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PubMed1987

Control of malaria and filariasis vectors in South India.

Community participation is increasingly seen as a major component of successful control programmes against parasitic diseases. One of the strongest exponents of this has been the Vector Control Research Centre (VCRC) in Pondicherry, South India (Fig. 1), who have successfully motivated and involved village communities in vector control activities with considerable success against malaria and filariasis vectors. Their largest single programme, the Filariasis Control Demonstration Project in Pondicherry Town, has now been handed to the Pondicherry State Government, while the VCRC's work on malaria and filariasis control is now expanding throughout other parts of India. As this article shows, much has been learnt from these projects, not just about control techniques but also about education, administration and decision-making.

Journal Article↗
PubMed1995

Socio-cultural and behavioural aspects of mosquito-borne lymphatic filariasis in Thailand: a qualitative analysis.

This study examines the contribution of socio-cultural and behavioural factors in mosquito-borne lymphatic filariasis transmission in Southern Thailand. Research was conducted in Nakorn-srithamarat province, which is noted for having the nation's highest Brugia malayi filariasis morbidity rate. Factors examined include traditional knowledge and cultural beliefs concerning etiology, transmission and symptomatology; perceived susceptibility and severity: social stigma: social support in disease prevention and control; and behavioural risk factors and illness behaviours. Data were collected through a multi-method, predominantly qualitative-based approach, including rapid survey and mapping, group interviews, focus group discussions, indepth interviews, and participant observation. Results indicate that poor knowledge and lay, indigenous, traditional belief systems contribute to high risk behaviours, and inappropriate preventive, illness and treatment choice behaviours. Behavioural models for explaining filariasis risk, preventive, illness and treatment choice behaviours are presented. Finally, recommendations for more effective health education programmes are offered.

Adolescent↗
PubMed2006

Mathematical models and lymphatic filariasis control: endpoints and optimal interventions.

The current global initiative to eliminate lymphatic filariasis is a major renewed commitment to reduce or eliminate the burden of one of the major helminth infections from resource-poor communities of the world. Mathematical models of filariasis transmission can serve as an effective tool for guiding the scientific development and management of successful community-level intervention programmes by acting as analytical frameworks for integrating knowledge regarding parasite transmission dynamics with programmatic factors. However, the power of these tools for supporting control interventions will be realized fully only if researchers address the current uncertainties and gaps in data and knowledge of filarial population dynamics and the effectiveness of currently proposed filariasis intervention options.

Animals↗
PubMed2002

The economic loss due to treatment costs and work loss to individuals with chronic lymphatic filariasis in rural communities of Orissa, India.

This paper is based on 1 year round case control study to investigate the economic burden, in terms of treatment costs and loss of work to people affected with chronic lymphatic filariasis in rural communities of Orissa, Eastern India. Around three-fourths of the chronic patients have sought treatment for their condition and spent, on average an amount of INR 396 (approximately US$ 8.7) per year. The major component of the expenditure is the cost of medicines. The data on loss of work time due to chronic condition reveal that the total absenteeism to the work is significantly higher among chronic filariasis patients than controls. The total number of working hours spent per day by patients and controls are 4.94 and 6.06, respectively with a significant difference. The total absenteeism and the total number of working hours per day are influenced significantly by disease condition and other personal characteristics, namely age, sex and family type. The chronic patients lose a total of 68 days of work per year, which is equivalent to 19% of the total working time of the year. The present results show that the chronic conditions of lymphatic filariasis pose considerable burden on the patient, family and community.

Absenteeism↗
PubMed1998

A review of the present status of lymphatic filariasis in Vietnam.

Establishing the current status of an infectious disease forms the starting point of any attempt at parasite control. Although data on the prevalence and distribution of lymphatic filariasis exist for Vietnam from the early 1900s, the present situation regarding the disease is less well-known. Here, we review the results of recent surveys conducted by the Institute of Malariology, Parasitology and Entomology, Hanoi, to update the existing information on filariasis epidemiology and distribution for this country. The present results are from surveys carried out on some 135,000 individuals in 24 provinces of Vietnam. The highest prevalences of microfilaraemia (primarily Brugia malayi ) are observed in lowland areas of the Red River Delta and in Quang-binh Province where the survey results show microfilaraemia (mf) prevalences in the range of 0.9-5.5%. The most common type of chronic clinical manifestation is shown to be leg elephantiasis. A significant finding is that an overall decrease in mf prevalence was observed to occur in five communities which were surveyed twice over an 11-21-year period, even though no interventions were carried out between the two surveys. The changes are probably caused by environmental changes, such as increased standards of housing and drainage. Studies on the effect of selective chemotherapy and mass chemotherapy using diethylcarbamazine showed reductions in community mf prevalences of 69 and 72-88%, respectively. Furthermore, cats do not appear to represent significant reservoirs of infection. These findings of geographical restriction of infection, effective and well-tolerated drug therapy, low significance of animal reservoirs, together with the existence of an effective national health network, suggest a good prognosis for the control of filariasis in this country.

