Edge Artificial Intelligence (AI) for real-time automatic quantification of filariasis in mobile microscopy

Filariasis, a neglected tropical disease caused by roundworms, is a significant public health concern in many tropical countries. Microscopic examination of blood samples can detect and differentiate parasite species, but it is time consuming and requires expert microscopists, a resource that is not always available. In this context, artificial intelligence (AI) can assist in the diagnosis of this disease by automatically detecting and differentiating microfilariae. In line with the target product profile for lymphatic filariasis as defined by the World Health Organization, we developed an edge AI system running on a smartphone whose camera is aligned with the ocular of an optical microscope that detects and differentiates filarias species in real time without the internet connection. Our object detection algorithm that uses the Single-Shot Detection (SSD) MobileNet V2 detection model was developed with 115 cases, 85 cases with 1903 fields of view and 3342 labels for model training, and 30 cases with 484 fields of view and 873 labels for model validation before clinical validation, is able to detect microfilariae at 10x magnification and distinguishes four species of them at 40x magnification: Loa loa, Mansonella perstans, Wuchereria bancrofti, and Brugia malayi. We validated our augmented microscopy system in the clinical environment by replicating the diagnostic workflow encompassed examinations at 10x and 40x with the assistance of the AI models analyzing 18 samples with the AI running on a middle range smartphone. It achieved an overall precision of 94.14%, recall of 91.90% and F1 score of 93.01% for the screening algorithm and 95.46%, 97.81% and 96.62% for the species differentiation algorithm respectively. This innovative solution has the potential to support filariasis diagnosis and monitoring, particularly in resource-limited settings where access to expert technicians and laboratory equipment is scarce.

Impact assessment of onchocerciasis through lymphatic filariasis transmission assessment surveys using Ov-16 rapid diagnostic tests in Sierra Leone

BACKGROUND

Onchocerciasis is endemic in 14 of Sierra Leone's 16 districts with high prevalence (47-88.5%) according to skin snips at baseline. After 11 rounds of mass treatment with ivermectin with good coverage, an impact assessment was conducted in 2017 to assess the progress towards eliminating onchocerciasis in the country.

METHODS

A cluster survey was conducted, either integrated with lymphatic filariasis (LF) transmission assessment survey (TAS) or standalone with the LF TAS sampling strategy in 12 (now 14) endemic districts. Finger prick blood samples of randomly selected children in Grades 1-4 were tested in the field using SD Bioline Onchocerciasis IgG4 rapid tests.

RESULTS

In total, 17,402 children aged 4-19 years in 177 schools were tested, and data from 17,364 children aged 4-14 years (14,230 children aged 5-9 years) were analyzed. Three hundred forty-six children were confirmed positive for Ov-16 IgG4 antibodies, a prevalence of 2.0% (95% CI 1.8-2.2%) in children aged 4-14 years with prevalence increasing with age. Prevalence in boys (2.4%; 95% CI 2.1-2.7%) was higher than in girls (1.6%; 95% CI 1.4-1.9%). There was a trend of continued reduction from baseline to 2010. Using data from children aged 5-9 years, overall prevalence was 1.7% (95% CI 1.5-1.9%). The site prevalence ranged from 0 to 33.3% (median prevalence = 0.0%): < 2% in 127 schools, 2 to < 5% in 34 schools and ≥ 5% in 16 schools. There was a significant difference in average prevalence between districts. Using spatial analysis, the Ov-16 IgG4 antibody prevalence was predicted to be < 2% in coastal areas and in large parts of Koinadugu, Bombali and Tonkolili Districts, while high prevalence (> 5%) was predicted in some focal areas, centered in Karene, Kailahun and Moyamba/Tonkolili.

CONCLUSIONS

Low Ov-16 IgG4 antibody prevalence was shown in most areas across Sierra Leone. In particular, low seroprevalence in children aged 5-9 years suggests that the infection was reduced to a low level after 11 rounds of treatment intervention. Sierra Leone has made major progress towards elimination of onchocerciasis. However, attention must be paid to those high prevalence focal areas.

Platelet functions in lymphatic filariasis patients

Filariasis is a chronic disease where parasitic worms survive in human hosts even for decades and lead to complications like lymphedema and elephantiasis. Despite the persistent existence of filarial parasites in human hosts, fatal and thrombotic complications are not known, unlike other parasitic diseases like malaria. This suggests that filarial parasites might be affecting the host's platelet functions. This study was conducted to examine platelet functions in confirmed filariasis patients and healthy controls. Results showed that filariasis patients had larger platelets, inhibited aggregation, and slower speed of aggregation, compared to controls. However, in vivo markers of platelet activation and degranulation (beta thromboglobulin and soluble P-selectin) were not affected. Observations suggested that there is increased platelet turnover, cellular apoptosis and inhibited platelet functions in filariasis patients compared to controls. Platelet function inhibition was not associated with the duration of disease, lymphedema-affected organs, or gender of patients. This study confirms that filarial parasites modulate platelet functions in human hosts.

Prevalence of zoonotic (brugian) filariasis in Asia: A proportional meta-analysis

Lymphatic filariasis is a public health problem and targeted for global elimination. WHO recommends mass drug administration to interrupt transmission of the parasites involved. There are concerns that transmission interruption may be difficult in areas of zoonotic filarial infections. This study aimed to estimate the pooled prevalence of zoonotic brugian filariasis, and to compare the pooled prevalence of brugian filariasis in human and animal populations in the same area based on available studies. A comprehensive literature search was conducted in health-related electronic databases (PubMed, Ovid MEDLINE, Index Medicus, google scholar). A random-effect meta-analysis of the pooled overall prevalence of filariasis in animal populations was conducted. Sixteen studies from four different Asian countries were identified. Studies were conducted most frequently in Thailand (n = 7), followed by Malaysia (n = 5), India (n = 3), and Sri Lanka (n = 1). Regardless of animal group, the pooled overall prevalence of animal Brugia infections was 13% (95%CI: 7-21%, I2:98%, 16 studies). On stratification, the pooled overall prevalence in the animal population was 19% (95%CI: 1-50%, I2: 99%, 3 studies) in India, 8% (95%CI: 2-7%, I2: 97%, 5 studies) in Malaysia, and 13% (95%CI: 7-20%, I2: 94%, 7 studies) in Thailand. The prevalence in the animal population was 17% (95%CI: 13-21%, 1 study) in Sri Lanka. The pooled overall prevalence of Brugia malayi was 13% (95%CI: 7-21%, I2:98%, 12 studies), while for Brugia pahangi this was 12% (95%CI: 7-19%, I2:86%, 7 studies). Regardless of animal group, geographic area, or diagnostic test, the prevalence of B. malayi was consistently high. On stratification by animal category, the pooled overall prevalence was 10% (95%CI: 6-14%, I2:92%, 13 studies) in cats, 12% (95%CI: 2-28%, I2: 99%, 6 studies) in dogs, and 55% (95%CI: 47-63%, 1 study) in leaf-eating monkeys. The findings show the extent of zoonotic Brugiainfections in domestic cats and dogs, suggesting that these animals are potential reservoirs for human brugian filariasis in the study countries. To substantiate this with more accuracy, future well designed whole genomic sequencing of individual mf collected from humans and B. malayi infected animals in the same area are needed.

"Whenever I tell her to wear slippers, she turns a deaf ear. She never listens": a qualitative descriptive research on the barriers to basic lymphedema management and quality of life in lymphatic filariasis patients in a rural block of eastern India

BACKGROUND

Chronic lymphatic filariasis patients in Bihar, India, need management of lymphedema to live a disability-free life. For patients who have recurrent attacks of acute dermato-lymphangio-adenitis (ADLA), World Health Organization (WHO) has recommended simple home-based measures that include maintaining hygiene, skin care, and limb movement. However, patients in rural areas are unable to adopt them, resulting in a vicious cycle of ADLA attacks. There might be multiple realities from patients' and healthcare workers' perspectives that were unexplored. Qualitative research was deemed best suitable to identify the barriers to carrying out home-based lymphedema practices that adversely affected quality of life.

METHODS

The qualitative descriptive study was conducted in two villages in the rural field practice area under a tertiary care hospital in Bihar. Researchers purposively selected ten participants, including patients affected by lymphedema, their caregivers, the grassroots healthcare workers, and the block health manager. In-depth interviews were conducted using a semi-structured interview guide. Data were entered into QDA Miner Lite, where researchers did attribute, in-vivo, process, descriptive, emotion, and holistic coding, followed by content analysis, where categories and themes emerged from the codes.

