Cross sectional study reveals a high percentage of asymptomatic Plasmodium vivax infection in the Amazon Rio Negro area, Brazil

Suárez-Mútis, Martha Cecília; Cuervo, Patrícia; Leoratti, Fabiana M. S.; Moraes-Avila, Sandra L.; Ferreira, Antônio Walter; Fernandes, Octávio; Coura, José Rodrigues

doi:10.1590/s0036-46652007000300005

Cited by 50 publications

(43 citation statements)

References 22 publications

(29 reference statements)

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“…The gametocyte carriage of 8.6% observed in the present study is similar to the rate of 10.8% reported in Kenya [38]. Gametocyte carriers are reservoirs of infection that play a key role in continuous malaria transmission [5,10,41]; thus, the almajirai could serve as a source of infection to larger populations, challenging control measures.…”

Section: Discussionsupporting

confidence: 76%

Asymptomatic falciparum malaria and genetic polymorphisms of Pfcrt K76T and Pfmdr1 N86Y among almajirai in northeast Nigeria

Balogun

Sandabe

Bdliya

et al. 2016

J Infect Dev Ctries

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Introduction: Malaria remains a public health challenge, especially in sub-Saharan Africa where asymptomatic malaria is not uncommon. In the present study, the prevalence of asymptomatic falciparum malaria was investigated in almajirai, and the genetic polymorphisms of chloroquine (CQ) resistance biomarkers were assessed. Methodology: A total of 440 apparently healthy almajirai between 3 and 12 years of age were randomly enrolled in Maiduguri, northeast Nigeria, between July and December 2010. Parasitemia and gametocytemia were assessed by light microscopy, and polymorphisms of Pfcrt K76T and Pfmdr1 N86Y were detected by nested polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) techniques. Results: The mean age of the subjects was 8.3 ± 4.5 years, with subjects ≤ 5 years accounting for 10.7% (47/440) of the population. Prevalence of asymptomatic falciparum parasitemia and gametocytemia were 12.7% (56/440) and 8.6% (38/440), respectively. Geometric mean parasite density (GMPD) was 240 (160-630) parasites/µL, while geometric mean gametocyte density (GMGD) was 53 (24-96) gametocytes/µL. The GMPD was higher among subjects ≤ 5 years of age (p = 0.027). Pfcrt 76T was detected in 5.4% (3/56) of the isolates, and no isolates harbored Pfmdr1 86Y mutant. Conclusions: The study reveals asymptomatic falciparum malaria in almajirai and low levels of Pfcrt 76T and Pfmdr1 86Y alleles. These findings could hinder malaria control measures, and hence almajirai should be incorporated into malaria control programs.

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Section: Discussionsupporting

confidence: 76%

Asymptomatic falciparum malaria and genetic polymorphisms of Pfcrt K76T and Pfmdr1 N86Y among almajirai in northeast Nigeria

Balogun

Sandabe

Bdliya

et al. 2016

J Infect Dev Ctries

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“…However, due to the very low parasitaemia (sometimes submicroscopic) presented by these patients, it is possible that platelet counts are normal and parallel clinical symptoms (Suarez-Mutis et al 2007).…”

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confidence: 97%

Thrombocytopenia in malaria: who cares?

