Quantitative egg excretion and work capacity in a Gezira population infected with Schistosoma mansoni

Career perspective: Kenneth J. Collins

A career interest in thermoregulation research has included wide contrasts in the subjects of enquiry, extending from heat stroke to hypothermia, special investigations in many different purpose-built climatic chambers, laboratory-based biomedical studies together with hospital practice, and field work in tropical climates to physiological surveys on urban populations in temperate environments. The scientific process and need to focus on careful planning of experiments, using the most appropriate methods, selecting the right controls and eventually applying correct statistical analysis do not always follow a smooth transition, as illustrated in this account. The result of endeavour to resolve a human environmental problem, however, is greatly satisfying, and sometimes becomes a unique experience when the solution reveals new fundamental facts.

Infection with Schistosoma mansoni has an Effect on Quality of Life, but not on Physical Fitness in Schoolchildren in Mwanza Region, North-Western Tanzania: A Cross-Sectional Study

Background

Infection with Schistosoma mansoni negatively impact children’s physical health and may influence their general well-being. The aim of this study was to investigate the effect of S. mansoni infections on a panel of morbidity indicators with emphasis on quality of life (PedsQL; measured in four different dimensions) and physical fitness (measured as VO₂ max) among 572 schoolchildren aged 7–8 years.

Methodology/Principal findings

Prevalence of S. mansoni infections was 58.7%, with an arithmetic mean (95% CI) among positives of 207.3 (169.2–245.4) eggs per gram (epg). Most infections were light (56.5%), while 16.4% had heavy infections. Girls had significantly higher arithmetic mean intensities (95% CI) than boys (247.4 (189.2–305.6) vs. 153.2 (110.6–195.8); P = 0.004). A total of 30.1% were anaemic with no sex difference. Stunting and wasting was found in less than 10% of the population. There was no association between S. mansoni prevalence or intensities and the following parameters: anthropometry, anaemia, liver or spleen pathology in neither univariable nor multivariable linear regression analyses. However, in univariable analyses children with S. mansoni infection had a significantly lower score in emotional PedsQL (95% CI) than uninfected (77.3 (74.5–80.1) vs. 82.7 (79.9–85.5); P = 0.033) and infected children had a higher VO₂ max (95% CI) compared to uninfected (51.4 (51.0–51.8) vs. 50.8 (50.3–51.3); P = 0.042). In multivariable linear regression analyses, age, S. mansoni infection, haemoglobin and VO₂ max were significant predictors for emotional PedsQL while significant predictors for VO₂ max were physical PedsQL, height, age and haemoglobin. S. mansoni infection was thus not retained in the multivariable regression analyses on VO₂ max.

Conclusions/Significance

Of the measured morbidity parameters, S. mansoni infection had a significant effect on the emotional dimension of quality of life, but not on physical fitness. If PedsQL should be a useful tool to measure schistosome related morbidity, more in depth studies are needed in order to refine the tool so it focuses more on aspects of quality of life that may be affected by schistosome infections.

Millions of school-age children in Tanzania are infected with Schistosoma mansoni which have an impact on their physical health by reducing growth and fitness, causing anaemia and liver and spleen pathology. Apart from these measurable physical parameters, self-rating of well-being by administration of quality of life questionnaires has been proposed for measuring schistosome related morbidity. A total of 572 schoolchildren aged 7–8 years were examined for S. mansoni infection, anaemia, malnutrition and liver/spleen enlargement. Furthermore, the children participated in a 20 metres shuttle run fitness test and answered a quality of life questionnaire for children. While there was no association between S. mansoni prevalence or intensities and anaemia, malnutrition, fitness or organ enlargement, S. mansoni infected children had a significantly lower self-perceived emotional quality of life. Thus, infected children were more often scared, sad, angry or worried about their future compared to their uninfected peers. More in depth studies are needed in order to refine the questionnaire so it focuses more on aspects of quality of life that may be affected by schistosome infections.

Effect of schistosomiasis and soil-transmitted helminth infections on physical fitness of school children in Côte d'Ivoire

Background

Schistosomiasis and soil-transmitted helminthiasis are important public health problems in sub-Saharan Africa causing malnutrition, anemia, and retardation of physical and cognitive development. However, the effect of these diseases on physical fitness remains to be determined.

