Lymphatic filariasis: new insights into an old disease

A Landscape on Lymphatic Filariasis with its Effects and Recent Advanced Treatments

Lymphatic filariasis is an infection caused by parasites that poses a significant health, social, and economic burden, affecting a vast population that exceeds 120 million individuals globally. The Etiology of the infection is attributed to three nematode parasites, namely Wuchereria bancrofti, B. timori, and Brugia malayi, as well as which are phylogenetically related. These parasites are transmitted to humans via mosquitoes belonging to the Anopheles, Aedes genera, and Culex. As per the estimation provided by the WHO, the current number of individuals infected with filariasis stands at approximately 120 million across 81 countries. Furthermore, it is estimated that around 1.34 billion individuals reside in regions that are endemic to filariasis, thereby putting them at risk of contracting the disease. Different synthetic drugs such as Ivermectin, Doxycycline, Albendazole, and Suramin are used in the treatment. Some natural plants are Azadirachta indica, Tinospora cordifolia, Zingiber officinal, as well as, some marine sources are also included for better treatment. We also touch briefly on a few additional filarial diseases. Although there are only a few medications available to treat filariasis, their frequent usage may result in drug resistance. Furthermore, there is no effective vaccination for the treatment of filariasis. Due to these restrictions, it has been crucial to create new anti-filarial medications, which motivates researchers to find novel pharmaceuticals with anti-filarial action. In this article, we examine the latest achievements in the anti-filarial area, including the many forms of filariasis and their historical contexts, elimination programmes, various therapeutic classes (both synthetic and natural), investigated product-derived targets as well as clinical investigations.

Stage-Dependent Increase of Systemic Immune Activation and CCR5+CD4+ T Cells in Filarial Driven Lymphedema in Ghana and Tanzania

Chronic lymphedema caused by infection of Wuchereria bancrofti is a disfiguring disease that leads to physical disability, stigmatization, and reduced quality of life. The edematous changes occur mainly on the lower extremities and can progress over time due to secondary bacterial infections. In this study, we characterized participants with filarial lymphedema from Ghana and Tanzania as having low (stage 1-2), intermediate (stage 3-4), or advanced (stage 5-7) lymphedema to determine CD4⁺ T cell activation patterns and markers associated with immune cell exhaustion. A flow cytometry-based analysis of peripheral whole blood revealed different T cell phenotypes within participants with different stages of filarial lymphedema. In detail, increased frequencies of CD4⁺HLA-DR⁺CD38⁺ T cells were associated with higher stages of filarial lymphedema in patients from Ghana and Tanzania. In addition, significantly increased frequencies of CCR5⁺CD4⁺ T cells were seen in Ghanaian participants with advanced LE stages, which was not observed in the Tanzanian cohort. The frequencies of CD8⁺PD-1⁺ T cells were augmented in individuals with higher stage lymphedema in both countries. These findings show distinct activation and exhaustion patterns in lymphedema patients but reveal that immunological findings differ between West and East African countries.

The Impact of the COVID-19 Pandemic on People With Lymphedema in an Endemic Area for Lymphatic Filariasis in Brazil

Objectives: To investigate the repercussions of the COVID-19 pandemic on lymphedema patients from an endemic area of lymphatic filariasis. Methods: The study descriptive compared sociodemographic and clinical aspects, risk of falling and quality of life, prior and during the COVID-19 pandemic in 28 lymphedema patients, older than 18 years old and under investigation of filarial infection. For the evaluation of functional mobility, the Time Up and Go test and The Medical Outcome Study Short Form-36 Health for quality of life, was used. Results: An increase in interdigital and dermal lesions, a higher frequency of acute dermatolymphangioadenitis crises and risk of falling, worsening of quality of life in the domains of physical functioning, general health, vitality, and mental health during the pandemic was observed. Conclusion: Our findings of clinical worsening and quality of life of patients during the COVID-19 pandemic indicate the need to reinforce the goal of the Lymphatic Filariasis Program regarding the follow-up of these patients in the actions of the Global Program for the Elimination of Lymphatic Filariasis, due to the discontinuity in the care during the pandemic.

Essential Oils as Novel Anthelmintic Drug Candidates

Helminths, with an estimated 1.5 billion annual global infections, are one of the major health challenges worldwide. The current strategy of the World Health Organization to prevent helminth infection includes increasing hygienic awareness, providing better sanitation and preventative anthelmintic drug therapy in vulnerable populations. Nowadays, anthelmintic drugs are used heavily in livestock, both in case of infection and as a preventative measure. However, this has led to the development of resistance against several of the most common drugs, such as levamisole, ivermectin and thiabendazole. As many as 70% of the livestock in developed countries now has helminths that are drug resistant, and multiple resistance is common. Because of this, novel anthelmintics are urgently needed to help combat large-scale production losses. Prior to this review, no comprehensive review of the anthelmintic effects of essential oils and their components existed. Multiple review articles have been published on the uses of a single plant and its extracts that only briefly touch upon their anthelmintic activity. This review aims to provide a detailed overview of essential oils and their components as anthelmintic treatment against a wider variety of helminths.

Mosquitoes and Mosquito-Borne Diseases in Vietnam

Mosquito-borne diseases pose a significant threat to humans in almost every part of the world. Key factors such as global warming, climatic conditions, rapid urbanisation, frequent human relocation, and widespread deforestation significantly increase the number of mosquitoes and mosquito-borne diseases in Vietnam, and elsewhere around the world. In southeast Asia, and notably in Vietnam, national mosquito control programmes contribute to reducing the risk of mosquito-borne disease transmission, however, malaria and dengue remain a threat to public health. The aim of our review is to provide a complete checklist of all Vietnamese mosquitoes that have been recognised, as well as an overview of mosquito-borne diseases in Vietnam. A total of 281 mosquito species of 42 subgenera and 22 genera exist in Vietnam. Of those, Anopheles, Aedes, and Culex are found to be potential vectors for mosquito-borne diseases. Major mosquito-borne diseases in high-incidence areas of Vietnam include malaria, dengue, and Japanese encephalitis. This review may be useful to entomological researchers for future surveys of Vietnamese mosquitoes and to decision-makers responsible for vector control tactics.