RESULTS

Three themes emerged: the inherent nature of disease, patient-related factors, and healthcare system-related factors. The fifteen identified barriers were low awareness, low adherence, low health-seeking behavior, poor personal hygiene, and categories like signs and symptoms, seasonal factors, hampered activities of daily living, hopelessness from not getting cured, psychosocial difficulty, lack of capacity building and receipt of incentives by healthcare workers, unavailability of laboratory diagnosis and management of complications at the facility, inconsistent drug supply, and no financial assistance.

CONCLUSIONS

Accessibility to WaSH, regular training of home-based care, increasing the capacity and motivation of grassroots workers, and the generation of in-depth awareness among the patients are required to achieve the elimination of filariasis, with MMDP as a key component of that strategy for endemic districts across the whole country.

Characterization of a novel microfilarial antigen for diagnosis of Wuchereria bancrofti infections

Background

Lymphatic filariasis (LF) is a neglected tropical disease caused by the filarial nematodes Wuchereria bancrofti, Brugia malayi and Brugia timori. The Global Program to Eliminate LF uses mass drug administration (MDA) of anti-filarial drugs that clear microfilariae (Mf) from blood to interrupt transmission by mosquitos. New diagnostic tools are needed to assess the impact of MDA on bancroftian filariasis, because available serologic tests can remain positive after successful treatment.

Methodology/Principal findings

We identified Wb-bhp-1, which encodes a W. bancrofti homologue of BmR1, the B. malayi protein used in the Brugia Rapid antibody test for brugian filariasis. Wb-bhp-1 has a single exon that encodes a 16.3 kD protein (Wb-Bhp-1) with 45% amino acid identity to BmR1. Immunohistology shows that anti-Wb-Bhp-1 antibodies primarily bind to Mf. Plasma from 124 of 224 (55%) microfilaremic individuals had IgG4 antibodies to Wb-Bhp-1 by ELISA. Serologic reactivity to Wb-Bhp-1 varied widely with samples from different regions (sensitivity range 32–92%), with 77% sensitivity for 116 samples collected from microfilaremic individuals outside of sub-Saharan Africa. This variable sensitivity highlights the importance of validating new diagnostic tests for parasitic diseases with samples from different geographical regions. Individuals with higher Mf counts were more likely to have anti-Wb-Bhp-1 antibodies. Cross-reactivity was observed with a minority of plasma samples from people with onchocerciasis (17%) or loiasis (10%). We also identified, cloned and characterized BmR1 homologues from O. volvulus and L. loa that have 41% and 38% identity to BmR1, respectively. However, antibody assays with these antigens were not sensitive for onchocerciasis or loiasis.

Conclusions

Wb-Bhp-1 is a novel antigen that is useful for serologic diagnosis of bancroftian filariasis. Additional studies are needed to assess the value of this antigen for monitoring the success of filariasis elimination programs.

Lymphatic filariasis (LF) is a highly disabling and stigmatizing disease caused by parasitic worms that are transmitted by mosquitoes. There is a coordinated global effort to eliminate LF based on mass drug administration (MDA) of donated anti-filarial medications. Improved methods are needed to determine when transmission of the infection has been interrupted in previously endemic areas so that MDA can be safely stopped. This paper reports the discovery and characterization of a novel W. bancrofti antigen, Wb-Bhp-1, which is a homologue of the Brugia malayi protein used in antibody tests to monitor filariasis elimination in areas of Asia where LF is caused by Brugia species. We show that a test for IgG4 antibodies to Wb-Bhp-1 was fairly specific for W. bancrofti infection. However, the sensitivity of this test varied by the geographic origin of the samples. Sensitivity was highest for samples collected in the Indo-Pacific region and lowest for samples collected in Côte d’Ivoire. Geographic differences in the parasite or the human immune responses to infection may account for this variability. This range in sensitivity highlights the importance of validating new diagnostic tests for parasitic diseases with samples from different geographical regions.

Diagnostics to support elimination of lymphatic filariasis-Development of two target product profiles

As lymphatic filariasis (LF) programs move closer to established targets for validation elimination of LF as a public health problem, diagnostic tools capable of supporting the needs of the programs are critical for success. Known limitations of existing diagnostic tools make it challenging to have confidence that program endpoints have been achieved. In 2019, the World Health Organization (WHO) established a Diagnostic Technical Advisory Group (DTAG) for Neglected Tropical Diseases tasked with prioritizing diagnostic needs including defining use-cases and target product profiles (TPPs) for needed tools. Subsequently, disease-specific DTAG subgroups, including one focused on LF, were established to develop TPPs and use-case analyses to be used by product developers. Here, we describe the development of two priority TPPs for LF diagnostics needed for making decisions for stopping mass drug administration (MDA) of a triple drug regimen and surveillance. Utilizing the WHO core TPP development process as the framework, the LF subgroup convened to discuss and determine attributes required for each use case. TPPs considered the following parameters: product use, design, performance, product configuration and cost, and access and equity. Version 1.0 TPPs for two use cases were published by WHO on 12 March 2021 within the WHO Global Observatory on Health Research and Development. A common TPP characteristic that emerged in both use cases was the need to identify new biomarkers that would allow for greater precision in program delivery. As LF diagnostic tests are rarely used for individual clinical diagnosis, it became apparent that reliance on population-based surveys for decision making requires consideration of test performance in the context of such surveys. In low prevalence settings, the number of false positive test results may lead to unnecessary continuation or resumption of MDA, thus wasting valuable resources and time. Therefore, highly specific diagnostic tools are paramount when used to measure low thresholds. The TPP process brought to the forefront the importance of linking use case, program platform and diagnostic performance characteristics when defining required criteria for diagnostic tools.

Achievements and challenges of lymphatic filariasis elimination in Sierra Leone

Background

Lymphatic filariasis (LF) is targeted for elimination in Sierra Leone. Epidemiological coverage of mass drug administration (MDA) with ivermectin and albendazole had been reported >65% in all 12 districts annually. Eight districts qualified to implement transmission assessment survey (TAS) in 2013 but were deferred until 2017 due to the Ebola outbreak (2014–2016). In 2017, four districts qualified for conducting a repeat pre-TAS after completing three more rounds of MDA and the final two districts were also eligible to implement a pre-TAS.

Methodology/Principal findings

For TAS, eight districts were surveyed as four evaluation units (EU). A school-based survey was conducted in children aged 6–7 years from 30 clusters per EU. For pre-TAS, one sentinel and one spot check site per district (with 2 spot check sites in Bombali) were selected and 300–350 persons aged 5 years and above were selected. For both surveys, finger prick blood samples were tested using the Filariasis Test Strips (FTS).

For TAS, 7,143 children aged 6–7 years were surveyed across four EUs, and positives were found in three EUs, all below the critical cut-off value for each EU. For the repeat pre-TAS/pre-TAS, 3,994 persons over five years of age were surveyed. The Western Area Urban had FTS prevalence of 0.7% in two sites and qualified for TAS, while other five districts had sites with antigenemia prevalence >2%: 9.1–25.9% in Bombali, 7.5–19.4% in Koinadugu, 6.1–2.9% in Kailahun, 1.3–2.3% in Kenema and 1.7% - 3.7% in Western Area Rural.

Conclusions/Significance

Eight districts in Sierra Leone have successfully passed TAS1 and stopped MDA, with one more district qualified for conducting TAS1, a significant progress towards LF elimination. However, great challenges exist in eliminating LF from the whole country with repeated failure of pre-TAS in border districts. Effort needs to be intensified to achieve LF elimination.

