This paper discusses five parasitic diseases: American trypanosomiasis (Chagas disease), dracunculiasis, lymphatic filariasis, onchocerciasis and schistosomiasis. The available technology and health infrastructures in developing countries permit the eradication of dracunculiasis and the elimination of lymphatic filariasis due to Wuchereria bancrofti. Blindness due to onchocerciasis and transmission of this disease will be prevented in eleven West African countries; transmission of Chagas disease will be interrupted. A well-coordinated international effort is required to ensure that scarce resources are not wasted, efforts are not duplicated, and planned national programmes are well supported. (+info)
Efficacy of five annual single doses of diethylcarbamazine for treatment of lymphatic filariasis in Fiji.
Annual single-dose treatments with diethylcarbamazine citrate (DEC) at a dose of 6 mg/kg have been reported effective in reducing microfilariae (mf) rate and density and applicable to large-scale filariasis control campaigns. However, the efficacy of such treatments has not been studied quantitatively in relation to different pretreatment levels of endemicity. This study of 32 villages in Fiji revealed that five treatments repeated annually steadily reduced village mf rate, and that the degree of reduction was not influenced by pretreatment levels of mf density or rate. This indicates that an annual dosage scheme is applicable to high-endemicity areas. The results also suggest that such treatment affected juvenile forms of Wuchereria bancrofti and may prevent them from reproducing. (+info)
Treatment costs and loss of work time to individuals with chronic lymphatic filariasis in rural communities in south India.
This year-round case-control study investigated treatment costs and work time loss to people affected by chronic lymphatic filariasis in two rural communities in south India. About three-quarters of the patients sought treatment for filariasis at least once and 52% of them paid for treatment, incurring a mean annual expenditure of Rs. 72 (US $2.1; range Rs. 0-1360 (US $39.0)). Doctor's fees and medicines constituted 57% and 23% of treatment costs. The proportion of people seeking treatment was smaller and treatment costs constituted a higher proportion of household income in lower income groups. Most patients did not leave work, but spent only 4.36+/-3.41 h per day on economic activity compared to 5.25+/-3.52 h worked by controls; the mean difference of 0.89+/-4.20 h per day was highly significant (P<0.01). This loss of work time is perpetual, as chronic disease manifestations are mostly irreversible. An estimated 8% of potential male labour input is lost due to the disease. Regression analyses revealed that lymphatic filariasis has a significant effect on work time allotted to economic activity (P<0.05) but not on absenteeism from work (P>0.05). Female patients spent 0.31+/-1.42 h less on domestic activity compared to their matched controls (P<0.05). The results clearly show that the chronic form of lymphatic filariasis inflicts a considerable economic burden on affected individuals. (+info)
Anti-filarial IgG4 in men and women living in Brugia malayi-endemic areas.
To assess whether antifilarial IgG4 can be used to study various epidemiological facets of filarial infections, we studied this isotype in 238 individuals resident in areas endemic for brugian filariasis, focusing on the differences between men and women. In the study area, the prevalence of microfilariae was 6.7% and the prevalence of antifilarial IgG4 was 49.2%. All microfilariae carriers were positive for antifilarial IgG4, whereas a proportion of the endemic normals (94/208) and clephantiasis patients (7/14) had IgG4 antibodies to filarial antigens. Data were analysed as a function of gender in distinct clinical groups and stratified for age. The prevalence of microfilariae was higher in males in all age groups, as reflected in significantly higher antifilarial IgG4 antibody levels compared to females. The prevalence of IgG4 increased to reach a plateau at the age of 30 years in both males and females. These results indicate that antifilarial IgG4 antibodies can reflect the differences in the extent of infection in males and females as measured by microfilarial counts, and that this parameter can be used for epidemiological assessments of filarial infection. (+info)
Helminth- and Bacillus Calmette-Guerin-induced immunity in children sensitized in utero to filariasis and schistosomiasis.
