Evaluation of a rapid and inexpensive dipstick assay for the diagnosis of Plasmodium falciparum malaria.

Rapid, accurate and affordable methods are needed for the diagnosis of malaria. Reported here is an evaluation of a new immunochromatographic strip, the PATH Falciparum Malaria IC Strip, which is impregnated with an immobilized IgM monoclonal antibody that binds to the HRP-II antigen of Plasmodium falciparum. In contrast to other commercially available kits marketed for the rapid diagnosis of falciparum malaria, this kit should be affordable in the malaria-endemic world. Using microscopy and polymerase chain reaction (PCR)-based methods as reference standards, we compared two versions of the PATH test for the detection of P. falciparum infection in 200 febrile travellers. As determined by PCR and microscopy, 148 travellers had malaria, 50 of whom (33.8%) were infected with P. falciparum. Compared with PCR, the two versions of the PATH test had initial sensitivities of 90% and 88% and specificities of 97% and 96%, respectively, for the detection of falciparum malaria. When discrepant samples were retested blindly with a modified procedure (increased sample volume and longer washing step) the sensitivity and specificity of both kits improved to 96% and 99%, respectively. The two remaining false negatives occurred in samples with < 100 parasites per microliter of blood. The accuracy, simplicity and predicted low cost may make this test a useful diagnostic tool in malaria-endemic areas.     

A rapid in vitro assay system using anti-bromodeoxyuridine for drug susceptibility of Plasmodium falciparum

Drug effects were monitored by the measurement of bromodeoxyuridine (BrdU) incorporation into parasite deoxyribonucleic acid (DNA). Cells are pulse-labelled with BrdU and those which are synthesizing DNA incorporate BrdU into their DNA. Anti-BrdU is used to identify cells undergoing DNA synthesis at the time of the pulse. Concentration-effect curves were determined for chloroquine, pyrimethamine and quinine in culture for only 3 h in RPMI 1640 medium supplemented with BrdU. Different strains of Plasmodium falciparum could be distinguished when BrdU uptake was monitored by the ELISA. This assay offers a fast and accurate method of monitoring the effects of a variety of antimalarial drugs.     

A dipstick ELISA for rapid detection of human blood meals in mosquitoes.

A dot-enzyme-linked immunosorbent assay, dot-ELISA, that allows for identification of human blood meals in mosquitoes in less than 2 h is presented. Strips of mylar-backed nitrocellulose paper, the dipstick, may be inoculated with anti-human capture antibody, blocked, dried and stored for at least 3 months before use. The Dipstick ELISA consistently detected human blood meals at 24 h post-blood meal in frozen Anopheles mosquitoes and at 32 h post-blood meal on samples eluted off filter-paper smears. This ELISA detects human IgG at dilutions of 1:25,600, and produces strong positive results at dilutions between 1:400 and 1:12,800. The Dipstick ELISA is highly specific, and no false positives were detected when tested against cow, horse, goat, dog, cat, pig, rabbit, mouse, rat, chicken, raccoon and opossum sera. All reagents for the assay are commercially available. The Dipstick ELISA meets requirements for a rapid and simple assay for the identification of human blood meals and should have particular application to short-term field studies and emergency epidemiological investigations. A modified protocol, the Trough ELISA, which treats dipsticks jointly in disposable pipet troughs during the conjugate and substrate steps, was developed and produced as a kit. The Trough ELISA produces 1-4% random false positives, and we recommend that the Trough ELISA not be used.     

Validity,reliability and ease of use in the field of five rapid tests for the diagnosis of Plasmodium falciparum malaria in Uganda

A study was conducted to measure the overall performance of several rapid diagnostic tests for Plasmodium falciparum infection, in order to select the most appropriate test to be used in the field. A total of 742 patients attending the out-patient department of Mbarara Hospital with a clinical suspicion of malaria were included in the study. For each patient, a thick/thin film and 5 rapid tests based on the detection of histidine-rich protein II (HRP-II) (Paracheck Pf dipstick and device, ParaHIT f, Malaria Rapid and BIO P.F.) were performed. Outcomes were validity, inter-reader reliability and 'ease of use in the field', measured by both the general characteristics of the test and by the opinion of the readers. About half (57%) of the patients were positive for P. falciparum. The Paracheck Pf (dipstick and device) was considered as the most appropriate for the use in the field, being sensitive (97%), moderately specific (88%), reliable (kappa coefficient = 0.97), easy to use and cheap (about US$ 0.5/test). The ParaHIT f represented a good alternative.     

