Biomedical subjects

Annette Olsen

Publications and source records attributed to Annette Olsen.

12 recordsLinked to original sources

PubMed2006

Cross-sectional parasitological survey for helminth infections among fish farmers in Nghe An province, Vietnam.

A total of 964 adult fish farmers in five eastern districts in Nghe An province, Vietnam were investigated in late 2004 for food-borne trematodes and other helminth infections using duplicate Kato-Katz thick smears prepared from single stool samples. Eggs of fish-borne trematodes and of Fasciolopsis buski were found in 0.6 and 0.7% of farmers, respectively. Infection prevalences with soil-transmitted helminths (STHs), namely Ascaris lumbricoides, Trichuris trichiura and hookworm, were 34.8, 50.7 and 51.3%, respectively, and 81.8% were infected with at least one of the three STHs. While A. lumbricoides and T. trichiura were more prevalent in the eastern districts compared to the more western districts, the opposite was true for hookworm infections. The widespread prevalence of STH infections in fish farmers suggests that control of these infections in school-age children only may be inadequate. Identification of the human behavioural factors and environmental features responsible for the distribution and frequency of STHs among adults is needed as well as a sensitive diagnostic test of fish-borne trematodes at species level.

Adult↗

PubMed2006

Impact of repeated mass treatment on human Oesophagostomum and hookworm infections in northern Ghana.

Oesophagostomum bifurcum is a common parasite of humans causing disease in parts of northern Ghana and northern Togo. The impact of repeated mass treatment with albendazole on infection with O. bifurcum and hookworm is analysed and the results compared with those in a control area where no treatment was given. At baseline, O. bifurcum and hookworm prevalences were 53.0% and 86.9%, respectively (n=1011). After 12 months, following two rounds of albendazole treatment, prevalences decreased significantly to 5.4% for O. bifurcum and 36.8% for hookworm (n=535). Twenty-four months after the baseline survey and following a total of four rounds of treatment, prevalences were further reduced to 0.8% and 23.4% for O. bifurcum and hookworm, respectively (n=478). Overall, there was a significant decrease in the larval counts, measured as geometric mean larval count per 4 g of stool of O. bifurcum from 3.0 to 0.1 and of hookworm from 47.2 to 1.8. The fourth mass treatment was carried out in April 2003 by the Lymphatic Filariasis Elimination Programme. Overall, compliance to treatment varied from 70% to 80%. In the control area, Oesophagostomum prevalence increased from 18.5% to 37.0% and the intensity from 0.4 to 1.4. For hookworm, both prevalence (86.1-91.3%) and intensity (54.8-74.3) increased but not to a significant level. The prospects of eliminating human oesophagostomiasis from the intervention area, while simultaneously achieving an important reduction of hookworm prevalences by albendazole mass treatment, are discussed.

Adolescent↗

PubMed2005

Epidemiology of helminth infections and their relationship to clinical malaria in southwest Uganda.

It has recently been suggested that helminth infections may adversely influence susceptibility to other infections, including malaria. To investigate this hypothesis in a sub-Saharan African setting, surveys of helminth infections were conducted in 2003 among individuals who had been under weekly active case detection for clinical malaria during the preceding 18 months in four villages in Kabale District, southwest Uganda. Overall, 47.3% of individuals had at least one intestinal nematode species infection: hookworm, Ascaris lumbricoides and Trichuris trichiura were detected in 32.1, 17.4 and 8.1% of individuals, respectively. We found evidence of significant household clustering of A. lumbricoides, T. trichiura and hookworm, and clustering of heavy infection of each species. The association between helminth infection and clinical malaria was investigated in two villages and no evidence for an association was observed between the presence of infection or heavy infection and risk of malaria.

Animals↗

PubMed2005

Ecological covariates of Ascaris lumbricoides infection in schoolchildren from rural KwaZulu-Natal, South Africa.

