In Silico Identification of Novel Biomarkers and Development of New Rapid Diagnostic Tests for the Filarial Parasites Mansonella perstans and Mansonella ozzardi

Diversity of Culicoides in the middle belt of Ghana with Implications on the transmission of Mansonella perstans; a molecular approach

BACKGROUND

Culicoides, also known as biting midges, carry pathogens which include Mansonella perstans. Mansonella perstans is a nematode parasite implicated in a number of disease outcomes. Even though a high prevalence of about 75% M. perstans infection has been recorded in some communities in the middle belt of Ghana, and a wide diversity of Culicoides species has been identified, the exact Culicoides species transmitting M. perstans in Ghana has not yet been deciphered. This study therefore aimed at assessing the species diversity of Culicoides and their role in the transmission of M. perstans in the middle belt of Ghana.

METHODS

Culicoides species were sampled from 11 communities in the Asante-Akim North and Sene West districts in the middle belt of Ghana. Centre for Disease Control (CDC) UV light traps, as well as human bait (i.e. human landing catch and engorged catch) methods were used to assess the species abundance and diversity of Culicoides in the study communities in the wet and dry season. A colorimetric Loop-Mediated Isothermal Amplification (LAMP) assay was performed to assess the vector competence of the various Culicoides species.

RESULTS

A total of 4810 Culicoides from 6 species were sampled. These included Culicoides inornatipennis, C. milnei, C. schultzei, C. grahamii, C. neavei, and C. imicola. Culicoides imicola was the most abundant species (56%) followed by C. grahamii (16%). Light traps sampled the most diverse species (6 species). Human landing catch and engorged catch methods identified three anthropophilic species, C. grahamii, C. milnei, and C. inornatipennis, with C. grahamii being the most anthropophilic with a peak biting time between the hours of 5 p.m. to 6 p.m. Generally, there was relatively higher species abundance in the wet than dry season. LAMP assay identified C. grahamii as the potential vector for M. perstans transmission in the middle belt of Ghana.

CONCLUSIONS

For the first time, we have demonstrated that C. grahamii is the potential competent vector for M. perstans transmission in the middle belt of Ghana. It is more abundant in the rainy season and has a peak biting time between the hours of 5 and 6 p.m.

Culicoides Species of the Rain Forest Belt of the Littoral Region of Cameroon: Their Incrimination in the Transmission of Mansonella perstans

Biting midges belonging to the genus Culicoides are tiny stout-shaped hematophagous insects and are thought to transmit the filarial nematode Mansonella perstans. Little is known about the Culicoides fauna in the rain forest belt of the Littoral Region of Cameroon. This study was designed to investigate the diversity, abundance and distribution of Culicoides spp. and their role as the purported vector(s) of M. perstans. Overnight light trap collections and human landing catches (HLCs) revealed eight species of Culicoides with C. grahamii being the most abundant species followed by C. milnei. Four anthropophilic species (C. inornatipennis, C. grahamii, C. fulvithorax and C. milnei) were determined by the HLCs with a higher abundance in the 4-6 p.m. collections. The drop trap technique and Mp419 LAMP assay confirmed C. milnei to be the most efficient vector in enabling the development of the microfilarial stage to the infective larval form of M. perstans. The LAMP assay also revealed that natural transmission of this nematode is fostered by C. milnei and C. grahamii in the wild. In conclusion, C. milnei was shown to be the main vector of M. perstans in the rain forest belt of the Littoral Region of Cameroon.

Filarial disease in the Brazilian Amazon and emerging opportunities for treatment and control

