Search

Background: Malaria is the parasitic disease with the highest morbidity and mortality worldwide. Angola is one of the five sub-Saharan African countries with the highest malaria burden. Real-time PCR diagnosis in endemic areas has not been implemented due to its high cost and the need for adequate infrastructure. Dried blood spots (DBSs) are an alternative for collecting, preserving, and transporting blood samples to reference laboratories. The objective of the study was to assess the efficacy of DBS as a sampling method for malaria research studies employing real-time PCR. Methods: The study was divided into two phases: (i) prospective study at the Hospital Universitario Vall d'Hebron (HUVH) to compare real-time PCR from whole blood or DBS, including 12 venous blood samples from patients with positive real-time PCR for Plasmodium spp. and 10 quality control samples (nine infected samples and one negative control). Samples were collected as DBSs (10, 20, 50 µl/circle). Samples from both phases of the study were analyzed by generic real-time PCR (Plasmodium spp.) and the subsequent positive samples underwent species-specific real-time PCR (Plasmodium species) and (ii) cross-sectional study conducted at the Hospital Nossa Senhora da Paz, Cubal (Angola), including 200 participants with fever. For each patient, a fresh capillary blood specimen [for thin and thick blood films and rapid diagnostic test (RDT)] and venous blood, collected as DBSs (two 10-µl circles were combined for a total volume of 20 µl of DBS), were obtained. DBSs were sent to HUVH, Barcelona, Spain. Results: (i) Real-time PCR from whole blood collection was positive for 100% of the 21 Plasmodium spp.-infected samples, whereas real-time PCR from DBSs detected Plasmodium spp. infection at lower proportions: 76.19% (16/21) for 10 µl, 85.71% (18/21) for 20 µl, 88.24% (15/17) for 50 µl and 85.71% (18/21) for 100 µl DBSs. (ii) Field diagnosis (microscopy and/or RDT) showed a 51.5% (103/200) positivity rate, while 50% (100/200) of the DBS samples tested positive by real-time PCR. Using field diagnosis as the reference method, the sensitivity of real-time PCR in DBS samples was 77.67% with a specificity of 79.38%. Plasmodium species were identified in 86 samples by real-time PCR: 81.40% (16/86) were caused by Plasmodium falciparum, 11.63% (10/86) were coinfections of P. falciparum + P. malariae, 4.65% (4/86) were P. falciparum + P. ovale, and 2.33% (2/86) were triple coinfections. Conclusions: The DBS volume used for DNA extraction is a determining factor in the performance of real-time PCR for Plasmodium DNA detection. A DBS volume of 50–100 µl appears to be optimal for malaria diagnosis and Plasmodium species determination by real-time PCR. DBS is a suitable method for sample collection in Cubal followed by real-time PCR analysis in a reference laboratory. [ABSTRACT FROM AUTHOR]