Lymphatic filariasis or elephantiasis is targeted for elimination in Sierra Leone, with annual mass treatment with ivermectin and albendazole, and required coverage was achieved in all 12 districts annually. In 2017, transmission assessment survey (TAS) was conducted in eight districts to assess whether treatment can be stopped and pre-TAS was conducted in six other districts to assess whether TAS can be conducted. Eight TAS districts were surveyed as four evaluation units (EU), and a school-based survey was conducted in 1703–1926 children aged 6–7 years from 30 clusters per EU. Six pre-TAS districts were surveyed with one sentinel and one/two spot check sites per district and 300–350 persons aged ≥5 years were tested. All tests were using the Filariasis Test Strips with finger prick blood samples. There were 0–7 positive cases in each TAS EU respectively, all below the critical cut-off value, confirming that mass treatment was no longer needed in these eight districts, a significant progress towards LF elimination. One district had prevalence of <1% in two sites and qualified for TAS, while other five districts had sites with prevalence >2%, suggesting that mass treatment needs to continue. Repeated failure of pre-TAS poses great challenge to eliminate LF in Sierra Leone.YMB is the former NTDP manager and coordinated the MDAs with AC and MS. JBK designed and oversaw the early NTDP and baseline surveys. JP, MB designed and led the TAS, pre-TAS field work data collection. MB and VRS conducted the data analysis. VRS and MH reanalysed the coverage data. YZ produced the point prevalence map. MH drafted the manuscript. MH and YZ revised the manuscript. All authors reviewed and approved the final manuscript.

Novel Diagnostics for Kaposi Sarcoma and Other Skin Diseases in Resource-Limited Settings

In resource-limited settings, point-of-care diagnostic devices have the potential to reduce diagnostic delays and improve epidemiologic surveillance of dermatologic conditions. We outline novel-point-of care diagnostics that have recently been developed for dermatologic conditions that primarily affect patients living in resource-limited settings, namely, Kaposi sarcoma, cutaneous leishmaniasis, leprosy, Buruli ulcer, yaws, onchocerciasis, and lymphatic filariasis. All of the technologies described in this article are prototypes, and some have undergone field testing. These devices still require validation in real-world settings and effective pricing to have a major impact on dermatologic care in resource-limited settings.

Mapping lymphatic filariasis in Loa loa endemic health districts naïve for ivermectin mass administration and situated in the forested zone of Cameroon

BACKGROUND

The control of lymphatic filariasis (LF) caused by Wuchereria bancrofti in the Central African Region has been hampered by the presence of Loa loa due to severe adverse events that arise in the treatment with ivermectin. The immunochromatographic test (ICT) cards used for mapping LF demonstrated cross-reactivity with L. loa and posed the problem of delineating the LF map. To verify LF endemicity in forest areas of Cameroon where mass drug administration (MDA) has not been ongoing, we used the recently developed strategy that combined serology, microscopy and molecular techniques.

METHODS

This study was carried out in 124 communities in 31 health districts (HDs) where L. loa is present. At least 125 persons per site were screened. Diurnal blood samples were investigated for circulating filarial antigen (CFA) by FTS and for L. loa microfilariae (mf) using TBF. FTS positive individuals were further subjected to night blood collection for detecting W. bancrofti. qPCR was used to detect DNA of the parasites.

RESULTS

Overall, 14,446 individuals took part in this study, 233 participants tested positive with FTS in 29 HDs, with positivity rates ranging from 0.0 to 8.2%. No W. bancrofti mf was found in the night blood of any individuals but L. loa mf were found in both day and night blood of participants who were FTS positive. Also, qPCR revealed that no W. bancrofti but L.loa DNA was found with dry bloodspot. Positive FTS results were strongly associated with high L. loa mf load. Similarly, a strong positive association was observed between FTS positivity and L loa prevalence.

CONCLUSIONS

Using a combination of parasitological and molecular tools, we were unable to find evidence of W. bancrofti presence in the 31 HDs, but L. loa instead. Therefore, LF is not endemic and LF MDA is not required in these districts.

Progress towards lymphatic filariasis elimination in Ghana from 2000-2016: Analysis of microfilaria prevalence data from 430 communities

BACKGROUND

Ghana started its national programme to eliminate lymphatic filariasis (LF) in 2000, with mass drug administration (MDA) with ivermectin and albendazole as main strategy. We review the progress towards elimination that was made by 2016 for all endemic districts of Ghana and analyze microfilaria (mf) prevalence from sentinel and spot-check sites in endemic districts.

METHODS

We reviewed district level data on the history of MDA and outcomes of transmission assessment surveys (TAS). We further collated and analyzed mf prevalence data from sentinel and spot-check sites.

RESULTS

MDA was initiated in 2001-2006 in all 98 endemic districts; by the end of 2016, 81 had stopped MDA after passing TAS and after an average of 11 rounds of treatment (range 8-14 rounds). The median reported coverage for the communities was 77-80%. Mf prevalence survey data were available for 430 communities from 78/98 endemic districts. Baseline mf prevalence data were available for 53 communities, with an average mf prevalence of 8.7% (0-45.7%). Repeated measurements were available for 78 communities, showing a steep decrease in mean mf prevalence in the first few years of MDA, followed by a gradual further decline. In the 2013 and 2014 surveys, 7 and 10 communities respectively were identified with mf prevalence still above 1% (maximum 5.6%). Fifteen of the communities above threshold are all within districts where MDA was still ongoing by 2016.

CONCLUSIONS

The MDA programme of the Ghana Health Services has reduced mf prevalence in sentinel sites below the 1% threshold in 81/98 endemic districts in Ghana, yet 15 communities within 13 districts (MDA ongoing by 2016) had higher prevalence than this threshold during the surveys in 2013 and 2014. These districts may need to intensify interventions to achieve the WHO 2020 target.

Lymphatic Filariasis

Lymphatic filariasis (LF) is a parasitic infection that is spread by mosquitos infected with worm larvae. Several factors will affect the global prevalence of LF in the future. A growing body of evidence suggests that climate change will influence the spread of parasitic diseases and their vectors. Lymphatic filariasis is the leading cause of permanent disfigurement and the second most common cause of long-term disability in the world.

Epidemiological screening and xenomonitoring for human lymphatic filariasis infection in select districts in the states of Maharashtra and Karnataka, India

Lymphatic filariasis (LF) is a mosquito-transmitted tropical neglected parasitic infection that currently affects over 120 million people around the world and another 856 million people are at risk of acquiring the infection. Mass Drug Administration (MDA) spearheaded by the World Health Organization is the only current strategy to control this infection in endemic areas. In this study, we performed an epidemiological survey in select regions in the southern parts of India to determine the current status of LF infection in subjects. Night blood samples were collected from 916 subjects after proper consent and were screened for the presence of circulating microfilariae of Wuchereria bancrofti in their peripheral blood. Our results showed the presence of 51 (5.56%) cases of human LF infection in the surveyed areas including new cases for LF, which were not recorded previously. Given the presence of new cases of LF infections, we trapped mosquitoes from these regions and screened for the presence of W. bancrofti L3 specific Ssp1 DNA repeat sequences by PCR. Our results confirmed the presence of LF infection in the mosquitoes collected from six out of nine districts that we surveyed. These findings confirm active transmission of LF infection in all of the areas that we surveyed, despite several years of MDA treatment. The findings in this study suggest potential reemergence of LF infection in most of the areas we surveyed and warrants for a more stringent strategy for controlling LF in these endemic areas.

Evaluation of the effect of mass drug administration against lymphatic filariasis in three health districts and public health implications: study of 12 epidemiological surveillance sites in Burkina Faso

The implementation of mass drug administration (MDA) campaigns of albendazole (400 mg) and ivermectin (150-200 μm/kg) since 2001 has helped to change the epidemiological profile of lymphatic filariasis (LF) in many health districts in Burkina Faso. From 2002 to 2016, 14 rounds of MDA have taken place in the Central East zone, with therapeutic coverage exceeding 65%. The objective of the current study was to evaluate the impact of MDA in the fight against LF at 12 sentinel and spot-check sites. This descriptive cross-sectional study surveyed subjects aged 5 years and older between April and July 2017 at these 12 sites. The blood smear performed on nocturnal samples was used to diagnose Wuchereria bancrofti infection. The study included 4364 subjects. Their mean age was 20.55 years with a standard deviation of 14.22 and a range of 5 to 96 years. The overall prevalence of microfilaremia was 0.62% (27/4364), with rates exceeding 1% at three (3) sites. The average microfilaremia density was 106 μf/mL. The overall prevalence of morbidity was low (0.91%), predominantly lymphedema (0.60%). The MDA strategy has helped to reduce the prevalence of LF significantly in Burkina Faso, but some outbreaks still have microfilarial prevalence greater than 1%. Continuation of the additional 2-year strategy with improved adherence to treatment and vector control would help break LF transmission.

