Filaria Journal - Most accessed articles

Animated documentation of the filaria dance sign (FDS) in bancroftian filariasis

Sabine Mand — 2003-02-27T00:00:00Z

Background: Ultrasonography is able to detect adult Wuchereria bancrofti worms in scrotal lymphatic vessels of infected men on account of the characteristic pattern of adult worm movements, known as the filarial dance sign. Furthermore, the technique is able to delineate associated pathology, such as hydrocoele and lymphoedema, which can be diagnosed in early stages. Ultrasonography is also useful in the assessment of macrofilaricidal effects of antifilarial medication.The purpose of this study was to evaluate the usefulness of scrotal ultrasonography, in combination with a new method of digital documentation, in men infected with Wuchereria bancrofti. Methods: Ultrasonography of the scrotal areas was carried out in 33 male patients from an endemic area in Ghana using a hand-carried ultrasound system and a linear array transducer at 7.5 MHz. Wuchereria bancrofti infection was also assessed by quantification of night blood microfilaraemia and semi-quantitative detection of circulating filarial antigen. Ultrasound findings were documented by print outs and by Digital Video sequences directly exported from the ultrasound machine which were edited in Final Cut Pro 3® and exported, using QuickTime® Pro, as MPEG-1 video. Results: Worm nests, i.e. dilated lymphatic vessels with the characteristic movement patterns of worms, were found in all patients, and typical examples of larger as well as smaller nests are presented through MPEG-1 video in b- and m-modes as well as Colour Doppler and Pulse Wave Doppler images. Conclusion: In this study, the filarial dance sign is being made available on the Internet to readers through MPEG-1 video. This method allows for demonstration of movement patterns rather than static images. In addition, the pathologic ultrasonographic signs of filariasis can be rapidly relayed over great distances and may be helpful to other investigators or clinicians in the diagnosis of patients infected with Wuchereria bancrofti.

Morbidity management in the Global Programme to Eliminate Lymphatic Filariasis: a review of the scientific literature

David Addiss — 2007-02-15T00:00:00Z

The Global Programme to Eliminate Lymphatic Filariasis (GPELF) has two major goals: to interrupt transmission of the parasite and to provide care for those who suffer the devastating clinical manifestations of the disease (morbidity control). This latter goal addresses three filariasis-related conditions: acute inflammatory episodes; lymphoedema; and hydrocele. Research during the last decade has confirmed the importance of bacteria as a cause of acute inflammatory episodes in filariasis-endemic areas, known as acute dermatolymphangioadenitis (ADLA). Current lymphoedema management strategies are based on the central role of ADLA as a trigger for lymphoedema progression. Simple intervention packages are in use that have resulted in dramatic reductions in ADLA rates, a lower prevalence of chronic inflammatory cells in the dermis and subdermis, and improvement in quality of life. During the past decade, the socioeconomic impact of ADLA and lymphoedema in filariasis-endemic areas has received increasing attention. Numerous operational research questions remain to be answered regarding how best to optimize, scale up, monitor, and evaluate lymphoedema management programmes. Of the clinical manifestations targeted by the GPELF, hydrocele has been the focus of the least attention. Basic information is lacking on the effectiveness and complications of hydrocele surgery and risk of post-operative hydrocele recurrence in filariasis-endemic areas. Data on the impact of mass administration of antifilarial drugs on filarial morbidity are inconsistent. Several studies report reductions in acute inflammatory episodes, lymphoedema, and/or hydrocele following mass drug administration, but other studies report no such association. Assessing the public health impact of mass treatment with antifilarial drugs is important for programme advocacy and morbidity control strategies. Thus, although our knowledge of filariasis-related morbidity and its treatment has expanded in recent years, much work remains to be done to address the needs of more than 40 million persons who suffer worldwide from these conditions.

Contributions of different mosquito species to the transmission of lymphatic filariasis in central Nigeria: Implications for monitoring infection by PCR in mosquito pools

Audrey Lenhart — 2007-11-29T00:00:00Z

Background: Members of the Anopheles gambiae complex are important vectors of lymphatic filariasis (LF) in sub-Saharan Africa, but little is known about the relative contributions of all mosquitoes to lymphatic filariasis transmission in this area. Methods: Over a 28 month period, mosquitoes were collected from 13 villages in Plateau and Nasarawa states in central Nigeria and dissected to determine W. bancrofti infection status. Wings and legs from a subset of the mosquitoes visually identified as A. gambiae s.l. were identified by PCR as either A. gambiae s.s. or A. arabiensis. Results: A. gambiae s.s peaked in abundance during the rainy season while A. arabiensis predominated during drier parts of the year. Both species were found equally likely to be infected with the developing stages (L1-L3) of W. bancrofti (9.2% and 11.1%, respectively). Fewer A. funestus (1.1%, p < 0.001) were infected than A. gambiae s.l. Conclusion: Understanding the relative contributions of morphologically indistinguishable species to LF transmission is essential if PCR is to be performed on mosquito pools. In the study area, the use of mosquito pools composed of A. gambiae sibling species would not be problematic, as both A. gambiae s.s. and A. arabiensis contribute equally to LF transmission.

