Medicine

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Author: search.filters.author.Amarasekera, N.D.D.M.Subject: search.filters.subject.Helminthiasis

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    Effect of mass chemotherapy for filariasis control on soil-transmitted helminth infection in Western Province of Sri Lanka
    (The Royal Society of Tropical Medicine and Hygiene, 2007) Gunawardena, N.K.; Amarasekera, N.D.D.M.; Pathmeswaran, A.; de Silva, N.R.
    In July 2006, Sri Lanka completed five rounds of annual mass drug administration (MDA) with diethylcarbamazine citrate and albendazole as part of its national programme for elimination of lymphatic filariasis. Albendazole is also highly effective against soil-transmitted helminths (STH). This study was carried out to assess the impact of repeated annual MDA on STH infections in the Western Province of Sri Lanka, an area that is co-endemic for lymphatic filariasis and STH. A total of 17 schools in the Western Province were selected because they were included in a national survey of the health of school children in Grade 5 in 2003, when one round of MDA had been completed. Faecal samples were obtained again in 2006 (after five rounds of MDA), from one randomly selected class of Grade 5 students in the same schools. In both surveys, faecal samples were examined using the modified Kato-Katz technique. The prevalence and intensity of roundworm, whipworm and hookworm infections in 2003 and 2006 were compared using chi-square or Z-test for a difference between two percentages. Faecal samples from 255 children were examined in 2003; 448 were examined in 2006. Roundworm prevalence was marginally lower in 2006 (4.0%) than in 2003 (4.7%), as was hookworm (0.2% vs 0.4%) whereas whipworm prevalence was higher (13.8% vs 9.4%). Mean egg counts for all three infections were marginally higher in 2006. However, none of these differences were statistically significant. Compliance with MDA in 2006, as reported by the school children examined, was only 59%. These results indicate that four annual roundsof MDA with diethylcarbamazine and citrate and albendazole had virtually no impact on STH infections in the study area. It is likely that inclusion of of albendazole in MDA for lymphatic filariasis does not have much impact on STH infections in areas of low endemicity, unless very high coverage rates are achieved.
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    The Effect of intestinal nematode infections on atopic diseases in children
    (Allergy and Immunology Society of Sri Lanka, 2009) Amarasekera, N.D.D.M.; Gunawardena, N.K.; de Silva, N.R.; Douglas, J.; O'Hehir, R.; Weerasinghe, A.
    BACKGROUND : The effect of helminth infections on atopic diseases and allergic sensitization is controversial. Little is known about the effect of infection on atopic diseases in children living in areas where both intestinal nematodes and Toxocara infections are prevalent. OBJECTIVE : To examine the association between atopic diseases and helminth infection among children exposed to both intestinal nematodes and Toxocara. METHODS: Children attending grade 5 (age group 9-11 years) in 17 schools in the Western Province of Sri Lanka were recruited. The association of atopic diseases (asthma, rhinitis, eczema) with active intestinal nematode infections (excreting eggs in faeces) and with exposure to Toxocara (specific IgG antibodies in serum) was investigated. A child was deemed sensitized if positive for at least one of the allergens tested (Dermatophagoides pteronyssinus, Blomia tropicalis, cockroach, cat epithelium, grass pollen), based on specific IgE levels in serum. RESULTS: A total of 640 children participated in the study; serum analysis was done in 203. Active intestinal nematode infection appeared to reduce the risk of atopic diseases (OR 0.47, P=0.016) whereas Toxocara exposure did not (OR 0.85 P=0.602). When specific IgE levels against Blomia tropicalis, the most common allergen in the study group (67.5%), were expressed as percentages of the total IgE levels for each child, infected children had significantly lower levels compared to uninfected children (P=0.001). CONCLUSIONS : Intestinal nematode infections seem to protect against atopic diseases in children in Sri Lanka. Polyclonal IgE synthesis may be involved in this protection.