Following the successful eradication of Wuchereria bancrofti, there are now just three species of conventional microfilaremic human filarial parasites endemic to the Brazilian Amazon region: Mansonella ozzardi, Mansonella perstans and Onchocerca volvulus. The zoonotic filarial parasite Dirofilaria immitis is also found in the Amazon region as are several sylvatic filarial parasites, some of which have been recorded causing zoonoses and some of which have never been recorded outside the region. Onchocerca volvulus is only found in the Amazonia onchocerciasis focus in the Brazilian state of Roraima where it affects the people of the Yanomami tribe living around the densely forested Venezuela border region. Mansonella ozzardi is by far the most common filarial parasite in Brazil and has a broad but patchy distribution throughout the western Amazon region. Recorded in the Brazilian states of Acre, Roraima, Matto Grosso, and within almost every municipality of Amazonas state, it is believed that pollution of the urban stream and river systems prevents the development of the simuliid vectors of M. ozzardi and explains the parasite's reduced distribution within urban areas and an absence of recent reports from the state capital Manaus. Decades of WHO-led periodic ivermectin treatment of Yanomami tribe's people have resulted in the partial suppression of O. volvulus transmission in this focus and has also probably affected the transmission of M. ozzardi in the region. Mansonella perstans, O. volvulus and very probably M. ozzardi infections can all be treated and most likely cured with a 4-6-week treatment course of doxycycline. The Brazilian Ministry of Health does not, however, presently recommend any treatment for mansonellosis infections and thus parasitic infections outside the Amazonia focus are typically left untreated. While the long treatment courses required for doxycycline-based mansonellosis therapies preclude their use in control programmes, new fast-acting filarial drug treatments are likely to soon become available for the treatment of both onchocerciasis and mansonellosis in the Amazon region. Filarial disease management in the Brazilian Amazon is thus likely to become dramatically more viable at a time when the public health importance of these diseases is increasingly being recognized.

Redescription, molecular characterisation and Wolbachia endosymbionts of Mansonella (Tupainema) dunni (Mullin & Orihel, 1972) (Spirurida: Onchocercidae) from the common treeshrew Tupaia glis Diard & Duvaucel (Mammalia: Scandentia) in Peninsular Malaysia

The genus Mansonella Faust, 1929 includes 29 species, mainly parasites of platyrrhine monkeys in South America and anthropoid apes in Africa. In Malaysia, Mansonella (Tupainema) dunni (Mullin & Orihel, 1972) was described from the common treeshrew Tupaia glis Diard & Duvaucel (Scandentia). In a recent classification of the genus Mansonella, seven subgenera were proposed, with M. (Tup.) dunni as a monotypic species in the subgenus Tupainema. In this study, we collected new material of M. (Tup.) dunni from common treeshrews in Peninsular Malaysia and redescribed the morphological features of this species. We found that M. (Tup.) dunni differs from M. (Cutifilaria) perforata Uni et al., 2004 from sika deer Cervus nippon (Cetartiodactyla) in Japan, with regards to morphological features and predilection sites in their respective hosts. Based on multi-locus sequence analyses, we examined the molecular phylogeny of M. (Tup.) dunni and its Wolbachia genotype. Species of the genus Mansonella grouped monophyletically in clade ONC5 and M. (Tup.) dunni was placed in the most derived position within this genus. Mansonella (Tup.) dunni was closely related to M. (M.) ozzardi (Manson, 1897) from humans in Central and South America, and most distant from M. (C.) perforata. The calculated p-distances between the cox1 gene sequences for M. (Tup.) dunni and its congeners were 13.09% for M. (M.) ozzardi and 15.6-16.15% for M. (C.) perforata. The molecular phylogeny of Mansonella spp. thus corroborates their morphological differences. We determined that M. (Tup.) dunni harbours Wolbachia endosymbionts of the supergroup F genotype, in keeping with all other Mansonella species screened to date.

Molecular Surveillance Detects High Prevalence of the Neglected Parasite Mansonella ozzardi in the Colombian Amazon

BACKGROUND

Mansonellosis is an undermapped insect-transmitted disease caused by filarial nematodes that are estimated to infect hundreds of millions of people. Despite their prevalence, there are many outstanding questions regarding the general biology and health impacts of the responsible parasites. Historical reports suggest that the Colombian Amazon is endemic for mansonellosis and may serve as an ideal location to pursue these questions.

METHODS

We deployed molecular and classical approaches to survey Mansonella prevalence among adults belonging to indigenous communities along the Amazon River and its tributaries near Leticia, Colombia.

RESULTS

Loop-mediated isothermal amplification (LAMP) assays on whole-blood samples detected a much higher prevalence of Mansonella ozzardi infection (approximately 40%) compared to blood smear microscopy or LAMP performed using plasma, likely reflecting greater sensitivity and the ability to detect low microfilaremias and occult infections. Mansonella infection rates increased with age and were higher among men. Genomic analysis confirmed the presence of M. ozzardi that clusters closely with strains sequenced in neighboring countries. We successfully cryopreserved M. ozzardi microfilariae, advancing the prospects of rearing infective larvae in controlled settings.

CONCLUSION

These data suggest an underestimation of true mansonellosis prevalence, and we expect that these methods will help facilitate the study of mansonellosis in endemic and laboratory settings.

