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PubMed2004

Mathematical modelling and the control of lymphatic filariasis.

The current global initiative to eliminate lymphatic filariasis represents one of the largest mass drug administration programmes ever conceived for the control of a parasitic disease. Yet, it is still not known whether the WHO-recommended primary strategy of applying annual single-dose mass chemotherapy with a combination of two drugs for 4-6 years will effectively break parasite transmission from all endemic communities. Here we review recent work on the development and application of a deterministic mathematical model of filariasis transmission, to show how models of parasite transmission will help resolve the key currently debated questions regarding the ultimate effectiveness of the global strategy to control filariasis. These critical questions include the required duration of mass treatment in different endemic areas, the optimal drug coverage required to meet control targets within prescribed timeframes, the impact and importance of adding vector control to mass chemotherapy regimens, and the likelihood of the development of drug resistance by treated worm populations. The results demonstrate the vital role that integrating these models into control programming can have in providing effective decision-support frameworks for undertaking the optimal design and monitoring of regional and global filariasis-control programmes. Operationally, the models show that the effectiveness of the strategy to achieve filariasis control will be determined by successfully addressing two key factors: the need to maintain high community treatment coverages, and the need to include vector control measures especially in areas of high endemicity.

Animals↗
PubMed1996

Re-assessing the global prevalence and distribution of lymphatic filariasis.

This paper estimates the global burden of lymphatic filariasis based on a review of the published literature on infection and disease surveys. A method for aggregating and projecting prevalence data from individual studies to national, regional and global levels, which also facilitates the estimation of gender and age-specific burdens, is presented. The method weights in favour of the larger, and hence presumbably more reliable, studies and relies on estimated empirical relationships between gender, age, infection and disease in order to correct studies with incomplete data. The results presented here suggest that although the overall prevalence of filariasis cases is 2.0% globally (approximately totalling 119 million cases), the disease continues to be of considerable local importance, particularly in India and Sub-Saharan Africa. Estimates by age and gender clearly show that, unlike other helminth infections, filariasis is mainly a disease of the adult and older age-classes and appears to be more prevalent in males. This work suggests that the derivation of more accurate estimates of the burden of filariasis will require a better understanding of both the epidemiology and the spatial aspects of infection and disease. It also suggests that filariasis is preventable based on a geographically targeted strategy for control.

Age Factors↗
PubMed2000

Development of rapid assessment procedures for the delimitation of lymphatic filariasis-endemic areas.

Lymphatic filariasis caused by Wuchereria bancrofti is a major public health problem in 73 tropical and subtropical countries including India. Delimitation of endemic areas is essential to plan control operations. The current method of night blood survey (NBS) for delimitation is cumbersome, time-consuming and expensive. Therefore, there is a need to develop assessment procedures which can rapidly delimit endemic areas. For this purpose we evaluated three procedures: direct interviewing of key informants using structured questionnaires, an indirect method of a self-administered questionnaires to key informants and physical examination by health workers for the presence of chronic filarial disease. Thirty rural communities in a filariasis-endemic region in Cuddalore district in Tamil Nadu State in southern India constituted the study population. The determination of filariasis endemicity in the village communities assessed by the above procedures was compared in terms of rapidity, specificity, sensitivity and cost with the microfilaria rate and disease rate obtained by night blood sample survey and clinical examination by physicians. Prevalence score, control preference score and weighted mean number of cases with filarial disease per village were calculated using the key informant questionnaire techniques. While the prevalence and control preference score showed low sensitivity and moderate specificity, weighted mean number of cases showed high sensitivity and moderate specificity in identifying endemic villages. The prevalence of disease as determined by the physical examination of a sample population by health workers was highly sensitive in identifying communities endemic for filariasis. The degree of association between the disease rates estimated by physician and trained health workers was significant (r = 0.56; P < 0.05). These observations suggest that the weighted mean number of cases per village obtained through key informant techniques may be considered at a primary level to crudely identify endemic areas, followed by physical examination by health workers for filariasis, since it is relatively cheap and rapid.