Identification and characterization of Loa loa antigens responsible for cross-reactivity with rapid diagnostic tests for lymphatic filariasis

The Global Program to Eliminate Lymphatic Filariasis (LF) relies on rapid diagnostic tests (RDTs) to determine where annual mass drug administration for LF is required and when it can be stopped. These tests detect a Wuchereria bancrofti glycoprotein in the blood of infected persons via a carbohydrate moiety recognized by the monoclonal antibodies AD12 and DH6.5. Loiasis cross-reactivity with LF RDTs has recently been recognized as a serious obstacle to LF elimination in loiasis-endemic areas. To better understand the nature of this cross-reactivity, we used the DH6.5 antibody to immunoaffinity purify Loa loa antigens from the sera of individuals with a positive RDT due to loiasis. Immunoblot analysis revealed many circulating AD12/DH6.5-reactive antigens, and proteomic analysis identified multiple L. loa proteins in LF RDT-positive loiasis sera. These included both secreted and somatic proteins, suggesting that they may be released by dying L. loa adult worms and/or microfilariae. Unlike the single high molecular weight W. bancrofti circulating filarial antigen that is reliably present in the blood of persons with bancroftian filariasis, reactive L. loa antigens appeared to be only transiently present in the blood of a subset of persons with loiasis. These key differences between the circulating antigens of W. bancrofti and L. loa can be used to differentiate positive results generated by both species and may lead to improved diagnostic tests for LF and loiasis.

Lymphatic filariasis is a disfiguring parasitic infection tens of millions of people in more than 70 countries. The global effort to eliminate LF transmission via mass drug administration (MDA) relies on rapid diagnostic tests (RDTs) to identify infected individuals and map afflicted areas. This effort is complicated in loiasis-endemic nations of central Africa for two reasons. First, persons with heavy L. loa infections may suffer severe adverse events, including death, following treatment with MDA medications. Second, it is now clear that RDT testing for LF can be unreliable in areas with loiasis, since many L. loa-infected individuals, especially those with heavy infections, test positive by LF RDT in the absence of infection with W. bancrofti (the causative agent of LF in Africa). We report here the identity and characteristics of multiple L. loa antigens found in RDT-positive sera that bind to antibodies used in LF RDTs. Understanding the differences between these cross-reactive antigens and the circulating filarial antigen of W. bancrofti may lead to development of improved diagnostic tests for LF and loiasis to facilitate elimination of filarial infections in Sub-Saharan Africa.

Effects of lyophilization and storage temperature on Wuchereria bancrofti antigen sensitivity and stability

OBJECTIVE

Antigen-based rapid diagnostic tests for Lymphatic filariasis (LF) do not come with external quality control (QC) materials, and research and disease control programmes rely on stored positive samples. This study was undertaken to evaluate the use of lyophilized Wuchereria bancrofti antigen positive plasma samples to serve as QC materials for LF diagnostic tests. 10 well characterized W. bancrofti positive samples were lyophilized and stored at 4, 28 and 40 °C. The samples were evaluated using the Alere Filariasis Test Strips before lyophilization, and after 1 and 3 months of storage. The sensitivity and stability of the lyophilized samples were evaluated.

RESULTS

The results revealed a loss of sensitivity and stability with increasing temperature and duration of storage. The results are further discussed in terms of the use of dried blood spot (DBS) in diagnostic studies on LF, and the need for thoughtful DBS preparation and storage.

How elimination of lymphatic filariasis as a public health problem in the Kingdom of Cambodia was achieved

BACKGROUND

Endemicity of lymphatic filariasis (LF) in Cambodia was proven in 1956 when microfilariae were detected in mosquitos in the Kratié province. In 2001, an extensive study confirmed the presence of both Brugia malayi and Wuchereria bancrofti microfilariae. In 2003, the Ministry of Health established a national task force to develop policies and strategies for controlling and eliminating neglected tropical diseases (NTDs), with the goal of eliminating LF by 2015. This article summarizes the work accomplished to eliminate LF as a public health problem in Cambodia.

METHODS

The National Program to Eliminate Lymphatic Filariasis made excellent progress in the goal towards elimination due to strong collaboration between ministries, intensive supervision by national staff, and advocacy for mobilization of internal and external resources. Mass drug administration (MDA) with diethylcarbamazine citrate and albendazole was conducted in six implementation units, achieving > 70% epidemiological coverage for five consecutive rounds, from 2005 to 2009. In 2006, in 14 provinces, healthcare workers developed a line list of lymphedema and hydrocele patients, many of whom were > 40 years old and had been affected by LF for many years. The national program also trained healthcare workers and provincial and district staff in morbidity management and disability prevention, and designated health centers to provide care for lymphedema and acute attack. Two reference hospitals were designated to administer hydrocele surgery.

RESULTS

Effectiveness of MDA was proven with transmission assessment surveys. These found that less than 1% of school children had antigenemia in 2010, which fell to 0% in both 2013 and 2015. A separate survey in one province in 2015 using Brugia Rapid tests to test for LF antibody found one child positive among 1677 children. The list of chronic LF patients was most recently updated and confirmed in 2011-2012, with 32 lymphoedema patients and 17 hydrocele patients listed. All lymphedema patients had been trained on self-management and all hydrocele patients had been offered free surgery.

CONCLUSIONS

Due to the success of the MDA and the development of health center capacity for patient care, along with benefits gained from socioeconomic improvements and other interventions against vector-borne diseases and NTDs, Cambodia was validated by the World Health Organization as achieving LF elimination as a public health problem in 2016.

Successful multi-modal treatment of grade IV lymphedema in lymphatic filariasis: A case study

We present an integrated therapeutic approach performed on a 37 year old female with giant lymphedema (Grade IV) due to lymphatic filariasis of 27 years duration. Our therapeutic approaches consisted of a basic foot care program for two weeks, followed by a course of oral penicillin for a week including conservative treatment with complete decongestive therapy (CDT) together with respiratory physiotherapy and walking exercises. In addition, advanced surgical techniques with supra-fascial excision of alternate lumps in three stages over an interval of ten days followed by a nodo-venal shunt resulted in reversing the stage IV lymphedema condition. Over a ten year follow-up, the patient remains essentially unchanged confirming the success of the treatment without any recurrence or complications. Finally, by combining multimodal treatment, we were able to achieve a near normal limb in Stage III and Stage IV lymphedema of the lower limb in lymphatic filariasis.

Colorimetric tests for diagnosis of filarial infection and vector surveillance using non-instrumented nucleic acid loop-mediated isothermal amplification (NINA-LAMP)

Accurate detection of filarial parasites in humans is essential for the implementation and evaluation of mass drug administration programs to control onchocerciasis and lymphatic filariasis. Determining the infection levels in vector populations is also important for assessing transmission, deciding when drug treatments may be terminated and for monitoring recrudescence. Immunological methods to detect infection in humans are available, however, cross-reactivity issues have been reported. Nucleic acid-based molecular assays offer high levels of specificity and sensitivity, and can be used to detect infection in both humans and vectors. In this study we developed loop-mediated isothermal amplification (LAMP) tests to detect three different filarial DNAs in human and insect samples using pH sensitive dyes for enhanced visual detection of amplification. Furthermore, reactions were performed in a portable, non-instrumented nucleic acid amplification (NINA) device that provides a stable heat source for LAMP. The efficacy of several strand displacing DNA polymerases were evaluated in combination with neutral red or phenol red dyes. Colorimetric NINA-LAMP assays targeting Brugia Hha I repeat, Onchocerca volvulus GST1a and Wuchereria bancrofti LDR each exhibit species-specificity and are also highly sensitive, detecting DNA equivalent to 1/10-1/5000^th of one microfilaria. Reaction times varied depending on whether a single copy gene (70 minutes, O. volvulus) or repetitive DNA (40 min, B. malayi and W. bancrofti) was employed as a biomarker. The NINA heater can be used to detect multiple infections simultaneously. The accuracy, simplicity and versatility of the technology suggests that colorimetric NINA-LAMP assays are ideally suited for monitoring the success of filariasis control programs.

Costs of Transmission Assessment Surveys to Provide Evidence for the Elimination of Lymphatic Filariasis

Background

To reach the global goal of elimination of lymphatic filariasis as a public health problem by 2020, national programs will have to implement a series of transmission assessment surveys (TAS) to determine prevalence of the disease by evaluation unit. It is expected that 4,671 surveys will be required by 2020. Planning in advance for the costs associated with these surveys is essential to ensure that the required resources are available for this essential program activity.