OBJECTIVES: To identify environmental factors that could serve to predict Ascaris lumbricoides infection patterns and thus guide control efforts in the absence of epidemiological information; to assess whether A. lumbricoides infection is positively associated with the soil clay content. METHODS: Information on A. lumbricoides infection and re-infection in a cohort of primary schoolchildren and interview data on their socioeconomic background and behaviour were combined with environmental data using a geographical information system (GIS). Multivariate models served to explore the covariation of environmental and infection patterns adjusted for possible confounders. RESULTS: Prevalence maps and spatial statistics revealed considerable spatial clustering of infection in the small study area. Logistic multivariate regression models showed strong positive associations of infection with vegetation density measured as the normalized difference vegetation index (NDVI) at baseline [odds ratio (OR) for a 10% increase: 1.82; 95% confidence interval (95% CI): 1.24-2.68; P=0.002] and after re-infection (OR: 2.22; 95% CI: 1.71-2.87; P<0.001). We also found a strong negative association of re-infection with the sun exposure of the soil surface as estimated from digital elevation models (OR: 0.78; 95% CI: 0.88; P<0.001). The soil clay content was only moderately positively associated with infection and re-infection. Socioeconomic and behavioural variables, although correlated with A. lumbricoides infection, did not appear to confound the above associations in the demographically homogeneous study area. Spatial analysis of the model residuals suggested that as the models accounted for most of the spatial pattern, the model standard errors should not be affected by spatial clustering. CONCLUSION: NDVI seems to have a high potential for the prediction of A. lumbricoides infection as it was strongly associated with infection patterns in the study area. Further advantages are that NDVI information is easy to use, affordable and available with global coverage.

Aluminum Silicates↗

PubMed2005

Ecologic covariates of hookworm infection and reinfection in rural Kwazulu-natal/south Africa: a geographic information system-based study.

Information on hookworm infection and re-infection in a cohort of primary school children and interview data on their socioeconomic background and behavior were combined with environmental data using a geographic information system (GIS). Multivariate models served to explore the covariation of environmental and infection patterns adjusted for possible confounders. Our aim was to identify environmental factors that might serve to predict infection and thus guide control efforts when epidemiologic information is insufficient. Furthermore, we wanted to establish whether soil type has a genuine influence on hookworm infection. Prevalence maps and spatial statistics showed considerable spatial clustering of infection in the small ( approximately 28 x 16 km) study area. The multivariate logistic regression models showed strong positive associations of infection at baseline (baseline prevalence = 83.2%) with settlement density (odds ratio [OR] = 1.24, 95% confidence interval [CI] = 1.10-1.38) and vegetation density (OR = 1.66, 95% CI = 1.25-2.22) and a strong negative association with the clay content of the soil (OR = 0.67, 95% CI = 0.62-0.73). Similar but weaker correlations were found after re-infection. Socioeconomic status and behavior did not seem to confound these associations. Spatial analysis of the model residuals suggested that because the models accounted for most of the spatial pattern, the model standard errors were not affected by spatial clustering. Our study shows that the pattern of hookworm infection is strongly influenced by several environmental factors. The GIS-aided prediction of areas in need of treatment is therefore a promising tool to guide control efforts when epidemiologic information is insufficient.

Child↗

PubMed2004

Patterns of Schistosoma haematobium infection, impact of praziquantel treatment and re-infection after treatment in a cohort of schoolchildren from rural KwaZulu-Natal/South Africa.

BACKGROUND: Schistosomiasis is one of the major health problems in tropical and sub-tropical countries, with school age children usually being the most affected group. In 1998 the Department of Health of the province of KwaZulu-Natal established a pilot programme for helminth control that aimed at regularly treating primary school children for schistosome and intestinal helminth infections. This article describes the baseline situation and the impact of treatment on S. haematobium infection in a cohort of schoolchildren attending grade 3 in a rural part of the province. METHODS: Primary schoolchildren from Maputaland in northern KwaZulu-Natal were examined for Schistosoma haematobium infection, treated with praziquantel and re-examined four times over one year after treatment in order to assess the impact of treatment and patterns of infection and re-infection. RESULTS: Praziquantel treatment was highly efficacious at three weeks after treatment when judged by egg reduction rate (95.3%) and cure rate of heavy infections (94.1%). The apparent overall cure rate three weeks after treatment (57.9%) was much lower but improved to 80.7% at 41 weeks after treatment. Re-infection with S. haematobium was low and appeared to be limited to the hot and rainy summer. Analysis of only one urine specimen per child considerably underestimated prevalence when compared to the analysis of two specimens, but both approaches provided similar estimates of the proportion of heavy infections and of average infection intensity in the population. CONCLUSION: According to WHO guidelines the high prevalence and intensity of S. haematobium infection necessitate regular treatment of schoolchildren in the area. The seasonal transmission pattern together with the slow pace of re-infection suggest that one treatment per year, applied after the end of summer, is sufficient to keep S. haematobium infection in the area at low levels.

Adolescent↗

PubMed2004

Patterns of geohelminth infection, impact of albendazole treatment and re-infection after treatment in schoolchildren from rural KwaZulu-Natal/South-Africa.

