Rapid detection of malaria infection in vivo by laser desorption mass spectrometry

Rapid diagnosis leading to effective treatment is essential to control escalating infectious diseases such as malaria. Malaria pigment (hemozoin) detection by laser desorption mass spectometry (LDMS) was recently shown to be a sensitive (<10 parasites/muL) technique for detecting Plasmodium falciparum parasites cultured in human blood. To examine the use of LDMS in a rapid new malaria screening assay, we followed the time course of P. yoelii infections in mice in parallel with light microscopy and a colorimetric hemozoin assay. Hemozoin was detected by LDMS in 0.3 muL of blood within two days of infection independently of the inoculating dose of 10(6), 10(4), or 10(2) parasite-infected erythrocytes. Microscopy and colorimetric hemozoin determinations lagged the LDMS detection of infections by 2-4 and 3-5 days, respectively, except at the highest inoculation dose. The LDMS detection of hemozoin is a potentially more rapid screen than light microscopy for detecting malaria infection in this mouse model at parasitemias <0.1%.     

Competition for red blood cells can enhance Plasmodium vivax parasitemia in mixed-species malaria infections

We assess the consequences of competition for red blood cells (RBCs) in co-infections with the two major agents of human malaria, Plasmodium vivax and Plasmodium falciparum, using differential equations to model the population dynamics of RBCs and parasites. P. vivax parasitizes only the youngest RBCs, but this can reduce the broader RBC population susceptible to P. falciparum. We found that competition for RBCs typically causes one species to suppress the other, depending on their relative reproduction rates and timing of inoculation. However, if the species' reproduction rates are nearly equal, transient increases in RBC production stimulated by the presence of P. falciparum may boost P. vivax parasitemia above its single-species infection level. Conversely, P. falciparum parasitemia is rarely enhanced above its single-species level. Furthermore, transients in RBC production can induce coupled oscillations in the parasitemia of both species. These results are remarkably robust to changes in model parameters.     

巴基斯坦输入性间日疟一例

患者,男性,28岁,工人。4周前突发寒战、高热,体温40℃,伴头昏、胸痛、乏力及全身肌肉酸痛,予以扑热息痛、抗生素及激素治疗,退热。近2周出现间歇性畏寒、发热伴头昏、胸闷,于2004年1月26日入院。     

Rapid, real-time detection of acute HIV infection in patients in Africa

BACKGROUND: We conducted a prospective study to evaluate methods of detecting clients with sexually transmitted diseases (STDs) who were acutely coinfected with human immunodeficiency virus (HIV) in Lilongwe, Malawi. METHODS: After informed consent was obtained, all clients with acute STDs were offered voluntary HIV counseling and testing by 2 rapid antibody tests. Samples from rapid test-negative or -discordant subjects were pooled (50 : 5 : 1) and tested for HIV RNA. Western blots were performed on all rapid test-discordant specimens with detectable HIV RNA. A subset of specimens received p24 antigen testing with standard and/or ultrasensitive methods. Patients with possible acute HIV infection were followed to confirm seroconversion. RESULTS: A total of 1450 clients (34% female and 66% male) agreed to testing, of whom 588 (40.55%) had established HIV infection and 21 (1.45%) had acute infection. Discordant rapid antibody tests identified 7 of 21 (33.3% sensitivity), standard p24 antigen identified 12 of 16 (75% sensitivity), and ultrasensitive p24 antigen identified 15 of 17 (88% sensitivity) acute cases. By definition, the sensitivity of the RNA assay was 100%. CONCLUSIONS: Real-time pooled RNA testing for the detection of acute HIV infection is feasible in resource-limited settings. However, parallel rapid testing and p24 antigen testing are technologically simpler and together may detect approximately 90% of acute cases.     