The geographical distribution of lymphatic filariasis infection in Malawi

Bagrey Ngwira — 2007-11-29T00:00:00Z

Mapping distribution of lymphatic filariasis (LF) is a prerequisite for planning national elimination programmes. Results from a nation wide mapping survey for lymphatic filariasis (LF) in Malawi are presented. Thirty-five villages were sampled from 23 districts excluding three districts (Karonga, Chikwawa and Nsanje) that had already been mapped and Likoma, an Island, where access was not possible in the time frame of the survey. Antigenaemia prevalence [based on immunochromatographic card tests (ICT)] ranged from 0% to 35.9%. Villages from the western side of the country and distant from the lake tended to be of lower prevalence. The exception was a village in Mchinji district on the Malawi-Zambia border where a prevalence of 18.2% was found. In contrast villages from lake shore districts [Salima, Mangochi, Balaka and Ntcheu (Bwanje valley)] and Phalombe had prevalences of over 20%.A national map is developed which incorporates data from surveys in Karonga, Chikwawa and Nsanje districts, carried out in 2000. There is a marked decline in prevalence with increasing altitude. Further analysis revealed a strong negative correlation (R2 = 0.7 p < 0.001) between altitude and prevalence. These results suggest that the lake shore, Phalombe plain and the lower Shire valley will be priority areas for the Malawi LF elimination programme. Implications of these findings as regards implementing a national LF elimination programme in Malawi are discussed.

The Elimination of Lymphatic Filariasis: A Strategy for Poverty Alleviation and Sustainable Development – Perspectives from the Philippines

Jamie Galvez Tan — 2003-07-21T00:00:00Z

Background: Within the Philippines areas endemic for lymphatic filariasis are in regions with the highest incidence of poverty. Out of a total of 79 provinces, 39 have a higher poverty incidence than the national average and 30 of these 39 provinces are endemic for lymphatic filariasis.DiscussionRecognizing that provinces endemic for lymphatic filariasis (LF) are also the poorest provinces, the elimination of lymphatic filariasis in these areas presents significant opportunities to reduce poverty and inequalities in health. The implementation of an effective national programme for the elimination of lymphatic filariasis will provide means for sustainable development at national, local and community levels.SummaryThe elimination of lymphatic filariasis as a public health problem is a 20-year strategic plan for the world community, with the vision of all endemic communities free of transmission of lymphatic filariasis by 2020 and with the commitment to ensure the delivery of quality technologies and human services to eliminate lymphatic filariasis worldwide through a multi-stakeholder global alliance of all endemic countries. This global goal of elimination of lymphatic filariasis is a significant opportunity for partnerships – a world with less poverty through sustainable development and free from the scourge of lymphatic filariasis.

Monitoring lymphatic filariasis interventions: Adult mosquito sampling, and improved PCR - based pool screening method for Wuchereria bancrofti infection in Anopheles mosquitoes

Daniel Boakye — 2007-11-29T00:00:00Z

Background: Monitoring and evaluation are essential to the successful implementation of mass drug administration programmes for LF elimination. Monitoring transmission when it is low requires both large numbers of mosquito vectors and sensitive methods for detecting Wuchereria bancrofti infections in them. PCR-based methods are preferred over classical dissections but the best protocol so far achieved detection of one L3 Wuchereria bancrofti larva in a pool of 35–50 Anopheles mosquitoes. It also lacks consistency and remains still a costly tool. Hence we decided to improve upon this to achieve detection in a pool of 100 or more by enhancing the quality of the template DNA. Prior to this we also evaluated three vector sampling methods in the context of numbers for monitoring. Methods: Human landing, pyrethrium spray and light traps catches were conducted concurrently at sites in an LF endemic district in Ghana and the numbers obtained compared. Two DNA extraction methods; Bender buffer and phenol/chloroform purification, and DNAeasy Tissue kit (Quaigen Inc) were used on pools of 25, 50, 75 100 and 150 mosquitoes each seeded with one L3 or its quivalent amount of DNA. Then another set of extracted DNA by the two methods was subjected to Dynal bead purification method (using capture oligonucleotide primers). These were used as template DNA in PCR to amplify W. bancrofti sequences. The best PCR result was then evaluated in the field at five sites by comparing its results (infections per 1000 mosquitoes) with that of dissection of roughly equal samples sizes. Results: The largest numbers of mosquitoes were obtained with the human landing catches at all the sites sampled. Although PCR detection of one L3 in pools of 25, 50 and 75 mosquitoes was consistent irrespective of the extraction method, that of one L3 in 100 was only achieved with the kit-extracted DNA/Dynal bead purification method. Infections were found at only two sites by both dissection and pool-screening being 14.3 and 19 versus 13.4 and 20.1 per 1000 Anopheles mosquitoes respectively, which were not statistically significantDiscussion and conclusionHLC still remains the best option for sampling for the large numbers of mosquitoes required for monitoring transmission during MDA programmes, when vector population densities are high and classical indices of transmission are required. One – in – 100 detection is an improvement on previous PCR pool-screening methods, which in our opinion was a result of the introduction of the extra step of parasite DNA capture using Dynal/beads. As pool sizes increase the insects DNA will swamp parasite DNA making the latter less available for an efficient PCR, therefore we propose either additional steps of parasite DNA capture or real-time PCR to improve further the pool screening method. The study also attests also to the applicability of Katholi et al's algorithm developed for determining onchocerciasis prevalence in LF studies.