Evaluating and mitigating the potential indirect effect of COVID-19 on control programmes for seven neglected tropical diseases: a modelling study

Background

In line with movement restrictions and physical distancing essential for the control of the COVID-19 pandemic, WHO recommended postponement of all neglected tropical disease (NTD) control activities that involve community-based surveys, active case finding, and mass drug administration in April, 2020. Following revised guidance later in 2020, and after interruptions to NTD programmes of varying lengths, NTD programmes gradually restarted in the context of an ongoing pandemic. However, ongoing challenges and service gaps have been reported. This study aimed to evaluate the potential effect of the programmatic interruptions and strategies to mitigate this effect.

Methods

For seven NTDs, namely soil-transmitted helminths, schistosomiasis, lymphatic filariasis, onchocerciasis, trachoma, visceral leishmaniasis, and human African trypanosomiasis, we used mathematical transmission models to simulate the effect of programme interruptions on the dynamics of each of these diseases in different endemic settings. We also explored the potential benefit of implementing mitigation strategies, primarily in terms of minimising the delays to control targets.

Findings

We show that the effect of the COVID-19-induced interruption in terms of delay to achieving elimination goals might in some cases be much longer than the duration of the interruption. For schistosomiasis, onchocerciasis, trachoma, and visceral leishmaniasis, a mean delay of 2–3 years for a 1-year interruption is predicted in areas of highest prevalence. We also show that these delays can largely be mitigated by measures such as additional mass drug administration or enhanced case-finding.

Interpretation

The COVID-19 pandemic has brought infectious disease control to the forefront of global consciousness. It is essential that the NTDs, so long neglected in terms of research and financial support, are not overlooked, and remain a priority in health service planning and funding.

Funding

Bill & Melinda Gates Foundation, Medical Research Council, and the UK Foreign, Commonwealth & Development Office.

Performance of Field's Stain Compared with Conventional Giemsa Stain for the Rapid Detection of Blood Microfilariae in Gabon

Filarial infections caused by Loa loa and Mansonella perstans are a considerable public health burden in rural regions of Central Africa. Rapid diagnostic tools for the detection of microfilariae in the blood are needed. Field's stain is a rapid staining technique for microscopic slides originally established for malaria diagnostics. It requires less than 1 minute of staining compared with conventional staining protocols requiring at least 15 to 20 minutes for staining and could thus significantly accelerate diagnostics for human filariasis. Here we evaluated Field's stain as a rapid staining technique in comparison to Giemsa stain for the detection of microfilariae in peripheral blood. Blood smears were collected from 175 participants residing in the region of Lambaréné and Fougamou, Gabon. Each participant's samples were stained in parallel with Field's stain and conventional Giemsa stain. Slides were then microscopically assessed and compared for qualitative and quantitative results by a blinded assessor for the two endemic filarial blood pathogens M. perstans and L. loa. Field's stain shows excellent diagnostic performance characteristics for L. loa microfilariae compared with Giemsa staining. Concordance was favorable for M. perstans although lower than for L. loa. Field's stain offers a rapid alternative to Giemsa stain for detection of L. loa microfilariae in thick blood smears. This could help accelerate diagnostics of blood filarial pathogens in mass screening programs or resource constrained health care institutions with high patient load.

Role of Transcriptional and Epigenetic Regulation in Lymphatic Endothelial Cell Development

The lymphatic system is critical for maintaining the homeostasis of lipids and interstitial fluid and regulating the immune cell development and functions. Developmental anomaly-induced lymphatic dysfunction is associated with various pathological conditions, including lymphedema, inflammation, and cancer. Most lymphatic endothelial cells (LECs) are derived from a subset of endothelial cells in the cardinal vein. However, recent studies have reported that the developmental origin of LECs is heterogeneous. Multiple regulatory mechanisms, including those mediated by signaling pathways, transcription factors, and epigenetic pathways, are involved in lymphatic development and functions. Recent studies have demonstrated that the epigenetic regulation of transcription is critical for embryonic LEC development and functions. In addition to the chromatin structures, epigenetic modifications may modulate transcriptional signatures during the development or differentiation of LECs. Therefore, the understanding of the epigenetic mechanisms involved in the development and function of the lymphatic system can aid in the management of various congenital or acquired lymphatic disorders. Future studies must determine the role of other epigenetic factors and changes in mammalian lymphatic development and function. Here, the recent findings on key factors involved in the development of the lymphatic system and their epigenetic regulation, LEC origins from different organs, and lymphatic diseases are reviewed.

Lymphatic filariasis in 2016 in American Samoa: Identifying clustering and hotspots using non-spatial and three spatial analytical methods

Background

American Samoa completed seven rounds of mass drug administration from 2000–2006 as part of the Global Programme to Eliminate Lymphatic Filariasis (LF). However, resurgence was confirmed in 2016 through WHO-recommended school-based transmission assessment survey and a community-based survey. This paper uses data from the 2016 community survey to compare different spatial and non-spatial methods to characterise clustering and hotspots of LF.

Method

Non-spatial clustering of infection markers (antigen [Ag], microfilaraemia [Mf], and antibodies (Ab [Wb123, Bm14, Bm33]) was assessed using intra-cluster correlation coefficients (ICC) at household and village levels. Spatial dependence, clustering and hotspots were examined using semivariograms, Kulldorf’s scan statistic and Getis-Ord Gi* statistics based on locations of surveyed households.

Results

The survey included 2671 persons (750 households, 730 unique locations in 30 villages). ICCs were higher at household (0.20–0.69) than village levels (0.10–0.30) for all infection markers. Semivariograms identified significant spatial dependency for all markers (range 207–562 metres). Using Kulldorff’s scan statistic, significant spatial clustering was observed in two previously known locations of ongoing transmission: for all markers in Fagali’i and all Abs in Vaitogi. Getis-Ord Gi* statistic identified hotspots of all markers in Fagali’i, Vaitogi, and Pago Pago-Anua areas. A hotspot of Ag and Wb123 Ab was identified around the villages of Nua-Seetaga-Asili. Bm14 and Bm33 Ab hotspots were seen in Maleimi and Vaitogi-Ili’ili-Tafuna.

Conclusion

Our study demonstrated the utility of different non-spatial and spatial methods for investigating clustering and hotspots, the benefits of using multiple infection markers, and the value of triangulating results between methods.