Rapid diagnostic testing for malaria

Malaria rapid diagnostic devices (MRDD) have been developed with the hope that they would offer accurate, reliable, rapid, cheap and easily available alternatives to traditional methods of malaria diagnosis. The results from early malaria rapid diagnostic studies were quite promising, especially for detecting Plasmodium falciparum at densities of more than 100-500 parasites/microl. Despite the introduction of these devices over a decade ago, only a few target antigens have been introduced. Of greater concern, these devices have shown limitations in sensitivity, ability to differentiate species and robustness under field conditions in the tropics. Recent trials have revealed wide variability in sensitivity both within and between products. We review the recent trials assessing MRDD use for the diagnosis of P. falciparum and non-P. falciparum infections in endemic and non-endemic countries and describe the various aspects of these devices which need further improvement. High quality, accurate, rapid and affordable diagnostic tools are urgently needed now that new antimalarial regimens, characterized by higher cost and increased toxicity, have been introduced more widely in response to emerging multi-drug resistance.     

Rapid detection of Mycobacterium tuberculosis infection by enumeration of antigen-specific T cells

There is no reliable means of detecting latent M. tuberculosis infection, and even in patients with active tuberculosis, infection is often unconfirmed. We hypothesized that M. tuberculosis antigen-specific T cells might reliably indicate infection. We enumerated peripheral blood-derived interferon gamma (IFN-gamma)-secreting T cells responding to epitopes from ESAT-6, an antigen that is highly specific for M. tuberculosis complex but absent from BCG, in four groups of individuals. Forty-five of 47 patients with bacteriologically confirmed tuberculosis had ESAT-6-specific IFN-gamma-secreting T cells, compared with four of 47 patients with nontuberculous illnesses, indicating that these T cells are an accurate marker of M. tuberculosis infection. This assay thus has a sensitivity of 96% (95% confidence interval [CI] 92-100) for detecting M. tuberculosis infection in this patient population. By comparison, of the 26 patients with tuberculosis who had a diagnostic tuberculin skin test (TST), only 18 (69%) were positive (p = 0.003). In addition, 22 of 26 (85%) TST-positive exposed household contacts had ESAT-6-specific T cells, whereas zero of 26 unexposed BCG-vaccinated subjects responded. This approach enables rapid detection of M. tuberculosis infection in patients with active tuberculosis and in exposed asymptomatic individuals at high risk of latent infection; it also successfully distinguishes between M. tuberculosis infection and BCG vaccination. This capability may facilitate tuberculosis control in nonendemic regions.     

Identification of human malaria parasites and detection of mixed infection in Thai patients by nested PCR

The species-specific nested PCR previously described by Snounou and others, for detecting the four species of human malaria parasites, is evaluated in the current study testing 40 blood samples from malaria patients admitted during July-September, 2003, at the Hospital for Tropical Diseases, Faculty of Tropical Medicine, Mahidol University, Thailand. Parasite DNA of each blood sample was extracted and purified by QIAamp. DNA mini kit. Nested PCR was performed using genus-specific primers for the first PCR cycle and species-specific primer for the second cycle. Thin and thick smears were also made, stained with Giemsa, and examined by expert microscopists. Only one of 40 samples (2.5%) was identified as Plasmodium malariae infection by both microscopy and nested PCR. Twenty blood samples (50%) were identified as Plasmodium falciparum infections by both methods. However, 19 blood samples (47.5%) were reported as Plasmodium vivax infections by microscopic methods, whereas nested PCR could detect a mixed infection of Plasmodium vivax and Plasmodium falciparum in one sample taken from a young girl with 8 ameboid trophozoites of P. vivax per 200 white blood cells. These results demonstrated that the nested PCR assay surpasses microscopy and also offers a clear advantage in the detection of mixed infections, which is important not only for successful medical treatment, but also for the study of malaria epidemiology.     

Rapid detection of cytomegalovirus pulmonary infection by bronchoalveolar lavage and centrifugation culture

Cytomegalovirus infection remains a major cause of morbidity and mortality in marrow transplant recipients. Results of a rapid centrifugation viral culture of bronchoalveolar lavage specimens from 33 marrow transplant recipients with pneumonia were compared with those for conventional viral culture of concurrently or subsequently obtained lung tissue. The centrifugation culture results were also compared to results of cytologic and immunochemical examination of these specimens. Centrifugation culture was positive within 16 hours of inoculation in 22 of 23 (96%) specimens from patients with positive conventional culture of lung tissue. Detection of cells positive for cytomegalovirus by immunofluorescent antibody staining or cytologic identification was less sensitive (59% and 29%, respectively). There was no evidence of cytomegalovirus in specimens from patients without evidence of cytomegalovirus pulmonary infection by any technique. The sensitivity (96%) and specificity (100%) of centrifugation culture of specimens from marrow transplant recipients approach that of viral culture of lung tissue.     