The search for better treatment strategies for mansonellosis: an expert perspective

INTRODUCTION

Four species of the Mansonella genus infect millions of people across sub-Saharan Africa and Central and South America. Most infections are asymptomatic, but mansonellosis can be associated with nonspecific clinical manifestations such as fever, headache, arthralgia, and ocular lesions (M. ozzardi); pruritus, arthralgia, abdominal pain, angioedema, skin rash, and fatigue (M. perstans and perhaps Mansonella sp. 'DEUX'); and pruritic dermatitis and chronic lymphadenitis (M. perstans).

AREAS COVERED

We searched the PubMed and SciELO databases for publications on mansonelliasis in English, Spanish, Portuguese, or French that appeared until 1 May 2023. Literature data show that anthelmintics - single-dose ivermectin for M. ozzardi, repeated doses of mebendazole alone or in combination with diethylcarbamazine (DEC) for M. perstans, and DEC alone for M. streptocerca - are effective against microfilariae. Antibiotics that target Wolbachia endosymbionts, such as doxycycline, are likely to kill adult worms of most, if not all, Mansonella species, but the currently recommended 6-week regimen is relatively impractical. New anthelmintics and shorter antibiotic regimens (e.g. with rifampin) have shown promise in experimental filarial infections and may proceed to clinical trials.

EXPERT OPINION

We recommend that human infections with Mansonella species be treated, regardless of any apparent clinical manifestations. We argue that mansonellosis, despite being widely considered a benign infection, may represent a direct or indirect cause of significant morbidity that remains poorly characterized at present.

The design and development of a study protocol to investigate Onchocerca volvulus, Loa loa and Mansonella perstans-mediated modulation of the metabolic and immunological profile in lean and obese individuals in Cameroon

BACKGROUND

Life-style metabolic diseases are steadily rising, not only in developed countries, but also in low- and middle-income countries, presenting a global health problem. Metabolic disorders like type 2 diabetes and cardiovascular diseases are among the ten leading causes of death defined by the WHO in 2019. Results from animal and observational human studies suggest a connection between the decline in human helminth infections and rise of life-style-associated metabolic diseases in developing regions. This trial was designed to investigate filarial infections and their impact on metabolic diseases in Cameroon. We hypothesize that the induction of regulatory immune responses during filarial infection reduces obesity-induced low-grade inflammatory immune responses and thereby improves metabolic parameters, whereas anthelmintic treatment abolishes this protective effect.

METHODS/DESIGN

Participants infected with Mansonella perstans, Onchocerca volvulus and/or Loa loa being lean (BMI <25), overweight (BMI >25 and <30) or clinically obese (BMI ≥30) from Littoral regions of Cameroon will be evaluated for their parasitological, immunological, metabolic and biochemical profile before and after treatment of their parasitic infections. Anthropomorphic measurements and a detailed questionnaire will complement our analysis. The investigation will assess blood immune cell populations, serum adipokines and cytokines that could be influenced by the parasite infection and/or metabolic diseases. Further, parameters like blood glucose, homeostatic model assessment of insulin resistance (HOMA-IR), circulating lipids and circulating makers of liver function will be monitored. Parameters will be assessed before treatment, 12 and 18 months after treatment.

CONCLUSION

The focus of this study is to obtain a comprehensive metabolic profile of the participants in rural areas of Cameroon and to investigate the relationship between filarial immunomodulation and metabolic diseases. This study will elucidate the effect of anti-filarial treatment on the metabolic and immunological parameters that partake in the development of insulin resistance, narrowing in on a potential protective effect of filarial infections on metabolic diseases.

TRIAL REGISTRATION

doi.org/10.1186/ISRCTN43845142, ISRCTN43845142 February 2020 Trial title Effects of filarial parasite infection on type 2 diabetes Issue date: 27.10.22, V.1.