Lymphatic Filariasis: A Systematic Review on Morbidity and Its Repercussions in Countries in the Americas

The Global Program to Eliminate Lymphatic Filariasis (GPELF) is a program that aims to eliminate lymphatic filariasis by 2030. The GPELF strategy is based on interrupting transmission using mass drug administration (MDA) and, in parallel, managing morbidity cases. However, it has been seen that there is a shortage of research in the literature and public policies regarding this last pillar. In this study, we reviewed the literature and available information regarding the burden of filarial morbidity. In addition, we identified that in the Americas, the implementation of structured services with regard to morbidity assistance in the Americas was scarce. We formed a review that aimed to assess the pathogenesis, epidemiology, repercussions, and treatment of filarial morbidity in countries in the Americas where lymphatic filariasis is endemic. Structured searches were carried out on PubMed, LILACS, Scopus, and Web of Science databases without time and language restrictions. Three reviewers evaluated the 2150 studies and performed data extraction, and quality assessment by assigning scores to the studies found. The current literature and available information on the burden of filarial morbidity, as well as the implementation of structured services with regard to morbidity assistance in the Americas, were all found to be scarce. Now that this knowledge gap has been identified, both health services and researchers need to seek the implementation and enhancement of the maintenance of GPELF strategies that relate to the morbidity pillar.

Microbial Toxins in Insect and Nematode Pest Biocontrol

Invertebrate pests, such as insects and nematodes, not only cause or transmit human and livestock diseases but also impose serious crop losses by direct injury as well as vectoring pathogenic microbes. The damage is global but greater in developing countries, where human health and food security are more at risk. Although synthetic pesticides have been in use, biological control measures offer advantages via their biodegradability, environmental safety and precise targeting. This is amply demonstrated by the successful and widespread use of Bacillusthuringiensis to control mosquitos and many plant pests, the latter by the transgenic expression of insecticidal proteins from B. thuringiensis in crop plants. Here, I discuss the prospects of using bacterial and fungal toxins for pest control, including the molecular basis of their biocidal activity.

[Physiopathology of vulvar elephantiasis of filarial origin. A case report]

Genital filariasis is an uncommon infectious entity in the western world. It has characteristic clinical features and a well-recognized endemic area that causes typical histological alterations. We report a case of a 32-year-old woman, a native of Mozambique, who presented with vulvar elephantiasis as a pendulous tumor with a maximum diameter of 15cm. A large part of the genital mass was resected. Microscopically, hyperkeratosis with irregular acanthosis, a notable thickening of dermis with dense fibrosis and inflammatory clusters of patchy distribution, mostly made up of plasma cells, was seen. Since the parasite was not observed, an exclusion diagnosis was made, as frequently happens with this lesion.

Geographic Spatial Distribution Patterns of Dirofilaria immitis and Brugia pahangi Infection in Community Dogs in Chiang Mai, Thailand

Simple Summary

Filariasis is emerging as a public health concern for humans, dogs, cats, and other wildlife species, and is frequently found in southeast Asian countries. The present study confirmed the species of filarial nematodes in free-roaming dogs from temple communities. Two species were found: Dirofilaria immitis infection and, for the first time, Brugia pahangi. The occurrence of the two species was comparable. Geographic spatial distribution revealed the abundance of D. immitis and B. pahangi in the central areas at altitudes less than 400 m. However, at higher altitudes between 400 and 800 m, we found a significantly higher number of B. pahangi infections than D. immitis infections. In conclusion, D. immitis and B. pahangi were the most common filarial infections found in community dogs in Northern Thailand. Dogs might be an important reservoir for B. pahangi in that region. The population dynamics of the mosquito vector of B. pahangi across altitudinal gradients merits further study.

Abstract

Filariasis is emerging as a public health concern in tropical and subtropical areas. Filariasis is an endemic problem commonly found in southeast Asian countries. Using the PCR-restriction fragment length polymorphism (PCR-RFLP) of the ITS1 region with Vsp I, the overall prevalence rates of Dirofilaria immitis (12.2% (41/337); 95% confidence interval: 9.1–16.1%) and Brugia pahangi (8.3% (28/337); 95% confidence interval: 5.8–11.8%) were determined based on 337 free-roaming community dogs from 20 districts in Northern Thailand. Microfilaremia was found in only 6.2% of dogs (21/337). Co-infection with D. immitis and B. pahangi was observed in two dogs. Of the 215 blood samples examined using a Canine Heartworm Ag Kit, only 3.72% (eight dogs) were D. immitis antigen positive. Among these eight, six dogs had occult D. immitis infections. In terms of geographic distribution, we found the abundance of D. immitis and B. pahangi in the central areas at altitudes less than 400 m to be 12.1% and 10.3%, respectively. In contrast, at higher altitudes between 400 and 800 m, a significantly higher number of B. pahangi compared with D. immitis infected individuals were observed at 14.29% and 4.1%, respectively. In conclusion, D. immitis and B. pahangi were the most common filarial infections found in community dogs in Northern Thailand. Dogs might be an important reservoir of B. pahangi in that region. Increasing awareness and concern and including proper deworming programs for community dogs should be endorsed to reduce the transmission risk. Additionally, the population dynamics of the mosquito vector of B. pahangi across altitudinal gradients deserved further investigation.

COVID-19 unfolding filariasis: The first case of SARS-CoV-2 and Wuchereria bancrofti coinfection

With the evolution of the Coronavirus Disease 2019 (COVID-19) pandemic, the number of patients brought to medical attention has increased. This has led to the unmasking of many coexisting occult infections and comorbidities such as tuberculosis, dengue, human immunodeficiency viral infection, diabetes, and hypertension. We report the first case of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, unveiling the diagnosis of asymptomatic filariasis. A 37-year-old gentleman presented with shortness of breath, fever, and cough. He was found to have COVID-19 pneumonia. During his stay, microfilaria of Wuchereria bancrofti was detected incidentally on a blood smear exam. Consequently, the patient received appropriate treatment for both conditions. In order not to miss relevant concomitant diagnoses, it is prudent to keep a broad differential diagnosis when faced with SARS-CoV-2–infected patients; this is especially true when atypical symptoms are present or in areas endemic with other infections.