Usefulness of the "OptiMAL Rapid Malaria test" for rapid detection of malaria imported to Poland

In this survey the use of OptiMAL test for rapid diagnosis of malaria was evaluated. It was proved that this test allowed to diagnose the Plasmodium sp. antigen in 72% of examined blood specimens, 82% for P. falciparum infection and 69% for P. vivax, whereas P. ovale was not detected at all. The test sensitivity depended on the parasitemia level. It showed a sensitivity of 100% for parasitemia density exceeded 1%, 95.4% with the parasitemia ranging from 0.1-0.99%. For lower parasite density, the test's sensitivity was of 32 and 60%. The OptiMAL test showed a 99.1% specificity thus it revealed to be significantly high.     

Microfluidic approaches to malaria detection

Microfluidic systems are under development to address a variety of medical problems. Key advantages of micrototal analysis systems based on microfluidic technology are the promise of small size and the integration of sample handling and measurement functions within a single, automated device having low mass-production costs. Here, we review the spectrum of methods currently used to detect malaria, consider their advantages and disadvantages, and discuss their adaptability towards integration into small, automated micro total analysis systems. Molecular amplification methods emerge as leading candidates for chip-based systems because they offer extremely high sensitivity, the ability to recognize malaria species and strain, and they will be adaptable to the detection of new genotypic signatures that will emerge from current genomic-based research of the disease. Current approaches to the development of chip-based molecular amplification are considered with special emphasis on flow-through PCR, and we present for the first time the method of malaria specimen preparation by dielectrophoretic field-flow-fractionation. Although many challenges must be addressed to realize a micrototal analysis system for malaria diagnosis, it is concluded that the potential benefits of the approach are well worth pursuing.     

Dietary modulation of malaria infection in rats.

Feeding of wistar albino rats on low protein and energy diet (4% protein) caused suppression of parasitaemia when infected with Plasmodium berghei besides causing a depressed immune response. The refeeding of protein energy deficient rats on normal protein and energy diet (18% protein) for four weeks resulted in the normal course of parasitaemia after P. berghei infection. The present study was carried out to find the cause of suppression of malaria in protein energy deficient rats. The experiments revealed re-elevation of malaria parasitaemia when rats were fed on low protein diets supplemented with p-amino-benzoic acid (PABA). Moreover, the parasite persisted at subpatent levels in tissues in protein energy deficient rats and resulted in the development of antimalarial antibodies. Low protein energy diet could cause deficiency of certain essential nutrients required for the parasite, PABA being one of them, and hence suppresses the parasitaemia to subpatent levels. As a result, sufficient antigenic stimulus is provided to the host so that the host develops an immune response which might in turn help in further suppression of parasitaemia to subpatent levels.     

Indoor residual spraying with alphacypermethrin controls malaria in Pakistan: a community-randomized trial