Methodology and Findings

Retrospective cost data was collected from reports from 13 countries which implemented a total of 105 TAS surveys following a standardized World Health Organization (WHO) protocol between 2012 and 2014. The median cost per survey was $21,170 (including the costs for rapid diagnostic tests [RDTs]) and $9,540 excluding those costs. Median cost per cluster sampled (without RDT costs) was $101. Analysis of costs (excluding RDTs) by category showed that the main cost drivers were personnel and travel.

Conclusion

Transmission assessment surveys are critical to collect evidence to validate elimination of LF as a public health problem. National programs and donors can use the costing results to adequately plan and forecast the resources required to undertake the necessary activities to conduct high-quality transmission assessment surveys.

As national programs are nearing elimination of lymphatic filariasis as a public health problem, questions have been raised about the cost of collecting the data necessary for documenting validation of elimination. A series of standardized population-based surveys is necessary to determine prevalence of infection in endemic areas. The authors retrospectively collected data on the costs of these surveys from 13 countries to determine median cost per survey and per cluster sampled. Costs were found to be comparable with other neglected tropical disease surveys. The major cost drivers were personnel and travel for supporting collection of data in the field. National programs and donors can use these results to plan and advocate more effectively for sufficient resources to support validation of elimination.

The Diagnosis and Treatment of Peripheral Lymphedema: 2016 Consensus Document of the International Society of Lymphology

This International Society of Lymphology (ISL) Consensus Document is the latest revision of the 1995 Document for the evaluation and management of peripheral lymphedema (1). It is based upon modifications: [A] suggested and published following the 1997 XVI International Congress of Lymphology (ICL) in Madrid, Spain (2), discussed at the 1999 XVII ICL in Chennai, India (3), and considered/ confirmed at the 2000 (ISL) Executive Committee meeting in Hinterzarten, Germany (4); [B] derived from integration of discussions and written comments obtained during and following the 2001 XVIII ICL in Genoa, Italy as modified at the 2003 ISL Executive Committee meeting in Cordoba, Argentina (5); [C] suggested from comments, criticisms, and rebuttals as published in the December 2004 issue of Lymphology (6); [D] discussed in both the 2005 XX ICL in Salvador, Brazil and the 2007 XXI ICL in Shanghai, China and modified at the 2008 Executive Committee meeting in Naples, Italy (7,8);[E] modified from discussions and written comments from the 2009 XXII ICL in Sydney, Australia, the 2011 XXIII ICL in Malmö, Sweden, the 2012 Executive Committee Meetings (9),and [F] from discussions at the 2013 XXIV ICL in Rome, Italy, and the 2015 XXV ICL in San Francisco, USA, as well as multiple written comments and feedback from Executive Committee and other ISL members during the 2016 drafting. The document attempts to amalgamate the broad spectrum of protocols and practices advocated worldwide for the diagnosis and treatment of peripheral lymphedema into a coordinated proclamation representing a “Consensus” of the international community based on various levels of evidence. The document is not meant to override individual clinical considerations for complex patients nor to stifle progress. It is also not meant to be a legal formulation from which variations define medical malpractice. The Society understands that in some clinics the method of treatment derives from national standards while in others access to medical equipment and supplies is limited; therefore the suggested treatments might be impractical. Adaptability and inclusiveness does come at the price that members can rightly be critical of what they see as vagueness or imprecision in definitions, qualifiers in the choice of words (e.g., the use of “may... perhaps... unclear”, etc.) and mentions (albeit without endorsement) of treatment options supported by limited hard data. Most members are frustrated by the reality that NO treatment method has really undergone a satisfactory meta-analysis (let alone rigorous, randomized, stratified, long-term, controlled study). With this understanding, the absence of definitive answers and optimally conducted clinical trials, and with emerging technologies and new approaches and discoveries on the horizon, some degree of uncertainty, ambiguity, and flexibility along with dissatisfaction with current lymphedema evaluation and management is appropriate and to be expected. We continue to struggle to keep the document concise while balancing the need for depth and details. With these considerations in mind, we believe that this 2016 version presents a Consensus that embraces the entire ISL membership, rises above national standards, identifies and stimulates promising areas for future research, and represents the best judgment of the ISL membership on how to approach patients with peripheral lymphedema in the light of currently available evidence. Therefore, the document has been, and should continue to be, challenged and debated in the pages of Lymphology (e.g., as Letters to the Editor) and ideally will remain a continued focal point for robust discussion at local, national and international conferences in lymphology and related disciplines. We further anticipate as experience evolves and new ideas and technologies emerge that this “living document” will undergo further periodic revision and refinement as the practice and conceptual foundations of medicine and specifically lymphology change and advance.

Giant Scrotal Hydrocele and Bilateral Leg Lymphedema as Clinical Manifestation of Chronic Lymphatic Filariasis

A 51-year-old male came with the complaint of recurrent swelling in the scrotum and legs. Swelling of the scrotum first appeared 17 years ago in the left scrotum approximately the same size as an apple and underwent surgery. However, 2 years after surgery, the swelling reemerged and gradually increase in size in both scrotums. Left leg swelling began to emerge 5 years ago followed by right leg 3 years after. The patient lives in Sarmi regency Papua province (endemic).

Measurement of Circulating Filarial Antigen Levels in Human Blood with a Point-of-Care Test Strip and a Portable Spectrodensitometer

The Alere Filariasis Test Strip (FTS) is a qualitative, point-of-care diagnostic tool that detects Wuchereria bancrofti circulating filarial antigen (CFA) in human blood, serum, or plasma. The Global Program to Eliminate Lymphatic Filariasis employs the FTS for mapping filariasis-endemic areas and assessing the success of elimination efforts. The objective of this study was to explore the relationship between the intensity of positive test lines obtained by FTS with CFA levels as determined by enzyme-linked immunosorbent assay (ELISA) with blood and plasma samples from 188 individuals who live in a filariasis-endemic area. The intensity of the FTS test line was assessed visually to provide a semiquantitative score (visual Filariasis Test Strip [vFTS]), and line intensity was measured with a portable spectrodensitometer (quantitative Filariasis Test Strip [qFTS]). These results were compared with antigen levels measured by ELISA in plasma from the same subjects. qFTS measurements were highly correlated with vFTS scores (ρ = 0.94; P < 0.001) and with plasma CFA levels (ρ = 0.91; P < 0.001). Thus, qFTS assessment is a convenient method for quantifying W. bancrofti CFA levels in human blood, which are correlated with adult worm burdens. This tool may be useful for assessing the impact of treatment on adult filarial worms in individuals and communities.

Evaluation of immuno diagnostic assay for the exposure of stage specific filarial infection

Lymphatic filariasis is a debilitating diseases caused by filarial parasitic nematodes. The infection may be acquired in childhood but the symptoms become apparent only in later life. To evaluate the success of any intervention, sensitive diagnostics were used to identify infection among endemic normals that are likely to develop microfilaremia in due course of time. Capture assay was standardized using the recombinant protein Brugia malayi Abundant Larval Transcript-2 (ALT-2) specific monoclonal and poly-clonal antibodies and evaluated with serum samples of clinical groups from high and low filarial infection area individuals (HIA/LIA), Endemic Normal (EN, n = 478), microfilaeremics (MF, n = 77), chronic pathology (CP, n = 57) and non endemic normal (NEN, n = 20). In order to assess stage-specific infection, ALT-2 capture assay was compared with the early reported Venom allergen homologue (VAH) and microfilariae specific SXP-1 capture assays. Of the 632 serum samples tested, ALT-2 and VAH capture assays detected circulating filarial antigen (CFA) in 57% and 52% of HIA-EN individuals, respectively. As expected, the VAH and SXP-1 capture assays were positive for 100 % of MF individuals. The described capture assays can be useful for the detection of early and stage-specific filarial infections in endemic regions of developing countries.