Field evaluation of the QBC technique for rapid diagnosis of vivax malaria.

The QBC (quantitative buffy coat) technique was compared with that of the Giemsa-stained thick blood film (GTF) under field conditions in Junlian and Mingshan counties, Sichuan, China, for rapid diagnosis of vivax malaria. Blood samples were collected from 364 volunteer villagers, and each sample was examined with both the QBC and GTF techniques. For each GTF sample (10 microliters of blood), as many as 300 oil-immersion fields were examined; each QBC tube was inspected for up to 5 minutes. The GTF technique resulted in 86 positive blood samples and 278 negative; the QBC technique indicated 89 positive and 275 negative samples. Relative to the results obtained with GTF, the QBC technique had a sensitivity and specificity of 87.2% and 95.0%, respectively; concordance between the tests was 93.1%. The median time-to-positive diagnosis with the QBC technique (1.12 min) was 11% of that with GTF. The distribution of different developmental stages of Plasmodium vivax parasites was also examined in the centrifuged QBC tubes: all stages except schizonts could be found in the lower part of the platelet zone (the interphase between the monocyte and platelet layers), especially ring forms.     

Guidelines for treatment of cystic and alveolar echinococcosis in humans. WHO Informal Working Group on Echinococcosis.

Summarized in this article are recent experiences in the treatment of human cystic echinococcosis (CE) and alveolar echinococcosis (AE) of the liver caused by the metacestode stages of Echinococcus granulosus and E. multilocularis, respectively. For CE, surgery remains the first choice for treatment with the potential to remove totally the parasite and completely cure the patient. However, chemotherapy with benzimidazole compounds (albendazole or mebendazole) and the recently developed PAIR procedure (puncture-aspiration-injection-re-aspiration) with concomitant chemotherapy offer further options for treatment of CE cases. Chemotherapy is not yet satisfactory: cure can be expected in about 30% of patients and improvement in 30-50%, after 12 months'' follow-up. AE is generally a severe disease, with over 90% mortality in untreated patients. Radical surgery is recommended in all operable cases but has to be followed by chemotherapy for at least 2 years. Inoperable cases and patients who have undergone nonradical resection or liver transplantation require continuous chemotherapy for many years. Long-term chemotherapy may significantly prolong survival, even for inoperable patients with severe AE. Liver transplantation may be indicated as a life-saving measure for patients with severe liver dysfunction, but is associated with a relatively high risk of proliferation of intraoperatively undetected parasite remnants. Details of indications, contraindications, treatment schedules and other aspects are discussed.     

线性探针技术快速诊断本溪地区耐多药肺结核效果评价

目的 评价线性探针技术(LPA)在本溪地区快速检测结核分枝杆菌利福平和异烟肼耐药性的特异性和敏感性。 方法 采用传统罗氏培养法培养2013年3月-2014年6月期间全市县区所有登记的414例涂阳肺结核患者痰标本,获得菌株经比例法药物敏感性试验和线性探针技术检测利福平和异烟肼耐药性,并以比例法药物敏感性试验为金标准分析线性探针方法的特异性和敏感性。 结果 经培养获得394株结核分枝杆菌菌株,与比例法药物敏感性试验相比较,线性探针技术检测利福平和异烟肼的特异性分别为97.9%和96.6%,敏感性分别为91.1%和81.3%;对耐多药检测的特异性和敏感性分别为98.8%和89.9%。 结论 线性探针技术是一快速、敏感、特异的诊断结核分枝杆菌利福平、异烟肼耐药和耐多药(MDR)的有效方法,可在本溪地区推广应用。     

A comparison of two DNA probes, one specific for Plasmodium falciparum and one with wider reactivity, in the diagnosis of malaria

The sensitivity and specificity of 2 probes for the detection of malarial infection was studied. 399 blood samples from Gambian children were tested in a deoxyribonucleic acid (DNA) hybridization assay, and the results compared with the microscopical findings from thick blood films. 8 additional pure Plasmodium malariae and 14 pure P. vivax samples were also assayed. One probe, containing a 21 base pair tandem repeat and highly specific for P. falciparum, detected this species in all except 2 of 74 samples with a parasitaemia of 250 per microliter or more; the overall sensitivity of the probe was 76%. The other probe, a 6 kilobase pair organelle DNA, is conserved in all Plasmodium species so far tested. Its sensitivity for P. falciparum was lower than the 21 base pair repeat, but it detected P. vivax and P. malariae at low levels of parasitaemia, and thus could be useful in field studies.     