Animals↗
PubMed2002

Lymphatic filariasis: new insights into an old disease.

Lymphatic filariasis has afflicted people in the tropical areas of the world for thousands of years but even up to comparatively recent times it has been poorly understood and its importance under recognised. In the last 2 decades or so there has been a flurry of activity in filariasis research, which has provided new insights into the global problem of filariasis, the pathogenesis of filarial disease, diagnosis and control.

Animals↗
PubMedDate not supplied

A randomized double-blind placebo-controlled field trial of ivermectin and albendazole alone and in combination for the treatment of lymphatic filariasis in Ghana.

The efficacy and safety of single-dose ivermectin (150-200 micrograms/kg) and albendazole (400 mg) treatment administered separately or in combination for Wuchereria bancrofti infections were assessed in 1996-98 in a randomized double-blind placebo-controlled field trial in Ghana: 1425 individuals from 4 lymphatic filariasis-endemic villages, 340 of whom were microfilaria (mf)-positive before treatment, were randomized into 4 groups to receive albendazole alone, ivermectin alone, combination of albendazole and ivermectin, or placebo, respectively. Individuals were followed for 5 days after treatment to record any adverse reactions, and the effect of treatment on microfilaraemia was monitored in night-blood samples after 3, 6 and 12 months. Treatment efficacy was analysed for 236 mf-positive individuals who had > or = 100 mf/mL of blood and who were also present for examination at 12 months after treatment. Compared to the placebo group, the ivermectin and combination groups both showed statistically significant reductions in geometric mean mf intensities at the follow-up examinations (to 6.7% and 0.9%, 9.9% and 6.9%, and 21.7% and 11.4% of pre-treatment levels, respectively, at 3, 6 and 12 months after treatment). Compared to the ivermectin group, however, the reduction in the combination group was significantly greater only at 3 months after treatment, but not after 6 or 12 months. The albendazole group showed a slow but non-significant reduction over the same period. Adverse reactions were few and mostly mild (no severe reactions were recorded), and no significant differences were observed between the treatment groups. Both ivermectin and combination treatment thus appeared effective and safe for treatment of lymphatic filariasis, but the difference in efficacy was minor and the study did not provide clear evidence for the combination drug therapy, as compared to ivermectin therapy alone, to be superior for control of lymphatic filariasis.

Adolescent↗
PubMedDate not supplied

Lymphatic filariasis in Uganda: baseline investigations in Lira, Soroti and Katakwi districts.

Baseline epidemiological investigations on lymphatic filariasis were conducted for the first time in Uganda in 3 communities in the districts of Lira (Alebtong area), Soroti (Lwala area) and Katakwi (Obalanga area), located to the north of Lake Kyoga at an altitude of 1000-1100 m above sea level. Individuals from the communities were examined, in April-August 1998, for Wuchereria bancrofti specific circulating antigen (by ICT card test), microfilaraemia (by counting chamber and stained blood-smear techniques) and chronic clinical manifestations of lymphatic filariasis. Endophilic mosquitoes were sampled and dissected for filarial larvae. Prevalences of circulating filarial antigen positivity were 29%, 18% and 30% in the Alebtong, Lwala and Obalanga communities, respectively. Microfilaria (mf) prevalences were 18%, 9% and 21%, and geometric mean mf intensities among mf-positive individuals were 306, 171 and 402 mf/mL blood, in the same communities. Examination of stained blood smears revealed mf of both W. bancrofti and Mansonella perstans, but more than 80% of mf-positive individuals harboured the first of these parasites. Prevalences of hydrocoele in adult (> or = 20 years) males were 28%, 7% and 17%, and prevalences of limb elephantiasis in adults were 9%, 4% and 4%, in the Alebtong, Lwala and Obalanga communities, respectively. Anopheles gambiae s.l. (mainly An. gambiae s.s.) and An. funestus were common in all 3 communities, and showed W. bancrofti infectivity rates of 1.1-1.7% and 1.3-2.9%, respectively. It is concluded that lymphatic filariasis is highly endemic in these high-altitude areas of Uganda, with An. gambiae s.l. and An. funestus being the main vectors.

