Lymphatic filariasis in Ghana: entomological investigation of transmission dynamics and intensity in communities served by irrigation systems in the Upper East Region of Ghana.
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We conducted an entomological study to document the effect of irrigation on the vectors and transmission dynamics of lymphatic filariasis in the Upper East Region of Ghana. Mosquitoes were collected by indoor spraying of houses in a cluster of communities located around irrigation projects (Tono and Vea) and others without reservoirs (Azoka). Anopheles gambiae s.s. was the dominant species and major vector, followed by An. funestus. Anopheles arabiensis constituted 9--14% of the An. gambiae complex but none were infective. Culex quinquefasciatus was also not infective in these communities. Chromosomal examinations showed that >60% (n=280--386) of the An. gambiae s.s. in irrigated communities were Mopti forms whilst 73% (n=224) in the non-irrigated area were Savannah forms. Infectivity rates (2.3--2.8 vs. 0.25), worm load (1.62--2.04 vs. 1.0), annual bites per person (6.50--8.83 vs. 0.47) and annual transmission potential (13.26--14.30 vs. 0.47) were significantly higher in irrigated communities. (+info)
Genetic polymorphisms in molecules of innate immunity and susceptibility to infection with Wuchereria bancrofti in South India.
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A pilot study was conducted to determine if host genetic factors influence susceptibility and outcomes in human filariasis. Using the candidate gene approach, a well-characterized population in South India was studied using common polymorphisms in six genes (CHIT1, MPO, NRAMP, CYBA, NCF2, and MBL2). A total of 216 individuals from South India were genotyped; 67 normal (N), 63 asymptomatic microfilaria positive (MF+), 50 with chronic lymphatic dysfunction/elephantiasis (CP), and 36 tropical pulmonary eosinophilia (TPE). An association was observed between the HH variant CHIT1 genotype, which correlates with decreased activity and levels of chitotriosidase and susceptibility to filarial infection (MF+ and CP; P = 0.013). The heterozygosity of CHIT1 gene was over-represented in the normal individuals (P = 0.034). The XX genotype of the promoter region in MBL2 was associated with susceptibility to filariasis (P = 0.0093). Since analysis for MBL-sufficient vs insufficient haplotypes was not informative, it is possible the MBL2 promoter association results from linkage disequilibrium with neighboring loci. We have identified two polymorphisms, CHIT1 and MBL2 that are associated with susceptibility to human filarial infection, findings that merit further follow-up in a larger study. (+info)
Lymphatic filariasis: an infection of childhood.
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Lymphatic filariasis (LF), already recognized as a widespread, seriously handicapping disease of adults, was generally thought to occur only sporadically in children. New, highly sensitive diagnostic tests (antigen detection, ultrasound examination) now reveal, however, that LF is first acquired in childhood, often with as many as one-third of children infected before age 5. Initial damage to the lymphatic system by the parasites generally remains subclinical for years or gives rise only to non-specific presentations of adenitis/adenopathy; however, especially after puberty the characteristic clinical features of the adult disease syndromes (lymphoedema, hydrocoele) manifest themselves. Recognizing that LF disease starts its development in childhood has immediate practical implications both for management and prevention of the disease in individual patients and for the broader public health efforts to overcome all childhood illnesses. For the new World Health Organization (WHO)-supported, public-/private-sector collaboration (Global Alliance) to eliminate LF through once-yearly drug treatment, this recognition means that children will be not only the principal beneficiaries of LF elimination but also a population particularly important to target in order for the programme to achieve its twin goals of interrupting transmission and preventing disease. (+info)
Lymphatic filariasis in children: adenopathy and its evolution in two young girls.
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Lymphatic filariasis is a widespread infectious disease of children in endemic areas, but little is known about the early lymphatic damage in children and its evolution, either with or without treatment. Two girls (ages 6 and 12 years) from a Wuchereria bancrofti endemic region of Brazil presented with chronic inguinal adenopathy. Neither had microfilaremia. By ultrasound both were shown to have living adult worms in their enlarged inguinal nodes and had occult local lymphatic damage (lymphangiectasis). One girl spontaneously developed acute adenitis in the affected node prior to any intervention; this adenitis resolved within 10 days and was associated with the progressive disappearance over 45-90 days of all local abnormalities detectable by ultrasound. In the other child, after treatment with a single dose of diethylcarbamazine (DEC), the same clinical picture of transient adenitis and resolving abnormalities (detectable by ultrasound) occurred. These findings demonstrated filariasis as the cause of adenopathy in children, and also both spontaneous and treatment-induced worm-death, with subsequent reversal of lymphatic abnormalities. (+info)
Sensitive and specific enzyme-linked immunosorbent assay for the diagnosis of Wuchereria bancrofti infection in urine samples.