Background: Malaria is the parasitic disease with the highest morbimortality worldwide. The World Health Organization (WHO) estimates that there were approximately 249 million cases in 2022, of which 3.4% were in Angola. Diagnosis is based on parasite identification by microscopy examination, antigen detection, and/or molecular tests, such as polymerase chain reaction (PCR). This study aimed to evaluate the usefulness of real-time PCR as a diagnostic method for malaria in an endemic area (Cubal, Angola). Methods: A cross-sectional study was carried out at the Hospital Nossa Senhora da Paz in Cubal, Angola, including 200 patients who consulted for febrile syndrome between May and July 2022. From each patient, a capillary blood sample was obtained by finger prick for malaria field diagnosis [microscopy and rapid diagnostic test (RDT)] and venous blood sample for real-time PCR performed at the Hospital Universitario Vall d'Hebron in Barcelona, Spain. Any participant with a positive result from at least one of these three methods was diagnosed with malaria. Results: Of the 200 participants included, 54% were female and the median age was 7 years. Malaria was diagnosed by at least one of the three techniques (microscopy, RDT, and/or real-time PCR) in 58% of the participants, with RDT having the highest percentage of positivity (49%), followed by real-time PCR (39.5%) and microscopy (33.5%). Of the 61 discordant samples, 4 were only positive by microscopy, 13 by real-time PCR, and 26 by RDT. Plasmodium falciparum was the most frequent species detected (90.63%), followed by P. malariae (17.19%) and P. ovale (9.38%). Coinfections were detected in ten participants (15.63%): six (60%) were caused by P. falciparum and P. malariae, three (30%) by P. falciparum and P. ovale, and one (10%) triple infection with these three species. In addition, it was observed that P. falciparum and P. malariae coinfection significantly increased the parasite density of the latter. Conclusions: RDT was the technique with the highest positivity rate, followed by real-time PCR and microscopy. The results of the real-time PCR may have been underestimated due to suboptimal storage conditions during the transportation of the DNA eluates. However, real-time PCR techniques have an important role in the surveillance of circulating Plasmodium species, given the epidemiological importance of the increase in non-falciparum species in the country, and can provide an estimate of the intensity of infection. [ABSTRACT FROM AUTHOR]

Background: Strongyloides stercoralis infection is a common neglected tropical disease distributed worldwide, mainly in tropical and subtropical climates. The impact of S. stercoralis infections on human health ranges from mild asymptomatic infections to chronic strongyloidiasis unnoticeable until the host is immunosuppressed. In severe strongyloidiasis, a syndrome of hyperinfection and larval dissemination to various organs can occur with high mortality rates. The diagnosis of strongyloidiasis is challenging because of the absence of a single standard reference test with high sensitivity and specificity, which also makes it difficult to estimate the accuracy of other diagnostic tests. This study aimed to evaluate, for the first time, the use of an easy-to-perform loop-mediated isothermal amplification (LAMP) colorimetric assay (named Strong-LAMP) for the molecular screening of strongyloidiasis in stool samples from patients in a low-resource endemic area in Cubal, Angola. To compare different LAMP application scenarios, the performance of the Strong-LAMP under field conditions in Angola was reassessed in a well-equipped reference laboratory in Spain and compared with a quantitative polymerase chain reaction (qPCR) method. Methods: A total of 192 stool samples were collected from adult population in Cubal, Angola, and examined by parasitological methods (direct saline microscopy and Baermann's technique). DNA was extracted from each stool sample using a commercial kit and tested by the colorimetric Strong-LAMP assay for the detection of Strongyloides spp. under field conditions. Furthermore, all samples were shipped to a well-equipped laboratory in Spain, reanalysed by the same procedure and compared with a qPCR method. The overall results after testing were compared. Results: Strongyloides stercoralis larvae were identified by direct saline microscopy and Baermann in a total of 10/192 (5.2%) and 18/192 (9.4%) stool samples, respectively. Other helminth and protozoan species were also identified. The Strong-LAMP-positive results were visually detected in 69/192 (35.9%) stool samples. The comparison of Strong-LAMP results in field conditions and at a reference laboratory matched in a total of 146/192 (76.0%) samples. A total of 24/192 (12.5%) stool samples tested positive by qPCR. Conclusions: This is the first study in which colorimetric Strong-LAMP has been clinically evaluated in a resource-poor strongyloidiasis endemic area. Strong-LAMP has been shown to be more effective in screening for strongyloidiasis than parasitological methods under field conditions and qPCR in the laboratory. Our Strong-LAMP has proven to be a field-friendly and highly accurate molecular test for the diagnosis of strongyloidiasis. [ABSTRACT FROM AUTHOR]