Adolescent↗
PubMed2000

The impact of lymphatic filariasis on labour inputs in southern India: results of a multi-site study.

A multi-site study was undertaken, in the rural areas of three districts in Tamil Nadu state, in southern India, to examine the impact of acute and chronic forms of lymphatic filariasis, caused by infection with Wuchereria bancrofti, on labour inputs. More than half of the acute episodes of adenolymphangitis (ADL) observed in the study communities caused total disability. The mean (S.D.) time that each ADL case was able to allocate to economic activity each day during these acute episodes was much less than seen in the controls matched for sex, age and occupation [0.97 (2.36) v. 4.48 (3.82) h; P < 0.01]. The acute disease also severely affected domestic activities, with female ADL cases spending only 1.54 (2.12) h/day on domestic activity, compared with 4.18 (2.61) h by controls. The subjects with chronic filariasis also spent significantly less time in economic activity than their matched controls [4.40 (3.79) v. 5.13 (3.83) h/day; P < 0.01). Although the acute episodes have a dramatic effect on the productivity of the affected individual, the labour loss caused by chronic disease is more serious, as the manifestations of chronic disease mostly affect the most productive age-groups, persist for life and are mostly irreversible. The adverse impact of acute and chronic filariasis was observed in males and females, farmers and non-farmers and during the rainy, winter and summer seasons. It is estimated that about 3.8% of the potential labour inputs of the men and 0.77% of those of the women were lost because of lymphatic filariasis. In addition to this loss, the total economic burden of the disease must include the costs of treatment and other health care and of the resources spent on control programmes. Estimates of the disease burden are likely to be useful in determining the costs and benefits of the recently launched campaign to eliminate lymphatic filariasis.

Acute Disease↗
PubMed2000

Mapping of lymphatic filariasis in India.

The derivation of detailed epidemiological maps, at the relevant spatial resolution, is being increasingly recognized as vital to the effective design and implementation of successful programmes for the control of parasites and their vectors. Geographical information systems (GIS) and a recently complied database on the distribution of lymphatic filariasis in India have now been used to develop the first maps at district-level (i.e. the level at which control against this parasite will be enacted in India) of filariasis endemicity in this country. The derived maps indicate both the substantial extent as well as the marked variability in the geographical distribution of this disease in India. The causative infection and/or the symptomatic disease were detected in most (257) of the 289 districts surveyed up to 1995. Currently there may be up to 27.09 million microfilaraemics, 20.83 million cases of symptomatic filariasis, and about 429.32 million individuals potentially at risk of infection in the country. Probability mapping, based on data quantiles, clearly indicates that the risk of filarial infection in India is not constant throughout the country but exhibits strong regional trends. Filariasis in general may be a particular problem of the eastern half of the country. The results indicate the potentially vital role that GIS-based mapping approaches can play in the development of filariasis-control campaigns in India and elsewhere.

Elephantiasis, Filarial↗
PubMed2001

Current status and future prospects of the Global Lymphatic Filariasis Programme.

Lymphatic filariasis is recognized as one of the world's most disabling diseases. Adult lymphatic filarial nematodes live for several years; they infest the lymphatic and blood systems, and are transmitted via mosquito vectors. Acute and chronic disease can develop, manifesting as acute inflammation, hydrocoele, lymphoedema and elephantiasis. The development of a global programme for the elimination of lymphatic filariasis (focusing on disease caused by Wuchereria bancrofti) followed a resolution by the World Health Assembly in 1997 that endemic countries should develop programmes to eliminate lymphatic filariasis as a public health problem. This developed from an earlier recommendation by the International Task Force for Disease Eradication in 1993 that lymphatic filariasis was one of six diseases that could, in theory, be eradicated. Herein we review the current status and future prospects of the Global Lymphatic Filariasis Programme, which was launched in 2000.

Animals↗
PubMed2006

A campaign of "communication for behavioural impact" to improve mass drug administrations against lymphatic filariasis: structure, implementation and impact on people's knowledge and treatment coverage.