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    Reduced risk of atopic diseases among schoolchildren infected with intestinal Nematodes
    (Federation of Immunology Societies of Asia-Oceania, 2008) Amarasekera, N.D.D.M.; Gunawardena, N.K.; de Silva, N.R.; Pathmeswaran, A.; Douglass, J.; O’Hehir, R.; Weerasinghe, A.
    BACKGROUND: The effect of helminth infections on atopic diseases and allergic sensitization is controversial. Little is known about the effect of infection on atopic diseases in children living in areas where both intestinal nematodes and Toxocara infections are prevalent. OBJECTIVE : To examine the association between atopic diseases and helminth infection among children exposed to both intestinal nematodes and Toxocara. METHODS: Children attending grade 5 (age group 9-11 years) in 17 schools in the Western Province of Sri Lanka were recruited. The association of atopic diseases (asthma, rhinitis, eczema) with active intestinal nematode infections (excreting eggs in faeces) and with exposure to Toxocara (specific IgG antibodies in serum) was investigate. A child was deemed sensitized if positive for at least one of the allergens tested (Dermatophagoides pteronyssinus, Blomia tropicalis, cockroach, cat epithelium, grass pollen), based on specific IgE levels in serum. RESULTS : A total of 640 children participated in the study; serum analysis was done in 203. Active intestinal nematode infection appeared to reduce the risk of atopic diseases (OR 0.47, P=0.0I6) whereas Toxocara exposure did not (OR 0.85, P=0.602). When specific IgE levels against Blomia tropicalis, the most common allergen in the study group (67.5%), were expressed as percentages of the total IgE levels for each child, infected children had significantly lower levels compared to uninfected children (P=0.001). CONCLUSIONS : Intestinal nematode infections seem to protect against atopic diseases in children in the tropics. Polyclonal IgE synthesis may be involved in this protection.
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    Association between serum total IgE, allergic diseases and geohelminth infections in Sri Lankan children
    (BioMed Central, 2007) Amarasekera, N.D.D.M.; Gunawardena, N.K.; de Silva, N.R.; Douglass, J.; O’Hehir, R.E.; Weerasinghe, A.
    BACKGROUND: Elevated levels of total IgE (tIgE) in serum are characteristic of allergic diseases. Levels of tIgE are influenced by genetic predisposition, age, sex and helminth infections. However, the association between tIgE and allergic diseases in children living in areas endemic for helminth infections is not clear. The aim of our study was to assess the relationship between tIgE, allergic diseases and geohelminth infections in children. METHODS: A total of 640 schoolchildren 9Y11 years of age was selected by stratified random sampling. Data regarding allergic diseases (asthma, rhinitis and eczema) were collected by a standard questionnaire given to the parent or guardian. Screening for helminth infections was done by examining their fresh stool samples by modified Kato-Katz technique. Serum tIgE was measured by Fluoroenzymeimmunoassay in 67 geohelminth-positive subjects and in a comparable group of geohelminth-negative subjects. RESULTS: The mean age in the study population was 10 years (SDT0.3). The prevalence of geohelminth infection was 15.5%. Trichuris trichiura (14.3%) was the most common followed by Ascaris lumbricoides (4.2%) and hookworm (0.2%). Mixed infection was detected in 20.3% of infected children. Infection intensity was light in 68.9% of infected children while 28.4% and 2.7% showed moderate and heavy infection respectively. The cumulative prevalence of allergic diseases was 33.7%. Prevalence of asthma, rhinitis and eczema was 17%, 21.4% and 5% respectively. Serum tIgE concentrations showed a positively skewed distribution. Geometric mean (GM) for tIgE for the geohelminth infected group (1039.9kU/L) was significantly higher than that of the non-infected group (575.4kU/L) (p = 0.004). It was also higher in the allergic group (933.3kU/L) than in the non-allergic group (639.7kU/L) but the difference was not statistically significant (p = 0.068). The GM for tIgE for non-allergic children in the study population was much higher than that seen in non-allergic children in developed countries. CONCLUSION: Serum tIgE concentration was strongly associated with the presence of geohelminth infections in children. Serum tIgE may not be a useful marker for allergic diseases in children living in areas endemic for geohelminth infections. © 2007 World Allergy Organization
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