Methodology

We investigated the relationship between schistosomiasis, soil-transmitted helminthiasis and physical performance of children, controlling for potential confounding of Plasmodium spp. infections and environmental parameters (i.e., ambient air temperature and humidity). A cross-sectional survey was carried out among 156 school children aged 7–15 years from Côte d'Ivoire. Each child had two stool and two urine samples examined for helminth eggs by microscopy. Additionally, children underwent a clinical examination, were tested for Plasmodium spp. infection with a rapid diagnostic test, and performed a maximal multistage 20 m shuttle run test to assess their maximal oxygen uptake (VO₂ max) as a proxy for physical fitness.

Principal Findings

The prevalence of Schistosoma haematobium, Plasmodium spp., Schistosoma mansoni, hookworm and Ascaris lumbricoides infections was 85.3%, 71.2%, 53.8%, 13.5% and 1.3%, respectively. Children with single, dual, triple, quadruple and quintuple species infections showed VO₂ max of 52.7, 53.1, 52.2, 52.6 and 55.6 ml kg⁻¹ min⁻¹, respectively. The VO₂ max of children with no parasite infections was 53.5 ml kg⁻¹ min⁻¹. No statistically significant difference was detected between any groups. Multivariable analysis revealed that VO₂ max was influenced by sex (reference: female, coef. = 4.02, p<0.001) and age (years, coef. = −1.23, p<0.001), but not by helminth infection and intensity, Plasmodium spp. infection, and environmental parameters.

Conclusion/Significance

School-aged children in Côte d'Ivoire showed good physical fitness, irrespective of their helminth infection status. Future studies on children's physical fitness in settings where helminthiasis and malaria co-exist should include pre- and post-intervention evaluations and the measurement of hemoglobin and hematocrit levels and nutritional parameters as potential co-factors to determine whether interventions further improve upon fitness.

The burden of parasitic worm infections is considerable, particularly in developing countries. It is acknowledged that parasitic worm infections negatively impact on children's school performance and physical development. A deeper understanding of these linkages is important for updating burden of disease measures. We investigated the relationship between worm infection status and physical fitness of 156 school children from Côte d'Ivoire and controlled for potential confounding of Plasmodium infection (the causative agent of malaria) and environmental parameters (temperature and humidity). Children were diagnosed for parasitic worm and Plasmodium infections, examined by a physician, and participated in a 20 m shuttle run test to assess their maximal oxygen uptake (VO₂ max) as a proxy for physical fitness. Most of the children had parasitic worms and a Plasmodium infection. Nevertheless, their physical fitness was excellent (average VO₂ max: 52.7 ml kg⁻¹ min⁻¹). The level of VO₂ max was only influenced by sex and age, but not by parasitic worms and Plasmodium infections. In future studies, the dynamics of children's physical performance should be assessed before and after control interventions, including the assessment of blood hemoglobin, hematocrit, and nutritional indicators to determine whether physical fitness in worm- and Plasmodium-infected individuals can be further improved.

Studies of impact on physical fitness and working capacity of patients with advanced Schistosomiasis japonica in Susong County, Anhui Province

