The oral microbiota plays an important role in buccal health and in diseases such as periodontitis and meningitis. The study of the human oral bacteria has so far focused on subjects from Western societies, while little is known about subjects from isolated communities. This work determined the composition of the oral mucosa microbiota from six Amazon Amerindians, and tested a sample preservation alternative to freezing. Paired oral swabs were taken from six adults of Guahibo ethnicity living in the community of Platanillal, Amazonas State, Venezuela. Replicate swabs were preserved in liquid nitrogen and in Aware Messenger fluid (Calypte). Buccal DNA was extracted, and the V2 region of the 16S rRNA gene was amplified and pyrosequenced. A total of 17 214 oral bacterial sequences were obtained from the six subjects; these were binned into 1034 OTUs from 10 phyla, 30 families and 51 genera. The oral mucosa was highly dominated by four phyla: Firmicutes (mostly the genera Streptococcus and Veillonella), Proteobacteria (mostly Neisseria), Bacterioidetes (Prevotella) and Actinobacteria (Micrococcineae). Although the microbiota were similar at the phylum level, the Amerindians shared only 62 % of the families and 23 % of the genera with non-Amerindians from previous studies, and had a lower richness of genera (51 vs 177 reported in non-Amerindians). The Amerindians carried unidentified members of the phyla Bacteroidetes, Firmicutes and Proteobacteria and their microbiota included soil bacteria Gp1 (Acidobacteriaceae) and Xylanibacter (Prevotellaceae), and the rare genus Phocoenobacter (Pasteurellaceae). Preserving buccal swabs in the Aware Messenger oral fluid collection device substantially altered the bacterial composition in comparison to freezing, and therefore this method cannot be used to preserve samples for the study of microbial communities.

Delivery mode shapes the acquisition and structure of the initial microbiota across multiple body habitats in newborns.

Upon delivery, the neonate is exposed for the first time to a wide array of microbes from a variety of sources, including maternal bacteria. Although prior studies have suggested that delivery mode shapes the microbiota's establishment and, subsequently, its role in child health, most researchers have focused on specific bacterial taxa or on a single body habitat, the gut. Thus, the initiation stage of human microbiome development remains obscure. The goal of the present study was to obtain a community-wide perspective on the influence of delivery mode and body habitat on the neonate's first microbiota. We used multiplexed 16S rRNA gene pyrosequencing to characterize bacterial communities from mothers and their newborn babies, four born vaginally and six born via Cesarean section. Mothers' skin, oral mucosa, and vagina were sampled 1 h before delivery, and neonates' skin, oral mucosa, and nasopharyngeal aspirate were sampled <5 min, and meconium <24 h, after delivery. We found that in direct contrast to the highly differentiated communities of their mothers, neonates harbored bacterial communities that were undifferentiated across multiple body habitats, regardless of delivery mode. Our results also show that vaginally delivered infants acquired bacterial communities resembling their own mother's vaginal microbiota, dominated by Lactobacillus, Prevotella, or Sneathia spp., and C-section infants harbored bacterial communities similar to those found on the skin surface, dominated by Staphylococcus, Corynebacterium, and Propionibacterium spp. These findings establish an important baseline for studies tracking the human microbiome's successional development in different body habitats following different delivery modes, and their associated effects on infant health.

A rapid malaria appraisal in the Venezuelan Amazon.

BACKGROUND: While the federal state of Amazonas bears the highest risk for malaria in Venezuela (2007: 68.4 cases/1000 inhabitants), little comprehensive information about the malaria situation is available from this area. The purpose of this rapid malaria appraisal (RMA) was to provide baseline data about malaria and malaria control in Amazonas. METHODS: The RMA methodology corresponds to a rapid health impact assessment (HIA) as described in the 1999 Gothenburg consensus. In conjunction with the actors of the malaria surveillance system, all useful data and information, which were accessible within a limited time-frame of five visits to Amazonas, were collected, analysed and interpreted. RESULTS: Mortality from malaria is low (< 1 in 105) and slide positivity rates have stayed at the same level for the last two decades (15% +/- 6% (SD)). Active case detection accounts for ca. 40% of slides taken. The coverage of the censured population with malaria notification points (NPs) has been achieved in recent years. The main parasite is Plasmodium vivax (84% of cases). The proportion of Plasmodium falciparum is on the decline, possibly driven by the introduction of cost-free artemisinin-based combination therapy (ACT) (1988: 33.4%; 2007: 15.4%). Monitoring and documentation is complete, systematic and consistent, but poorly digitalized. Malaria transmission displayed a visible lag behind rainfall in the capital municipality of Atures, but not in the other municipalities. In comparison to reference microscopy, quality of field microscopy and rapid diagnostic tests (RDTs) is suboptimal (kappa < 0.75). Hot spots of malaria risk were seen in some indigenous ethnic groups. Conflicting strategies in respect of training of community health workers (CHW) and the introduction of new diagnostic tools (RDTs) were observed. CONCLUSION: Malaria control is possible, even in tropical rain forest areas, if the health system is working adequately. Interventions have to be carefully designed and the features of the particular local Latin American context considered.

How should nets be dried after insecticide treatment in the field?

