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      Prevalence of asymptomatic Plasmodium vivax infections in the north-eastern focus of malaria of Venezuela Translated title: Prevalencia de infecciones asintomáticas por Plasmodium vivax en el foco malárico oriental de Venezuela

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          Abstract

          Malaria remains as a public health problem in Venezuela. In 2015 there were 136,402 cases reported by the Ministry of Popular Power for Health, being the parasite prevalence 73.95% for Plasmodium vivax, 17.6% for Plasmodium falciparum, 0.0095% for Plasmodium malariae and 8.42% mixed infections (P. vivax + P. falciparum). During the period 1999-2002 the number of cases in Venezuela ranged between 21,685 and 29,337, being the Sucre State with highest levels of malaria prevalence, with Plasmodium vivax as the unique specie in this region. In 2002 the Municipality of Cajigal had the highest Annual Parasite Incidence (API) of country, being 260 cases per 1000 inhabitants. In view of the difficulty in controlling malaria in this area, the prevalence of asymptomatic carriers was investigated as one of the epidemiological factors contributing to the persistence of malaria transmission. One hundred fifty people were included in the study, with no history of recent malaria infection, or any symptom and also, not having used antimalarial drugs during the 30 days prior to study entry. To do this, a malaria Rapid Diagnostic Test (mRDTs) was used for the determination of antigenemic (OptiMAL®) and PCR (polymerase chain reaction) in conjunction with the reference "Gold Standard", the conventional thick and thin blood smears (TTBS). It was found a prevalence of infection of 1.33% by mRDTs and TTBS and 8% by PCR which allowed the detection of 10 asymptomatic cases in addition, with a sensitivity and specificity of 100% and 93.4% respectively. The presence of asymptomatic carriers in this area reveals the difficulties that face the Malaria Control Program in the eventual elimination of this specific malaria foci. It is necessary reinforces the maintenance of the epidemiological surveillance using more sensitive diagnostic techniques, as well as to adapt the control measures based on the current findings.

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          A genus- and species-specific nested polymerase chain reaction malaria detection assay for epidemiologic studies.

          A nested polymerase chain reaction (PCR) assay that uses Plasmodium genus-specific primers for the initial PCR (nest 1) amplification and either genus- or species-specific primers for the nest 2 amplifications was tested on laboratory and field samples. With in vitro cultured Plasmodium falciparum-infected blood samples, it was capable of detecting six parasites/microl of blood using DNA prepared from 25-microl blood spots on filter paper. The assay was evaluated on fingerprick blood samples collected on filter paper from 129 individuals living in a malaria-endemic area in Malaysia. Malaria prevalence by genus-specific nested PCR was 35.6% (46 of 129) compared with 28.7% (37 of 129) by microscopy. The nested PCR detected seven more malaria samples than microscopy in the first round of microscopic examination, malaria in three microscopically negative samples, six double infections identified as single infections by microscopy and one triple infection identified as a double infection by microscopy. The nested PCR assay described is a sensitive technique for collecting accurate malaria epidemiologic data. When coupled with simple blood spot sampling, it is particularly useful for screening communities in remote regions of the world.
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            Mortality and morbidity from malaria among children in a rural area of The Gambia, West Africa.

            Mortality and morbidity from malaria were measured among 3000 children under the age of 7 years in a rural area of The Gambia, West Africa. Using a post-mortem questionnaire technique, malaria was identified as the probable cause of 4% of infant deaths and of 25% of deaths in children aged 1 to 4 years. The malaria mortality rate was 6.3 per 1000 per year in infants and 10.7 per 1000 per year in children aged 1 to 4 years. Morbidity surveys suggested that children under the age of 7 years experienced about one clinical episode of malaria per year. Calculation of attributable fractions showed that malaria may be responsible for about 40% of episodes of fever in children. Although the overall level of parasitaemia showed little seasonal variation, the clinical impact of malaria was highly seasonal; all malaria deaths and a high proportion of febrile episodes were recorded during a limited period at the end of the rainy season.
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              High prevalence of asymptomatic Plasmodium vivax and Plasmodium falciparum infections in native Amazonian populations.

              The epidemiology of malaria in 2 riverine localities in Rondĵnia, Brazilian western Amazĵnia, was assessed by a 1-year study at Portuchuelo, and a cross-sectional survey at riverine communities at Rio Machado (= Ji-Parana). Plasmodium spp. infections were diagnosed by light microscopy and by polymerase chain reaction (PCR) amplification of ribosomal DNA. PCR was 6-7 times more efficient than microscopy for detecting plasmodial infections. Both Plasmodium vivax and Plasmodium falciparum infections occurred as asymptomatic and symptomatic forms of the disease. The relation between symptomatic and asymptomatic clinical forms was roughly similar for both species of Plasmodium. Symptomless patients were monitored for 2 months. The prevalence of symptomless infections was 4-5 times higher than the symptomatic ones--respectively, 20% and 4.6% for Portuchuelo and 49.5% and 10% for Ji-Parana. Symptomatic malaria occurred mostly in patients in younger age groups. In contrast, there was a significant association of symptomless malaria with older age groups (medians of 26.5 and 21 years, respectively, for Portuchuelo and Ji-Parana), whereas the age medians for symptomatic malaria were 14 and 8 years, respectively, in the 2 regions. Symptomatic malaria also was more prevalent in groups living for shorter times in Amazĵnia (13 and 4 years, respectively, for Portuchuelo and Ji-ParanA) as compared with symptomless malaria, which was more prevalent in groups living for longer periods in the region (medians of 25.5 and 18 years, respectively, for Portuchuelo and Ji-Paraná). The high prevalence of symptomless malaria may pose new problems for the currently adopted strategy for the control of malaria in the Amazonian region, which is essentially based on the treatment of symptomatic patients.
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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                bmsa
                Boletín de Malariología y Salud Ambiental
                Bol Mal Salud Amb
                Instituto de Altos Estudios en Salud Pública Dr. Arnoldo Gabaldon (Maracay, Aragua,, Venezuela )
                1690-4648
                December 2016
                : 56
                : 2
                : 160-171
                Affiliations
                [06] Caracas orgnameInstituto de Estudios Avanzados IDEA orgdiv1Centro de Biociencias
                [03] Miranda orgnameCentro de Microbiología y Biología Celular, IVIC, Altos de Pipe orgdiv1Laboratorio de Inmunoparasitología
                [05] orgnameHospital Domingo Luciani orgdiv1Instituto Venezolano del Seguro Social Venezuela
                [01] Caracas orgnameUniversidad Central de Venezuela orgdiv1Facultad de Medicina orgdiv2Escuela de Medicina Luis Razetti albinawide@ 123456yahoo.com
                [04] orgnameUniversitat de Valencia orgdiv1Facultad de Farmacia orgdiv2Departamento de Parasitología España
                [07] orgnameFacultad de Medicina orgdiv1Instituto de Medicina Tropical orgdiv2Facultad de Medicina Caracas
                [02] Caracas orgnameMinisterio del Poder Popular para la Salud orgdiv1Instituto Nacional de Higiene Rafael Rangel
                Article
                S1690-46482016000200006
                f7047f4d-ef81-42ac-a271-9f1475153fed

                http://creativecommons.org/licenses/by/4.0/

                History
                : 20 December 2016
                : 18 August 2016
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 57, Pages: 12
                Product

                SciELO Venezuela


                PCR,Malaria asintomática,Plasmodium vivax,Gota Gruesa y Extendido de Sangre (GGES),Prueba rápida de diagnóstico OptiMAL®,Asymptomatic malaria,thick and thin blood smears (TTBS),mRDTs,OptiMAL®

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