BACKGROUND: Geohelminth infection is a major health problem of children from rural areas of developing countries. In an attempt to reduce this burden, the Department of Health of the province of KwaZulu-Natal (KZN) established in 1998 a programme for helminth control that aimed at regularly treating primary school children for schistosomiasis and intestinal helminths. This article describes the baseline situation and the effect of treatment on geohelminth infection in a rural part of the province. METHODS: Grade 3 schoolchildren from Maputaland in northern KZN were examined for infections with hookworm, Ascaris lumbricoides, and Trichuris trichiura, treated twice with 400 mg albendazole and re-examined several times over one year after the first treatment in order to assess the impact of treatment and patterns of infection and re-infection. RESULTS: The hookworm prevalence in the study population (83.2%) was considerably higher than in other parts of the province whereas T. trichiura and especially A. lumbricoides prevalences (57.2 and 19.4%, respectively) were much lower than elsewhere on the KZN coastal plain. Single dose treatment with albendazole was very effective against hookworm and A. lumbricoides with cure rates (CR) of 78.8 and 96.4% and egg reduction rates (ERR) of 93.2 and 97.7%, respectively. It was exceptionally ineffective against T. trichiura (CR = 12.7%, ERR = 24.8%). Re-infection with hookworm and A. lumbricoides over 29 weeks after treatment was considerable but still well below pre-treatment levels. CONCLUSION: High geohelminth prevalences and re-infection rates in the study population confirm the need for regular treatment of primary school children in the area. The low effectiveness of single course albendazole treatment against T. trichiura infection however demands consideration of alternative treatment approaches.

Albendazole↗

PubMed2004

Low-dose iron supplementation does not increase HIV-1 load.

Observational data suggest that iron may increase HIV replication and the rate of progression of HIV infection. This is worrying, and may impede the international commitment to combat iron deficiency. However, it is crucial to clarify the role of iron in HIV infections, since iron is universally administered to anaemic patients and pregnant women, even in areas with high HIV prevalence. Based on a historical iron trial, we assessed the effect of 60 mg of elemental iron given twice weekly over four month on HIV-1 viral load. There was no effect on viral load, but effects of higher doses of iron cannot be excluded.

Adolescent↗

PubMed2004

Effects of iron and multimicronutrient supplementation on geophagy: a two-by-two factorial study among Zambian schoolchildren in Lusaka.

Geophagy has been associated with iron deficiency and anaemia, but no causal relationship has been established. To clarify this, we conducted a two-by-two factorial randomised, controlled trial on the effect of iron and multimicronutrient supplementation on geophagy in Zambian schoolchildren in Lusaka, from February to December 2001. Of the 406 children, 212 (52.2%) were girls and the mean (range) age was 10.2 (7-15) years. Geophagy was reported by 302 (74.4%) and more often in girls than in boys (80.2 vs. 67.7%, P = 0.007). The mean (range) daily earth intake was 25.2 (1-200) g. Geophageous children had more often geophageous relatives than non-geophageous children (79.5 vs. 1.9%, P < 0.001). Geophageous children had lower serum ferritin (20.5 vs. 25.0 microg/l, P = 0.032) but not haemoglobin (Hb) (129.2 vs. 130.4 g/l, P = 0.59), than non-geophageous. Among those with Hb < 130 g/l, geophageous children had significantly higher prevalence (53.7 vs. 30.6%, P = 0.024) of Ascaris lumbricoides infection than non-geophageous. The prevalence of geophagy (74.4 to 51.6%) and the intake of earth (25.3 to 15.0 g/day) declined (P = 0.001 and P < 0.001, respectively) among the 220 (54.2%) children followed-up. In bivariate analysis, non-iron supplementation reduced the prevalence of geophagy more than iron supplementation did, but this was not confirmed in the multiple logistic regression analysis. Multimicronutrients had no effect on either geophagy prevalence or earth intake. Geophagy was prevalent and associated with iron deficiency, but iron supplementation had no effects on geophageous behaviour. Geophagy could be a copied behaviour and the association between geophagy and iron deficiency due to impaired iron absorption following earth eating.

Adolescent↗

PubMed2003

Experience with school-based interventions against soil-transmitted helminths and extension of coverage to non-enrolled children.