To assess the impact level on physical fitness and working capacity in patients with advanced Schistosomiasis japonica, a field study was carried out. According to the records of patients with advanced schistosomiasis in Susong County, Anhui Province, 48 advanced cases without other serious chronic diseases from endemic areas in two townships and 56 healthy individuals from non-endemic area, served as control group with matched ages between 40 and 70 years and matched sex were investigated with questionnaire, anthropometric measure and hemoglobin level. The impairment level of the liver was measured by ultrasonography and physical fitness was measured by the Step test in the case and control groups. All situations including lifestyle, working, socio-economic status and residing environment was similar in the case and control groups. Average height and weight was significantly lower in the case group than in the control group (height = 156.29 and 159.41 cm; weight = 50.72 and 53.92 kg; respectively, all P < 0.05). Thirteen individuals (28.3%) in the case group had moderate reduction of working capacity or even unable to work, but only seven (12.7%) individuals in the control group had moderate reduction of working capacity and all in the control group were able to work (P < 0.01). In the past 1 year, the average working days lost was 4.11 days in the case group and 0.86 day in the control group (P < 0.01). Both groups differed significantly in symptoms of abdominal pain, diarrhea and weakness (all P < 0.05). Twenty-one cases (43.8%) had grade II impairment of the liver and eight cases (16.7%) had grade III impairment of the liver in the case group, whereas seven individuals (12.7%) had grade II impairment of the liver in the control group (P < 0.01), as assessed by ultrasound. The hemoglobin levels and the power of gripping in the case group were significantly lower than those in the control group (Hb = 111.06 and 122.27 g/l; grip = 303.83 and 344.20 N, respectively, all P < 0.01). Physical fitness scores showed the control group (score: 71.84) was significantly fitter than the case group (score: 61.09, P < 0.01). Compared with the control group, the physical fitness of the case group reduced by 15%. The results showed that physical fitness and working capacity were reduced in advanced cases. Although most of the cases were treated and had reached a status of 'clinical cure', the impact on physical fitness and working capacity still existed.

The physical fitness and work performance of agricultural workers infected with Schistosoma mansoni in Zimbabwe

Stool specimens were collected from 1995 sugarcane cutters on the Hippo Valley and Triangle sugar estates, Zimbabwe, in order to determine the prevalence and intensity of Schistosoma mansoni infection. Pathological changes normally ascribed to S. mansoni infection were assessed in the infected cutters, by ultrasonography before treatment. The height, weight, age, haemoglobin levels, blood pressure and body fat of the infected and uninfected control study subjects, standardized by age, were determined. Those with elevated blood pressure were excluded from the study. Physical fitness and work performances were assessed in 287 infected and 210 uninfected cane cutters aged (mean +/- S.D.) 36.5 +/- 7.5 years. Despite the finding that all the subjects were of good nutritional status and generally physically fit, a t-test showed a significant improvement (P < 0.01) in the performance of the infected cutters following treatment; age-related physical performance, measured by the Harvard Step Test, increased by 4.3% and work output, measured as the amount of cane cut in a given time, rose by 16.6%. Although the physical and work performances of the uninfected control subjects also increased over the same period, this trend, attributed to occupational physical exercise, was not statistically significant (P > 0.05). Significant correlations were found between both infection intensity-related pre-treatment physical fitness (P < 0.05) and work performance (P < 0.01) and prevalence of Symmers' peri-portal fibrosis.

Bilharzia and the boys: questioning common assumptions

There is insufficient and inadequate information to gauge the impact of schistosomal infection on the health of women. Biomedical research has equated women's health with the study of reproductive performance and reproductive organs and this narrow focus has left a number of important questions unanswered. Attempts to explore the economic and social aspects of schistosomal infection have been minimal and most research has focused on men rather than women. It has two characteristics: first, economists have relied on single performance indicators which are rooted in the cultural traditions of the research workers rather than the participants. Second, questionnaires have been used to elicit perceptions of health and illness; and local, culturally-specific information has not even been used to formulate the questions. Future research assessing the social and economic aspects of infection among women would be enhanced by undertaking inter-disciplinary research, with an ethnographic component; and blending qualitative with quantitative methods. Research assessing the impact of schistosomal infection on daily activities has been undertaken in Omdurman aj Jadida, Sudan. Biomedical and continuous observational data were blended with ethnographic information and the analyses of these data suggest that Schistosoma mansoni exerts a differential impact on female activity patterns. That is, infection by S. mansoni significantly impaired female activities in the agricultural sphere whereas infection by S. mansoni did not have any significant impact on female activities in the domestic sphere. Variations in the nature and extent of work undertaken by these two groups of women as well as differential exposure to solar radiation probably accounts for these recorded differences. The limited and tentative nature of biomedical, economic, sociological and anthropological information assessing the impact of schistosomal infection on the health of women adds to the current controversies about whether schistosomiasis should continue to be given priority as a public health problem. Further research is essential to clarify this important issue.