In the mass drug administrations (MDA) that form the principal strategy of the Global Programme to Eliminate Lymphatic Filariasis, treatment coverages of at least 65%-80% will be needed if the programme is to be successful. In the Indian state of Tamil Nadu, where treatment coverages were typically <65%, a comprehensive strategy of advocacy and communication, called the "communication for behavioural impact" (COMBI) campaign, has been developed and implemented, in an attempt to improve treatment coverage. This strategy combined advocacy, aimed at state-, district- and village-level administrations, with communication activities targeted at individual communities. The main aim was to alter the behaviour of many of those included in the rounds of MDA, so that they would be more likely to accept and consume the diethylcarbamazine tablets offered to them. The COMBI campaign had two variants, COMBI(+) and the more intensive COMBI(+ +), each of which has been implemented in six districts. Both the variants included the "personal selling" of treatment, via door-to-door visiting by a total of 113,500 filaria-prevention assistants. These assistants were able to visit 34%-49% of the households in each target community. In the COMBI(+ +) districts, up to 44% and 38% of households received information on lymphatic filariasis and its elimination via television commercials and posters, respectively. Overall, 78% of the villages in the COMBI(+ +) districts and 33% of those in the COMBI(+) districts were considered to have had good exposure to the communication campaign. At the end of this campaign about 30% more people (than pre-campaign) believed that lymphatic filariasis could be eliminated and many of those targeted considered lymphatic filariasis to be a dreadful disease, knew that a particular day had been designated "Filaria Day", and thought that the tablets offered in MDA should be consumed to prevent or eliminate the disease. Apparently as the result of the COMBI campaign, drug consumption increased, from 33% of those living in endemic communities, to 37% in the COMBI(+) districts and to 49% in the COMBI(+ +). Coverages as high as 65%-73% were recorded among those who had had the maximum exposure to the communication campaign. These results indicate that the COMBI campaign favourably changed the perception and behaviour of the people towards the elimination of lymphatic filariasis. The costs of the COMBI(+) and COMBI(+ +) strategies were only U.S.$0.002 and U.S.$0.009 per capita, respectively.

Attitude to Health↗
PubMed2006

Delimitation of lymphatic filariasis transmission risk areas: a geo-environmental approach.

BACKGROUND: The Global Programme to Eliminate Lymphatic Filariasis (GPELF) depends upon Mass Drug Administration (MDA) to interrupt transmission. Therefore, delimitation of transmission risk areas is an important step, and hence we attempted to define a geo-environmental risk model (GERM) for determining the areas of potential transmission of lymphatic filariasis. METHODS: A range of geo-environmental variables has been selected, and customized on GIS platform to develop GERM for identifying the areas of filariasis transmission in terms of "risk" and "non-risk". The model was validated through a 'ground truth study' following standard procedure using GIS tools for sampling and Immuno-chromotographic Test (ICT) for screening the individuals. RESULTS: A map for filariasis transmission was created and stratified into different spatial entities, "risk' and "non-risk", depending on Filariasis Transmission Risk Index (FTRI). The model estimation corroborated well with the ground (observed) data. CONCLUSION: The geo-environmental risk model developed on GIS platform is useful for spatial delimitation purpose on a macro scale.

Journal Article↗
PubMed1987

Parasite antigens in sera and urine of patients with bancroftian and brugian filariasis detected by sandwich ELISA with monoclonal antibodies.

We developed a sandwich enzyme-linked immunosorbent assay to detect circulating parasite antigens in human lymphatic filariasis. The assay utilizes a polyclonal rabbit antifilarial antiserum to capture, and a monoclonal antibody to identify, circulating parasite antigen. Using this assay, we found that greater than 95% of sera from microfilaremic donors with bancroftian or brugian filariasis, approximately 60% of sera from microfilaremic patients with hydroceles, chyluria, or elephantiasis, and 15%-20% of sera from asymptomatic residents of filariasis-endemic areas evidently contain filarial antigens. Antigen was also detected in the urine of some microfilaremic patients. Serum levels of antigen detected with one monoclonal antibody, ES34, correlated well with microfilarial density in night blood. In contrast, less than 5% of sera from residents of areas where lymphatic filariasis is not endemic reacted in the assay, even though approximately one-third of the donors whose sera were tested were known to be infected with intestinal nematodes. The assay was designed to be flexible enough to allow the parallel use of multiple monoclonal antibodies with different specificities and simple enough to be applicable in most areas where lymphatic filariasis is endemic.