Acute Lymphatic Filariasis Infection in United States Armed Forces Personnel Deployed to the Pacific Area of Operations during World War II Provides Important Lessons for Today

The deployment of United States (US) Armed Forces personnel into the central Pacific islands of Samoa and Tonga, which is highly-endemic for lymphatic filariasis (LF), resulted in thousands of cases of the acute form of this disease and greatly reduced their ability to carry out their mission. The major driving factor for the intensity of transmission was the aggressiveness and efficiency of the Aedes species mosquito vectors, especially the day-biting Ae. Polynesiensis. The paper reminds us of the danger that tropical diseases can pose for troops sent into endemic areas and constant and careful surveillance that is required to prevent rapid resurgence of Aedes-transmitted LF in populations, where the LF elimination program has been successful.

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

Mansonelliasis is a widespread yet neglected tropical infection of humans in Africa and South America caused by the filarial nematodes, Mansonella perstans, M. ozzardi, M. rodhaini and M. streptocerca. Clinical symptoms are non-distinct and diagnosis mainly relies on the detection of microfilariae in skin or blood. Species-specific DNA repeat sequences have been used as highly sensitive biomarkers for filarial nematodes. We have developed a bioinformatic pipeline to mine Illumina reads obtained from sequencing M. perstans and M. ozzardi genomic DNA for new repeat biomarker candidates which were used to develop loop-mediated isothermal amplification (LAMP) diagnostic tests. The M. perstans assay based on the Mp419 repeat has a limit of detection of 0.1 pg, equivalent of 1/1000^th of a microfilaria, while the M. ozzardi assay based on the Mo2 repeat can detect as little as 0.01 pg. Both LAMP tests possess remarkable species-specificity as they did not amplify non-target DNAs from closely related filarial species, human or vectors. We show that both assays perform successfully on infected human samples. Additionally, we demonstrate the suitability of Mp419 to detect M. perstans infection in Culicoides midges. These new tools are field deployable and suitable for the surveillance of these understudied filarial infections.

Detection of helminths by loop-mediated isothermal amplification assay: a review of updated technology and future outlook

BACKGROUND

Helminths are endemic in more than half of the world's countries, raising serious public health concerns. Accurate diagnosis of helminth infection is crucial to control strategies. Traditional parasitological methods, serological tests and PCR-based assays are the major means of the diagnosis of helminth infection, but they are time-consuming and/or expensive, and sometimes provide inaccurate results. Loop mediated isothermal amplification (LAMP) assay, a sensitive, simple and rapid method was therefore developed for detection of helminths. This study aims to discuss the current status of application of LAMP on helminths detection and to make a comprehensive evaluation about this updated technology and its future outlook by comparing with several other diagnostic methods.

MAIN BODY

This review summarizes LAMP assay applied for helminth detection and helminthiasis surveillance. The basic principle of LAMP is introduced to help better understand its characteristics and each reported assay is assessed mainly based on its detection sensitivity, specificity and limitations, in comparison with other common diagnostic tests. Moreover, we discuss the limitations of the assays so as to clarify some potential ways of improvement.

CONCLUSIONS

Here, we summarize and discuss the advantages, disadvantages and promising future of LAMP in heliminth detection, which is expected to help update current knowledge and future perspectives of LAMP in highly sensitive and specific diagnosis and surveillance of helminthiasis and other parasitic diseases, and can contribute to the elimination of the diseases from endemic areas.

Elimination of lymphatic filariasis as a public health problem in Niue under PacELF, 1999-2016

BACKGROUND

Lymphatic filariasis (LF) is a mosquito-borne parasitic disease which is targeted for elimination as a public health problem worldwide. Niue is a small self-governing South Pacific island nation with approximately 1600 residents that was formerly LF endemic. Here, we review the progress made towards eliminating LF in Niue since 1999.

METHODS

This study has reviewed all the available literature relating to LF in Niue to assess surveillance efforts and the elimination of transmission. Reviewed documentation included both published and unpublished works including historical reports of LF, WHO PacELF records, and Niue Country Reports of the national LF elimination program.

FINDINGS

Niue conducted mapping of baseline LF endemicity by testing the total present and consenting population for LF antigen with immunochromatographic test (ICT) in 1999, when circulating filarial antigen prevalence was 3.1% (n = 1794). Five nationwide annual mass drug administration (MDA) rounds with albendazole (400 mg) and diethylcarbamazine citrate (DEC) were undertaken from 2000 to 2004, with coverage reported from distribution records ranging from 78 to 99% of the eligible population, which excluded pregnant women and children under 2 years of age. A further whole population survey using ICT in 2001 found 1.3% positive (n = 1630). In 2004, antigen prevalence had reduced to 0.2% (n = 1285). A similar post-MDA survey in 2009 indicated antigen prevalence to be 0.5% (n = 1378). Seven positive cases were re-tested and re-treated every six months until negative.

CONCLUSIONS

After five rounds of MDA, Niue had reduced the LF antigen population prevalence in all ages from 3.1% to below 1% and maintained this prevalence for a further  five years. Due to Niue's small population, surveillance was done by whole population surveys. Niue's results support the WHO recommended strategy that five to six rounds of annual MDA with effective population coverage can successfully interrupt the transmission of LF. Niue received official acknowledgement of the validation of elimination of LF as a public health problem by the WHO Director-General and WHO Western Pacific Regional Office (WPRO) Regional Director at the 67th session of the Regional Committee for the Western Pacific held in Manila in October 2016.

The History of Bancroftian Lymphatic Filariasis in Australasia and Oceania: Is There a Threat of Re-Occurrence in Mainland Australia?

Lymphatic filariasis (LF) infects an estimated 120 million people worldwide, with a further 856 million considered at risk of infection and requiring preventative chemotherapy. The majority of LF infections are caused by Wuchereria bancrofti, named in honour of the Australian physician Joseph Bancroft, with the remainder due to Brugia malayi and B. timori. Infection with LF through the bite of an infected mosquito, can lead to the development of the condition known as elephantiasis, where swelling due to oedema leads to loss of function in the affected area and thickening of the skin, 'like an elephant'. LF has previously been endemic in Australia, although currently, no autochthonous cases occur there. Human immigration to Australia from LF-endemic countries, including those close to Australia, and the presence of susceptible mosquitoes that can act as suitable vectors, heighten the possibility of the reintroduction of LF into this country. In this review, we examine the history of LF in Australia and Oceania and weigh up the potential risk of its re-occurrence on mainland Australia.