Adolescent↗
PubMedDate not supplied

Long-term efficacy of single-dose combinations of albendazole, ivermectin and diethylcarbamazine for the treatment of bancroftian filariasis.

In a 'blinded' trial (in Sri Lanka, 1996-98) of 47 male asymptomatic microfilaraemic subjects with Wuchereria bancrofti infection, the safety, tolerability and filaricidal efficacy of 3 single-dose combination regimens were compared: albendazole 400 mg with ivermectin 200 micrograms/kg, albendazole 400 mg with diethylcarbamazine citrate (DEC) 6 mg/kg or albendazole 600 mg with ivermectin 400 micrograms/kg. Treated subjects were followed-up for 24 months. This represents the first long-term study using combinations of albendazole with DEC or ivermectin in the above doses against bancroftian filariasis. All subjects had pre-treatment microfilaria (mf) counts over 100/mL. All 3 treatments significantly reduced mf counts, with the albendazole-DEC-treated group showing the lowest mf levels at 18 and 24 months post-treatment. Filarial antigen tests suggested that all 3 treatments had significant activity against adult W. bancrofti; albendazole-DEC combination had the greatest activity according to this test, with antigen levels decreasing to 30.5% of pre-treatment antigen levels, 24 months after therapy. All 3 treatments were clinically safe and well tolerated. These results suggest that a single dose of albendazole 400 mg together with DEC 6 mg/kg is a safe and effective combination for suppression of microfilaraemia of bancroftian filariasis that could be considered for use in filariasis control programmes based on mass treatment of endemic populations.

Adolescent↗
PubMed2004

Safety, tolerability, efficacy and plasma concentrations of diethylcarbamazine and albendazole co-administration in a field study in an area endemic for lymphatic filariasis in India.

Filariasis control programmes are moving towards a strategy of repeated single-dose mass treatment of endemic populations. Using a combination, such as albendazole (ALB) to diethylcarbamazine (DEC) gives both macrofilaricidal and anti-helmintic activity. However, the safety of the combination versus DEC alone should be established in field studies in large populations prior to incorporation into national programmes. The present study compared the safety, tolerability, and efficacy of single doses of DEC 6 mg/kg + ALB placebo with DEC 6 mg/kg + ALB 400 mg in populations living in two filariasis endemic villages in the district of Wardha in western India. The study was double blind, parallel group, and randomized. Safety and tolerability study were studied in males and females older than 5 years. Safety was assessed by monitoring if adverse events (AEs) over 5 days affected daily acivities. Subjects in the 2 treatment groups experienced insignificantly different effects on daily activities and the combination was shown to be safe. Efficacy was evaluated by microfilaraemia (Mf), immunochromatographic test (ICT) and ultrasonography (USG) at 0, 3, 6, and 12 months of follow up. The efficacy study enrolled 103 male patients (aged 18-50 years) in microfilariae positive, clinical disease and asymptomatic, amicrofilaremic groups. There was no significant difference in efficacy between groups at 12 months. Within the Mf positive group, significant differences were seen in microfilaraemia (P < 0.001) with both treatments, and in USG (P < 0.001 and P < 0.004 respectively), at 12 months. The present field study has shown the combination of DEC + ALB to be as safe as the single drug DEC and thus the combination can be put in use in the national filariasis control programmes. Both drugs were adequately absorbed. The study at present does not provide evidence for the greater efficacy of the combination at 12 months follow up. While the safety of the combination has been ascertained, the incorporation or otherwise of ALB into national programmes for greater efficacy must await results of studies with longer follow up.

Adolescent↗
PubMed2000

The economic burden of lymphatic filariasis in India.

Lymphatic filariasis affects 119 million people living in 73 countries, with India accounting for 40% of the global prevalence of infection. Despite its debilitating effects, lymphatic filariasis is given very low control priority. One of the reasons for this is paucity of information on the economic burden of the disease. Recent studies in rural areas of south India have shown that the treatment costs and loss of work time due to the disease are considerable. Based on the results of these studies, Kapa Ramaiah et al. here estimate the annual economic loss because of lymphatic filariasis for India and discuss the implications of their findings.

Adolescent↗
PubMed2000

Lymphatic filariasis in the Philippines.