Antibodies, Monoclonal↗
PubMed1998

Bancroftian filariasis in Egypt: visualization of adult worms and subclinical lymphatic pathology by scrotal ultrasound.

The purpose of this study was to explore the value of scrotal ultrasound as a means of evaluating Bancroftian filariasis. Color Doppler ultrasound examinations were performed to look for subclinical hydroceles and motile adult filarial worms (dancing worms) in dilated lymphatics. Sixty-one male subjects from a filariasis-endemic area in Egypt were studied including 19 clinically normal microfilaria (MF) carriers (seven with dancing worms and eight with subclinical hydroceles), 13 MF-negative subjects with positive filarial antigen test results (three with dancing worms and seven with subclinical hydroceles), 22 exposed subjects with no MF and negative antigen test results (no dancing worms, four subclinical hydroceles), and seven subjects with clinical filariasis (no dancing worms, seven hydroceles). Thus, all men tested with clinical filariasis and most clinically normal subjects with either microfilaremia or filarial antigenemia had abnormal ultrasound examination results. Ultrasound findings often changed after therapy with diethylcarbamazine, with disappearance of dancing worms and development of new scrotal calcifications or hydroceles. This study confirms the value of scrotal ultrasound as a means of noninvasively visualizing adult filarial worms and assessing subclinical lymphatic damage in Bancroftian filariasis.

Adult↗
PubMed1990

Choice & integration of different approaches to case detection with special reference to brugian filariasis in south India.

Treatment following rapid case detection in population, particularly the target age classes, which record high prevalence, is necessary for effective control of lymphatic filariasis. Conventional door-to-door surveys resulted in delay in detection of parasite carriers and patients with clinical filariasis, particularly in rural areas. An integration with other approaches like school surveys, health camps, filariasis clinics and microfilaria detection camps (MDC) was found effective in covering a much larger population in brugian filariasis case detection in an endemic area in south India. The MDCs organized through Integrated Child Development Scheme (ICDS MDC) yielded a good coverage of pre-school children. School surveys were ideal in covering children en masse. Community MDCs and health camps arranged with active community participation were useful in covering adolescents and young adults in large numbers. The filariasis clinic was effective in screening older adults above 30 yr. The relative efficiency of these approaches in terms of time and manpower utilization has been discussed.

Adolescent↗
PubMed1993

Lymphatic abnormalities in human filariasis as depicted by lymphangioscintigraphy.

BACKGROUND: Investigation into filarial lymphedema has been hampered by the lack of a simple, safe, and easily repeated test to image the peripheral lymphatic system. Recent refinements in radionuclide lymphangioscintigraphy have established this noninvasive technique as the initial procedure of choice for visualizing lymphatics. Accordingly, we applied lymphangioscintigraphy to patients with filariasis and, for purposes of interpretation, compared the findings with those in patients with non-filarial lymphedema. METHODS: Thirty-three patients with classic symptoms or signs consistent with acute or chronic filariasis underwent lymphangioscintigraphy, and the findings were compared with those in five patients without lymphatic dysfunction and in 50 other patients with primary or secondary lymphedema without exposure to filariasis. RESULTS: As in patients with nonfilarial lymphedema, scintigraphic abnormalities in the 33 patients with filariasis included delayed or absent tracer transport of the radiotracer (25 patients), tortuous and bizarre deep lymphatics (seven patients), dermal diffusion (15 patients), retrograde tracer flow (six patients), and faint or absent regional nodal visualization (14 patients). Even in patients with long-standing filarial lymphedema, peripheral trunks were often visualized (at least in part), and regional nodes and more central lymphatics sometimes filled after light exercise. In some of the latter patients, however, discrete lymphatic trunks were not detected. CONCLUSION: Lymphangioscintigraphy is a simple, safe, reliable, noninvasive method with which to examine the peripheral lymphatic system, including truncal and nodal abnormalities, in endemic populations with occult and overt lymphatic filariasis.