Assessment of macrofilaricidal activity of leaf extracts of Terminalia sp. against bovine filarial parasite Setaria cervi

Antifilarial potential of three medicinal plants namely, Terminalia bellerica, Terminalia chebula and Terminalia catappa was explored using Setaria cervi, a bovine filarial parasite at concentrations of 2.5, 5 and 10mg/ml. Amongst all the extracts, methanol extract of T. bellerica showed highest macrofilaricidal activity i.e. 84.63±1.11 at 10mg/ml in MTT reduction assay with IC₅₀ value of 2.7mg/ml. which was better than the standard DEC i.e. 79.22±3.1% at 10mg/ml with IC₅₀ value 2.84mg/ml. Other plant extracts showed mild in vitro macrofilaricidal activity. T. bellerica methanol extract exhibited significant GST activity of 18.86±0.21 and 12.83±0.03μM/ml/min at 5 and 10mg/ml with percentage inhibition value of 73.96% and 82.29% respectively. DEC showed GST activity value of 40.03±4.14 and 21.48±6.44μM/ml/min with percentage inhibition value of 21.76% and 58.01% at 5 and 10mg/ml respectively. Thus, methanol extract of leaves of T. bellerica exhibited highly significant antifilarial potential and needs detailed analysis.

Discovery of Culex pipiens associated tunisia virus: a new ssRNA(+) virus representing a new insect associated virus family

In the global context of arboviral emergence, deep sequencing unlocks the discovery of new mosquito-borne viruses. Mosquitoes of the species Culex pipiens, C. torrentium, and C. hortensis were sampled from 22 locations worldwide for transcriptomic analyses. A virus discovery pipeline was used to analyze the dataset of 0.7 billion reads comprising 22 individual transcriptomes. Two closely related 6.8 kb viral genomes were identified in C. pipiens and named as Culex pipiens associated tunisia virus (CpATV) strains Ayed and Jedaida. The CpATV genome contained four ORFs. ORF1 possessed helicase and RNA-dependent RNA polymerase (RdRp) domains related to new viral sequences recently found mainly in dipterans. ORF2 and 4 contained a capsid protein domain showing strong homology with Virgaviridae plant viruses. ORF3 displayed similarities with eukaryotic Rhoptry domain and a merozoite surface protein (MSP7) domain only found in mosquito-transmitted Plasmodium, suggesting possible interactions between CpATV and vertebrate cells. Estimation of a strong purifying selection exerted on each ORFs and the presence of a polymorphism maintained in the coding region of ORF3 suggested that both CpATV sequences are genuine functional viruses. CpATV is part of an entirely new and highly diversified group of viruses recently found in insects, and that bears the genomic hallmarks of a new viral family.

Morphological and molecular characteristics of Malayfilaria sofiani Uni, Mat Udin & Takaoka n. g., n. sp. (Nematoda: Filarioidea) from the common treeshrew Tupaia glis Diard & Duvaucel (Mammalia: Scandentia) in Peninsular Malaysia

Background

The filarial nematodes Wuchereria bancrofti (Cobbold, 1877), Brugia malayi (Brug, 1927) and B. timori Partono, Purnomo, Dennis, Atmosoedjono, Oemijati & Cross, 1977 cause lymphatic diseases in humans in the tropics, while B. pahangi (Buckley & Edeson, 1956) infects carnivores and causes zoonotic diseases in humans in Malaysia. Wuchereria bancrofti, W. kalimantani Palmieri, Pulnomo, Dennis & Marwoto, 1980 and six out of ten Brugia spp. have been described from Australia, Southeast Asia, Sri Lanka and India. However, the origin and evolution of the species in the Wuchereria-Brugia clade remain unclear. While investigating the diversity of filarial parasites in Malaysia, we discovered an undescribed species in the common treeshrew Tupaia glis Diard & Duvaucel (Mammalia: Scandentia).

Methods

We examined 81 common treeshrews from 14 areas in nine states and the Federal Territory of Peninsular Malaysia for filarial parasites. Once any filariae that were found had been isolated, we examined their morphological characteristics and determined the partial sequences of their mitochondrial cytochrome c oxidase subunit 1 (cox1) and 12S rRNA genes. Polymerase chain reaction (PCR) products of the internal transcribed spacer 1 (ITS1) region were then cloned into the pGEM-T vector, and the recombinant plasmids were used as templates for sequencing.

Results

Malayfilaria sofiani Uni, Mat Udin & Takaoka, n. g., n. sp. is described based on the morphological characteristics of adults and microfilariae found in common treeshrews from Jeram Pasu, Kelantan, Malaysia. The Kimura 2-parameter distance between the cox1 gene sequences of the new species and W. bancrofti was 11.8%. Based on the three gene sequences, the new species forms a monophyletic clade with W. bancrofti and Brugia spp. The adult parasites were found in tissues surrounding the lymph nodes of the neck of common treeshrews.

Conclusions

The newly described species appears most closely related to Wuchereria spp. and Brugia spp., but differs from these in several morphological characteristics. Molecular analyses based on the cox1 and 12S rRNA genes and the ITS1 region indicated that this species differs from both W. bancrofti and Brugia spp. at the genus level. We thus propose a new genus, Malayfilaria, along with the new species M. sofiani.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2105-9) contains supplementary material, which is available to authorized users.

Helminth infection during pregnancy: insights from evolutionary ecology

Helminths are parasitic nematodes and trematodes, grouped together because of morphological similarities and commonalities in the effects infections have on hosts. These include complications such as anemia and biasing of immune responses, which can alter susceptibility for other diseases. For pregnant women, these complications might have implications for pregnancy outcomes or neonatal health. Here, I review studies of helminth infections during pregnancy, and ask the following questions: Do helminths affect maternal health or pregnancy outcomes? Are there consequences of maternal infection for infants? What are the effects of antihelminth treatment during pregnancy? The evidence suggests that the answers to these questions depend on the particular helminth species in question, maternal nutritional status, and the presence or absence of comorbid infection with other species, such as malaria. Moreover, there may also be unexpected consequences of treatment, as maternal infections can affect the priming of infant immune systems, with potential effects on infants later in life. These complex interactions suggest that a consideration of the evolutionary history of human–helminth interactions, as well as the ecological context of infections, can help to clarify an understanding of these host–parasite interactions and provide direction for future investigations.

