Sensitivity of microscopy compared to molecular diagnosis of p. Falciparum: implications on malaria treatment in epidemic areas in kenya

Myoglobin Cast Nephropathy Diagnosed on Renal Biopsy in a Patient Treated for Malarial Infection

Myoglobin cast nephropathy occurs in cases of acute renal injury in which large amounts of myoglobin accumulate in the renal tubules, presenting as muscle pain, reddish-brown urine, and elevated creatine kinase levels. Our case describes a 60-year-old male who came to the emergency department with fevers, mild abdominal pain, and constitutional symptoms one day after returning to the United States from a trip to Nigeria. Initial workup demonstrated an acute kidney injury and elevated aminotransferase levels and the patient was started onatovaquone-proguanil for possible malaria given a recent diagnosis in Nigeria. Two days later, the patient was found to have rhabdomyolysis, resulting in a renal biopsy that showed myoglobin cast nephropathy. Previous literature has suggested mechanisms for the development of rhabdomyolysis in malarial infection, including inflammatory processes, direct effect of parasite accumulation, and drug-induced toxicity. Our case further implicates antimalarial therapy as a cause of rhabdomyolysis and increases awareness of myoglobin cast nephropathy as a potential complication of malaria.

Comparative evaluation of traditional and molecular diagnostic methods for malaria: An analysis of performance

Purpose

As we edge closer to the eradication of malaria, several methods for detecting Plasmodium species have been developed, including peripheral blood smear examination (PBS), rapid diagnostic tests (RDTs), serological evaluations, fluorescent microscopy, polymerase chain reactions (PCRs), fluorescent in situ hybridization, and flow cytometry. The suitability of these tools for routine diagnosis requires evaluation, considering both their diagnostic accuracy and cost-effectiveness.

Materials and Methods

Our study compared four diagnostic techniques for malaria: PBS, quantitative buffy coat (QBC), RDT, and PCR. We used PCR as the benchmark standard and statistically assessed the performance of PBS, QBC, and RDT against PCR in detecting malaria. Adopting a prospective observational approach, we collected blood samples from 117 patients exhibiting the symptoms suggestive of malaria.

Results

The findings from our study showed that PBS had a positivity rate of 93.4%, with a 95% confidence interval (CI) of 0.881-0.987, indicating reliable results for a similar population. The QBC assay demonstrated an elevated positivity rate of 96.7% with a solid 95% CI of 0.930-1.000. Although the RDT had a slightly lower rate of 92.4%, it still delivered dependable results, presenting a significant 95% CI of 0.868-0.980, ensuring a robust diagnostic performance compared to PCR.

Conclusion

PCR is a reliable test when the identification of the specific species is inconclusive. Conversely, the commonly used PBS occasionally overlooks positive malaria cases due to the specialized skills needed for accurate reading. The cost-effective RDT is feasible for field operations without the need for expert knowledge. However, it fails to differentiate between old and new infections. Meanwhile, the QBC test, known for its sensitivity and speed, can be consistently employed for malaria diagnosis in a tertiary care settings.

Significant number of Plasmodium vivax mono-infections by PCR misidentified as mixed infections (P. vivax/P. falciparum) by microscopy and rapid diagnostic tests: malaria diagnostic challenges in Ethiopia

BACKGROUND

Plasmodium vivax malaria is now recognized as a cause of severe morbidity and mortality, resulting in a substantial negative effect on health especially in endemic countries. Accurate and prompt diagnosis and treatment of P. vivax malaria is vital for the control and elimination of the disease.

METHODS

A cross-sectional study was conducted from February 2021 to September 2022 at five malaria endemic sites in Ethiopia including Aribaminch, Shewarobit, Metehara, Gambella, and Dubti. A total of 365 samples that were diagnosed positive for P. vivax (mono and mixed infection) using RDT, site level microscopists and expert microscopists were selected for PCR. Statistical analyses were performed to calculate the proportions, agreement (k), frequencies, and ranges among different diagnostic methods. Fisher's exact tests and correlation test were used to detect associations and relationship between different variables.

RESULTS

Of the 365 samples, 324 (88.8%), 37(10.1%), 2 (0.5%), and 2 (0.5%) were P. vivax (mono), P. vivax/Plasmodium falciparum (mixed), P. falciparum (mono) and negative by PCR, respectively. The overall agreement of rapid diagnostic test (RDT), site level microscopy and expert microscopists result with PCR was 90.41% (k: 0.49), 90.96% (k: 0.53), and 80.27% (k: 0.24). The overall prevalence of sexual (gametocyte) stage P. vivax in the study population was 215/361 (59.6%). The majority of these 215 samples (180; 83.7%) had below 1000 parasites/µl, with only four samples (1.9%) had ≥ 5000 parasites/µl. The gametocyte density was found to be weakly positive but statically significant with asexual parasitaemia (r = 0.31; p < 0.001).

