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.     

Epidemiological and morbidity assessment of Schistosoma japonicum infection in a migrant fisherman community, the Dongting Lake region, China

We assessed the epidemiology and morbidity related to Schistosoma japonicum infection by both parasitological (Kato-Katz method and miracidium hatching test) and ultrasound examination in a migrant fisherman community (n = 106) from the Dongting Lake region in China in 2001. A prevalence of 69.8% and a mean infection intensity of 66.5 eggs per gram (epg) were recorded for this group. Males had a higher level of infection (77%) and intensity (92.2 epg) compared with females (58% and 28.6 epg, respectively). Subjects aged 11-20 years had the highest prevalence of infection (91%) and the heaviest infection intensity (85.3 epg) among all age groups. Twenty-six percent of the subjects had not been treated previously for schistosomiasis. Parenchymal fibrosis (> or = stage II) detected by ultrasound and spleen enlargement (or splenectomy) occurred in 37% and 9% of subjects, respectively. Portal vein dilation was detected in 18% subjects, and 58% (11/19) of those patients with portal vein enlargement were shown to have parenchymal fibrosis (> or = stage II). These results indicate that S. japonicum infection and related morbidity in mobile fisherman is still unacceptably high despite the fact that China has implemented a Schistosomiasis Control Project financed by a World Bank Loan for a period of 8 years since 1992. Clearly, new approaches for schistosomiasis control, especially in communities like these mobile fishermen, should be explored.     

The morbidity of schistosomiasis mansoni in the highland focus of Lake Cohoha, Burundi

Morbidity due to infection with Schistosoma mansoni was investigated in a recently discovered highland focus around Lake Cohoha, Burundi. The distribution of the infection was very focal and morbidity patterns in populations from an endemic area A (prevalence 38%, mean egg load of positive subjects 231 eggs per gram [epg]), a less affected area B (16%, 90 epg) and a virtually non-endemic area C (5%, 45 epg), were compared; apart from schistosomiasis, the profiles of these populations were highly similar. The overall frequencies of diarrhoea were 36%, 25%, and 19%, respectively; of abdominal pain 86%, 78%, and 83%; of fatigue 7%, 2%, and 1%; of left lobe hepatomegaly 30%, 18%, and 9%; of right lobe hepatomegaly 18%, 10%, and 5%; of splenomegaly 18%, 10%, and 7%. Organomegaly was generally mild, even in area A. Within area A, the association between the presence of infection and diarrhoea, fatigue, hepatomegaly and splenomegaly was significant, but far less impressive than the results of the community-based comparison with areas B and C. The correlation with intensity was limited to an increased prevalence of diarrhoea and fatigue in the highest egg count group, and a more gradual increase (varying with age) in hepatomegaly and splenomegaly. The data are compared to other morbidity studies in subsaharan Africa, in particular one in the nearby Rusizi Plain. The lesser impact of malaria, the higher egg loads, the recent establishment of the focus and possibly parasite strain differences may account for the more apparent and more important schistosomiasis morbidity in the Cohoha focus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epidemiology of schistosomiasis mansoni in a low endemic area

We discuss the epidemiological patterns of schistosomiasis mansoni in areas with low transmission in Brazil. We define as areas of low endemicity those where the prevalence is less than 10%, the number Schistosoma mansoni eggs per gram of feces (epg) is less than 96, and carriers are asymptomatic. Data are from the county of Pedro de Toledo in the Ribeira Valley (S?o Paulo State) and were collected randomly according to the aggregate pattern of S. mansoni within the hosts. We suggest the replacement of parasitological methods by more sensitive and specific serological techniques. The main risk factor for infection is type of leisure activity. Infection is more frequent in the 10-14, 15-19, and 20-24-year age brackets. Geometric mean epg is 58.5. Intensity of infections correlates well (rs = 0.745) with prevalence. The highest index of potential contamination is in the 5-20-year age bracket (57.6%). Autochthonous cases show close association with Biomphalaria tenagophila, which has a low infection rate (2%). Prevalence, incidence, and intensity of infection patterns are similar to those of moderate and high endemic areas. Social and cultural aspects must be studied in order to obtain a global epidemiological view of schistosomiasis.     

A 13-year follow-up of treatment and snail control in an area endemic for Schistosoma mansoni in Brazil: incidence of infection and reinfection.