Lymphatic filariasis caused by Wuchereria bancrofti and Brugia malayi is endemic throughout most of the southern half of the Philippine archipelago. Economic and manpower shortages prior to 1996 made it difficult to acquire new prevalence data and vector control data concurrently from all provinces. Nevertheless, analysis of cumulative prevalence data on filariasis indicates the persistence of filariasis in each of the three major island groups - Luzon, Visayas and Mindanao - including 45 out of 77 provinces. Here, Michael Kron and colleagues summarize the prevalence data, and review host, parasite and vector characteristics relevant to the design and implementation of disease control initiatives in the Philippines planned for the year 2000.

Animals↗
PubMed2000

Pathogenesis of lymphatic disease in bancroftian filariasis: a clinical perspective.

The pathogenesis of lymphatic filariasis has been a matter of debate for many decades. Here, Gerusa Dreyer and colleagues propose a dynamic model of bancroftian filariasis, integrating clinical, parasitological, surgical, therapeutic, ultrasonographic and histopathological data. This model has profound implications for filariasis control programs and the management of the individual patient.

Albendazole↗
PubMed2001

Ambient temperature effects on the extrinsic incubation period of Wuchereria bancrofti in Aedes polynesiensis: implications for filariasis transmission dynamics and distribution in French Polynesia.

Temperature effects on development of the human filarial parasite Wuchereria bancrofti (Cobbold) (Filaridea: Onchocercidae) in the main Pacific vector Aedes polynesiensis Marks (Diptera: Culicidae) are analysed in relation to ambient climatic conditions. A statistical model of the extrinsic cycle duration as a function of temperature is described and used to distinguish three patterns of W. bancrofti transmission dynamics: continuous, fluctuating and discontinuous, occurring from north to south geographically among French Polynesian archipelagos. In the northerly Marquesas Islands (8-11 degrees S) filariasis transmission is continuous and very active, facilitated by perennially high temperatures combined with constantly high rates of man-vector contact. In the southerly Australes Islands (21-28 degrees S) filariasis transmission is seasonally discontinuous and, during the cooler months (May-September), the model predicts virtually no transmission because the cycle duration exceeds the life expectancy of the vector. In the Society Islands (16-18 degrees S), between the Marquesas and Australes, transmission is predicted to be intermediate as expected from their latitude, with seasonally fluctuating transmission potential. In the Tuamotu Islands (also geographically intermediate: 14-23 degrees S), with theoretically perennial transmission potential, transmission occurs only intermittently, being limited by other human and environmental factors whereby man-vector contact is confined to seasonal agricultural situations. Generally, among French Polynesian archipelagos where Aedes polynesiensis is the vector, the transmission potential for W. bancrofti and resulting disease manifestations of lymphatic filariasis in humans are correlated with ambient temperature due to the degree of southern latitude.

Aedes↗
PubMed1998

Permethrin-impregnated bednet effects on resting and feeding behaviour of lymphatic filariasis vector mosquitoes in Kenya.

The impact of permethrin-impregnated bednets on resting and feeding behaviour of mosquito vectors of Wuchereria bancrofti, causing human lymphatic filariasis was studied in six pairs of villages (treated and untreated) before and after intervention. The study villages were in Kwale District, near the coast of Kenya, where Bancroftian filariasis is highly endemic, transmitted by a combination of both anopheline and culicine mosquito vectors. Mosquitoes were collected weekly in each village, indoors (using pyrethrum spray catches) and outdoors (using pit traps) during 3-4 months following the long rainy season. Of the filariasis vector species of mosquitoes collected in 1994 before intervention. 33.6% were members of the Anopheles gambiae complex, 30% were An. funestus and 36.4% were Culex quinquefasciatus. PCR analysis of the An. gambiae complex species collected in 1995 demonstrated that 98.5% were An. gambiae sensu stricto. 1% An. arabiensis and 0.5% An. merus. Introduction of impregnated bednets in 1995 significantly reduced the number of indoor-resting An. gambiae s.l. by 94.6% and An. funestus by 96.7%, but there was no change in the number of Cx quinquefasciatus collected indoors. The number of outdoor-resting An. gambiae s.l. was significantly reduced, whereas densities of An. funestus and Cx quinquefasciatus remained unaffected outdoors. ELISA analysis of mosquito bloodmeals showed a shift from human to animal feeding after the introduction of treated nets. The human blood index (HBI) for indoor resting Cx quinquefasciatus was reduced from 93.1% to 14.4%. Vector potential based on the HBI and mosquito density was estimated to be reduced by 99% for An. gambiae s.l., 98% for An. funestus and 97% for Cx quinquefasciatus and vectorial capacity would be suppressed even more by the impact on the vector survival rates (not measured). These results suggest that permethrin-impregnated bednets give effective personal protection against transmission of W. bancrofti by An. gambiae, An. funestus and Cx quinquefasciatus in East Africa.