CONCLUSION

Both microscopy and RDT showed moderate agreement with PCR in the detection and identification of P. vivax (mono) and P. vivax/P. falciparum (mixed) infections. Therefore, to achieve malaria elimination goals, strengthening routine malaria diagnostic methods by implementing diagnostic tools with a good performance in detecting and accurately identifying malaria species in clinical settings is recommended.

Advances and challenges in automated malaria diagnosis using digital microscopy imaging with artificial intelligence tools: A review

Malaria is an infectious disease caused by parasites of the genus Plasmodium spp. It is transmitted to humans by the bite of an infected female Anopheles mosquito. It is the most common disease in resource-poor settings, with 241 million malaria cases reported in 2020 according to the World Health Organization. Optical microscopy examination of blood smears is the gold standard technique for malaria diagnosis; however, it is a time-consuming method and a well-trained microscopist is needed to perform the microbiological diagnosis. New techniques based on digital imaging analysis by deep learning and artificial intelligence methods are a challenging alternative tool for the diagnosis of infectious diseases. In particular, systems based on Convolutional Neural Networks for image detection of the malaria parasites emulate the microscopy visualization of an expert. Microscope automation provides a fast and low-cost diagnosis, requiring less supervision. Smartphones are a suitable option for microscopic diagnosis, allowing image capture and software identification of parasites. In addition, image analysis techniques could be a fast and optimal solution for the diagnosis of malaria, tuberculosis, or Neglected Tropical Diseases in endemic areas with low resources. The implementation of automated diagnosis by using smartphone applications and new digital imaging technologies in low-income areas is a challenge to achieve. Moreover, automating the movement of the microscope slide and image autofocusing of the samples by hardware implementation would systemize the procedure. These new diagnostic tools would join the global effort to fight against pandemic malaria and other infectious and poverty-related diseases.

Malaria Detection Accelerated: Combing a High-Throughput NanoZoomer Platform with a ParasiteMacro Algorithm

Eradication of malaria, a mosquito-borne parasitic disease that hijacks human red blood cells, is a global priority. Microscopy remains the gold standard hallmark for diagnosis and estimation of parasitemia for malaria, to date. However, this approach is time-consuming and requires much expertise especially in malaria-endemic countries or in areas with low-density malaria infection. Thus, there is a need for accurate malaria diagnosis/parasitemia estimation with standardized, fast, and more reliable methods. To this end, we performed a proof-of-concept study using the automated imaging (NanoZoomer) platform to detect the malarial parasite in infected blood. The approach can be used as a steppingstone for malaria diagnosis and parasitemia estimation. Additionally, we created an algorithm (ParasiteMacro) compatible with free online imaging software (ImageJ) that can be used with low magnification objectives (e.g., 5×, 10×, and 20×) both in the NanoZoomer and routine microscope. The novel approach to estimate malarial parasitemia based on modern technologies compared to manual light microscopy demonstrated 100% sensitivity, 87% specificity, a 100% negative predictive value (NPV) and a 93% positive predictive value (PPV). The manual and automated malaria counts showed a good Pearson correlation for low- (R2 = 0.9377, r = 0.9683 and p < 0.0001) as well as high- parasitemia (R2 = 0.8170, r = 0.9044 and p < 0.0001) with low estimation errors. Our robust strategy that identifies and quantifies malaria can play a pivotal role in disease control strategies.

Utilization of 18s ribosomal RNA LAMP for detecting Plasmodium falciparum in microscopy and rapid diagnostic test negative patients