Molecular surveillance detects high prevalence of the neglected parasite Mansonella ozzardi in the Colombian Amazon

Mansonellosis is an undermapped insect-transmitted disease caused by filarial nematodes that are estimated to infect hundreds of millions of people globally. Despite their prevalence, there are many outstanding questions regarding the general biology and health impacts of the responsible parasites. Historical reports suggest that the Colombian Amazon is endemic for mansonellosis and may serve as an ideal location to pursue these questions in the backdrop of other endemic and emerging pathogens. We deployed molecular and classical diagnostic approaches to survey Mansonella prevalence among adults belonging to indigenous communities along the Amazon River and its tributaries near Leticia, Colombia. Deployment of a loop-mediated isothermal amplification (LAMP) assay on blood samples revealed an infection prevalence of ∼40% for Mansonella ozzardi . This assay identified significantly more infections than blood smear microscopy or LAMP assays performed using plasma, likely reflecting greater sensitivity and the ability to detect low microfilaremias or occult infections. Mansonella infection rates increased with age and were higher among males compared to females. Genomic analysis confirmed the presence of M. ozzardi that clusters closely with strains sequenced in neighboring countries. We successfully cryopreserved and revitalized M. ozzardi microfilariae, advancing the prospects of rearing infective larvae in controlled settings. These data suggest an underestimation of true mansonellosis prevalence, and we expect that these methods will help facilitate the study of mansonellosis in endemic and laboratory settings.

Genomes of the human filarial parasites Mansonella perstans and Mansonella ozzardi

The filarial parasites Mansonella ozzardi and Mansonella perstans, causative agents of mansonellosis, infect hundreds of millions of people worldwide, yet remain among the most understudied of the human filarial pathogens. M. ozzardi is highly prevalent in Latin American countries and Caribbean Islands, while M. perstans is predominantly found in sub-Saharan Africa as well as in a few areas in South America. In addition to the differences in their geographical distribution, the two parasites are transmitted by different insect vectors, as well as exhibit differences in their responses to commonly used anthelminthic drugs. The lack of genome information has hindered investigations into the biology and evolution of Mansonella parasites and understanding the molecular basis of the clinical differences between species. In the current study, high quality genomes of two independent clinical isolates of M. perstans from Cameroon and two M. ozzardi isolates one from Brazil and one from Venezuela are reported. The genomes are approximately 76 Mb in size, encode about 10,000 genes each, and are largely complete based on BUSCO scores of about 90%, similar to other completed filarial genomes. These sequences represent the first genomes from Mansonella parasites and enabled a comparative genomic analysis of the similarities and differences between Mansonella and other filarial parasites. Horizontal DNA transfers (HDT) from mitochondria (nuMTs) as well as transfers from genomes of endosymbiotic Wolbachia bacteria (nuWTs) to the host nuclear genome were identified and analyzed. Sequence comparisons and phylogenetic analysis of known targets of anti-filarial drugs diethylcarbamazine (DEC), ivermectin and mebendazole revealed that all known target genes were present in both species, except for the DEC target encoded by gon-2 gene, which is fragmented in genome assemblies from both M. ozzardi isolates. These new reference genome sequences will provide a valuable resource for further studies on biology, symbiosis, evolution and drug discovery.

Filariasis research - from basic research to drug development and novel diagnostics, over a decade of research at the Institute for Medical Microbiology, Immunology and Parasitology, Bonn, Germany

Filariae are vector borne parasitic nematodes, endemic in tropical and subtropical regions causing avoidable infections ranging from asymptomatic to stigmatizing and disfiguring disease. The filarial species that are the major focus of our institution's research are Onchocerca volvulus causing onchocerciasis (river blindness), Wuchereria bancrofti and Brugia spp. causing lymphatic filariasis (elephantiasis), Loa loa causing loiasis (African eye worm), and Mansonella spp causing mansonellosis. This paper aims to showcase the contribution of our institution and our collaborating partners to filarial research and covers decades of long research spanning basic research using the Litomosoides sigmodontis animal model to development of drugs and novel diagnostics. Research with the L. sigmodontis model has been extensively useful in elucidating protective immune responses against filariae as well as in identifying the mechanisms of filarial immunomodulation during metabolic, autoimmune and infectious diseases. The institute for Medical Microbiology, Immunology and Parasitology (IMMIP), University Hospital Bonn (UKB), Bonn, Germany has also been actively involved in translational research in contributing to the identification of new drug targets and pre-clinical drug research with successful and ongoing partnership with sub-Saharan Africa, mainly Ghana (the Kumasi Centre for Collaborative Research (KCCR)), Cameroon (University of Buea (UB)) and Togo (Laboratoire de Microbiologie et de Contrôle de Qualité des Denrées Alimentaires (LAMICODA)), Asia and industry partners. Further, in the direction of developing novel diagnostics that are sensitive, time, and labour saving, we have developed sensitive qPCRs as well as LAMP assays and are currently working on artificial intelligence based histology analysis for onchocerciasis. The article also highlights our ongoing research and the need for novel animal models and new drug targets.