Expression levels and codon usage patterns in nuclear genes of the filarial nematode Wucheraria bancrofti and the blood fluke Schistosoma haematobium

Synonymous codons are used with different frequencies, a phenomenon known as codon bias, which exists in many genomes and is mainly resolute by mutation and selection. To elucidate the genetic characteristics and evolutionary relationship of Wucheraria bancrofti and Schistosoma haematobium we examined the pattern of synonymous codon usage in nuclear genes of both the species. The mean overall GC contents of W. bancrofti and S. haematobium were 43.41 and 36.37%, respectively, which suggests that genes in both the species were AT rich. The value of the High Effective Number of Codons in both species suggests that codon usage bias was weak. Both species had a wide range of P3 distribution in the neutrality plot, with a significant correlation between P12 and P3. The codons were closer to the axes in correspondence analysis, suggesting that mutation pressure influenced the codon usage pattern in these species. We have identified the more frequently used codons in these species, most codons ending with an A or T. The nucleotides A/T and C/G were not proportionally used at the third position of codons, which reveals that natural selection might influence the codon usage patterns. The regression equation of P12 on P3 suggests that natural selection might have played a major role, while mutational pressure played a minor role in codon usage pattern in both species. These results form the basis of exploring the evolutionary mechanisms and the heterologous expression of medically important proteins of W. bancrofti and S. haematobium.

The inclusion of international migrants in Brazilian healthcare system policies: the case of Haitians in the state of Amazonas

Resumo A partir do enfoque etnográfico sobre as redes sociais articuladas em torno da questão do imigrante no Amazonas, o artigo reflete sobre como o Sistema Único de Saúde (SUS) respondeu às demandas colocadas por um contingente inesperado de novos usuários, tendo em vista os princípios doutrinários que lhe dão sustentação, especialmente o da equidade. O foco é a onda de imigração haitiana rumo ao Brasil, iniciada em fevereiro de 2010 pelos estados fronteiriços da região Norte: Acre, Rondônia e Amazonas, concentrando-se neste último, descrevendo alguns aspectos do período mais crítico da imigração (entre março de 2010 e março de 2012) e sua recepção pelo SUS.

Is there a risk of filarial infection during long-term missions in Haiti?

BACKGROUND

Haiti has the highest prevalence of lymphatic filariasis (Wuchereria bancrofti) in the Western Hemisphere. Still, the risk of filarial infection for long-term visitors such as humanitarian aid workers or military personnel is uncertain. The presented study analyzed the exposure to W. bancrofti in Chilean participants of the UN Stabilization Mission in Haiti (MINUSTAH) in 2011.

METHODS

Blood samples collected from 531 participants were screened for antifilarial antibodies by IgG ELISA, and, if positive, analyzed by immunofluorescence assay (IFA), IgG4 ELISA, Real-Time PCR, and circulating filarial antigen (CFA) card test.

RESULTS

ELISA screening was positive in 10 cases. Seroconversion occurred in only two cases (0.38%) based on ELISA values determined in samples taken before and after deployment. Positive IgG ELISA values could not be confirmed by IFA and IgG4 ELISA. Real-Time PCR and CFA testing did not reveal the presence of filaria.

CONCLUSIONS

Our data indicate that in the examined cohort of MINUSTAH participants in 2011, the risk of filarial exposure or infection was low.

A Systematic Study on Structure and Function of ATPase of Wuchereria bancrofti

BACKGROUND

Analyzing the structures and functions of different proteins of Wuchereria bancrofti is very important because till date no effective drug or vaccine has been discovered to treat lymphatic filariasis (LF). ATPase is one of the most important proteins of Wuchereria bancrofti. Adenosine triphosphate (ATP) converts into adenosine diphosphate (ADP) and a free phosphate ion by the action of these ATPase enzymes. Energy releases from these dephosphorylation reactions drive the other chemical reactions in the cell.

MATERIALS AND METHODS

In this study we worked on the protein ATPase of Wuchereria bancrofti which has been annotated from National Center for Biotechnology Information (NCBI). Various computational tools and databases have been used to determine the various characteristics of that enzyme such as physiochemical properties, secondary structure, three-dimensional (3D) structure, conserved domain, epitope, and their molecular evolutionary relationship.

RESULT

Subcellular localization of ATPase was identified and we have found that 55.5% are localized in the cytoplasm. Secondary and 3D structure of this protein was also predicted. Both structure and function analysis of ATPase of Wuchereria bancrofti showed unique nonhomologous epitope sites and nonhomologous antigenicity sites. Moreover, it resulted in 15 ligand drug-binding sites in its tertiary structure.

CONCLUSION

Structure prediction of these proteins and detection of binding sites and antigenicity sites from this study would indicate a potential target aiding docking studies for therapeutic designing against filariasis.

Chitosan coated alginate micro particles for the oral delivery of antifilarial drugs and combinations for intervention in Brugia malayi induced lymphatic filariasis

Mechanism of targeting of MPs and absorption through Peyer’s patches, to lymphatics where an adult worm resides.

An integrated in vitro imaging platform for characterizing filarial parasite behavior within a multicellular microenvironment

Lymphatic Filariasis, a Neglected Tropical Disease, is caused by thread-like parasitic worms, including B. malayi, which migrate to the human lymphatic system following transmission. The parasites reside in collecting lymphatic vessels and lymph nodes for years, often resulting in lymphedema, elephantiasis or hydrocele. The mechanisms driving worm migration and retention within the lymphatics are currently unknown. We have developed an integrated in vitro imaging platform capable of quantifying B. malayi migration and behavior in a multicellular microenvironment relevant to the initial site of worm injection by incorporating the worm in a Polydimethylsiloxane (PDMS) microchannel in the presence of human dermal lymphatic endothelial cells (LECs) and human dermal fibroblasts (HDFs). The platform utilizes a motorized controllable microscope with CO2 and temperature regulation to allow for worm tracking experiments with high resolution over large length and time scales. Using post-acquisition algorithms, we quantified four parameters: 1) speed, 2) thrashing intensity, 3) percentage of time spent in a given cell region and 4) persistence ratio. We demonstrated the utility of our system by quantifying these parameters for L3 B. malayi in the presence of LECs and HDFs. Speed and thrashing increased in the presence of both cell types and were altered within minutes upon exposure to the anthelmintic drug, tetramisole. The worms displayed no targeted migration towards either cell type for the time course of this study (3 hours). When cells were not present in the chamber, worm thrashing correlated directly with worm speed. However, this correlation was lost in the presence of cells. The described platform provides the ability to further study B. malayi migration and behavior.