In this study, Plasmodium falciparum was detected in patients that were declared negative for malaria microscopy and rapid diagnostic test kit (mRDT), using Plasmodium 18s rRNA loop-mediated isothermal amplification (LAMP) technique. The main aim of this study was to assess the usefulness of LAMP assay for detecting pre-clinical malaria, when microscopy and mRDT were less sensitive. DNA was obtained from 100 μL of whole blood using the boil and spin method. Subsequently, the Plasmodium 18s rRNA LAMP assay was performed to amplify the specific Plasmodium 18s rRNA gene. Microscopy and mRDT negative samples [697/2223 (31.2%)] were used for this study. Compared to frequencies obtained for the other demographic variables, most of the patients were < 6 years (37.7%), females (59.0%), peri-urban dwellers (39.0%) and patients that sought outpatient department services (39.3%). Overall, the prevalence of Plasmodium 18s rRNA was 17.5%. when stratified by study variables, Plasmodium 18s rRNA LAMP positivity was higher in patients over 30 years [58/122 (54.2%)], males [69/122 (56.5%)], rural dwellers [69/122 (56.5%)] and patients that sought OPD services [68/122 (55.7%)]. The risk of being infected with Plasmodium when routine tests were negative was higher in 15-30-year group (OR = 3.03, 95% CI: 1.6-5.8, p = 0.0007), patients > 30 years (OR = 15.2, 95% CI: 8.3-27.7, p<0.001), males (OR = 2.1, 95% CI: 1.4-3.2, p = 0.0002) and rural dwellers (OR = 2.2, 95% CI:1.4-3.6, p = 0.0009). However, risk was lower in post-natal children (OR = 0.3, 95% CI: 0.18-0.51, p<0.001). Majority (81.5%) of the infected patients presented with headache, herpes labialis, diarrhea and vomiting. We demonstrated the lack of sensitivities of microscopy and mRDT for one-time diagnosis of malaria. Therefore, it is essential to utilize a sensitive technique such as Plasmodium 18s rRNA LAMP to increase the detection rate of Plasmodium infection.

The effect of malaria on haemoglobin concentrations: a nationally representative household fixed-effects study of 17,599 children under 5 years of age in Burkina Faso

Background

Although the association between malaria and anaemia is widely studied in patient cohorts, the population-representative causal effects of malaria on anaemia remain unknown. This study estimated the malaria-induced decrease in haemoglobin levels among young children in malaria-endemic Burkina Faso.

Methods

The study was based on pooled individual-level nationally representative health survey data (2010–2011, 2014, 2017–2018) from 17 599 children under 5 years of age. This data was used to estimate the effects of malaria on haemoglobin concentration, controlling for household fixed-effects, age, and sex in a series of regression analyses. The fixed-effects controlled for observed and unobserved confounding on the household level and allowed to determine the impact of malaria infection status on haemoglobin levels and anaemia prevalence. Furthermore, the diagnostic results from microscopy and rapid diagnostic tests were leveraged to provide a quasi-longitudinal perspective of acute and prolonged effects after malaria infection.

Results

The prevalence of both malaria (survey prevalence ranging from 17.4% to 65.2%) and anaemia (survey prevalence ranging from 74% to 88.2%) was very high in the included surveys. Malaria was estimated to significantly reduce haemoglobin levels, with an overall effect of − 7.5 g/dL (95% CI − 8.5, − 6.5). Acute malaria resulted in a − 7.7 g/dL (95% CI − 8.8, − 6.6) decrease in haemoglobin levels. Recent malaria without current parasitaemia decreased haemoglobin concentration by − 7.1 g/dL (95% CI − 8.3, − 5.9). The in-sample predicted prevalence of severe anaemia was 9.4% among malaria positives, but only 2.2% among children without malaria.

Conclusion

Malaria infection has a strong detrimental effect on haemoglobin levels among young children in Burkina Faso. This effect seems to carry over even after acute infection, indicating prolonged haemoglobin reductions even after successful parasite-elimination. The quasi-experimental fixed-effect approach adds a population level perspective to existing clinical evidence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03948-z.

Prevalence of sickle cell disorders and malaria infection in children aged 1-12 years in the Volta Region, Ghana: a community-based study

Background

Alterations in the structure of haemoglobin (Hb) are usually brought about by point mutations affecting one or, in some cases, two codons encoding amino acids of the globin chains. One in three Ghanaians are said to have sickle cell disorders, whereas malaria continues to be one of the leading causes of mortality among children. This study determined the prevalence of sickle cell disorders and malaria infection among children aged 1–12 years in the Volta Region.

Methods

This was a community-based cross-sectional survey that involved 938 children aged 1–12 years selected from three districts, one each from the 3 geographical zones of the Volta Region using a multistage sampling method. Demographic information was collected using a standard questionnaire and anthropometric indices were measured. Isoelectric focusing (IEF) electrophoresis was used to determine the Hb genotypes and sub-microscopic parasites were determined by PCR.