Application of loop mediated isothermal amplification (LAMP) assays for the detection of Onchocerca volvulus, Loa loa and Mansonella perstans in humans and vectors

Conventional diagnosis of filarial infections is based on morphological identification of microfilariae using light microscopy and requires considerable expertise, is time-consuming, and can be subjective. Loop-mediated isothermal amplification (LAMP) has advantages over microscopy or PCR because of its operational simplicity, rapidity and versatility of readout options. LAMP assays represent a major step forward in improved filarial diagnostic tools suitable for low resource settings and field applicability. The study goal was to retrospectively evaluate the performance and suitability of the O-150, RF4, and Mp419 LAMP assays for diagnosing Onchocerca volvulus, Loa loa and Mansonella perstans infections, respectively, in humans and vectors under experimental and natural field conditions. Surveys were conducted in four health districts of Cameroon using skin snip and thick blood film methods to detect skin (O. volvulus) and blood (L. loa and M. perstans) dwelling microfilaria in humans. Engorged vectors (Simulium spp., Chrysops spp., and Culicoides spp.) were evaluated by LAMP. Dissected, wild-caught vectors were also analyzed. LAMP showed a prevalence of 40.4% (O. volvulus), 17.8% (L. loa) and 36.6% (M. perstans) versus 20.6% (O. volvulus), 17.4% (L. loa) and 33.8% (M. perstans) with microscopy. Simulium spp. were dissected for microscopy and pooled for LAMP. The O-150 LAMP assay infection rate was 4.3% versus 4.1% by microscopy. Chrysops spp. were dissected and analyzed individually in the LAMP assay. The RF4 LAMP assay infection rate was 23.5% versus 3.3% with microscopy. The RF4 LAMP assay also detected parasites in Chrysops spp. fed on low microfilaremic volunteers. The Mp419 LAMP assay infection rate was 0.2% for C. milnei and 0.04% for C. grahamii, while three other species were LAMP-negative. The sensitivity, species specificity, rapidity and ease of its use of these filarial LAMP assays, and validation of their performance in the field support use as alternatives to microscopy as diagnostic and surveillance tools in global health programs aimed to eliminate onchocerciasis.

Development and implementation of a simple and rapid extraction-free saliva SARS-CoV-2 RT-LAMP workflow for workplace surveillance

Effective management of the COVID-19 pandemic requires widespread and frequent testing of the population for SARS-CoV-2 infection. Saliva has emerged as an attractive alternative to nasopharyngeal samples for surveillance testing as it does not require specialized personnel or materials for its collection and can be easily provided by the patient. We have developed a simple, fast, and sensitive saliva-based testing workflow that requires minimal sample treatment and equipment. After sample inactivation, RNA is quickly released and stabilized in an optimized buffer, followed by reverse transcription loop-mediated isothermal amplification (RT-LAMP) and detection of positive samples using a colorimetric and/or fluorescent readout. The workflow was optimized using 1,670 negative samples collected from 172 different individuals over the course of 6 months. Each sample was spiked with 50 copies/μL of inactivated SARS-CoV-2 virus to monitor the efficiency of viral detection. Using pre-defined clinical samples, the test was determined to be 100% specific and 97% sensitive, with a limit of detection of 39 copies/mL. The method was successfully implemented in a CLIA laboratory setting for workplace surveillance and reporting. From April 2021-February 2022, more than 30,000 self-collected samples from 755 individuals were tested and 85 employees tested positive mainly during December and January, consistent with high infection rates in Massachusetts and nationwide.

Colorimetric and Real-Time Loop-Mediated Isothermal Amplification (LAMP) for Detection of Loa loa DNA in Human Blood Samples

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.