Adolescent↗
PubMed2006

Factors influencing drug compliance in the mass drug administration programme against filariasis in the Western province of Sri Lanka.

This descriptive, comparative, cross-sectional, randomized community-based study was done to determine factors influencing drug compliance in the mass drug administration (MDA) programme against filariasis in selected urban and rural populations within the Western province of Sri Lanka. The study population was selected using the cluster sampling method. Factors influencing drug compliance were determined by administration of an interviewer-based pre-tested questionnaire eliciting information regarding drug compliance, socio-economic status, educational background, knowledge, attitudes and practices with regard to the 2004 MDA. A total of 2319 people aged between 10 and 90 years (median 40) responded to the questionnaire. The belief that the MDA programme was beneficial was the most important factor affecting drug compliance, as revealed by multivariate analysis of the combined populations (P<0.001). This was so even in the urban population (P<0.001), while the belief regarding the severity (danger) of filariasis was important in the rural population (P=0.013), when the areas were considered individually. Therefore, it is essential for awareness programmes to highlight the dangers (complications) of the disease and to influence the community to perceive the benefits of a filariasis-free community as well as 'beyond filariasis' benefits of having albendazole given in combination in the MDA programme.

Adolescent↗
PubMed2006

Effect of yearly mass drug administration with diethylcarbamazine and albendazole on bancroftian filariasis in Egypt: a comprehensive assessment.

BACKGROUND: Egypt was one of the first countries to implement a national programme to eliminate lymphatic filariasis based on WHO's strategy of repeated rounds of mass drug administration (MDA) with diethylcarbamazine and albendazole (target population, 2.5 million in 181 localities). We assessed the effect of five yearly rounds of MDA on filariasis in four sentinel villages in Egypt. METHODS: We studied two areas with different infection rates before MDA: the Qalubyia study area had a low infection rate because of previous treatment with diethylcarbamazine; this was typical of most filariasis-endemic villages in Egypt before MDA. The Giza study area had a high baseline infection rate. We undertook repeated surveys in villages for treatment compliance and tests for microfilaraemia and circulating filarial antigenaemia, antibodies to filarial antigen Bm14 in schoolchildren, and infections in indoor-resting mosquitoes (assessed by PCR). FINDINGS: MDA compliance rates were excellent (>80%). In Giza after MDA, prevalence rates of microfilaraemia and circulating filarial antigenaemia fell from 11.5% to 1.2%, and from 19.0% to 4.8%, respectively (p<0.0001). Corresponding rates in Qalubyia fell from 3.1% to 0% and 13.6% to 3.1%, respectively (p<0.0001). Rates of antifilarial antibody and circulating filarial antigenaemia in schoolchildren (aged about 7-8 years), fell from 18.3% to 0.2% (p<0.0001) and from 10.0% to 0.4% (p<0.0001) in Giza, respectively, and from 1.7% to 0% and 1.7% to 0% (both p=0.13) in Qalubyia, respectively. Mosquito infection rates fell from 3.07% (95% CI 2.38-3.88) to 0.19% (0.08-0.38) in Giza and from 4.37% (3.07-5.99) to 0% (0-0.05) in Qalubyia. INTERPRETATION: MDA greatly affects variables related to infection (microfilaraemia and circulating filarial antigenaemia prevalence rates) and transmission (antifilarial antibodies in young children and mosquito infection rates). Our results suggest that after five rounds of MDA filariasis is likely to have been eliminated in most endemic localities in Egypt.

Albendazole↗
PubMed1990

[The epidemiological study on hepatitis B virus infection in Miyako district--relationship to the mass survey of filariasis].