Infection, nutrition and cognitive performance in children

The paper considers briefly the nature of cognition and its relationship to intelligence. The information processing model of human cognition is outlined and IQ and DQ are explained. The literature dealing with the effects of malnutrition and parasitic infection on cognitive performance and development in children is selectively reviewed. A speculative hypothesis concerning the psychological effects of parasitic infection is sketched and brief consideration is given to models and measures in research on development.

Cost analysis of schistosomiasis

Cost analysis of schistosomiasis is important both in assessing the economic impact of the disease and in identifying the most cost-effective approaches to control. Economic impact has been examined both within and without the health sector, but there is a lack of measurement of the effects of disease, or the threat of disease, on patterns of production and community development. The cost-effectiveness of control approaches has been examined empirically and by using static models. Future analyses require a stronger epidemiological basis incorporating realistic demography and the temporal dynamics of reinfection, and assessment of outcomes in terms of disease rather than infection.

Re-assessing disability: the impact of schistosomal infection on daily activities among women in Gezira Province, Sudan

Schistosoma mansoni is often perceived by governments and international aid agencies to present a major public health problem in the tropical and sub-tropical world. This perception persists in spite of the fact that biomedical practitioners and research workers disagree about the nature and extent of disease and disability caused by schistosomes. This paper raises the question of whether S. mansoni should continue to be given priority as a public health problem in Gezira Province, Sudan. Biomedical and continuous observational data are blended with ethnographic information in order to develop a more integrated picture of the impact of S. mansoni on daily activity patterns among women. Research took place in one village in the Gezira/Managil irrigation scheme. The study is characterized by a small sample and a paired design. That is, 11 infected women were paired with 11 uninfected women. These women were engaged in agricultural activities in the cotton picking season and they were matched for a wide range of social and economic factors that might otherwise have affected their working activities. Observations were conducted on a minute by minute basis in the cotton fields. These data, in combination with ethnographic information and data indicating female productive output, showed that infection with S. mansoni significantly altered activity patterns in the cotton fields. That is, infected women (with an arithmetic mean egg output of 1958 eggs/g) attempted to pick as much cotton as possible in the shortest time period feasible in the morning. This pattern was partially repeated by infected women who returned to the fields in the afternoon. However, a significant number of infected women felt too weak to sustain this work regime and the economic implications of this finding are discussed. Finally, Fisher's exact probability test showed that infected women were significantly less likely to undertake personal care activities between cotton picking sessions and this result suggests they may have been too tired and/or had a diminished perception of their own well-being. The implications of these results for public health policy in Gezira Province are discussed.

Schistosomiasis and the social patterning of infection

Social, cultural, behavioural and economic factors interact with local environmental and ecological factors to produce extraordinary variation in the epidemiology of schistosomiasis, including with respect to prevalence and intensity of infection and the potential for control. This article reviews the literature on schistosomiasis infection, primarily derived from African studies, to identify its major social themes. Research has demonstrated a strong link between economic development strategies, where irrigation has been introduced to boost agricultural production, and the increased transmission of infection. Water-contact studies have provided the fullest and most detailed descriptions of social risk factors, and have isolated age, sex, religion and occupation as primary risk factors. However, fuller explorations of the social and cultural context of infection have yet to be undertaken. The social context of water-related behaviour and patterns of water use within communities and households, the intersection of social and economic activities, and the significance that people give to these activities, remains poorly explored, and although research papers concerned with community-based interventions refer to poor community understanding of the cause, prevention and treatment of the disease, this domain has also received little scholarly attention. Finally, economic studies have focused primarily on working capacity, and extrapolated these findings to generalize about the impact that this might have on productivity, but have yet to address either household or community costs of schistosomiasis infection.

Schistosomiasis in childhood

Schistosomiasis is a parasitic disease of the tropics which is estimated to affect up to 300 million people worldwide. In endemic areas the childhood age group has the highest prevalence and intensity of infection. There are several distinct species of schistosomes. The principal organ system involved in Schistosoma haematobium infection is the urinary tract since parasite eggs penetrate the bladder and are excreted in the urine. Hematuria, proteinuria, leukocyturia and symptoms like dysuria or nocturia are the most common clinical presentations. Heavily infected patients show obstructive uropathy of different severity which may lead to renal failure. Intestinal schistosomiasis is caused by Schistosoma mansoni infection. Initial symptoms can be diarrhea and blood-tinged stool. Chronic infection is characterized by fibrotic involvement of the liver and consecutive portal hypertension. The diagnosis of schistosomiasis depends on the demonstration of schistosome eggs in human excreta or biopsy material. Imported cases of schistosomiasis to Europe show an increasing tendency due to expanding international travel. Furthermore imported cases are usually not diagnosed until years after the patients have left an endemic area. The treatment of choice is a single dose of praziquantel 40 m/kg bodyweight resulting in cure rates of around 90% and considerable reversibility of pathological abnormalities due to schistosome infections.