We conducted a community-randomized controlled trial in Pakistan to determine the efficacy of indoor residual spraying with alphacypermethrin ('Fendona', Cyanamid, NJ, USA), applied at 25 mg/m2, to prevent falciparum and vivax malaria. Wettable powder (WP) and suspension concentrate (SC) formulations were tested against an unsprayed control in an irrigated rice-growing area of Sheikhupura district, Punjab province. The study area of 180 km2 was divided into nine sectors, which were assigned at random to control, WP, or SC treatments in replicates of 3. Sentinel villages were selected from each sector for entomological and disease monitoring. Malaria was monitored by fortnightly active case detection (ACD) and by cross- sectional parasite surveys on schoolchildren. Mosquito populations were monitored by space spraying of rooms and by cattle-landing catches. The spray campaign took place in June 1997 and covered 96% of compounds. During the 7 months after spraying, the incidence of falciparum malaria was 95% lower and that of vivax malaria 80% lower in WP-sprayed than unsprayed sectors. Similar results were obtained for sectors sprayed with the SC formulation. Cross-sectional surveys gave estimates of efficacy comparable to those obtained by ACD. Anopheles culicifacies was 80% less abundant and A.stephensi, the predominant anopheline, was up to 68% less abundant in sprayed areas over the 7-month period. Reductions in anopheline parous rates indicated that the single-spray treatment was effective for the entire transmission season. Sprayed surfaces lacked odour, which contributed to the popularity of the campaign. Alphacypermethrin is a promising insecticide for the control of malaria in Pakistan and South Asia generally.     

Asymptomatic dengue infection in adults of major cities of Pakistan

Objective: To determine the asymptomatic dengue infection in adults of Pakistani population.Methods: This study was conducted in five major cities(Islamabad, Karachi, Lahore,Multan, and Peshawar) of Pakistan.A total of 5 230 adults aged 18 years and above without a history of dengue fever at any point in their life were enrolled from participating laboratories.Those who were confirmed for dengue previously were excluded.Of the total, 62.6%(n = 3 276) were male with an average age of 34.6 years.Participants were briefed about the objectives of the study, and written consent was obtained to perform dengue Ig G test using enzyme linked immunosorbent assay.The brief information related to age, gender and area was also taken on proforma.Results: Overall 32.3%(n = 1 691) was having asymptomatic dengue infection which was 67.5%(n = 756) in Karachi followed by 39.1%(n = 391) in Islamabad, 29.9%(n =316) in Lahore and 21%(n = 228) in Peshawar and none from Multan.More males were affected with asymptomatic dengue infection than females.The asymptomatic dengue infection was significantly higher in different cities; however, there was no significant difference with respect to age groups.Conclusions: The asymptomatic dengue infection is higher in cities i.e.Karachi,Islamabad and Lahore which are at risk of developing secondary dengue infections.There is a need of awareness among the public about secondary dengue infection.     

Automated detection of malaria pigment: feasibility for malaria diagnosing in an area with seasonal malaria in northern Namibia

OBJECTIVE: To evaluate the feasibility of automated malaria detection with the Cell-Dyn 3700 (Abbott Diagnostics, Santa Clara, CA, USA) haematology analyser for diagnosing malaria in northern Namibia. METHODS: From April to June 2003, all patients with a positive blood smear result and a subset of patients with no suspicion of malaria were included. Blood smear and a venous blood sample (to determine haemoglobin, platelet and malaria pigment levels) were collected from each patient. Malaria pigment test characteristics, correlations with blood parameters and pigment clearance time were calculated. Finally, a subset of blood samples was run twice to evaluate the consistency of test outcome. RESULTS: Two hundred and eight patients were included. Ninety had a positive blood smear result of which 84 tested positive for malaria pigment and 118 patients had a negative blood smear result of which four tested positive for malaria pigment. Test characteristics as compared with microscopy were as follows: sensitivity 0.93, specificity 0.97, positive predictive value 0.95, negative predictive value 0.95. Rerun of the blood samples resulted in a change of diagnosis in 14%. After 4 weeks, 33% of patients with an initially positive pigment result still tested positive. Malaria pigment was found to be negatively correlated with haemoglobin. CONCLUSIONS: Automated detection of malaria pigment is a useful diagnostic tool in this semi-rural area. In low-risk malaria season, the test can be used for diagnosing malaria because of the high sensitivity. In high-risk malaria season, the test can be used for excluding malaria in case of a negative pigment result because of the high specificity.     

The risks of malaria infection in Kenya in 2009

Background  

To design an effective strategy for the control of malaria requires a map of infection and disease risks to select appropriate suites of interventions. Advances in model based geo-statistics and malaria parasite prevalence data assemblies provide unique opportunities to redefine national Plasmodium falciparum risk distributions. Here we present a new map of malaria risk for Kenya in 2009.