Development and Validation of a Colorimetric Reverse Transcriptase Loop-Mediated Isothermal Amplification Assay for Detection of Eastern Equine Encephalitis Virus in Mosquitoes

Eastern equine encephalitis virus (EEEV) is a highly pathogenic alphavirus that causes periodic outbreaks in the eastern USA. Mosquito abatement programs are faced with various challenges with surveillance and control of EEEV and other mosquito-borne illnesses. Environmental sampling of mosquito populations can be technically complex. Here we report the identification of biomarkers, development and validation of a colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for the detection of EEEV. Positive samples are easily visualized by a color change from pink to yellow. The assay was validated using EEEV from viral culture, experimentally spiked mosquito pools, and previously tested mosquito pools. The RT-LAMP assay detected viral titers down to approximately 10% of what would be present in a single infectious mosquito, based upon EEEV viral titers determined by previous competency studies. The RT-LAMP assay efficiently detected EEEV in combined aliquots from previously homogenized pools of mosquitoes, allowing up to 250 individual mosquitoes to be tested in a single reaction. No false positive results were obtained from RNA prepared from negative mosquito pools acquired from known and potential EEEV vectors. The colorimetric RT-LAMP assay is highly accurate, technically simple, and does not require sophisticated equipment, making it a cost-effective alternative to real time reverse transcriptase-polymerase chain reaction (RT-PCR) for vector surveillance.

Deep Sequencing Reveals Occult Mansonellosis Coinfections in Residents From the Brazilian Amazon Village of São Gabriel da Cachoeira

Mansonella ozzardi and Mansonella perstans infections both cause mansonellosis but are usually treated differently. Using a real-time polymerase chain reaction assay and deep sequencing, we reveal the presence of mansonellosis coinfections that were undetectable by standard diagnostic methods. Our results confirm mansonellosis coinfections and have important implications for the disease's treatment and diagnosis.

Filariasis and transfusion-associated risk: a literature review

BACKGROUND AND OBJECTIVES

Filariae are parasitic worms that include the pathogens Loa loa, Onchocerca volvulus, Wuchereria bancrofti, Brugia spp. and Mansonella spp. which are endemic in parts of Africa, Asia, Asia-Pacific, South and Central America. Filariae have a wide clinical spectrum spanning asymptomatic infection to chronic debilitating disease including blindness and lymphedema. Despite successful eradication programmes, filarial infections remain an important -albeit neglected - source of morbidity. We sought to characterize the risk of transfusion transmission of microfilaria with a view to guide mitigation practices in both endemic and non-endemic countries.

MATERIALS AND METHODS

A scoping review of scientific publications as well as grey literature was carried out by a group of domain experts in microbiology, transfusion medicine and infectious diseases, representing the parasite subgroup of the International Society of Blood Transfusion.

RESULTS

Cases of transfusion-transmitted filariasis are rare and confined to case reports of variable quality. Transfusion-associated adverse events related to microfilariae are confined to isolated reports of transfusion reactions. Serious outcomes have not been reported. No known strategies have been implemented, specifically, to mitigate transfusion-transmitted filariasis yet routine blood donor screening for other transfusion-transmissible infections (e.g. hepatitis B, malaria) may indirectly defer donors with microfilaremia in endemic areas.

CONCLUSION

Rare examples of transfusion-transmitted filariasis, without serious clinical effect, suggest that filariasis poses low transfusion risk. Dedicated mitigation strategies against filarial transfusion transmission are not recommended. Given endemicity in low-resource regions, priority should be on the control of filariasis with public health measures.

Evaluation of LAMP for the diagnosis of Loa loa infection in dried blood spots compared to PCR-based assays and microscopy

BACKGROUND

Loa loa is a filarial species found exclusively in West and Central Africa. Microscopy is the traditional diagnosis method for human loiasis. Several molecular methods have developed as an alternative approach for identification of L. loa filarial parasites.

OBJECTIVES

The aim of this study was to evaluate a Loa-Loop-mediated isothermal amplification (LAMP) assay to diagnose loiasis disease on dried blood spots (DBS) samples, compared to microscopy, filaria-real time-polymerase chain reaction (PCR) and nested-Loa PCR.

METHODS

A total of 100 DBS samples and 100 blood smears were used for this study. DNA was extracted using saponin/Chelex method. DNA isolated was assayed by a Loa-LAMP assay in parallel to microscopy, filaria-real time PCR and nested-Loa PCR. The sensitivities and specificities of Loa-LAMP assay was computed comparing to each one of the reference methods.

FINDINGS

Loa-LAMP’s sensitivity was more than 90% and specificity was nearly 100% when compared to molecular methods. On the other hand, sensitivity was decreased a bit when Loa-LAMP faced microscopy, but keeping the other statistical values high.

MAIN CONCLUSIONS

Loa-LAMP is an appropriate method for loiasis diagnosis in endemic areas. Though, it has disadvantages like the reagents’ high price at the moment and not to be able to detect more filarial species at once.