A longitudinal study of antibodies to the Plasmodium falciparum antigen Pf155/RESA and immunity to malaria infection in adult Liberians

118 adult Liberians from 2 villages were studied prospectively for one year with monthly blood examinations for malaria parasites. The crude parasite rate was 41.5% and the crude gametocyte rate was 6.1%. The inoculation rate varied between 0.075 in the dry season and almost 0.4 in the rainy season, which is in accordance with other data from holoendemic areas. 47.5% (56) had a titre to the Pf155/RESA antigen less than or equal to 1/50 ('low responders') and 52.5% (62) had a titre of greater than or equal to 1/250 ('high responders'). The response was not age-dependent in this adult population, which may suggest that genetic factors are determining whether the individual become a high or low responder. Antibodies against the Pf155/RESA antigen were measured in 2 surveys 8 months apart, and the mean antibody response to Pf155/RESA and its EENV sequence was constant without seasonal variation. Pf155/RESA high responders had lower parasite densities during all 3 seasons surveyed, and Pf155/RESA high responders, with high antibody reactivity against the (EENV)6 sequence from the 3' repeat region of Pf155/RESA, had significantly lower parasite densities in the rainy season of 1987. The data suggest that high titres of antibodies to the Pf155/RESA antigen, and especially to its EENV sequence, might play a role in protective immunity in adults.     

A comparison of amodiaquine and sulfadoxine-pyrimethamine as first-line treatment of falciparum malaria in Kenya.

A randomized 14-day study in vivo compared the response of Plasmodium falciparum malaria to amodiaquine (35 mg/kg) and sulfadoxine-pyrimethamine (sulfadoxine, 25 mg/kg) in symptomatic outpatients at 2 sites in northern and western Kenya during 1993. Of the 239 patients recruited, 181 (76%) completed the study [84 (46%) on amodiaquine and 97 (54%) on sulfadoxine-pyrimethamine]. There were no significant differences in the parasitological, clinical or haematological responses between the 2 drug groups in both areas, with 18.5% resistance to amodiaquine versus 9.5% for sulfadoxine-pyrimethamine in the north and 35.1% against amodiaquine versus 34.5% for sulfadoxine-pyrimethamine in the west. In both sites defervescence was significantly more rapid with amodiaquine (P < 0.05) and true clinical failure (symptomatic illness with recurrent parasitaemia) was unusual (9%). As high-level resistance to chloroquine is widespread, both drugs are valuable alternatives. However, the significantly higher levels of resistance in the west may be a sign of the increased drug pressure in this holoendemic area and send an important warning concerning resistance to sulfadoxine-pyrimethamine.     

The effects of multiplication and synchronicity on the vascular distribution of parasites in falciparum malaria.

The sequestration of erythrocytes containing mature forms of Plasmodium falciparum in the microvasculature of vital organs may cause large discrepancies between the peripheral blood parasite count and the total body parasite burden in falciparum malaria. Despite this, parasitaemia is widely used as an indicator of prognosis and response to treatment. A simple mathematical model describing the changes in circulating and sequestered parasite numbers during acute falciparum malaria is presented. The model uses two parameters only; the standard deviation (SD) of parasite age since merogony (schizogony) as as a measure of synchronicity, and a multiplication factor each 48 h asexual life cycle. The model predicts that during the rising phase of the infection the ratio of circulating to sequestered parasites is dependent largely on the synchronicity of infection rather than multiplication rate, and that in synchronous infections parasitaemias will show considerable fluctuation when the mean stage of parasite development is in the second half of the asexual life cycle. The model fitted well to serial parasite counts from 4 patients with acute uncomplicated falciparum malaria whose infections failed to respond to ciprofloxacin. All four infections were synchronous (SD < or = 4 h), and showed large fluctuations in parasitaemia over short periods related to synchronous sequestration and subsequent reinvasion following merogony. The parasite multiplication rate was determined mainly by the efficiency of merogony or merozoite invasion rather than clearance of circulating parasitized erythrocytes. This suggests that the spleen is relatively inactive during the rising phase of the infection. Quinine treatment did not prevent sequestration but did stop subsequent multiplication.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of a real-time PCR assay for malaria diagnosis in patients from Vietnam and in returned travellers

