A trial of insecticide treated nets for malaria control in Yanomami communities in Amazonas, Venezuela

A community randomized controlled trial was carried out in an area of moderate malaria transmission in the Amazon region, in South East Venezuela, where the indigenous Yanomami population live. The aim of the project was to assess the impact of lambdacyhalothrin treated hammock nets (ITHNs), compared to placebo treated hammock nets (PTHNs), on the malaria incidence rate and on the malaria vector population Anopheles darlingi. In both arms of the study intensive early case detection was performed and prompt malaria treatment administered. Baseline data were collected one year before the intervention and a population of around 924 Yanomami was followed for two years. Despite the recent introduction of nets in the Yanomami villages and the adverse natural conditions in the area, the majority of Yanomami showed high compliance and took good care of the nets. Analysis performed by gas chromatography of samples taken from the nets dried in different ways, i. e. vertically or horizontally, in the sun or in the shade, showed that there were no significant differences between methods with the only exception of drying the nets horizontally and in the sun performing significantly worse then the others. In addition bioassays, with Aedes aegypti, showed that hammock nets treated at village level with lambdacyhalothrin (10 mg/m2) and dried vertically in the sun were effectively killing mosquitoes (87%) after six months of regular use and the mortality rate was 83% after washing the nets twice. The malaria incidence rate per thousand person years at risk was 114.6 in the IHTNs group and 186.8 in the PTHNs group. The adjusted rate ratios indicated that ITHNs prevent 55% (IRR: 0.44, 95% CI: 52-59%) of new malaria cases. ITHNs reduced the prevalence of parasitaemia by 87% (RR: 0.17, 95% CI: 0-45%) in the first cross-sectional survey carried out during the high transmission season, six months after the intervention. The prevalence of splenomegaly and of anaemia was low in both groups, and there was no evidence of reduction due to ITHNs. There was little evidence of a mass killing effect on the density of the vector population, although significant differences between study arms were found when the analysis was carried out adjusting for baseline An. darlingi density. The density of An. darlingi was 62% less in villages with ITHNs than those with PTHNs (density ratio: 0.38, 95% CI 52-70%). The main conclusion of the present study is that ITHNs can reduce malaria incidence in the area and it is the most feasible method of malaria control in a forested area where indigenous villages are scattered over a large territory.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A rapid malaria appraisal in the Venezuelan Amazon

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Caracterizaci\uf3n de criaderos de anofelinos (Diptera: Culicidae) vectores de malaria del Alto Orinoco, Amazonas, Venezuela

RUBIO-PALIS Y, MENARE C, QUINTO A, MAGRIS M, AMARISTA M. 2005. Caracterizaci\uf3n de criaderos de anofelinos (Diptera: Culicidae) vectores de malaria del Alto Orinoco, Amazonas, Venezuela. Entomotrtopica 20(1): 29-38. Between October 1999 and January 2000, anopheline breeding habitats were identified and characterized in the Ocamo area, municipality Upper Orinoco, Amazonas state, in southern Venezuela. During the study, 46 samples were taken from 4 types of larval habitats: lagoon (37), pond (2), stream (6) and pool (1). A total of 1 304 anopheline larvae were collected belonging to 8 species: Anopheles oswaldoi , A. darlingi, A. triannulatus, A. mattogrossensis, A. punctimacula, A. forattinii, A. braziliensis and A. peryassui. The most abundant and frequent species collected was A. oswaldoi, followed by A. triannulatus and A. darlingi. The remaining species accounted for 11% of the total anophelines identified. Larvae density was higher in the ponds (3.38 larvae/dip). The analysis of canonic correspondence (ACC) showed a strong spatial structure in relation to anopheline species and environmental variables. These results were confirmed a posteriori by the Monte Carlo permutation test, p= 0,01. The variables that explained the spatial distribution of A. oswaldoi, A. darlingi and A. mattogrossensis were: detritus (twigs and leafs), pH, water depth and temperature. Anopheles triannulatus preferred lagoons with floating vegetation and tall grasses. Higher density of inmature stages (DEL3, DEL4 and DEP-PA) were associated with shaded lagoons and abundant algae.RUBIO-PALIS Y, MENARE C, QUINTO A, MAGRIS M, AMARISTA M. 2005. Caracterizaci\uf3n de criaderos de anofelinos (Diptera: Culicidae) vectores de malaria del Alto Orinoco, Amazonas, Venezuela. Entomotrtopica 20(1): 29-38. Entre Octubre 1999 y Enero 2000 se identificaron y caracterizaron los habitats de los estad\uedos inmaduros de anofelinos en el \ue1rea de Ocamo, municipio Alto Orinoco, Amazonas, Venezuela. Se tomaron 46 muestras de cuatro tipos de criaderos: laguna, pozo, ca\uf1o y charco. Se colectaron 1 304 larvas de anofelinos de diferentes estadios, pertenecientes a: Anopheles oswaldoi , A. darlingi, A. triannulatus, A. braziliensis, A. mattogrossensis, A. punctimacula, A. forattinii y A. peryassui. La especie m\ue1s abundante fue A. oswaldoi, seguida por A. triannulatus y A. darlingi. Las dem\ue1s especies representaron 11% del total identificado. La densidad de larvas fue mayor en los criaderos tipo pozo (3.38 larvas/cuchar\uf3n). El an\ue1lisis de correspondencia can\uf3nica (ACC) realizado evidenci\uf3 una fuerte estructuraci\uf3n espacial en relaci\uf3n con las especies de anofelinos y variables ambientales. Este resultado fue ratificado a posteriori por la prueba de permutaci\uf3n de Monte Carlo, mostrando un nivel de significaci\uf3n de p= 0,01. Las variables que explican la distribuci\uf3n espacial de A. oswaldoi, A. darlingi y A. mattogrossensis son: detritos (palitos y hojas), pH, profundidad y temperatura. A. triannulatus mostr\uf3 preferencia por las lagunas con vegetaci\uf3n flotante y gram\uedneas altas. La densidad de estadios inmaduros DEL3, DEL4 y DEP-PA, es mayor en las lagunas con sombra permanente y abundantes algas