Animals↗
PubMed1996

A role for tumour necrosis factor-alpha in acute lymphatic filariasis.

A spectrum of clinical manifestations is a feature of human lymphatic filariasis. The acute disease is characterized by periodic and self limiting episodes of adenolymphangitis, fever and associated constitutional symptoms, while the chronic disease includes long lasting manifestations such as lymphoedema and/or hydrocoele. The microfilariae carriers are generally free of clinical symptoms. In the present study circulating Tumour Necrosis Factor (TNF-alpha) was measured in human bancroftian filariasis with different clinical manifestations. Significantly elevated levels were observed only in patients with acute disease and not in microfilariae carriers or in patients with chronic manifestations. A detailed analysis of the acute cases indicated an absence of correlation between TNF-alpha levels and duration of the episodes. However, a significant positive correlation was observed between the severity of the disease and the TNF-alpha levels. About 85% of the acute cases with severe manifestations showed raised levels of TNF-alpha while only 6.5% of mild cases showed such levels. Manifestation of fever was also significantly associated with higher levels of TNF-alpha-while 80% of acute cases with fever had significant levels only 24% of acute cases without fever had high levels of TNF-alpha. Based on these observations we propose a mediatory role for TNF-alpha in acute filariasis and the possible use of TNF-alpha inhibitors for clinical management of the disease.

Acute Disease↗
PubMed2001

Transmission intensity and the immunoepidemiology of bancroftian filariasis in East Africa.

Previous attempts to determine the interactions between filariasis transmission intensity, infection and chronic disease have been limited by a lack of a theoretical framework that allows the explicit examination of mechanisms that may link these variables at the community level. Here, we show how deterministic mathematical models, in conjunction with analyses of standardized field data from communities with varying parasite transmission intensities, can provide a particularly powerful framework for investigating this topic. These models were based on adult worm population dynamics, worm initiated chronic disease and two major forms of acquired immunity (larval- versus adult-worm generated) explicitly linked to community transmission intensity as measured by the Annual Transmission Potential (ATP). They were then fitted to data from low, moderate and moderately high transmission communities from East Africa to determine the mechanistic relationships between transmission, infection and observed filarial morbidity. The results indicate a profound effect of transmission intensity on patent infection and chronic disease, and on the generation and impact of immunity on these variables. For infection, the analysis indicates that in areas of higher parasite transmission, community-specific microfilarial rates may increase proportionately with transmission intensity until moderated by the generation of herd immunity. This supports recent suggestions that acquired immunity in filariasis is transmission driven and may be significant only in areas of high transmission. In East Africa, this transmission threshold is likely to be higher than an ATP of at least 100. A new finding from the analysis of the disease data is that per capita worm pathogenicity could increase with transmission intensity such that the prevalences of both hydrocele and lymphoedema, even without immunopathological involvement, may increase disproportionately with transmission intensity. For lymphoedema, this rise may be further accelerated with the onset of immunopathology. An intriguing finding is that there may be at least two types of immunity operating in filariasis: one implicated in anti-infection immunity and generated by past experience of adult worms, the other involved in immune-mediated pathology and based on cumulative experience of infective larvae. If confirmed, these findings have important implications for the new global initiative to achieve control of this disease.

Age Distribution↗
PubMed1997

Functional impairment caused by lymphatic filariasis in rural areas of south India.

The functional impairment caused by lymphatic filariasis was assessed through qualitative and quantitative methods in rural areas of Tamil Nadu, South India. About 66% of the patients said that their occupational activities were hampered by the disease. They either work fewer hours or alter their activity. Some had completely given up their job. Domestic chores of most of the female patients were also impeded. Most of those affected try to avoid travel. The disability was worse in patients with acute disease. In view of the results of our and other similar studies, the disability-adjusted life years lost due to lymphatic filariasis must be revised and the public health importance of the disease reassessed. Considerable functional impairment coupled with recent information on economic burden and productivity loss caused by lymphatic filariasis necessitates paying more attention to the control of the disease.

Adult↗