Lymphatic Filariasis (Elephantiasis) Elimination: A public health success and development opportunity

David Molyneux — 2003-09-09T00:00:00Z

Background: The Global Programme to Eliminate Lymphatic Filariasis, launched following World Health Assembly Resolution 50.29 (WHA 50.29), has been facilitated in its progress by new research findings, drug donations, the availability of diagnostic tools, disability management strategies to help those already suffering and the development of partnerships. The strategy recommended by the World Health Organization of annual treatment with a two-drug combination has proved safe.DiscussionUsing different approaches in several countries the elimination of lymphatic filariasis (LF) has been demonstrated to be feasible during earlier decades. These successes have been largely overlooked. However, the programme progress since 2000 has been remarkable – upscaling rapidly from 2 million treatments in 2000 to approximately 60 million in 2002. Around 34 countries had active programmes at the end of 2002. It is anticipated that there will be further expansion – but this will be dependent on additional resources becoming available. The programme also provides significant opportunities for other disease control programmes to deliver public health benefits on a large scale. Few public health programmes have upscaled so rapidly and so cost-effectively (<$0.03/treatment in some Asian settings) – one country treating 9–10 million people in a day (Sri Lanka). The LF programme is arguably the most effective pro-poor public health programme currently operating which is based on country commitment and partnerships supported by a global programme and alliance. Tables are provided to summarize programme characteristics, the benefits of LF elimination, opportunities for integration with other programmes and relevance to the Millennium Development Goals.SummaryLymphatic filariasis elimination is an "easy-to-do" inexpensive health intervention that provides considerable "beyond filariasis" benefits, exemplifies partnership and is easily evaluated. The success in global health action documented in this paper requires and deserves further support to bring to fruition elimination of lymphatic filariasis as a public health problem and health benefits to poor people. A future free of lymphatic filariasis will reduce poverty and bring better health to poor people, prevent disability, strengthen health systems and build partnerships.

Impact of ivermectin on onchocerciasis transmission: assessing the empirical evidence that repeated ivermectin mass treatments may lead to elimination/eradication in West-Africa

Gerard Borsboom — 2003-03-24T00:00:00Z

Background: The Onchocerciasis Control Program (OCP) in West Africa has been closed down at the end of 2002. All subsequent control will be transferred to the participating countries and will almost entirely be based on periodic mass treatment with ivermectin. This makes the question whether elimination of infection or eradication of onchocerciasis can be achieved using this strategy of critical importance. This study was undertaken to explore this issue. Methods: An empirical approach was adopted in which a comprehensive analysis was undertaken of available data on the impact of more than a decade of ivermectin treatment on onchocerciasis infection and transmission. Relevant entomological and epidemiological data from 14 river basins in the OCP and one basin in Cameroon were reviewed. Areas were distinguished by frequency of treatment (6-monthly or annually), endemicity level and additional control measures such as vector control. Assessment of results were in terms of epidemiological and entomological parameters, and as a measure of inputs, therapeutic and geographical coverage rates were used. Results: In all of the river basins studied, ivermectin treatment sharply reduced prevalence and intensity of infection. Significant transmission, however, is still ongoing in some basins after 10–12 years of ivermectin treatment. In other basins, transmission may have been interrupted, but this needs to be confirmed by in-depth evaluations. In one mesoendemic basin, where 20 rounds of four-monthly treatment reduced prevalence of infection to levels as low as 2–3%, there was significant recrudescence of infection within a few years after interruption of treatment. Conclusions: Ivermectin treatment has been very successful in eliminating onchocerciasis as a public health problem. However, the results presented in this paper make it almost certain that repeated ivermectin mass treatment will not lead to the elimination of transmission of onchocerciasis from West Africa. Data on 6-monthly treatments are not sufficient to draw definitive conclusions.