Results

The prevalence of sickling screening positive was 16.0% with an overall prevalence of sickle cell disorders being 2.0%. Among the individual genotypes making up the sickle cell disorders, genotype HbSF was the highest (0.9% as compared to 0.2%; HbSS, 0.6%; HbSC and 0.3%; HbSCF). Microscopic Plasmodium falciparum parasitaemia was detected among 5.5% of the children and 14.2% sub-microscopic prevalence by PCR. Children with sickle cell disorders were more likely to have sub-microscopic parasitaemia (AOR = 5.51 95%CI (2.15, 14.10), p < 0.001) as well as anaemia (AOR = 3.03 95% CI (1.04, 8.82), p = 0.042), compared to those with normal genotypes. There was no significant difference observed between sickle cell disorders and growth and development of the children screened.

Conclusions

Sickle cell disorders were significantly associated with sub-microscopic parasitaemia as well as anaemia in this study. Establishment of sickle cell clinics in the district and regional hospitals will help in the management of children with the disorder and also generate a national database on sickle cell disorders. National neonatal screening policies must also be put in place to help in early detection and management of these disorders.

The impact on malaria of biannual treatment with azithromycin in children age less than 5 years: a prospective study

Background

The MORDOR study, a cluster randomized clinical trial, showed that single-dose azithromycin (20 mg/kg) administered biannually for 2 years to preschool children reduced mortality; a study was conducted to determine its effect on clinical symptomatic episodes of malaria as a potential mechanism for mortality benefit.

Methods

A randomized control trial (RCT) was conducted, whereby 30 randomly selected communities in Kilosa District, Tanzania were randomized to receive 6-monthly treatment of children ages 1–59 months with single-dose azithromycin (20 mg/kg) vs. placebo. A prospective cohort study was nested within the RCT: children, aged 1 to 35 months at baseline, were randomly selected in each community and evaluated at 6-monthly intervals for 2 years. At each visit, the children were assessed for recent or ongoing fever and anti-malarial treatment; a rapid diagnostic test (RDT) for malaria was performed. The two major outcomes of interest were prevalence of RDT positivity and clinical malaria. The latter was defined as RDT-positivity with fever at time of evaluation and/or reported fever in the 3 days prior to evaluation. Methods that account for correlations at community level and within individuals over time were used to evaluate associations.

Results

At baseline, the prevalence rates in the children in the azithromycin and placebo arms were 17.6% vs. 15.5% for RDT positivity (p = 0.76) and 6.1% vs. 4.3% (p = 0.56) for clinical malaria. There was a decline in both RDT-positivity and clinical malaria over time in both arms. The difference by treatment assignment was not significant for clinical malaria; it was significant for RDT-positivity with greater odds of decline in the placebo arm (p = 0.01).

Conclusions

Lack of evidence for a significant difference in the prevalence of clinical malaria in children at any visit following treatment suggests that the effect of single-dose azithromycin on malaria is at best transient and limited in scope. Chance overrepresentation of non-seasonal transmission in the communities in the azithromycin arm may account for higher rates of RDT-positivity and less decline over time.

Trial registration Clinicaltrials.gov NCT02047981

Contrasting Asymptomatic and Drug Resistance Gene Prevalence of Plasmodium falciparum in Ghana: Implications on Seasonal Malaria Chemoprevention

Malaria is a significant public health problem in Ghana. Seasonal Malaria Chemoprevention (SMC) using a combination of sulfadoxine-pyrimethamine and amodiaquine has been implemented since 2015 in northern Ghana where malaria transmission is intense and seasonal. In this study, we estimated the prevalence of asymptomatic P. falciparum carriers in three ecological zones of Ghana, and compared the sensitivity and specificity of different molecular methods in identifying asymptomatic infections. Moreover, we examined the frequency of mutations in pfcrt, pfmdr1, pfdhfr, and pfdhps that relate to the ongoing SMC. A total of 535 asymptomatic schoolchildren were screened by microscopy and PCR (18s rRNA and TARE-2) methods. Among all samples, 28.6% were detected as positive by 18S nested PCR, whereas 19.6% were detected by microscopy. A high PCR-based asymptomatic prevalence was observed in the north (51%) compared to in the central (27.8%) and south (16.9%). The prevalence of pfdhfr-N51I/C59R/S108N/pfdhps-A437G quadruple mutant associated with sulfadoxine-pyrimethamine resistance was significantly higher in the north where SMC was implemented. Compared to 18S rRNA, TARE-2 serves as a more sensitive molecular marker for detecting submicroscopic asymptomatic infections in high and low transmission settings. These findings establish a baseline for monitoring P. falciparum prevalence and resistance in response to SMC over time.