Different procedures for drying polyamide (nylon) hammock nets (approximately 10 m2) posttreatment were evaluated. Forty-three nets were soaked for 10 min in a plastic bowl containing a solution of water and lambdacyhalothrin 0.05% (target dose of 10 mg/m2). Twenty-two freshly treated nets were put to dry in the sun: 13 of them hung vertically with the roof of the hammock net at the top and the hem at the bottom, and the other 9 were folded and laid flat on a plastic sheet. The rest of the nets (21) were dried in the shade: 11 of them hung vertically and 10 were folded flat on a plastic sheet. After 6-7 h, 2 15-cm2 samples of each net were cut, one on top of the lateral side and one 40 cm from the edge. Concentrations of lambdacyhalothrin were determined by gas chromatography-mass spectrometry on subsamples of netting (1 cm2). The mean insecticide concentrations of samples were compared between nets that were dried in the sun or in the shade, and placed to dry either hanging vertically or folded flat. In general, no differences were found between the mean insecticide concentrations of nets that were dried vertically in the sun or in the shade, or those dried flat in the shade. However, the mean dose was considerably lower in the remaining nets, which were dried flat in the sun. The reason for this is unclear but is hypothesized to be an effect of temperature. Results indicated that nets hung vertically either in the sun or shade dried faster than those laid flat. Based on the time to dry and mean insecticide extracted, it is recommended to hang treated nets vertically in the sun for drying.

Hyperreactive malarial splenomegaly is associated with low levels of antibodies against red blood cell and Plasmodium falciparum derived glycolipids in Yanomami Amerindians from Venezuela.

The immunological basis of the aberrant immune response in hyperreactive malarial splenomegaly (HMS) is poorly understood, but believed to be associated with polyclonal B cell activation by an unidentified malaria mitogen, leading to unregulated immunoglobulin and autoantibody production. HMS has been previously reported in Yanomami communities in the Upper Orinoco region of the Venezuelan Amazon. To investigate a possible association between antibody responses against Plasmodium falciparum and uninfected red blood cell (URBC) glycolipids and splenomegaly, a direct comparison of the parasite versus host anti-glycolipid antibody responses was made in an isolated community of this area. The anti-P. falciparum glycolipid (Pfglp) response was IgG3 dominated, whereas the uninfected red blood cell glycolipid (URBCglp) response showed a predominance of IgG1. The levels of IgG1 against Pfglp, and of IgG4 and IgM against URBCglp were significantly higher in women, while the anti-Pfglp or URBCglp IgM levels were inversely correlated with the degree of splenomegaly. Overall, these results suggest differential regulation of anti-parasite and autoreactive responses and that these responses may be linked to the development and evolution of HMS in this population exposed to endemic malaria. The high mortality rates associated with HMS point out that its early diagnosis together with the implementation of malaria control measures in these isolated Amerindian communities are a priority.

Vector bionomics and malaria transmission in the Upper Orinoco River, Southern Venezuela.

A longitudinal epidemiological and entomological study was carried out in Ocamo, Upper Orinoco River, between January 1994 and February 1995 to understand the dynamics of malaria transmission in this area. Malaria transmission occurs throughout the year with a peak in June at the beginning of the rainy season. The Annual Parasite Index was 1,279 per 1,000 populations at risk. Plasmodium falciparum infections accounted for 64% of all infections, P. vivax for 28%, and P. malariae for 4%. Mixed P. falciparum/P. vivax infections were diagnosed in 15 people representing 4% of total cases. Children under 10 years accounted for 58% of the cases; the risk for malaria in this age group was 77% higher than for those in the greater than 50 years age group. Anopheles darlingi was the predominant anopheline species landing on humans indoors with a biting peak between midnight and dawn. A significant positive correlation was found between malaria monthly incidence and mean number of An. darlingi caught. There was not a significant relationship between mean number of An. darlingi and rainfall or between incidence and rainfall. A total of 7295 anophelines were assayed by ELISA for detection of Plasmodium circumsporozoite (CS) protein. Only An. darlingi (55) was positive for CS proteins of P. falciparum (0.42%), P. malariae (0.25%), and P. vivax-247 (0.1%). The overall estimated entomological inoculation rate was 129 positive bites/person/year. The present study was the first longitudinal entomological and epidemiological study conducted in this area and set up the basic ground for subsequent intervention with insecticide-treated nets.

Vector bionomics and malaria transmission in the Upper Orinoco River, Southern Venezuela

A longitudinal epidemiological and entomological study was carried out in Ocamo, Upper Orinoco River, between January 1994 and February 1995 to understand the dynamics of malaria transmission in this area. Malaria transmission occurs throughout the year with a peak in June at the beginning of the rainy season. The Annual Parasite Index was 1,279 per 1,000 populations at risk. Plasmodium falciparum infections accounted for 64 percent of all infections, P. vivax for 28 percent, and P. malariae for 4 percent. Mixed P. falciparum/P. vivax infections were diagnosed in 15 people representing 4 percent of total cases. Children under 10 years accounted for 58 percent of the cases; the risk for malaria in this age group was 77 percent higher than for those in the greater than 50 years age group. Anopheles darlingi was the predominant anopheline species landing on humans indoors with a biting peak between midnight and dawn. A significant positive correlation was found between malaria monthly incidence and mean number of An. darlingi caught. There was not a significant relationship between mean number of An. darlingi and rainfall or between incidence and rainfall. A total of 7295 anophelines were assayed by ELISA for detection of Plasmodium circumsporozoite (CS) protein. Only An. darlingi (55) was positive for CS proteins of P. falciparum (0.42 percent), P. malariae (0.25 percent), and P. vivax-247 (0.1 percent). The overall estimated entomological inoculation rate was 129 positive bites/person/year. The present study was the first longitudinal entomological and epidemiological study conducted in this area and set up the basic ground for subsequent intervention with insecticide-treated nets.