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

AbstractBackgroundThe 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.MethodsWe 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.FindingsBased 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.InterpretationThis 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

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

A communal catalogue reveals Earth’s multiscale microbial diversity

Our growing awareness of the microbial world’s importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth’s microbial diversity

A communal catalogue reveals Earth's multiscale microbial diversity

Our growing awareness of the microbial world's importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth's microbial diversity.Peer reviewe

A trial of insecticide treated nets for malaria control in Yanomami communities in Amazonas, Venezuela

A community randomized controlled trial was carried out in an area of moderate malaria transmission in the Amazon region, in South East Venezuela, where the indigenous Yanomami population live. The aim of the project was to assess the impact of lambdacyhalothrin treated hammock nets (ITHNs), compared to placebo treated hammock nets (PTHNs), on the malaria incidence rate and on the malaria vector population Anopheles darlingi. In both arms of the study intensive early case detection was performed and prompt malaria treatment administered. Baseline data were collected one year before the intervention and a population of around 924 Yanomami was followed for two years. Despite the recent introduction of nets in the Yanomami villages and the adverse natural conditions in the area, the majority of Yanomami showed high compliance and took good care of the nets. Analysis performed by gas chromatography of samples taken from the nets dried in different ways, i. e. vertically or horizontally, in the sun or in the shade, showed that there were no significant differences between methods with the only exception of drying the nets horizontally and in the sun performing significantly worse then the others. In addition bioassays, with Aedes aegypti, showed that hammock nets treated at village level with lambdacyhalothrin (10 mg/m2) and dried vertically in the sun were effectively killing mosquitoes (87%) after six months of regular use and the mortality rate was 83% after washing the nets twice. The malaria incidence rate per thousand person years at risk was 114.6 in the IHTNs group and 186.8 in the PTHNs group. The adjusted rate ratios indicated that ITHNs prevent 55% (IRR: 0.44, 95% CI: 52-59%) of new malaria cases. ITHNs reduced the prevalence of parasitaemia by 87% (RR: 0.17, 95% CI: 0-45%) in the first cross-sectional survey carried out during the high transmission season, six months after the intervention. The prevalence of splenomegaly and of anaemia was low in both groups, and there was no evidence of reduction due to ITHNs. There was little evidence of a mass killing effect on the density of the vector population, although significant differences between study arms were found when the analysis was carried out adjusting for baseline An. darlingi density. The density of An. darlingi was 62% less in villages with ITHNs than those with PTHNs (density ratio: 0.38, 95% CI 52-70%). The main conclusion of the present study is that ITHNs can reduce malaria incidence in the area and it is the most feasible method of malaria control in a forested area where indigenous villages are scattered over a large territory

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