A focus on improving molecular diagnostic approaches to malaria control and elimination in low transmission settings: Review

The malaria elimination goal is back to the global agenda. Understanding its epidemiology in low transmission settings is crucial to design reliable strategies to detect a large reservoir of individuals infected with sub-microscopic (and often asymptomatic) infections characterized by low-parasite densities and gametocyte carriage. Traditional diagnostic methods such a light microscopy is widely used mainly in developing countries and as a result, the true picture of malaria epidemiology is misrepresented. In the last few decades, the advancement of molecular diagnostic tools significantly improved our understanding of the epidemiology of the diseases. However, the detection capacity of different molecular assays is determined by different factors such as the sensitivity of the assay and the transmission and infection dynamics of the disease particularly when there is low parasitic density in reservoir hosts. Hence, in this review, the epidemiology of malaria in low transmission settings and the priority in addressing the malaria control and elimination goals are highlighted.

Polychromophilus melanipherus and haemoplasma infections not associated with clinical signs in southern bent-winged bats (Miniopterus orianae bassanii) and eastern bent-winged bats (Miniopterus orianae oceanensis)

While bats are often viewed as carriers of infectious disease agents, little research has been conducted on the effects these pathogens may have on the bat populations themselves. The southern bent-winged bat (Miniopterus orianae bassanii) is a critically endangered subspecies endemic to south-eastern Australia. Population numbers of this bat have declined over the past 50 years, but the reasons for this are unclear. As part of a larger study to determine if disease could be a contributing factor to this decline, southern bent-winged bats from several locations in Victoria and South Australia were captured and examined for the presence of the blood parasite, Polychromophilus melanipherus, and haemoplasmas (Mycoplasma sp.). Results were compared with those obtained from populations of the more common, partially sympatric, eastern bent-winged bat (Miniopterus orianae oceanensis) from three different locations in Victoria. Both organisms were found in both subspecies (prevalence of P. melanipherus 60% by PCR for southern bent-winged bats compared with 46% for eastern bent-winged bats; prevalence of haemoplasmas 10% for southern bent-winged bats compared with 8% for eastern bent-winged bats), with no association between the probability of infection, body weight, abnormal blood parameters or any other indicators of ill health. However, Victorian southern bent-winged bats had heavier burdens of P. melanipherus than both the South Australian southern bent-winged bats and eastern bent-winged bats. Further investigations are required to determine if these differences are impacting population health.

Commit, hide and escape: the story of Plasmodium gametocytes

Malaria is the major cause of mortality and morbidity in tropical countries. The causative agent, Plasmodium sp., has a complex life cycle and is armed with various mechanisms which ensure its continuous transmission. Gametocytes represent the sexual stage of the parasite and are indispensable for the transmission of the parasite from the human host to the mosquito. Despite its vital role in the parasite's success, it is the least understood stage in the parasite's life cycle. The presence of gametocytes in asymptomatic populations and induction of gametocytogenesis by most antimalarial drugs warrants further investigation into its biology. With a renewed focus on malaria elimination and advent of modern technology available to biologists today, the field of gametocyte biology has developed swiftly, providing crucial insights into the molecular mechanisms driving sexual commitment. This review will summarise key current findings in the field of gametocyte biology and address the associated challenges faced in malaria detection, control and elimination.

Micro-epidemiology of mixed-species malaria infections in a rural population living in the Colombian Amazon region

Malaria outbreaks have been reported in recent years in the Colombian Amazon region, malaria has been re-emerging in areas where it was previously controlled. Information from malaria transmission networks and knowledge about the population characteristics influencing the dispersal of parasite species is limited. This study aimed to determine the distribution patterns of Plasmodium vivax, P. malariae and P. falciparum single and mixed infections, as well as the significant socio-spatial groupings relating to the appearance of such infections. An active search in 57 localities resulted in 2,106 symptomatic patients being enrolled. Parasitaemia levels were assessed by optical microscopy, and parasites were detected by PCR. The association between mixed infections (in 43.2% of the population) and socio-spatial factors was modelled using logistic regression and multiple correspondence analyses. P. vivax occurred most frequently (71.0%), followed by P. malariae (43.2%), in all localities. The results suggest that a parasite density-dependent regulation model (with fever playing a central role) was appropriate for modelling the frequency of mixed species infections in this population. This study highlights the under-reporting of Plasmodium spp. mixed infections in the malaria-endemic area of the Colombian Amazon region and the association between causative and environmental factors in such areas.