Background: Malaria is a globally distributed infectious disease. According to the World Health Organization, Angola is one of the six countries that account for over half the global malaria burden in terms of both malaria cases and deaths. Diagnosis of malaria still depends on microscopic examination of thin and thick blood smears and rapid diagnostic tests (RDTs), which often lack analytical and clinical sensitivity. Molecular methods could overcome these disadvantages. The aim of this study was to evaluate, for the first time to our knowledge, the performance of a loop-mediated isothermal amplification (LAMP) for the diagnosis of malaria in an endemic area in Cubal, Angola, and to assess the reproducibility at a reference laboratory. Methods: A total of 200 blood samples from patients attended at Hospital Nossa Senhora da Paz, Cubal, Angola, were analysed for Plasmodium spp. detection by microscopy, RDTs, and LAMP. LAMP assay was easily performed in a portable heating block, and the results were visualized by a simple colour change. Subsequently, the samples were sent to a reference laboratory in Spain to be reanalysed by the same colorimetric LAMP assay and also in real-time LAMP format. Results: In field tests, a total of 67/200 (33.5%) blood samples were microscopy-positive for Plasmodium spp., 98/200 RDT positive, and 112/200 (56%) LAMP positive. Using microscopy as reference standard, field LAMP detected more microscopy-positive samples than RDTs (66/67; 98% vs. 62/67; 92.5%). When samples were reanalysed at a reference laboratory in Spain using both colorimetric and real-time assays, the overall reproducibility achieved 84.5%. Conclusions: This is the first study to our knowledge in which LAMP has been clinically evaluated on blood samples in a resource-poor malaria-endemic area. The colorimetric LAMP proved to be more sensitive than microscopy and RDTs for malaria diagnosis in field conditions. Furthermore, LAMP showed an acceptable level of reproducibility in a reference laboratory. The possibility to use LAMP in a real-time format in a portable device reinforces the reliability of the assay for molecular diagnosis of malaria in resource-poor laboratories in endemic areas. [ABSTRACT FROM AUTHOR]

Crimean–Congo haemorrhagic fever (CCHF) is a potentially lethal tick-borne viral disease with a wide distribution. In Spain, 12 human cases of CCHF have been confirmed, with four deaths. The diagnosis of CCHF is hampered by the nonspecific symptoms, the high genetic diversity of CCHFV, and the biosafety requirements to manage the virus. RT-qPCR and serological tests are used for diagnosis with limitations. Reverse-transcription loop-mediated isothermal amplification (RT-LAMP) could be an effective alternative in the diagnosis of the disease. However, none of the few RT-LAMP assays developed to date has detected different CCHFV genotypes. Here, we designed a RT-LAMP using a degenerate primer set to compensate for the variability of the CCHFV target sequence. RT-LAMP was performed in colorimetric and real-time tests on RT-qPCR-confirmed CCHF patient samples notified in Spain in 2020 and 2021. Urine from an inpatient was analysed by RT-LAMP for the first time and compared with RT-qPCR. The amplicons obtained by RT-qPCR were sequenced and African III and European V genotypes were identified. RT-LAMP amplified both genotypes and was more sensitive than RT-qPCR in urine samples. We have developed a novel, rapid, specific, and sensitive RT-LAMP test that allows the detection of different CCHFV genotypes in clinical samples. This pan-CCHFV RT-LAMP detected viral RNA for the first time in urine samples. It can be easily performed as a single-tube isothermal colorimetric method on a portable platform in real time and without the need for expensive equipment, thus bringing molecular diagnostics closer to rural or resource-poor areas, where CCHF usually occurs. [ABSTRACT FROM AUTHOR]

Crimean-Congo hemorrhagic fever (CCHF) is a viral infectious disease for which distribution of the main vector, Hyalomma spp. ticks, is expanding. We analyzed all 10 cases of CCHF diagnosed in Spain during 2013-2021; case-patient median age was 56.5 years, and 7 were men. We identified CCHF virus genotypes III and V. Six case-patients acquired the infection in urban areas. Sixty percent of patients were infected in summer and 40% in spring. Two patients met criteria for hemophagocytic syndrome. Seven patients survived. The epidemiologic pattern of CCHF in Spain is based on occasional cases with an elevated mortality rate. Genotype III and, to a less extent also genotype V, CCHF circulates in humans in a common geographic area in Spain. Those data suggest that the expansion pathways are complex and may change over time. Physicians should remain alert to the possibility of new CCHF cases. [ABSTRACT FROM AUTHOR]