This paper reviews the experience with school-based interventions against soil-transmitted helminths with regard to reduction in prevalence, intensity of infection and morbidity. It also examines the existing experience with coverage of school-based programmes to non-enrolled children. However, as this experience is limited, the paper also seeks to give an overview of the need for school control programmes to include other segments of the community. The experiences from the programmes indicate that treatment should be performed twice or thrice yearly without prior diagnosis, should be school-based and involving schoolteachers assisted by health staff, if possible. The drugs of choice are a single dose of 400 mg albendazole or 500 mg mebendazole. If intensities of Trichuris trichiura or hookworm infections are high, a double or triple dose of one of these drugs could be considered to maximise reduction in intensities. For the benefit of growth and iron status, it should be considered to supplement with iron and other micronutrients. School-based programmes should include non-enrolled school age children and pre-school children, and the system of having 'treatment days' at school, where these groups are invited for treatment, seems to be a promising strategy. While antenatal clinics have been involved in the anthelminthic treatment of pregnant women, they have not covered non-pregnant adolescent girls and women. These could be offered treatment through the 'treatment days' at school mentioned earlier.

Animals↗

PubMedDate not supplied

Geophagy and its association with geohelminth infection in rural schoolchildren from northern KwaZulu-Natal, South Africa.

The social pattern of geophagy (soil-eating) and its possible role in the transmission of Ascaris lumbricoides, Trichuris trichiura and hookworm were investigated in a rural area of South Africa between March 1998 and July 1999. Schoolchildren (median age = 10.7 years; interquartile range 8.3-14.8 years) were examined for geohelminth infection at baseline and re-examined 3 and 29 weeks after treatment with albendazole. Interviews were conducted with the pupils in order to find out about their socio-economic background and their behaviour regarding geophagy. Soil-eating was less frequent in boys (39%), where it decreased with age, than in girls (53%), where no such age trend was apparent. The habit was more common in children from families of higher socio-economic status. The baseline prevalence of A. lumbricoides infection was higher in pupils who regularly ate soil from termite mounds (28%) when compared with non-geophageous pupils (19%; prevalence ratio (PR) = 1.46; 95% confidence interval (95% CI) 1.04-2.03). In contrast it was markedly lower in the groups who preferred eating tree termite soil (13%; PR = 0.67; 95% CI 0.43-1.04) or soil from other sources (8%; PR = 0.40; 95% CI 0.15-1.04). This pattern was still apparent after adjusting for possible confounders and was also found when analysing A. lumbricoides reinfection. In contrast, differences in prevalence of T. trichiura and hookworm infection between groups with different soil preference were small.

Adolescent↗

PubMedDate not supplied

Effects of multimicronutrient supplementation on helminth reinfection: a randomized, controlled trial in Kenyan schoolchildren.

A randomized, placebo-controlled, double-blind, two-by-two factorial trial was carried out among 977 schoolchildren from 19 primary schools in Nyanza Province, Kenya from February 1995 to February 1996. The interventions were multimicronutrient supplementation (vitamin A, 1000 micrograms; vitamin B1, 1.4 mg; vitamin B2, 1.6 mg; vitamin B6, 1.7 mg; vitamin B12, 2.0 micrograms; folate, 150 micrograms; niacin, 16 mg; vitamin C, 50 mg; vitamin D, 5 micrograms; vitamin E, 8 mg; iron, 18 mg; zinc, 20 mg; copper, 2.0 mg; iodine, 150 micrograms; selenium, 40 micrograms) and multihelminth chemotherapy (albendazole 600 mg in a single dose and/or praziquantel 40 mg/kg in a single dose). This paper reports the effects of the supplementation given on all school days on reinfection with hookworm, Ascaris lumbricoides, Trichuris trichiura and Schistosoma mansoni after 11 months. Baseline prevalence and geometric mean intensity for hookworm, A. lumbricoides, T. trichiura and S. mansoni in all children investigated were 54.7%, 13.8%, 45.6% and 70.0%, respectively and 8.6, 2.7, 5.9 and 19.4 eggs per gram (epg), respectively. Children received a mean of 2.3 multimicronutrient/placebo tablets per school week, giving a compliance rate of 46%. Children given multimicronutrients had a slightly, but significantly, lower intensity of S. mansoni reinfection compared with children given placebo (5.5 epg vs. 7.7 epg, P = 0.047). Multiple linear regression analyses controlling for baseline infection status confirmed this, as children who received micronutrients were reinfected with S. mansoni at only 69% of the intensity of those who received placebo. Multiple logistic regression analyses revealed that micronutrient supplementation was associated with a lower S. mansoni reinfection rate (odds ratio = 0.7) although this was only of borderline significance (P = 0.090). There were no significant differences in reinfection rates or intensities of hookworm, A. lumbricoides and T. trichiura. The effect on S. mansoni infection intensity is particularly interesting given the low compliance, suggesting that full micronutrient supplementation might have a role to play in S. mansoni control programmes.

Adolescent↗