Evaluation of the utility value of three diagnostic methods in the detection of malaria parasites in endemic area

Background

Malaria is a debilitating disease with high morbidity and mortality in Africa, commonly caused by different species of the genus Plasmodium in humans. Misdiagnosis is a major challenge in endemic areas because of other disease complications and technical expertise of the medical laboratory staff. Microscopic method using Giemsa-stained blood film has been the mainstay of diagnosis of malaria. However, since 1993 when rapid diagnostic test (RDT) kits were introduced, they have proved to be effective in the diagnosis of malaria. This study was aimed at comparing the accuracy of microscopy and RDTs in the diagnosis of malaria using nested PCR as the reference standard. Four hundred and twenty (420) venous blood specimens were collected from patients attending different General Hospitals in Ebonyi State with clinical symptoms of malaria. The samples were tested with Giemsa-stained microscopy and three RDTs. Fifty specimens were randomly selected for molecular analysis.

Results

Using different diagnostic methods, the prevalence of malaria among the subjects studied was 25.95% as detected by microscopy, prevalence found among the RDTs was 22.90, 15.20 and 54.80% for Carestart, SD Bioline PF and SD Bioline PF/PV, respectively. Molecular assay yielded a prevalence of 32%. The major specie identified was Plasmodium falciparum; there was co-infection of P. falciparum with Plasmodium malariae and Plasmodium ovale. The sensitivity and specificity of microscopy was 50.00 and 70.59% while that of the RDTs were (25.00 and 85.29%), (25.00 and 94.12%) and (68.75 and 52.94%) for Carestart, SD Bioline PF and SD Bioline PF/PV, respectively. Cohen’s kappa coefficient was used to measure the level of agreement of the methods with nested PCR. Microscopy showed a moderate measure of agreement (k = 0.491), Carestart showed a good measure of agreement (k = 0.611), SD Bioline PF showed a fair measure of agreement (k = 0.226) while SD Bioline PF/PV showed a poor measure of agreement (k = 0.172).

Conclusions

This study recommends that the policy of malaria diagnosis be changed such that the routine diagnosis of malaria is done by a combination of both microscopy and a RDT kit of high sensitivity and specificity so as to complement the errors associated with either of the methods. The finding of P. ovale in the study area necessitates an expanded molecular epidemiology of malaria within the study area.

Plasmodium malariae in the Colombian Amazon region: you don't diagnose what you don't suspect

Background

Malaria is a worldwide public health problem; parasites from the genus Plasmodium spp. are the aetiological agent of this disease. The parasite is mainly diagnosed by microscope-based techniques. However, these have limited sensitivity. Many asymptomatic infections are sub-microscopic and can only be detected by molecular methods. This study was aimed at comparing nested PCR results to those obtained by microscope for diagnosing malaria and to present epidemiological data regarding malaria in Colombia’s Amazon department.

Methods

A total of 1392 blood samples (taken by venepuncture) from symptomatic patients in Colombia’s Amazon department were analysed in parallel by thick blood smear (TBS) test and nested PCR for determining Plasmodium spp. infection and identifying infecting species, such as Plasmodium vivax, Plasmodium malariae and/or Plasmodium falciparum. Descriptive statistics were used for comparing the results from both tests regarding detection of the disease, typing infecting species and their prevalence in the study region. Bearing the microscope assay in mind as gold standard, PCR diagnosis performance was evaluated by statistical indicators.

Conclusion

The present study revealed great differences between both diagnostic tests, as well as suggesting high P. malariae prevalence from a molecular perspective. This differed profoundly from previous studies in this region of Colombia, usually based on the TBS test, suggesting that diagnosis by conventional techniques could lead to underestimating the prevalence of certain Plasmodium spp. having high circulation in this area. The present results highlight the need for modifying state malaria surveillance schemes for more efficient strategies regarding the detection of this disease in endemic areas. The importance of PCR as a back-up test in cases of low parasitaemia or mixed infection is also highlighted.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1629-3) contains supplementary material, which is available to authorized users.

Imported Malaria over Fifteen Years in an Inner City Teaching Hospital of Washington DC

As endemic malaria is not commonly seen in the United States, most of the cases diagnosed and reported are associated with travel to and from the endemic places of malaria. As the number of imported cases of malaria has been increasing since 1973, it is important to look into these cases to study the morbidity and mortality associated with this disease in the United States. In this study, we would like to share our experience in diagnosing and treating these patients at our institution. We did a retrospective chart review of 37 cases with a documented history of imported malaria from 1998 to 2012. Among them, 16 patients had complicated malaria during that study period, with a mean length of hospital stay of 3.5 days. Most common place of travel was Africa, and chemoprophylaxis was taken by only 11% of patients. Travel history plays a critical role in suspecting the diagnosis and in initiating prompt treatment.