Lacerda

Mourão

Coelho

et al. 2011

Mem. Inst. Oswaldo Cruz

172

168

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Key words: Plasmodium falciparum -Plasmodium vivax -malaria -thrombocytopenia -plateletsMalaria and thrombocytopenia • Marcus Vinícius Guimarães Lacerda et al. 53Data on the real burden of thrombocytopenia associated with malaria is contradictory in the literature and it is not usually considered when conducting patient selection. Table I shows the major publications estimating the frequency of thrombocytopenia. Most of these data were published in the late 1990s, probably in time with the surge in the availability of affordable automated machines capable of performing full blood counts (FBC). Manual platelet counting is time-consuming and usually needs to be requested by the physician with the routine blood count in most of the endemic areas for malaria. In only three publications is there an adequate randomised enrollment of patients with appropriate sample size calculation to estimate the frequency of bleeding and its association with the respective platelet count (Lacerda 2007, Silva 2009, Kochar et al. 2010. Only one study has ruled out other common causes of thrombocytopenia that are also endemic in the studied area (Lacerda 2007). There is a wide range of thrombocytopenia occurrence in these reports, which may be explained by distinct selection criteria of the enrolled patients. There are also differences in the selection of outpatients or inpatients from tertiary care centres that tend to present with severe thrombocytopenia. Furthermore, clinical manifestations of thrombocytopenia are usually described as case reports and most of these are due to P. vivax (Table II).In 2005, 138 of 684 (20.1%) malarial cases hospitalised in a tertiary care centre in Manaus had thrombocytopenia as the cause of admission, which corresponded to 6.8% of hospitalisations due to all causes in this reference institution (unpublished observations). Hospitalisation, however, does not add any benefit to the patient and because there is no evidence for any intervention, this simply increases public health costs in underdeveloped and under-resourced areas.Pathogenesis of malarial thrombocytopenia -Coagulation disturbances -A study based on 31 American soldiers in Vietnam with chloroquine-resistant falciparum malaria noted the following changes in the acute phase of the disease using the same patients as their own controls during convalescence: decrease in the platelet count and prothrombim activation time, increase in the activated thromboplastin time, and reduction in factors V, VII and VIII with normal fibrinogen (Dennis et al. 1967). This report suggested that thrombocytopenia was simply a consequence of the coagulation disorders presented by these patients, an idea that persisted for many decades in the literature. In another series of 21 patients with falciparum malaria, six had developed disseminated intravascular coagulation (DIC). The authors noted that the patients with more severe thrombocytopenia also had DIC and that there was correlation between platelet count and C3 protein levels. However, the reduction in C3 was pr...

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“…However, this method has not shown consistent results in hypo and mesoendemic areas in the American 9 or Easter Mediterranean 1 region where subpatent Plasmodium infections occur. In the Amazon region, Plasmodium-infected asymptomatic individuals are characterized as having low parasite densities which are at times even undetected by microscopy 2,11,14,15 .…”

Section: Discussionmentioning

confidence: 99%

“…A high percentage of cases occur in dispersed areas far from cities where health systems infrastructure is often deficient or absent. In recent years asymptomatic Plasmodium infections have been reported in the Amazon region 2,15 . Although a thick smear is the gold standard for malaria diagnosis, this method is not efficient for diagnosing sub patent parasites in asymptomatic Plasmodium infections 5,14 .…”

Section: Introductionmentioning

confidence: 99%

Evaluation of three different DNA extraction methods from blood samples collected in dried filter paper in Plasmodium subpatent infections from the Amazon region in Brazil

Miguel

Coura

Samudio

et al. 2013

Rev. Inst. Med. trop. S. Paulo

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SUMMARYAsymptomatic Plasmodium infection is a new challenge for public health in the American region. The polymerase chain reaction (PCR) is the best method for diagnosing subpatent parasitemias. In endemic areas, blood collection is hampered by geographical distances and deficient transport and storage conditions of the samples. Because DNA extraction from blood collected on filter paper is an efficient method for molecular studies in high parasitemic individuals, we investigated whether the technique could be an alternative for Plasmodium diagnosis among asymptomatic and pauciparasitemic subjects. In this report we compared three different methods (Chelex®-saponin, methanol and TRIS-EDTA) of DNA extraction from blood collected on filter paper from asymptomatic Plasmodium-infected individuals. Polymerase chain reaction assays for detection of Plasmodium species showed the best results when the Chelex®-saponin method was used. Even though the sensitivity of detection was approximately 66% and 31% for P. falciparum and P. vivax, respectively, this method did not show the effectiveness in DNA extraction required for molecular diagnosis of Plasmodium. The development of better methods for extracting DNA from blood collected on filter paper is important for the diagnosis of subpatent malarial infections in remote areas and would contribute to establishing the epidemiology of this form of infection.

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Cross sectional study reveals a high percentage of asymptomatic Plasmodium vivax infection in the Amazon Rio Negro area, Brazil

Cited by 50 publications

References 22 publications

Asymptomatic falciparum malaria and genetic polymorphisms of Pfcrt K76T and Pfmdr1 N86Y among almajirai in northeast Nigeria

Asymptomatic falciparum malaria and genetic polymorphisms of Pfcrt K76T and Pfmdr1 N86Y among almajirai in northeast Nigeria

Thrombocytopenia in malaria: who cares?

Evaluation of three different DNA extraction methods from blood samples collected in dried filter paper in Plasmodium subpatent infections from the Amazon region in Brazil

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