In search of a potential diagnostic tool for molecular characterization of lymphatic filariasis

Lymphatic filariasis (LF) is a chronic disease and is caused by the parasites Wuchereria bancrofti (W. bancrofti), Brugia malayi (B. malayi) and Brugia timori (B. timori). In the present study, Setaria cervi (S. cervi), a bovine filarial parasite has been used. Previously, it has been reported that the S. cervi shares some common proteins and antigenic determinants with that of human filarial parasite. The larval stages of filarial species usually cannot be identified by classical morphology. Hence, molecular characterization allows the identification of the parasites throughout all their developmental stages. The genomic DNA of S. cervi adult were isolated and estimated spectrophotometrically for the quantitative presence of DNA content. Screening of DNA sequences from filarial DNA GenBank and Expressed Sequence Tags (EST's) were performed for homologous sequences and then multiple sequence alignment was executed. The conserved sequences from multiple sequence alignment were used for In Silico primer designing. The successfully designed primers were used further in PCR amplifications. Therefore, in search of a promising diagnostic tool few genes were identified to be conserved in the human and bovine filariasis and these novel primers deigned may help to develop a promising diagnostic tool for identification of lymphatic filariasis.

Cross-Reactivity of Filariais ICT Cards in Areas of Contrasting Endemicity of Loa loa and Mansonella perstans in Cameroon: Implications for Shrinking of the Lymphatic Filariasis Map in the Central African Region

Background

Immunochromatographic card test (ICT) is a tool to map the distribution of Wuchereria bancrofti. In areas highly endemic for loaisis in DRC and Cameroon, a relationship has been envisaged between high L. loa microfilaria (Mf) loads and ICT positivity. However, similar associations have not been demonstrated from other areas with contrasting levels of L. loa endemicity. This study investigated the cross-reactivity of ICT when mapping lymphatic filariasis (LF) in areas with contrasting endemicity levels of loiasis and mansonellosis in Cameroon.

Methodology/Principal Findings

A cross-sectional study to assess the prevalence and intensity of W. bancrofti, L. loa and M. perstans was carried out in 42 villages across three regions (East, North-west and South-west) of the Cameroon rainforest domain. Diurnal blood was collected from participants for the detection of circulating filarial antigen (CFA) by ICT and assessment of Mf using a thick blood smear. Clinical manifestations of LF were also assessed. ICT positives and patients clinically diagnosed with lymphoedema were further subjected to night blood collection for the detection of W. bancrofti Mf. Overall, 2190 individuals took part in the study. Overall, 24 individuals residing in 14 communities were tested positive by ICT, with prevalence rates ranging from 0% in the South-west to 2.1% in the North-west. Lymphoedema were diagnosed in 20 individuals with the majority of cases found in the North-west (11/20), and none of them were tested positive by ICT. No Mf of W. bancrofti were found in the night blood of any individual with a positive ICT result or clinical lymphoedema. Positive ICT results were strongly associated with high L. loa Mf intensity with 21 subjects having more than 8,000 L. loa Mf ml/blood (Odds ratio = 15.4; 95%CI: 6.1–39.0; p < 0.001). Similarly, a strong positive association (Spearman’s rho = 0.900; p = 0.037) was observed between the prevalence of L. loa and ICT positivity by area: a rate of 1% or more of positive ICT results was found only in areas with an L. loa Mf prevalence above 15%. In contrast, there was no association between ICT positivity and M. perstans prevalence (Spearman’s rho = - 0.200; p = 0.747) and Mf density (Odds ratio = 1.8; 95%CI: 0.8–4.2; p = 0.192).

Conclusions/Significance

This study has confirmed the strong association between the ICT positivity and L. loa intensity (Mf/ml of blood) at the individual level. Furthermore, the study has demonstrated that ICT positivity is strongly associated with high L. loa prevalence. These results suggest that the main confounding factor for positive ICT test card results are high levels of L. loa. The findings may indicate that W. bancrofti is much less prevalent in the Central African region where L. loa is highly endemic than previously assumed and accurate re-mapping of the region would be very useful for shrinking of the map of LF distribution.

Mapping of lymphatic filariasis (LF) caused by W. brancrofti is usually done by employing a rapid diagnostic test that permits the detection of worm antigen in daytime blood. This is sometimes combined with a thick blood film (TBF) for microscopic examination, as confirmatory tool for detecting W. bancrofti Mf in peripheral night blood. During recent epidemiological surveys using immunochromatographic card test (ICT) to map LF in areas highly endemic for loiasis, positive card tests were observed in individuals’ amicrofilaremic for W. bancrofti during night TBF examination, as well as by parasite DNA detection. The possibility of ICT cross-reacting with L. loa antigen was envisaged, but so far associations between ICT positivity and L. loa endemicity levels and loads of Mf in day blood have not yet been established. Moreover, M. perstans another filaria with blood dwelling Mf, that is often sympatric with L. loa, could contribute to the observed ICT cross-reactivity. The authors investigated the cross-reactivity of ICT in areas with contrasting endemicity levels of L. loa and M. perstans in Cameroon. Results incriminated L. loa as the major confounder in ICT cross-reactivity, with significant association between ICT positivity and loiasis both at individual level (load of Mf/ml of blood) and endemicity level (Mf prevalence). M. perstans displayed no association with ICT positivity. The findings raised concerns about the specificity of the whole blood ICT used for LF mapping in loiasis co-endemic areas. The development of an algorithm for LF mapping in loiasis co-endemic areas will be important to validate the LF map obtained using ICT in Central Africa.

Immunodiagnostic Properties of Wucheraria bancrofti SXP-1, a Potential Filarial Diagnostic Candidate Expressed in Tobacco Plant, Nicotiana tabacum

Transgenic tobacco plants were developed expressing WbSXP-1, a diagnostic antigen isolated from the cDNA library of L3 stage larvae of Wucheraria bancrofti. This antigen produced by recombinant Escherichia coli has been demonstrated by to be successful as potential diagnostic candidate against lymphatic filariasis. A rapid format simple and qualitative flow through immune-filtration diagnostic kit has been developed for the identification of IgG antibodies to the recombinant WbSXP-1 and is being marketed by M/S Span Diagnostics Ltd in India and Africa. Here, we present the results of experiments on the transformation and expression of the same filarial antigen, WbSXP-1, in tobacco plant, Nicotiana tabacum, to produce plant-based diagnostic antigen. It was possible to successfully transform the tobacco plant with WbSXP-1, the integration of the parasite-specific gene in plants was confirmed by PCR amplification and the expression of the filarial protein by Western blotting. The immunoreactivity of the plant-produced WbSXP-1 was assessed based on its reaction with the monoclonal antibodies developed against the E. coli-produced protein. Immunological screening using clinical sera from patients indicates that the plant-produced protein is comparable to E. coli-produced diagnostic antigen. The result demonstrated that plants can be used as suitable expression systems for the production of diagnostic proteins against lymphatic filariasis, a neglected tropical infectious disease which has a negative impact on socioeconomic development. This is the first report of the integration, expression and efficacy of a diagnostic candidate of lymphatic filariasis in plants.Key MessageTransgenic tobacco plants with WbSXP-1, a filarial diagnostic candidate, were developed. The plant-produced protein showed immunoreactivity on par with the E. coli product.

Wuchereria bancrofti infection in rural tropical guinea savannah communities: Rapid epidemiological assessment using immunochromatographic card test and prevalence of hydrocoele

Lymphatic filariasis (LF) caused by the nematode Wuchereria bancrofti is a major public health concern in endemic communities worldwide. Among tropical diseases it is second to malaria in terms of disability adjusted life years. The Nigerian LF elimination programme has been slated for 2015. Currently, there is paucity of published data on the problem in rural Ebonyi State. This survey was conducted in six rural communities of southwestern Ebonyi State to assess its prevalence among the population and provide baseline data for incorporation into the national LF elimination programme. Immunochromatographic card test (ICT) for detecting circulating filarial antigen (CFA) using whole blood and overt clinical manifestations (lymphoedema and hydrocoele) were used as epidemiological tools. All the studied communities were endemic for active bancroftian filariasis. Of the 600 randomly selected subjects aged ≥10 years, an overall prevalence of 23.50% was established (range, 17.00 - 30.00%). Overall, the antigenaemic prevalence was similar; there was a trend of slightly higher prevalence in males (24.34%) than females (22.39%). The between-gender prevalence difference was not statistically significant (χ² = 8.16, df = 1, p = 0.05) based on CFA positivity. Antigenaemia prevalence was age-dependent, increased exponentially and peaked at 20.57% in subjects in the 40-49 years age category. Lymphoedema and hydrocoele attributable to W. bancrofti were observed in 4.05% of subjects examined. Generally, hydrocoele was observed in 1.69% males, whereas lymphoedema was presented by 2.36% (1.35% females; 1.01% males) of studied population. None of the male subjects had both the two clinical features. Results of this study showed that W. bancrofti infection is widespread in southwestern Ebonyi State, Nigeria, and is a major health issue. There is a need for mass mobilization, mass education and community involvement in sustained intervention programme toward lymphatic filariasis elimination.