Microscopic and molecular evidence of the presence of asymptomatic Plasmodium falciparum and Plasmodium vivax infections in an area with low, seasonal and unstable malaria transmission in Ethiopia

BACKGROUND

The presence of asymptomatic infections has serious implications for malaria elimination campaigns. Since asymptomatic carriers do not seek treatment for their infection and may become gametocyte carriers, they undoubtedly contribute to the persistence of malaria transmission in a population. The presence of asymptomatic parasitemias was noted in areas with seasonal malaria transmission. In Ethiopia there is a paucity of data regarding the prevalence of asymptomatic malaria carriage. This study was undertaken to assess the presence and prevalence of asymptomatic Plasmodium falciparum and Plasmodium vivax infections in south-central Oromia, Ethiopia.

METHODS

A total of 1094 apparently healthy individuals ≥ 2 years of age in south-central Oromia, Ethiopia, an area with seasonal and unstable malaria transmission, were screened for the presence of asymptomatic plasmodial infections. Finger-prick blood samples were taken from each participant for blood film preparation for microscopy and the rapid diagnostic test (RDT). Blood samples were also spotted on Whatman 3MM filter paper for parasite DNA extraction.

RESULTS

The prevalence of asymptomatic Plasmodium carriage (P. falciparum, P. vivax and mixed species) was 5.0 % (55/1,094) as determined by microscopy, while the prevalence as determined using RDT was 8.2 % (90/1,094). PCR was done on 47 of 55 microscopy-confirmed and on 79 of 90 RDT-confirmed samples. PCR detected parasite DNA in 89.4 % (42/47) of the microscopy-positive samples and in 77.2 % (61/79) of the RDT-positive samples. No significant difference was observed in the prevalence of asymptomatic P. falciparum or P. vivax infections in the study area (P > 0.1). However, the prevalence of asymptomatic parasitaemia was significantly associated with gender (OR = 0.47, P = 0.015; being higher in males than females) and age (X(2) = 25, P < 0.001; being higher in younger than in older individuals). Age and parasite densities had an inverse relationship.

CONCLUSIONS

This study confirms the presence of asymptomatic P. falciparum and P. vivax infections in south-central Oromia, an area with low, seasonal and unstable malaria transmission in Ethiopia. Of 55 microscopically confirmed asymptomatic infections, P. falciparum monoinfection accounted for 45.5 % and of 90 RDT positive asymptomatic infections, 66.7 % were P. falciparum. Although not statistically significant, P. falciparum accounted for a relatively large number of the asymptomatic infections as determined by both tests. The prevalence of asymptomatic parasitaemia was highest in the younger age group. HRP-2-based RDTs specific for P. falciparum showed high false positivity rate compared to Plasmodium lactate dehydrogenase (pLDH) specific to P. vivax. Although microscopy and RDT detected substantial numbers of asymptomatic infections in apparently healthy inhabitants, the use of a highly sensitive molecular diagnostics offers a more accurate assessment of the magnitude of asymptomatic infections.

Comparison of four methods for extracting DNA from dried blood on filter paper for PCR targeting the mitochondrial Plasmodium genome

BACKGROUND

Few studies comparing multiple methods for DNA extraction from dried blood spots (DBS) on filter paper for PCR targeting the Plasmodium genome have been done.

METHODS

Frequently-used methods for DNA extraction from DBS using Chelex-100, InstaGene Matrix, QIAamp DNA Mini Kit and TE buffer were compared on a dilution series of a standardized Plasmodium falciparum positive sample. The two DNA extraction methods resulting in the lowest limits of detection were compared by testing both on 31 P. falciparum positive samples collected under field conditions and stored for 4 years.

RESULTS

The Chelex-100, InstaGene Matrix and QIAamp DNA Mini Kit methods performed similarly, resulting in the detection of 0.5 to 2 parasites per microliter (p/µl). The same 13 clinical samples (13/31; 42%) were positive using both DNA extraction methods with the lowest limits of detection.

CONCLUSIONS

Simple and low-cost methods can be sensitive and useful in extracting DNA from DBS. Poor results on stored clinical DBS indicate that further studies on the impact of storage duration and conditions, and choice of filter paper should be performed.