Lymphatic filariasis: A view at pathological diversity

Filariasis is traditionally diagnosed following screening of peripheral smear for microfilaria. Clinically lymphatic filariasis mimics the common local diseases. Thus, it is plausible to observe this parasitic infection in histological sections. We encountered three such cases, which displayed diverse patterns of immune response. Presence of both dead and viable worm at the same foci suggests that such immune response could be the result of parasitic death. Histological features such as endothelial injury and granulomatous response attests to the role of Wolbachia bacteria in influencing tissue response.

Immunological characterization of recombinant Wuchereria bancrofti cuticular collagen (COL-4) as putative vaccine candidate for human lymphatic filariasis

OBJECTIVE

To elucidate immunoprophylactic potential of recombinant Wuchereria bancrofti (W. bancrofti) cuticular collagen (COL-4) in BALB/c mice and filarial clinical samples.

METHODS

col-4 gene was PCR amplified from W. bancrofti L3 cDNA library and cloned in pRSET B vector. Recombinant COL-4 was over expressed in salt inducible system and was purified by nickel affinity chromatography. Humoral and cellular responses were measured by ELISA and peripheral blood mononuclear cells (PBMC) of various filarial clinical samples respectively using purified recombinant COL-4 antigen. Then the protective immune responses of COL-4 immunized BALB/c mice were characterized.

RESULTS

Sequence analysis of COL-4 with human host proteins reveals lack of homology. The recombinant COL-4 was found to be at 15 kDa fusion protein. The affinity purified COL-4 showed significant reactivity with putatively immune sera and in a similar fashion it demonstrated marked proliferation in PBMC samples. Immunization studies in experimental filarial host (mice) elicited significant titers with protective antibody isotype profile (IgM and IgG). Cellular immune responses were also significant in terms of splenocytes proliferation assay on mice samples.

CONCLUSIONS

Our immunological findings in experimental host suggest Th2 mediated immune response. Hence, we propose that W. bancrofti COL-4 could be an efficacious vaccine candidate against lymphatic filariasis.

Diagnosis of brugian filariasis by loop-mediated isothermal amplification

In this study we developed and evaluated a Brugia Hha I repeat loop-mediated isothermal amplification (LAMP) assay for the rapid detection of Brugia genomic DNA. Amplification was detected using turbidity or fluorescence as readouts. Reactions generated a turbidity threshold value or a clear visual positive within 30 minutes using purified genomic DNA equivalent to one microfilaria. Similar results were obtained using DNA isolated from blood samples containing B. malayi microfilariae. Amplification was specific to B. malayi and B. timori, as no turbidity was observed using DNA from the related filarial parasites Wuchereria bancrofti, Onchocerca volvulus or Dirofilaria immitis, or from human or mosquito. Furthermore, the assay was most robust using a new strand-displacing DNA polymerase termed Bst 2.0 compared to wild-type Bst DNA polymerase, large fragment. The results indicate that the Brugia Hha I repeat LAMP assay is rapid, sensitive and Brugia-specific with the potential to be developed further as a field tool for diagnosis and mapping of brugian filariasis.

Brugian filariasis is a debilitating neglected tropical disease caused by infection with the filarial parasites Brugia malayi or Brugia timori. Adult worms live in the lymphatic system and produce large numbers of microfilariae that predominantly circulate in the blood at night. Bloodsucking mosquitoes spread the disease by ingesting microfilariae that develop into infective stage larvae in the insect. In rural areas, diagnosis still relies largely on microscopic examination of night blood and morphological assessment of stained microfilariae. Loop-mediated isothermal amplification (LAMP) is a technique that can amplify DNA with high specificity, sensitivity and rapidity under isothermal conditions. The operational simplicity, versatility and low-cost of the technique make it particularly appealing for use in diagnosis and geographical mapping of neglected tropical diseases. In the present study, we have developed and evaluated a Brugia Hha I repeat LAMP assay for the rapid detection of B. malayi and B. timori genomic DNA. The results indicate that the Brugia Hha I repeat LAMP diagnostic assay is sensitive and rapid, detecting a single microfilariae in blood within 30 minutes, and Brugia-specific. The test has the potential to be developed further as a field tool for use in the implementation and management of mass drug administration programs for brugian filariasis.

Immunopathogenesis of lymphatic filarial disease

Although two thirds of the 120 million people infected with lymph-dwelling filarial parasites have subclinical infections, ~40 million have lymphedema and/or other pathologic manifestations including hydroceles (and other forms of urogenital disease), episodic adenolymphangitis, tropical pulmonary eosinophilia, lymphedema, and (in its most severe form) elephantiasis. Adult filarial worms reside in the lymphatics and lymph nodes and induce changes that result in dilatation of lymphatics and thickening of the lymphatic vessel walls. Progressive lymphatic damage and pathology results from the summation of the effect of tissue alterations induced by both living and nonliving adult parasites, the host inflammatory response to the parasites and their secreted antigens, the host inflammatory response to the endosymbiont Wolbachia, and those seen as a consequence of secondary bacterial or fungal infections. Inflammatory damage induced by filarial parasites appears to be multifactorial, with endogenous parasite products, Wolbachia, and host immunity all playing important roles. This review will initially examine the prototypical immune responses engendered by the parasite and delineate the regulatory mechanisms elicited to prevent immune-mediated pathology. This will be followed by a discussion of the proposed mechanisms underlying pathogenesis, with the central theme being that pathogenesis is a two-step process-the first initiated by the parasite and host innate immune system and the second propagated mainly by the host's adaptive immune system and by other factors (including secondary infections).

Disability measurement for lymphatic filariasis: a review of generic tools used within morbidity management programs

Lymphatic filariasis (LF)-related disability affects 40 million people globally, making LF the leading cause of physical disability in the world. Despite this, there is limited research into how the impacts of LF-related disability are best measured. This article identifies the tools currently being used to measure LF-related disability and reviews their applicability against the known impacts of LF. The findings from the review show that the generic disability tools currently used by LF programs fail to measure the majority of known impacts of LF-related disability. The findings from the review support the development of an LF-specific disability measurement tool and raise doubt about the suitability of generic disability tools to assess disability related to neglected tropical diseases (NTDs) globally.