Infants and children are routinely vaccinated with bacillus Calmette-Guerin (BCG) in areas of the world where worm infections are common. Because maternal helminth infection during pregnancy can sensitize the developing fetus, we studied whether this prenatal immunity persists in childhood and modifies the immune response to BCG. Children and newborns living in rural Kenya, where BCG is administered at birth and filariasis and schistosomiasis are endemic, were examined. T cells from 2- to 10-year-old children of mothers without filariasis or schistosomiasis produced 10-fold more IFN-gamma in response to mycobacterial purified protein derivative than children of helminth-infected mothers (p < 0.01). This relationship was restricted to purified protein derivative because maternal infection status did not correlate with filarial Ag-driven IL-2, IFN-gamma, IL-4, or IL-5 responses by children. Prospective studies initiated at birth showed that helminth-specific T cell immunity acquired in utero is maintained until at least 10-14 mo of age in the absence of infection with either Wuchereria bancrofti or Schistosoma haematobium. Purified protein derivative-driven T cell IFN-gamma production evaluated 10-14 mo after BCG vaccination was 26-fold higher for infants who were not sensitized to filariae or schistosomes in utero relative to subjects who experienced prenatal sensitization (p < 0.01). These data indicate that helminth-specific immune responses acquired during gestation persist into childhood and that this prenatal sensitization biases T cell immunity induced by BCG vaccination away from type 1 IFN-gamma responses associated with protection against mycobacterial infection. (+info)
A longitudinal study of Bancroftian filariasis in the Nile Delta of Egypt: baseline data and one-year follow-up.
We initiated a longitudinal study of Bancroftian filariasis to improve understanding of dynamics and risk factors for infection in villages near Cairo, Egypt. Baseline prevalence rates for microfilaremia and filarial antigenemia for 1,853 subjects more than 9 years of age were 7.7% and 11.2%, respectively. Microfilaria counts, antigen levels, and microfilaremia incidence over a 1-year period were all significantly lower in older people. These findings suggest that humans develop partial immunity to Wuchereria bancrofti over time. One-year incidence rates for microfilaremia and antigenemia were 1.8% and 3.1%, respectively. Filarial antigenemia, IgG4 antibody to recombinant antigen BmM14, and household infection were all significant risk factors for microfilaremia incidence. Microfilaria counts and parasite antigen levels were significantly reduced by diethylcarbamazine therapy, but many infected subjects refused treatment, and most treated people were still infected one year later. Incident infections approximately balanced infections lost to produce an apparent state of dynamic equilibrium. (+info)
Acute disease episodes in a Wuchereria bancrofti-endemic area of Papua New Guinea.
Acute disease episodes of Bancroftian filariasis were monitored prospectively in a rural area of Papua New Guinea. The frequency and duration of episodes were recorded for the leg, arm, scrotum, and breast. A very high incidence of acute disease was observed; 0.31 episodes per person-year in the leg alone. Incidence generally increased with age, except in the breast, where episodes were concentrated in the reproductive age range. Males had slightly higher incidence than females in the leg and arm. Chronic disease was strongly associated with acute disease incidence in all locations. Microfilaremia had a statistically significant association with acute disease in the leg, arm, and breast, but not the scrotum. This study again demonstrates the high burden of acute manifestations of lymphatic filariasis, and provides new information on risk factors, which may lead to better understanding of etiology and control prospects. (+info)
Bloodmeal microfilariae density and the uptake and establishment of Wuchereria bancrofti infections in Culex quinquefasciatus and Aedes aegypti.
The relationship between ingestion of microfilariae (mf), production of infective larvae (L3) and mf density in human blood has been suggested as an important determinant in the transmission dynamics of lymphatic filariasis. Here we assess the role of these factors in determining the competence of a natural vector Culex quinquefasciatus and a non vector Aedes aegypti to transmit Wuchereria bancrofti. Mosquitoes were infected via a membrane feeding procedure. Both mosquito species ingested more than the expected number of microfilariae (concentrating factor was 1.28 and 1.81 for Cx. quinquefasciatus and Ae. aegypti, respectively) but Cx. quinquefasciatus ingested around twice as many mf as Ae. aegypti because its larger blood meal size. Ae. aegypti showed a faster mf migration capacity compared to Cx. quinquefasciatus but did not allow parasite maturation under our experimental conditions. Similar proportions of melanized parasites were observed in Ae. aegypti (2. 4%) and Cx. quinquefasciatus (2.1%). However, no relationship between rate of infection and melanization was observed. We conclude that in these conditions physiological factors governing parasite development in the thorax may be more important in limiting vectorial competence than the density of mf ingested. (+info)