Loop-mediated isothermal amplification (LAMP) is the most popular technology for point-of-care testing applications due its rapid, sensitive and specific detection with simple instrumentation compared to PCR-based methods. Many systems for reading the results of LAMP amplifications exist, including real-time fluorescence detection using fluorophore-labelled probes attached to oligonucleotide sequences complementary to the target nucleic acid. This methodology allows the simultaneous detection of multiple targets (multiplexing) in one LAMP assay. A method for multiplexing LAMP is the amplification by release of quenching (DARQ) technique by using a 5′-quencher modified LAMP primer annealed to 3′-fluorophore-labelled acting as detection oligonucleotide. The main application of multiplex LAMP is the rapid and accurate diagnosis of infectious diseases, allowing differentiation of co-infecting pathogens in a single reaction. Schistosomiasis, caused among other species by Schistosoma mansoni and strongyloidiasis, caused by Strongyloides stercoralis, are the most common helminth-parasite infections worldwide with overlapping distribution areas and high possibility of coinfections in the human population. It would be of great interest to develop a duplex LAMP to detect both pathogens in the same reaction. In this study, we investigate the use of our two previously developed and well-stablished LAMP assays for S. mansoni and Strongyloides spp. DNA detection in a new duplex real-time eight-primer system based on a modified DARQ probe method that can be performed in a portable isothermal fluorimeter with minimal laboratory resources. We also applied a strategy to stabilize the duplexed DARQ-LAMP mixtures at room temperature for use as ready-to-use formats facilitating analysis in field settings as point-of-care diagnostics for schistosomiasis and strongyloidiasis. [ABSTRACT FROM AUTHOR]

Objectives: Loa loa and Mansonella perstans are two very common filarial species in Africa. Although microscopy is the traditional diagnostic method for human filariasis, several polymerase chain reaction (PCR) methods have emerged as an alternative approach for identifying filarial parasites. The aim of this study is to compare three molecular methods and decide which is the most suitable for diagnosing human loiasis and mansonellosis in non‐endemic regions using dried blood spot (DBS) as a medium for sample collection and storage. Methods: A total of 100 DBS samples, with their corresponding thin and thick blood smears, were selected for this study. Microscopy was used as the reference method to diagnose and calculate the microfilaraemia. Filarial DNA was extracted using the saponin/Chelex method and the DNA isolated was assayed by Filaria‐real time‐PCR, filaria‐nested PCR, and cytochrome oxidase I PCR. All PCR products were subsequently purified and sequenced. The statistical values for each molecular test were calculated and compared. Results: Overall, 64 samples were identified as negative by all tests and a further 36 samples were positive by at least one of the methods used. The sensitivity and specificity were similar for the different molecular methods, all of which demonstrated good agreement with microscopy. Conclusions: Based on this study, and from a practical point of view (single and short amplification round), the optimal technique for diagnosing filarial infection in non‐endemic regions is filaria‐real time‐PCR, which presents high sensitivity and specificity and is also able to detect a wide range of human filariae. [ABSTRACT FROM AUTHOR]