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We developed an enzyme-linked immunosorbent assay (ELISA) that detects filaria-specific immunoglobulin G4 antibodies in unconcentrated urine. The ELISA was positive in 87 of 91 (95.6%) urine samples collected from people with Wuchereria bancrofti microfilariae, antigen, or both. Of 298 urine samples collected in Thailand, Lao People's Democratic Republic, and Japan, where no human filariasis is known, 295 (99.0%) were negative by ELISA. Various intestinal nematode and fluke infections did not interfere with the ELISA. Urine samples with sodium azide could be kept at 37 degrees C for 4 weeks, and the time of urine collection did not influence ELISA results. This ELISA can be used to identify endemic foci of filariasis. (+info)
Worm burden and host responsiveness in Wuchereria bancrofti infection: use of antigen detection to refine earlier assessments from the South Pacific.
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A population from the Wuchereria bancrofti-endemic island of Mauke was reevaluated retrospectively by use of the Og4C3 circulating antigen (CAg) enzyme-linked immunosorbent assay to assess active infection in relation to host responses by age and gender. Use of microfilaremia (Mf) alone misclassified approximately 50% of infected people, although CAg and Mf levels were positively correlated. Levels of CAg peaked between those aged 31-60 years; men aged > 60 years had a significantly higher CAg prevalence (> 90%) than women. Filaria-specific immunoglobulin (Ig) G4 reached maximum levels in both genders at age 51-60 years. By analysis of variance, both age and gender significantly influenced CAg and IgG4, with men having higher levels of both in the total population. Individuals positive for CAg had significantly lower lymphocyte proliferation responses to parasite antigen than did CAg-negative people, regardless of clinical status. This study reemphasizes the importance of CAg measurements for accurately assessing filarial prevalence and clinical status and demonstrates the relationship between active infection and immune responsiveness. (+info)
Effectiveness of community and health services-organized drug delivery strategies for elimination of lymphatic filariasis in rural areas of Tamil Nadu, India.
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Lymphatic filariasis (LF) is targeted for global elimination. Repeated annual single-dose mass treatment with antifilarials has been recommended as the principal strategy to achieve LF elimination. This requires an effective and sustainable strategy to deliver the drug, diethylcarbamazine (DEC), to communities. In this study, a new drug delivery strategy - community-directed treatment (comDT) - was developed and implemented and its effectiveness compared with that of the traditional health services-organized drug delivery, in rural areas of Tamil Nadu, India. Qualitative and quantitative data showed that the communities and health services were able to distribute the drug in almost all villages. The drug distribution rate and treatment compliance rate of comDT and health services treatment were statistically compared after adjusting them for clustering. Under the comDT 68% (n=20 villages; range: 0-97%) of the population received DEC, compared with 74% (n=20 villages; range: 48-95%) with the health services treatment strategy (P > 0.05). However, only about 53% (range: 0-91%) of comDT recipients and 59% (range: 32-79%) of those who received DEC from the health services consumed the drug (P > 0.05). Although statistically not significant, the distribution and compliance rates were lower under the comDT strategy. Also, the strategy's operationalization appears to be difficult because of some social factors, and the tradition of communities' dependence on health services for treatment, whereas health services-organized distribution was much less cumbersome and found to be more acceptable to people. However, the distribution (74%) and compliance rates (59%) achieved by health services were also only moderate and may not be adequate to eliminate LF in a reasonable time frame. Health services manpower alone may not be sufficient to distribute the drug. We conclude that drug distribution by health services is the best option for India and participation of the community volunteers and village level government staffs in the programme is necessary to effectively distribute the drug and attain the desirable levels of treatment compliance to eliminate LF. (+info)
Reactivity to bacterial, fungal, and parasite antigens in patients with lymphedema and elephantiasis.
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Both secondary infections and antifilarial immunity are thought to play roles in the development and progression of lymphedema. To investigate this issue, immune responses to a panel of bacterial, fungal, and parasite antigens were examined for women with lymphedema and elephantiasis (n = 28) and for women with no clinical evidence of lymphatic dysfunction who were either microfilaremic (Mf+, n = 23) or microfilaria- and filarial antigen-negative (Ag-, n = 24). The prevalence and intensity of delayed-type hypersensitivity (DTH) responses was similar for most recall antigens; for individual antigens, lymphedema patients were significantly more likely to be reactive only to Proteus. Lymphedema patients with a history of three or more attacks of adenolymphangitis in the last 18 months showed increased DTH reactivity to Trichophyton. Proliferative responses to fungal and bacterial antigens were similar for all three groups; however, antigen-negative women, independent of disease status, mounted greater responses to filarial antigen. In contrast, lymphedema patients had higher levels of antifilarial specific IgG1, IgG2, and IgG3 and higher IgG responses to streptolysin O than either Ag- or Mf+ women. In persons with lymphatic filariasis, immune reactivity is influenced by disease status as well as infection status. (+info)