Point-of-care quantification of blood-borne filarial parasites with a mobile phone microscope

Parasitic helminths cause debilitating diseases that affect millions of people in primarily low-resource settings. Efforts to eliminate onchocerciasis and lymphatic filariasis in Central Africa through mass drug administration have been suspended because of ivermectin-associated serious adverse events, including death, in patients infected with the filarial parasite Loa loa. To safely administer ivermectin for onchocerciasis or lymphatic filariasis in regions co-endemic with L. loa, a strategy termed "test and (not) treat" has been proposed whereby those with high levels of L. loa microfilariae (>30,000/ml) that put them at risk for life-threatening serious adverse events are identified and excluded from mass drug administration. To enable this, we developed a mobile phone-based video microscope that automatically quantifies L. loa microfilariae in whole blood loaded directly into a small glass capillary from a fingerprick without the need for conventional sample preparation or staining. This point-of-care device automatically captures and analyzes videos of microfilarial motion in whole blood using motorized sample scanning and onboard motion detection, minimizing input from health care workers and providing a quantification of microfilariae per milliliter of whole blood in under 2 min. To validate performance and usability of the mobile phone microscope, we tested 33 potentially Loa-infected patients in Cameroon and confirmed that automated counts correlated with manual thick smear counts (94% specificity; 100% sensitivity). Use of this technology to exclude patients from ivermectin-based treatment at the point of care in Loa-endemic regions would allow resumption/expansion of mass drug administration programs for onchocerciasis and lymphatic filariasis in Central Africa.

Molecular epidemiology, phylogeny and evolution of the filarial nematode Wuchereria bancrofti

Wuchereria bancrofti (Wb) is the most widely distributed of the three nematodes known to cause lymphatic filariasis (LF), the other two being Brugia malayi and Brugia timori. Current tools available to monitor LF are limited to diagnostic tests targeting DNA repeats, filarial antigens, and anti-filarial antibodies. While these tools are useful for detection and surveillance, elimination programs have yet to take full advantage of molecular typing for inferring infection history, strain fingerprinting, and evolution. To date, molecular typing approaches have included whole mitochondrial genomes, genotyping, targeted sequencing, and random amplified polymorphic DNA (RAPDs). These studies have revealed much about Wb biology. For example, in one study in Papua New Guinea researchers identified 5 major strains that were widespread and many minor strains some of which exhibit geographic stratification. Genome data, while rare, has been utilized to reconstruct evolutionary relationships among taxa of the Onchocercidae (the clade of filarial nematodes) and identify gene synteny. Their phylogeny reveals that speciation from the common ancestor of both B. malayi and Wb occurred around 5-6 millions years ago with shared ancestry to other filarial nematodes as recent as 15 million years ago. These discoveries hold promise for gene discovery and identifying drug targets in species that are more amenable to in vivo experiments. Continued technological developments in whole genome sequencing and data analysis will likely replace many other forms of molecular typing, multiplying the amount of data available on population structure, genetic diversity, and phylogenetics. Once widely available, the addition of population genetic data from genomic studies should hasten the elimination of LF parasites like Wb. Infectious disease control programs have benefited greatly from population genetics data and recently from population genomics data. However, while there is currently a surplus of data for diseases like malaria and HIV, there is a scarcity of this data for filarial nematodes. With the falling cost of genome sequencing, research on filarial nematodes could benefit from the addition of population genetics statistics and phylogenetics especially in dealing with elimination programs. A comprehensive review focusing on population genetics of filarial nematode does not yet exist. Here our goal is to provide a current overview of the molecular epidemiology of W. bancrofti (Wb) the primary causative agent of LF. We begin by reviewing studies utilizing molecular typing techniques with specific focus on genomic and population datasets. Next, we used whole mitochondrial genome data to construct a phylogeny and examine the evolutionary history of the Onchocercidae. Then, we provide a perspective to aid in understanding how population genetic techniques translate to modern epidemiology. Finally, we introduce the concept of genomic epidemiology and provide some examples that will aid in future studies of Wb.

Hydrocele fluid: can it be used for immunodiagnosis of lymphatic filariasis?

BACKGROUND & OBJECTIVES

Diagnosis of lymphatic filariasis using serum has been established but the utility of hydrocele fluid for the purpose is not exactly known. Since, hydrocele is a chronic form of the disease manifestation in a variety of situations and often poses difficulty in diagnosing its origin, we have evaluated the usefulness usage of hydrocele fluid for diagnosis of filarial origin of hydrocele in this study.

METHODS

Paired samples of serum and hydrocele fluid from 51 individuals with hydrocele, living in an endemic area of Wuchereria bancrofti were assessed. Circulating filarial antigen, filarial specific antibody and cytokine assay were performed in both serum and hydrocele fluid of patients.

RESULTS

Og4C3 assay detected circulating filarial antigen (CFA) in serum and corresponding hydrocele fluids. The level of IgG, IFN-γ and IL-10 were found to be high in CFA-negative, while IgM and IgE were high in CFApositive hydrocele fluid and serum samples associated with hydrocele. On the other hand neither CFA-positive nor CFA-negative hydrocele fluid and serum samples associated with hydrocele showed any difference in IgG4 level.

INTERPRETATION & CONCLUSION

This study showed that the filaria related antigens and antibodies found in serum can be detected with equal sensitivity in hydrocele fluid. Therefore, it can be used as an alternative to serum for immunodiagnosis of filariasis, and help monitoring the filarisis elimination programme.

Testicular swelling due to lymphatic filariasis after brief travel to Haiti

After 6 months of a trip to Haiti, a 25-year-old healthy man presented with a 6-week history of a very slow progressive intermittent bilateral testicular pain and swelling. The biopsies in both testicles revealed the presence of a dead filarial parasite. Polymerase chain reaction products of the DNA from the biopsy were shown to have a 100% identity to Wuchereria bancrofti. Despite being uncommon in travelers, this presentation of W. bancrofti highlights the possibility of acquiring W. bancrofti during short-term trips to highly endemic regions of the world (i.e., Haiti).

Final program evaluation methods and results of a National Lymphedema Management Program in Togo, West Africa

In order to eliminate Lymphatic Filariasis (LF) as a public health problem, the World Health Assembly recommends an approach which includes interruption of transmission of infection and the alleviation of morbidity. In 2000, the Togolese National Program to Eliminate Lymphatic Filariasis (PNELF) started the annual mass drug administrations and in 2007, the program added a morbidity component for the management of lymphedema. This manuscript describes the methods of an evaluation aimed at assessing the strengths and weaknesses of the Togolese National Lymphedema Morbidity Program. The evaluation was conducted through in-depth interviews with stakeholders at each programmatic level. Interviews focused on message dissemination, health provider training, patient self-care practices, social dynamics, and program impact. The evaluation demonstrated that the program strengths include the standardization and in-depth training of health staff, dissemination of the program's treatment message, a positive change in the community's perception of lymphedema, and successful patient recruitment and training in care techniques. The lessons learned from this evaluation helped to improve Togo's program, but may also provide guidance and strategies for other countries desiring to develop a morbidity program. The methods of program evaluation described in this paper can serve as a model for monitoring components of other decentralized national health programs in low resource settings.

Evaluation of the Og34C filter paper technique in lymphatic filariasis prevalence studies

Currently there are several tests which can be used for monitoring and evaluating lymphatic filariasis prevalence in mass drug administration (MDA) programs with the ICT as most commonly accepted field test. However, other techniques to determine circulating antigen are available that also could be suitable in these programs. Our aim was to determine the suitability of the Og4C3 filter paper technique to determine antigen prevalence for lymphatic filariasis. We compared multiple antigen methods during the course of baseline clinical prevalence studies in Papua, New Guinea in over 800 subjects. We found that the ICT and Og4C3 filter paper techniques and using blood from the ICT card in the Og4C3 ELISA were equivalent in performance and that the serum Og4C3 ELISA test detected significantly more antigenic individuals. In addition, we found that modification of the Og4C3 assay by removing the boiling step did not affect its performance. Our results indicate that the Og4C3 filter paper technique is suitable for use in elimination of transmission of lymphatic filariasis monitoring and evaluation programs, quality control of ICT testing could be accomplished by using blood from the ICT test card, and with appropriate logistics in place, venous sampling and testing by the serum Og4C3 ELISA is achievable in monitoring and evaluation and would better identify areas with low level antigenaemia prevalence and possible ongoing transmission.