Effects of exposure to cotton dust on energy expenditure in the textile industry

An assessment of energy expenditure has been made in 50 male textile workers and 30 male office cleaners. There was a statistically significant difference (P less than 0.001) in energy expenditure between textile workers and office cleaners amounting to 12 to 16%. While 33.3% of the textile group complained of chest disorders, none of the cleaners had such a complaint. FEV1 and FVC values of the textile workers were significantly lower (P less than 0.01) compared to those of the controls. There were no differences in body weight, lean body mass and socio-economic conditions of the two groups, however, the textile workers were younger and taller than the unexposed group. Exposure to cotton dust and respiratory and ventilatory impairments are suspected of causing a reduction in the energy expenditure of the textile workers.

The morbidity of schistosomiasis mansoni in Maniema (Zaire)

The morbidity of schistosomiasis mansoni was assessed in Makundju (population 547; prevalence 96%, mean egg load 791 epg) and Massimelo (pop. 363; prev. 19%, mean egg load 39 epg), 2 similar villages in the forest zone of Maniema, Zaire. The prevalences of other parasites including malaria (holoendemic) were comparable. "Intermittent diarrhoea" (mostly bloody) was a complaint of 55% and 3% of the populations, respectively, "intermittent abdominal pain" of 63% and 25%, and "fatigue" of 33% and 19%. Enlargement of the left liver lobe was present in 45% and 9% of the populations, right lobe hepatomegaly in 32% and 3%, splenomegaly in 29% and 9%. Hepatomegaly and splenomegaly in Makundju were often very impressive, and most frequent in the 6- to 18-year-old group. Anaemia (haematocrit less than or equal to 35%) was present in 30% and 9% of males and 36% and 21% of females. Mean length and weight were lower in Makundju for boys aged 11 to 18 years. Ergometric results (Astrand cyclometer, male adults only) were comparably low in both villages (mean VO2max. 19.3 and 18.9). Analysis of the data according to egg load within the Makundju community revealed a significant relationship only in the following cases: higher frequencies of diarrhoea, abdominal pain and fatigue in those excreting more than 200 epg compared with those excreting fewer; left lobe splenomegaly gradually increased with egg load in children under 18; in people over 40 it occurred at a higher frequency in those excreting more than 2000 epg than in those excreting fewer.(ABSTRACT TRUNCATED AT 250 WORDS)

Is the working capacity of Liberian industrial workers increased by regular malaria prophylaxis?

In a study of the impact of malaria prophylaxis upon the physical working capacity of Liberian industrial workers, two groups of men, one with and the other without malaria prophylaxis, were compared over a period of one year. At the beginning and at the end of the study, the haemoglobin concentration, haematocrit, blood volume and physical performance--measured by bicycle ergometry and expressed as work load at heart rate 170--were compared. No significant differences were found, either within or between the two groups. Routinely distributed malaria prophylaxis thus seems to be of little importance with respect to working capacity in this type of community, where malaria is meso-endemic.

A household framework for examining the social and economic consequences of tropical diseases

In spite of the fact that tropical diseases such as malaria and schistosomiasis are endemic in much of the world, little socioeconomic research has been conducted to provide planners and other policy-makers with a basis for understanding the behavioral implications of these diseases. This paper brings modern microeconomic theory to bear on an area of research which has lacked an adequate theoretical framework. It proposes to focus on the relationships between tropical diseases and their effects on the health status and functional capacity of the individual and ultimately on the social and economic performance of the individual household by using a broadly conceptualized new home economics framework. This paper not only presents factors to be considered in developing a conceptual framework, but also discusses research design and data considerations.