It has been well known that the transmission of HB virus is associated with mass inoculation and other medical procedures. In order to make clear the relation between HBV infection and the mass survey for filariasis on which sera of the examinees were drawn from their earlobes for the detecting of microfilaria with inadequately sterilized instruments, a epidemiological study was conducted in Miyako district. Okinawa prefecture, Japan, in which both HBV infection and filariasis were prevalent. A total of 2,231 inhabitants were investigated for HBV seromarkers. The over all positive rate of HBs antigen was 6.3% with the highest rate of 15.5% in the group of age 25 to 29. On the other hand, the prevalence rate of HBs antibody continued to increase along with age group, and remained to be over 60% after 30 years of age. The positive rates of both HBs antigen and antibody in the subject district were higher than those in other place of Okinawa prefecture or Japan. Comparing yearly attack rates of HBV chronologically, which were calculated from the age-specific HBV exposure rates in the district, the annual incidence of HBV infection was 6.1% (%/year) between 1954 to 1958, 5.2% (%/year) between 1959 to 1963, and then 4.4 (%/year) in the period of 1964 to 1968 in which the proportion of examinees for the survey of filariasis was the highest. In conclusion, the mass survey for filariasis was not the main factor contributing to the high prevalence of HBV infection in Miyako district.

Adolescent↗
PubMed2005

Bancroftian filariasis in an endemic area of Brazil: differences between genders during puberty.

Gender differences in susceptibility to infectious diseases have been observed in various studies. A survey was performed in a bancroftian filariasis endemic area in the city of Olinda, Brazil. All residents aged 5 years or older were examined by thick blood film. People aged 9 to 16 years were interviewed and also tested for filarial antigenaemia. Data were analyzed by contingency table methods and regression models. The risk of microfilaraemia for males was significantly higher. Among those aged 9 to 16 years, the analysis of gender and filariasis by age showed that boys from 15 to 16 years had a higher risk of infection than girls. No association was found between menarche and filariasis in girls. The data suggest that variations between gender in filariasis could result, at least in part, from an increase in susceptibility of men. This epidemiologic feature needs to be considered while formulating elimination plans.

Adolescent↗
PubMed2004

[Scientific knowledge and public health policies: reflections on the occurrence of filariasis in Recife, Pernambuco, Brazil].

This article discusses the relationship between the production of scientific knowledge on filariasis in Brazil and health policy-making and implementation related to control of the disease. The study presents a review of scientific output on filariasis from the creation of the Program to Combat Filariasis in the mid-20th century until the creation of the Unified National Health System (SUS) within the framework of decentralized control of endemic diseases in the country. The focus on empirical observations in Recife, a city where filariasis is present, highlights the relevant institutional processes and the role of various players. The hypothesis is that in the first half of the 20th century there was a lack of scientific knowledge and technological development to control the problem, but that after these advances were obtained, new requirements of a political nature came into play and acted as determinants for persistence of the endemic in the city.

Animals↗
PubMed2000

IgG- and IgG4-detected antigens of Dirofilaria immitis adult worms for bancroftian filariasis by enzyme-linked immunoelectrotransfer blot.

In Thailand, Wuchereria bancrofti filariasis has persisted along the border between Thailand and Myanmar, its dynamic distribution caused by the infected transmigrants between neighboring countries, and the availability of susceptible mosquito vectors. Dirofilaria immitis adult worm was used as a source of antigens, excretory-secretory (ES) and partial surface extracts, to detect human filariasis. ES products showed several stained bands with Coomassie brilliant blue ranging from 14.5-93 kDa and mostly being glycoproteins as shown by concurrent reaction with Concanavalin A, except those at 18, 16 and 14.5 kDa which stained only with Coomassie brilliant blue. Surface proteins of 33.5-91.5 kDa were stained with Coomassie brilliant blue and showed smear bands with Concanavalin A. By enzyme-linked immunoelectrotransfer blot, Bancroftian filariasis sera gave specific reactions with glycoprotein ES antigens at MW 20.5 kDa against anti-human IgG. A prominent band of 18 kDa appeared consistently with the IgG4-ES antigen system. Surface extracts reacting with IgG and IgG4 were considered to be unsuitable as antibodies from all cases of filariasis could not detect any bands.

Animals↗