Lymphedema in a 7-year-old boy infected with Wuchereria bancrofti in Sierra Leone: a case report

We present a case of congenital lymphedema in a 7-year-old boy in Sierra Leone with active filarial infection and penile edema. The genital edema with onset at 6 months of age may have been due to a congenital abnormality in lymphatic drainage. Other possible causes of childhood lymphedema, including Milroy's disease, are discussed.

Leprosy and lymphatic filariasis comorbidity: the case for an integrated functional limitation grading system

Worldwide, both lymphatic filariasis (LF) and leprosy are major causes of morbidity and functional limitation. Despite an abundance of data on the impairment caused by these infections in isolation, there is little data on disability in patients unfortunate enough to be affected by both infections. We present two cases of patients with LF and leprosy comorbidity. Both cases suffer from Grade 2 disability and chronic lymphedema in the same limb (left and right leg, respectively). These morbidities cause significant functional limitation in the patients' activities of daily living. Both LF and leprosy are endemic in India and their comorbid conditions contribute to functional limitation. However, there is still currently no integrated scale for assessment of interventions for functional limitation in these patients. Investigating and managing impairment and functional limitations individually is the least cost effective and sustainable strategy. Considering the similarities of caring for functional limitations in both diseases and assuming its efficacy, augmentation of LF care services with leprosy referral centres may be beneficial. Integrated approaches have been pilot tested at district level in states in India under the title 'Integrated Prevention of Deformity project' (IPoD). Further work is required to identify a reliable, holistic, functional impairment scoring system, which allows for comparison between diseases. This may help promote greater understanding of impairments and functional limitations these cause and allow effective monitoring and evaluation of all aspects, activities and stages of similar programmes.

Evaluation of Brugia malayi sheath protein (Shp-1) as a diagnostic antigen for human lymphatic filariasis

Lymphatic filariasis is the second leading cause of permanent long-term disability globally and control of this disease needs efficient diagnostic methods. In this study, abundantly expressing microfilarial sheath protein (Shp-1) from Brugia malayi was characterized as a filarial diagnostic candidate using samples from different clinical population. Monoclonal antibodies were developed against E. coli expressed recombinant Shp-1 in order to assess its efficiency in filarial antigen detection assay system. Endemic Normal (EN, n = 170), asymptomatic microfilaeremics (MF, n = 65), symptomatic chronic pathology (CP, n = 45) and non endemic normal (NEN, n = 10) sera were analyzed by antigen capture enzyme-linked immunosorbent assay. Of the 290 individuals, all MF individuals (both brugian and bancroftian) were positive in this assay followed by CP and EN. When compared with SXP-1 and Og4C3 antigen assays, all assays detected Wb MF correctly, Bm MF was detected by Shp-1 and SXP-1 assays, and only Shp-1 was able to detect EN (12%) and CP (29%). Results showed that this assay may be useful for monitoring prior to mass drug administration.

Development and Evaluation of a Rapid Flow-Through Immuno Filtration Test Using Recombinant Filarial Antigen for Diagnosis of Brugian and Bancroftian Filariasis

There is an imperative need to develop a rapid antibody test that can be used for diagnosis of clinical cases in travelers and expatriates, primary surveillance in areas of unknown endemicity, detection of early infection in childhood and for monitoring chemotherapeutic programs. A rapid-format, simple and qualitative flow through immuno filtration test has been developed for the identification of total IgG antibodies to recombinant filarial antigen WbSXP-1. This test system employs colloidal gold-protein A reagent as the antibody capture reagent. The sensitivity and specificity of the test was evaluated in a total of 1,230 serum samples. The sensitivity of the test was found to be 90.8% with brugian (n = 70) and 91.4% with bancroftian (n = 140) microfilaraemic subjects. The test showed minimum reactivity (4/10) with Loa loa microfilaria (MF) positive sera and no reactivity (0/20) with Onchocerca MF positive sera. This rapid diagnosis is found to be non-reactive with individuals having other parasitic diseases including schistosomiasis (n = 10), soil-transmitted helminthiases (n = 34) and protozoan infections (n = 33) indicating the potential of this test as a prospective method of diagnosis for both brugian and bancroftian lymphatic filariasis. Stability kinetics was studied at different temperatures and different time periods. The rapid flow-through immuno filtration test is advantageous since it can be stored at room temperature, is user friendly and is particularly applicable in the field as an initial screening method, for epidemiological monitoring of filarial infections in bancroftian and brugian endemic regions of the world.

Bancroftian filariasis in children and adolescents: clinical–pathological observations in 22 cases from an endemic area

In areas where bancroftian filariasis is endemic, the clinical manifestations of the disease, which are often very varied, appear most frequently during early adulthood or later. In consequence, very little attention, if any, has been given to the signs and symptoms of the disease in childhood. In an attempt to fill this gap, clinical and pathological observations were made, in Brazil, on 22 children (aged 2-15 years) who were infected with Wuchereria bancrofti. There was a predominance of lymph-node involvement. In all but three (14%) of the children (who had adult parasites in their intrascrotal lymphatic vessels), the adult worms were located in the afferent or efferent vessels of draining lymph nodes, predominantly in the inguinal region. None of the patients presented with distal lymphoedema, and the adenopathy was characterized by painless, localized, lymph-node enlargement, without signs of inflammation in the overlying skin. Histologically, the alterations in the lymphatic vessels and surrounding structures were similar to those described in adult patients, and depended essentially on adult-parasite viability. The localization of the adult worms in the paediatric cases was peculiar and distinct from that observed in adult patients, in whom the adult parasites are usually found in extra-nodal lymphatic vessels. In areas endemic for bancroftian filariasis, therefore, filarial infection should be considered as a possible cause of adenopathy. For the differential diagnosis of adenopathy in young patients from endemic areas, the authors recommend the use of ultrasound and other non-invasive diagnostic tools, as alternatives to excisional biopsies, which are often unnecessary in bancroftian filariasis.

Filariasis, with chyluria and nephrotic range proteinuria

28 yr female presented with (grade III) chyluria, with nephrotic range proteinuria and Ig M mesangial deposition in immunofluorescence, secondary to filariasis which was confirmed by serology and microfilaria in glomerulus,and successfully treated by Renal Pelvic instillation sclerotherapy with 0.2% povidine and medical treatment (Diethylcarbamazine). She was asymptomatic with follow up period of 19 months.

Laboratory and field evaluation of a new rapid test for detecting Wuchereria bancrofti antigen in human blood

Global Program to Eliminate Lymphatic Filariasis (GPELF) guidelines call for using filarial antigen testing to identify endemic areas that require mass drug administration (MDA) and for post-MDA surveillance. We compared a new filarial antigen test (the Alere Filariasis Test Strip) with the reference BinaxNOW Filariasis card test that has been used by the GPELF for more than 10 years. Laboratory testing of 227 archived serum or plasma samples showed that the two tests had similar high rates of sensitivity and specificity and > 99% agreement. However, the test strip detected 26.5% more people with filarial antigenemia (124/503 versus 98/503) and had better test result stability than the card test in a field study conducted in a filariasis-endemic area in Liberia. Based on its increased sensitivity and other practical advantages, we believe that the test strip represents a major step forward that will be welcomed by the GPELF and the filariasis research community.

A TaqMan-based multiplex real-time PCR assay for the simultaneous detection of Wuchereria bancrofti and Brugia malayi

With the Global Program for the Elimination of Lymphatic Filariasis continuing to make strides towards disease eradication, many locations endemic for the causative parasites of lymphatic filariasis are realizing a substantial decrease in levels of infection and rates of disease transmission. However, with measures of disease continuing to decline, the need for time-saving and economical molecular diagnostic assays capable of detecting low levels of parasite presence is increasing. This need is greatest in locations co-endemic for both Wuchereria bancrofti and Brugia parasites because testing for both causative agents individually results in significant increases in labor and reagent costs. Here we describe a multiplex, TaqMan-based, real-time PCR assay capable of simultaneously detecting W. bancrofti and Brugia malayi DNA extracted from human bloodspots or vector mosquito pools. With comparable sensitivity to established singleplex assays, this assay provides significant cost and labor savings for disease monitoring efforts in co-endemic locations.