Comparison of Giemsa microscopy with nested PCR for the diagnosis of malaria in North Gondar, north-west Ethiopia

BACKGROUND

Malaria remains one of the leading communicable diseases in Ethiopia. Early diagnosis combined with prompt treatment is one of the main strategies for malaria prevention and control. Despite its limitation, Giemsa microscopy is still considered to be the gold standard for malaria diagnosis. This study aimed to compare the performance of Giemsa microscopy with nested polymerase chain reaction (nPCR) for the diagnosis of malaria in north-west Ethiopia.

METHODS

A cross sectional study was conducted in public health facilities in North Gondar, from March 2013 to April 2013. A total number of 297 subjects with suspected malaria were enrolled in the study. Finger-prick blood samples were collected and examined for Plasmodium parasites using Giemsa microscopy and standard nPCR.

RESULTS

Among the study participants, 61.6% (183/297) patients tested positive for malaria by Giemsa microscopy of which, 72.1% (132/183) and 27.9% (51/183) were diagnosed as Plasmodium falciparum and Plasmodium vivax, respectively. By nPCR, 73.1% (217/297) were malaria-positive. Among microscopy-negative samples, 13.1% (39/297) samples turned malaria-positive in nPCR. In nPCR, the rate of mixed Plasmodium infections was 4.7% (14/297) and 3.03% (9/297) were positive for Plasmodium ovale. Using nPCR as reference the sensitivity, specificity, positive predictive and negative predictive values of Giemsa microscopy were 82.0%, 93.8%, 97.3% and 65.8%, respectively, with a good agreement (κ = 0.668) to nested PCR. The sensitivity and specificity of Giemsa microscopy in identifyingP. falciparium infections were 74.0% and 87.4% and 63.2% and 96.5% for P. vivax infections, respectively.

CONCLUSION

Although Giemsa microscopy remains the gold standard for malaria diagnosis in resource-limited environments, its sensitivity and specificity as compared to nPCR is limited suggesting exploration of novel rapid and simplified molecular techniques for malaria-endemic countries. A high rate of misclassification and misidentification highlights the importance of adequate training for staff involved in malaria diagnosis.

PCR targeting Plasmodium mitochondrial genome of DNA extracted from dried blood on filter paper compared to whole blood

BACKGROUND

Monitoring mortality and morbidity attributable to malaria is paramount to achieve elimination of malaria. Diagnosis of malaria is challenging and PCR is a reliable method for identifying malaria with high sensitivity. However, blood specimen collection and transport can be challenging and obtaining dried blood spots (DBS) on filter paper by finger-prick may have advantages over collecting whole blood by venepuncture.

METHODS

DBS and whole blood were collected from febrile children admitted at the general paediatric wards at a referral hospital in Dar es Salaam, Tanzania. DNA extracted from whole blood and from DBS was tested with a genus-specific PCR targeting the mitochondrial Plasmodium genome. Positive samples by PCR of DNA from whole blood were tested with species-specific PCR targeting the 18S rRNA locus, or sequencing if species-specific PCR was negative. Rapid diagnostic test (RDT) and thin blood smear microscopy was carried out on all patients where remnant whole blood and a blood slide, respectively, were available.

RESULTS

Positivity of PCR was 24.5 (78/319) and 11.2% (52/442) by whole blood and DBS, respectively. All samples positive on DBS were also positive on Plasmodium falciparum species-specific PCR. All RDT positive cases were also positive by DBS PCR. All but three cases with positive blood slides were also positive by DBS.

CONCLUSIONS

In this study, PCR for malaria mitochondrial DNA extracted from whole blood was more sensitive than from DBS. However, DBS are a practical alternative to whole blood and detected approximately the same number of cases as RDTs and, therefore, remain relevant for research purposes.

An overview of the clinical use of filter paper in the diagnosis of tropical diseases

Tropical infectious diseases diagnosis and surveillance are often hampered by difficulties of sample collection and transportation. Filter paper potentially provides a useful medium to help overcome such problems. We reviewed the literature on the use of filter paper, focusing on the evaluation of nucleic acid and serological assays for diagnosis of infectious diseases using dried blood spots (DBS) compared with recognized gold standards. We reviewed 296 eligible studies and included 101 studies evaluating DBS and 192 studies on other aspects of filter paper use. We also discuss the use of filter paper with other body fluids and for tropical veterinary medicine. In general, DBS perform with sensitivities and specificities similar or only slightly inferior to gold standard sample types. However, important problems were revealed with the uncritical use of DBS, inappropriate statistical analysis, and lack of standardized methodology. DBS have great potential to empower healthcare workers by making laboratory-based diagnostic tests more readily accessible, but additional and more rigorous research is needed.