Nucleic acid amplification diagnostics offer outstanding features of sensitivity and specificity. However, they still lack speed and robustness, require extensive infrastructure, and are neither affordable nor user-friendly. Thus, they have not been extensively applied in point-of-care diagnostics, particularly in low-resource settings. In this work, we have combined the loop-mediated isothermal amplification (LAMP) technology with a handheld portable device (SMART-LAMP) developed to perform real-time isothermal nucleic acid amplification reactions, based on simple colorimetric measurements, all of which are Bluetooth-controlled by a dedicated smartphone app. We have validated its diagnostic utility regarding different infectious diseases, including Schistosomiasis, Strongyloidiasis, and COVID-19, and analyzed clinical samples from suspected COVID-19 patients. Finally, we have proved that the combination of long-term stabilized LAMP master mixes, stored and transported at room temperature with our developed SMART-LAMP device, provides an improvement towards true point-of-care diagnosis of infectious diseases in settings with limited infrastructure. Our proposal could be easily adapted to the diagnosis of other infectious diseases. [ABSTRACT FROM AUTHOR]

Loiasis, caused by the filarial nematode Loa loa, is endemic in Central and West Africa. Loa loa has been associated with severe adverse reactions in high Loa-infected individuals receiving ivermectin during mass drug administration programs for the control of onchocerciasis and lymphatic filariasis. Diagnosis of loiasis still depends on microscopy in blood samples, but this is not effective for large-scale surveys. New diagnostics methods for loiasis are urgently needed. Previously, we developed a colorimetric high-sensitive and species-specific LAMP for Loa loa DNA detection. Here, we evaluate it in a set of 100 field-collected clinical samples stored as dried blood spots. In addition, Loa loa-LAMP was also evaluated in real-time testing and compared with microscopy and a specific PCR/nested PCR. A simple saponin/Chelex-based method was used to extract DNA. Colorimetric and real-time LAMP assays detected more samples with microscopy-confirmed Loa loa and Loa loa/Mansonella perstans mixed infections than PCR/nested-PCR. Samples with the highest Loa loa microfilariae counts were amplified faster in real-time LAMP assays. Our Loa loa-LAMP could be a promising molecular tool for the easy, rapid and accurate screening of patients for loiasis in endemic areas with low-resource settings. The real-time testing (feasible in a handheld device) could be very useful to rule out high-microfilariae loads in infected patients. [ABSTRACT FROM AUTHOR]

Background: Trichuris trichiura (human whipworm) infects an estimated 477 million individuals worldwide. In addition to T. trichiura, other Trichuris species can cause an uncommon zoonosis and a number of human cases have been reported. The diagnosis of trichuriasis has relied traditionally on microscopy. Recently, there is an effort to use molecular diagnostic methods, mainly qPCR. LAMP technology could be an alternative for qPCR especially in low-income endemic areas. Trichuris muris, the causative agent of trichuriasis in mice, is of great importance as a model for human trichuriasis. Here, we evaluate the diagnostic utility of a new LAMP assay in an active experimental mouse trichuriasis in parallel with parasitological method by using stool and, for the first time, urine samples. Methods: Stool and urine samples were collected from mice infected with eggs of T. muris. The dynamics of infection was determined by counting the number of eggs per gram of faeces. A LAMP based on the 18S rRNA gene from T. muris was designed. Sensitivity and specificity of LAMP was tested and compared with PCR. Stool and urine samples were analysed by both LAMP and PCR techniques. Results: Trichuris muris eggs were detected for the first time in faeces 35 days post-infection. LAMP resulted specific and no cross-reactions were found when using 18 DNA samples from different parasites. The detection limit of the LAMP assay was 2 pg of T. muris DNA. When testing stool samples by LAMP we obtained positive results on day 35 p.i. and urine samples showed amplification results on day 20 p.i., i.e. 15 days before the onset of T. muris eggs in faeces. Conclusions: To the best of our knowledge, we report, for the first time, a novel LAMP assay (Whip-LAMP) for sensitive detection of T. muris DNA in both stool and urine samples in a well-established mice experimental infection model. Considering the advantages of urine in molecular diagnosis in comparison to stool samples, should make us consider the possibility of starting the use urine specimens in molecular diagnosis and for field-based studies of human trichuriasis where possible. Further studies with clinical samples are still needed. [ABSTRACT FROM AUTHOR]