Comparative analysis of ITS1 nucleotide sequence reveals distinct genetic difference between Brugia malayi from Northeast Borneo and Thailand

Brugia malayi is one of the parasitic worms which causes lymphatic filariasis in humans. Its geographical distribution includes a large part of Asia. Despite its wide distribution, very little is known about the genetic variation and molecular epidemiology of this species. In this study, the internal transcribed spacer 1 (ITS1) nucleotide sequences of B. malayi from microfilaria-positive human blood samples in Northeast Borneo Island were determined, and compared with published ITS1 sequences of B. malayi isolated from cats and humans in Thailand. Multiple alignment analysis revealed that B. malayi ITS1 sequences from Northeast Borneo were more similar to each other than to those from Thailand. Phylogenetic trees inferred using Neighbour-Joining and Maximum Parsimony methods showed similar topology, with 2 distinct B. malayi clusters. The first cluster consisted of Northeast Borneo B. malayi isolates, whereas the second consisted of the Thailand isolates. The findings of this study suggest that B. malayi in Borneo Island has diverged significantly from those of mainland Asia, and this has implications for the diagnosis of B. malayi infection across the region using ITS1-based molecular techniques.

[Filariasis in clinical practice]

Filariases are infections caused by distinct species of nematodes. These infections are transmitted through insect bites and primarily affect lymph nodes and skin. Filariases are classified as neglected diseases and affect millions, producing severe disability and social stigma. This type of infection is rarely diagnosed in travellers, as prolonged stays in endemic areas are usually required acquire infection. Infections may be asymptomatic, and clinical manifestations depend on the host immune response to the infection and the parasite burden. Diagnosis is based on the demonstration of microfilariae in blood or skin, but there are other methods that support the diagnosis. Individual treatment is effective, but community interventions, mostly mass drug administration, have helped to diminish the incidence of filariases.

The emerging story of disability associated with lymphatic filariasis: a critical review

Globally, 40 million people live with the chronic effects of lymphatic filariasis (LF), making it the second leading cause of disability in the world. Despite this, there is limited research into the experiences of people living with the disease. This review summarises the research on the experiences of people living with LF disability. The review highlights the widespread social stigma and oppressive psychological issues that face most people living with LF-related disability. Physical manifestations of LF make daily activities and participation in community life difficult. The findings confirm the need for the Global Programme to Eliminate Lymphatic Filariasis (GPELF) to support morbidity management activities that address the complex biopsychosocial issues that people living with LF-related disability face.

Lymphatic filariasis: a method to identify subclinical lower limb change in PNG adolescents

Lymphedema related to lymphatic filariasis (LF) is a disabling condition that commonly manifests in adolescence. Fifty-three adolescents, 25 LF infected and 28 LF non-infected, in age and sex-matched groups, using the Binax ICT rapid card test for filarial antigen were recruited to the study. None of the participants had overt signs of lymphedema. Lymphedema assessment measures were used to assess lower limb tissue compressibility (tonometry), limb circumference (tape measure), intra- and extra-cellular fluid distribution (bioimpedance) and joint range of motion (goniometry). The mean tonometric measurements from the left, right, and dominant posterior thighs were significantly larger in participants with LF compared to participants who had tested negative for LF (p = 0.005, p = 0.004, and p = 0.003, respectively) indicating increased tissue compressibility in those adolescents with LF. ROC curve analysis to define optimal cut-off of the tonometry measurements indicated that at 3.5, sensitivity of this potential screening test is 100% (95%-CI = 86.3%, 100%) and specificity is 21.4% (95%-CI = 8.3%, 41.0%). It is proposed that this cut-off can be used to indicate tissue change characteristic of LF in an at-risk population of PNG adolescents. Further longitudinal research is required to establish if all those with tissue change subsequently develop lymphedema. However, thigh tonometry to identify early tissue change in LF positive adolescents may enable early intervention to minimize progression of lymphedema and prioritization of limited resources to those at greatest risk of developing lifetime morbidity.

The effects of lymphatic filariasis (LF) on the lymphatic system often become apparent during adolescence when the lower limb swells due to lymphedema and males develop hydrocele. Currently there is no simple or mobile field method to identify those at greatest risk of developing lymphedema or those with early subclinical lower limb change. Fifty-three adolescents, 25 LF infected and 28 LF non-infected were recruited to the study. The groups were compared with respect to lower limb tissue compressibility (tonometry), limb circumference (tape measure), intra- and extra-cellular fluid distribution (bioimpedance) and hip, knee and ankle joint range of motion (goniometry). Tonometry, is a simple, inexpensive tool, which measures the distance a plunger will indent the soft tissues. Those adolescents who were LF positive had significantly increased soft tissue compressibility when assessed with tonometry than adolescents who were LF negative. Tonometry has high levels of sensitivity to identify adolescents who test positive to LF. If we are able to identify adolescents before they have overt symptoms, management practices to decrease disease progression can be implemented. This could prevent lifetime morbidity and allow allocation of scarce resources to those identified to be most at risk of developing lymphedema.

Zoonotic Brugia pahangi filariasis in a suburbia of Kuala Lumpur City, Malaysia

Five local Malaysian patients with clinical manifestations consistent with lymphatic filariasis were referred to our medical centre between 2003 and 2006. Although no microfilariae (mf) were detected in their nocturnal blood samples, all were diagnosed to have lymphatic filariasis on the basis of clinical findings and positive serology results. PCR on their blood samples revealed that two of the patients were infected with Brugia pahangi, an animal filarial worm hitherto not known to cause human disease in the natural environment. All the patients were successfully treated with anti-filarial drugs: four patients were treated with a combination of diethylcarbamazine (DEC) and albendazole, and one with doxycycline. Four of them were residents of Petaling Jaya, a residential suburbia located 10 km southwest of Kuala Lumpur city, Malaysia. The fifth patient was a frequent visitor of the suburbia. This suburbia has no history or record of B. malayi infection. The most likely vector of the worm was Armigeres subalbatus as extensive entomological surveys within the suburbia revealed only adult females of this mosquito species were infected with B. pahangi larvae. Wild monkeys caught in the suburbia were free from B. pahangi mf, but domestic cats were mf positive. This suggests that infected cats might be the source of the zoonotic infection in the suburbia.