Real-time PCR diagnosis of malaria has advantages over traditional microscopic methods, especially when parasitaemia is low and when dealing with mixed infections. We have developed a new real-time PCR with specific genes in each Plasmodium species present only in one copy to identify the four pathogenic Plasmodium spp. for humans. The sensitivity was less than 25 parasites/microl. No cross-hybridisation was observed with human DNA or among the four Plasmodium spp. Using LightCycler PCR and conventional microscopy, we compared the diagnosis of malaria in patients from Vietnam and in returned European travellers with suspicion of malaria. In patients from Vietnam with suspicion of malaria, one mixed infection was observed by PCR only; the remaining data (54 of 55 patients) correlated with microscopy. In 79 patients without symptoms, low parasitaemia was detected in 7 samples by microscopy and in 16 samples by PCR. In returned travellers, PCR results were correlated with microscopy for all four species in 48 of 56 samples. The eight discrepant results were resolved in favour of real-time PCR diagnosis. This new real-time PCR is a rapid, accurate and efficient method for malaria diagnosis in returned travellers as well as for epidemiological studies or antimalarial efficiency trials in the field.     

Geographical distribution of falciparum malaria in the world and its relationship with the human development index (HDI): countries based on the WHO report in 2017

Journal of Public Health - Malaria is one of the most serious public health issues worldwide and is still responsible for the deaths of nearly half a million individuals every year worldwide. The...     

A randomized comparison of oral chloroquine and sulfadoxine-pyrimethamine for the treatment of uncomplicated Plasmodium falciparum malaria in Laos

Between June and October 2000 we conducted the first randomized trial in Laos comparing chloroquine (CQ) with sulfadoxine-pyrimethamine (SP) in the treatment of uncomplicated Plasmodium falciparum malaria (n = 29, 42-d follow-up, age > 5 years). The proportion of patients with treatment failure was high (CQ = 78%, RIII 46%; SP = 36%, RIII 15%). The treatment policy for uncomplicated P. falciparum malaria in Laos needs to be reviewed urgently.     

A human phase 1 vaccine clinical trial of the Plasmodium falciparum malaria vaccine candidate apical membrane antigen 1 in Montanide ISA720 adjuvant

A dose escalating, placebo-controlled phase 1 trial was conducted to test the safety and immunogenicity of a vaccine containing recombinant Plasmodium falciparum apical membrane antigen 1 (AMA1) formulated in Montanide ISA720. Three groups of volunteers were vaccinated intramuscularly with 5 microg, 20 microg or 80 microg of AMA1, respectively, in 0.5 mL of formulation at 0, 3 and 6 months. Anti-AMA1 antibody levels and T cell stimulation indices were measured before and after each vaccination. No vaccine-related serious adverse events were recorded. Most subjects generated a mild to moderate, transient local reaction after the first vaccination. Three subjects developed a local reaction approximately 10 days following vaccination. Six of the 29 subjects seroconverted. Only one of these developed a high antibody titre. However, the interpretation of this trial was compromised by a loss of potency of the formulated vaccine during the course of the study.     

A comparison of artesunate alone with combined artesunate and quinine in the parenteral treatment of acute falciparum malaria.

In some areas clinicians have combined parenteral artesunate and quinine in the belief that the 2 drugs would be additive or synergistic in severe malaria. A randomized comparison of the effectiveness of intravenous (i.v.) artesunate versus i.v. artesunate and i.v. quinine together on parasite clearance was conducted in 1998/99 amongst 69 patients with uncomplicated and severe Plasmodium falciparum malaria in western Thailand. The parasite clearance time did not differ significantly between the 2 treatment groups (P = 0.12), but adverse events were significantly more frequent in the artesunate plus quinine group (P = 0.05). Quinine did not have a significant antipyretic effect and artesunate did not affect the electrocardiographic QTc interval. There is no benefit evident from combining parenteral administration of these 2 antimalarial drugs in the acute phase of treatment.