Detection of SARS-CoV-2 is routinely performed in naso/oropharyngeal swabs samples from patients via RT-qPCR. The RT-LAMP technology has also been used for viral RNA detection in respiratory specimens with both high sensitivity and specificity. Recently, we developed a novel RT-LAMP test for SARS-CoV-2 RNA detection in nasopharyngeal swab specimens (named, N15-RT-LAMP) that can be performed as a single-tube colorimetric method, in a real-time platform, and as dry-LAMP. To date, there has been very little success in detecting SARS-CoV-2 RNA in urine by RT-qPCR, and the information regarding urine viral excretion is still scarce and not comprehensive. Here, we tested our N15-RT-LAMP on the urine of 300 patients admitted to the Hospital of Salamanca, Spain with clinical suspicion of COVID-19, who had a nasopharyngeal swab RT-qPCR-positive (n = 100), negative (n = 100), and positive with disease recovery (n = 100) result. The positive group was also tested by RT-qPCR for comparison to N15-RT-LAMP. Only a 4% positivity rate was found in the positive group via colorimetric N15-RT-LAMP and 2% via RT-qPCR. Our results are consistent with those obtained in other studies that the presence of SARS-CoV-2 RNA in urine is a very rare finding. The absence of SARS-CoV-2 RNA in urine in the recovered patients might suggest that the urinary route is very rarely used for viral particle clearance. [ABSTRACT FROM AUTHOR]

Schistosomiasis is a disease of great medical and veterinary importance in tropical and subtropical regions caused by different species of parasitic flatworms of the genus Schistosoma. The emergence of natural hybrids of schistosomes indicate the risk of possible infection to humans and their zoonotic potential, specifically for Schistosoma haematobium and S. bovis. Hybrid schistosomes have the potential to replace existing species, generate new resistances, pathologies and extending host ranges. Hybrids may also confuse the serological, molecular and parasitological diagnosis. Currently, LAMP technology based on detection of nucleic acids is used for detection of many agents, including schistosomes. Here, we evaluate our previously developed species-specific LAMP assays for S. haematobium, S. mansoni, S. bovis and also the genus-specific LAMP for the simultaneous detection of several Schistosoma species against both DNA from pure and, for the first time, S. haematobium x S. bovis hybrids. Proper operation was evaluated with DNA from hybrid schistosomes and with human urine samples artificially contaminated with parasites' DNA. LAMP was performed with and without prior DNA extraction. The genus-specific LAMP properly amplified pure Schistosoma species and different S. haematobium-S. bovis hybrids with different sensitivity. The Schistosoma spp.-LAMP method is potentially adaptable for field diagnosis and disease surveillance in schistosomiasis endemic areas where human infections by schistosome hybrids are increasingly common. [ABSTRACT FROM AUTHOR]

Human schistosomiasis is one of the most important parasitic diseases, causing around 250 million cases (mostly in Africa) and 280,000–500,000 deaths every year. Due to the limited resources and the far-removed nature of many endemic areas, the implementation of new, sensitive and specific diagnostic tools has had little success. This is particularly true for PCR-based molecular methods that require expensive equipment and trained personnel to be executed. Loop-mediated isothermal amplification (LAMP) along with other isothermal techniques appeared in the early 21st century as an alternative to those methods, overcoming some of the aforementioned limitations and achieving a more inexpensive diagnostic. However, to this date, neither LAMP nor any other isothermal technique have signified a meaningful change in the way schistosomiasis diagnosis is routinely performed. Here, we present the recent developments in LAMP-based schistosomiasis diagnosis. We expose the main advantages and disadvantages of LAMP technology over PCR and other classical diagnostic methods focusing in various research approaches on intermediate hosts, animal models and patients. We also examine its potential clinical application in post-therapy monitoring, as well as its usefulness as a point-of-care test. [ABSTRACT FROM AUTHOR]