Tolerability and efficacy of single dose albendazole, diethylcarbamazine citrate (DEC) or co-administration of albendazole with DEC in the clearance of Wuchereria bancrofti in asymptomatic microfilaraemic volunteers in Pondicherry, South India: a hospital-based study

Subhada Pani — 2002-10-10T00:00:00Z

Background: The tolerability and efficacy of single dose albendazole (400 mg), diethylcarbamazine citrate (DEC) (6 mg/kg bodyweight) or co-administration of albendazole (400 mg) + DEC (6 mg/kg bodyweight) was studied in 54 asymptomatic Wuchereria bancrofti microfilaraemic volunteers in a double blind hospital-based clinical study. Results: There was no significant difference in the overall incidence of adverse reactions between the three drug groups [42.1% (albendazole), 52.9% (DEC) and 61.1% (albendazole + DEC); P > 0.05]. The mean score of adverse reaction intensity did not differ significantly between the DEC and albendazole + DEC groups. However, the values in these two groups were significantly higher compared to that of albendazole alone [1.8 ± 3.0 (albendazole) vs. 5.6 ± 7.1 (DEC), 6.7 ± 6.6 (albendazole + DEC); P < 0.05]. By day 360 post-therapy there was no significant difference between the three drug groups in relation to the clearance of microfilaria [26.3% (albendazole), 17.6% (DEC), 27.8% (albendazole + DEC)], reduction in geometric mean parasite density [94.7% (albendazole), 89.5% (DEC), 95.4% (albendazole + DEC)] or reduction in filarial antigenaemia [83% (albendazole), 87% (DEC), 75% (albendazole + DEC)]. Furthermore, there was a significant decrease in mean geometric parasite density (P < 0.05) as well as antigenaemia optical density values (P < 0.01) between pre-therapy levels and day 360 post-therapy in all three groups. Conclusions: This study has shown that single dose albendazole (400 mg) has similar efficacy in the clearance of microfilaria as that of DEC or the co-administration of the two drugs. The results strengthen the rationale of using albendazole for mass annual single dose administration for the control of transmission of lymphatic filariasis.

Random Amplified Polymorphic DNA (RAPD) for differentiation between Thai and Myanmar strains of Wuchereria bancrofti

Surang Nuchprayoon — 2007-07-30T00:00:00Z

Background: Lymphatic filariasis (LF) is a mosquito-borne disease caused by mosquito-transmitted filarial nematodes, including Wuchereria bancrofti and Brugia malayi. The Lymphatic Filariasis Elimination Program in Thailand has reduced the prevalence of nocturnally subperiodic W. bancrofti (Thai strain), mainly transmitted by the Ochlerotatus (Aedes) niveus group in Thailand to 0.57/100,000 population. However, it is estimated that more than one million Myanmar migrants with high prevalence of bancroftian filariasis have settled in the large urban cities of Thailand. These infected migrants carry the nocturnally periodic W. bancrofti (Myanmar strain) which has Culex quinquefasciatus as the main mosquito vector. Although transmissions of the Myanmar strain of W. bancrofti by the Thai Cx. quinquefasciatus has never been reported, previous study showed that Cx. quinquefasciatus could nurture the Myanmar strain of W. bancrofti to the infective stage. Thus, the potential now exists for a re-emergence of bancroftian filariasis in Thailand. The present study was undertaken in an attempt to differentiate between the Thai and Myanmar strains of W. bancrofti. Methods: The microfilarial periodicity of Thai and the Myanmar strains of W. bancrofti were determined. Comparative morphology and morphometry of microfilariae and a study of random amplified polymorphic DNA (RAPD) was performed. The Nei's genetic distance was calculated, and a phylogenetic tree was constructed using the Unweighted Pair Group Method with Arithmetic mean (UPGMA). Results: The Thai strain of W. bancrofti was nocturnally subperiodic, and the Myanmar strain of W. bancrofti was nocturnally periodic. The body length, cephalic space length, and cephalic space width of the Thai strain of W. bancrofti were significantly larger than those of the Myanmar strain of W. bancrofti (p < 0.05). However, an overlapping mean of these parameters made it impractical for field application. RAPD-PCR profiles showed specific bands characteristic for the Myanmar strain of W. bancrofti. The phylogenetic tree indicated two genetically distinct clusters of the Thai and Myanmar strains of W. bancrofti.DiscussionThis study was the first report on the genetic polymorphism of the Thai and Myanmar strains of W. bancrofti. Differentiation between the Thai and Myanmar strains of W. bancrofti could not rely on morphological criteria alone. However, RAPD profiles revealed a significant diversity between the two strains. The RAPD-PCR technique was suitable for differentiating Thai and Myanmar strains of W. bancrofti. The RAPD marker could be used for epidemiological assessment of the Myanmar strains of W. bancrofti in Thailand.