The incidences of Schistosoma mansoni infection and reinfection were investigated in an endemic area of Brazil (Peri-Peri, State of Minas Gerais) where chemotherapy and snail control had been used for 13 years (1974-87). Two cohorts were followed: the first consisted of 584 individuals with no evidence of infection at entry (infection cohort), and the second comprised 296 individuals who were treated and did not eliminate eggs 8-12 months afterwards (reinfection cohort). The incidence of infection (per 100 person-years) decreased from 7.5 in 1974-77 to 3.6 in 1986-87, and that of reinfection from 21.3 in 1974-77 to 3.7 in 1986-87. Calendar period, age at risk, and sex were independently associated with both infection and reinfection, while a heavy S. mansoni egg count prior to treatment (> or = 500 epg (eggs per gram of stools)) was independently associated with reinfection. The geometric mean number of eggs after treatment among those reinfected (47 epg) was approximately half that among those infected for the first time (81.5 epg). Age at risk had the greatest effect on both infection and reinfection. The rate ratios of infection and reinfection were 3 to 6 times higher among individuals younger than 20 years than among those aged > or = 25 years, even after adjusting for confounders. This suggests the existence of a strong protective effect with increased age (because of biological and/or environmental factors) for both infection and reinfection.     

The relationship between morbidity and intensity of Schistosoma mansoni infection in a rural Zambian community

Six hundred and ninety-three individuals from an area endemic for S. mansoni infection had parasitological and physical examinations done. A morbidity questionnaire was also administered to each participant. Among those with S. mansoni infection, there was significant increase in watery diarrhoea, bloody diarrhoea, blood in stool and hepatomegaly. The severity of the disease appears to be directly related to the egg load and therefore these results give further justification for treatment of high intensity age groups in community based chemotherapy programmes designed to reduce morbidity in endemic areas.     

Human schistosomiasis mansoni: intensity of infection differentially affects the production of interleukin-10, interferon-gamma and interleukin-13 by soluble egg antigen or adult worm antigen stimulated cultures

The effect of the intensity of infection (eggs per gram faeces, epg) on the production of interferon-gamma (INF-gamma), interleukin (IL)-10 and IL-13 by peripheral blood mononuclear cells (PBMCs) from individuals living in a Schistosoma mansoni-endemic area was evaluated. In vitro stimulation of PBMCs with soluble egg antigen (SEA) resulted in significantly higher secretion levels of IFN-gamma in egg-negative individuals compared with those with an intensity of infection of more than 100 epg. In contrast, the egg-positive group produced significantly higher amounts of IL-10. Levels of IL-13 did not differ significantly between egg-positive and egg-negative groups. These findings suggest that IL-10 is an important cytokine in the control of the T helper cell (Th) type 1 responses during human S. mansoni infection, shifting the immune response from Th0 in egg-negative individuals from an endemic area to a Th2 polarization in chronic infected individuals.     

Two-year impact of praziquantel treatment for Schistosoma japonicum infection in China: re-infection, subclinical disease and fibrosis marker measurements

We studied a community cohort of 193 individuals exposed to endemic Schistosoma japonicum infection in the Dongting Lake region of China to assess subclinical morbidity and the 2-year benefit of curative therapy (praziquantel) administered in 1996. Prevalence and intensity of S. japonicum infection before treatment were 28% and 192 eggs per gram faeces (epg), respectively. Two years after cure, 22% of the cohort were re-infected, but with a lighter intensity (67 epg). Sixty-four subjects (37%) showed significant improvement in ultrasound parenchyma images after treatment and 51 subjects (54%) showed significant improvement of periportal fibrosis. Left-lobe enlargement also reversed (P < 0.05) and splenomegaly reversed in 6 of 8 cases and developed in only 1. Two years post-treatment a dilated portal vein became less frequent, but the decline was not significant (16% vs 11%, P < 0.05). The serum levels of laminin and collagen IV associated with re-infection and intensity and hyaluronic acid levels correlated with ultrasound findings (P < 0.01). Overall, treatment induced a marked decrease in subclinical hepatosplenic morbidity attributable to S. japonicum although low-intensity re-infection after treatment remained relatively frequent. Stratified analysis and logistic models evaluated potential confounding factors for assessment of treatment effects on hepatic fibrosis. S. japonicum infection and moderate-heavy alcohol intake interacted: improvement in parenchymal morbidity was impeded among drinkers (P < 0.05). Chemotherapy focused on at-risk residents controls prevalent subclinical hepatic fibrosis but re-infection indicates the need for complementary control strategies.     

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)     

Morbidity due to Schistosoma mansoni: an epidemiological assessment of distended abdomen syndrome in Ugandan school children with observations before and 1-year after anthelminthic chemotherapy

The objectives of this study were to determine the prevalence and distribution of distended abdomens among Ugandan school children across a range of eco-epidemiological settings and to investigate the relationship between distended abdomens and helminth infections, in particular Schistosoma mansoni, before and 1-year after anthelminthic treatment. A cross-sectional survey was conducted on 4354 school children across eight districts, with a longitudinal 1-year follow-up of 2644 children (60.7%). On both occasions, parasitological, biometrical and clinical data were collected for each child. Baseline prevalence of S. mansoni and hookworms was 44.3% and 51.8%, respectively. Distended abdomens, defined as an abdominal circumference ratio (ACR) >1.05, were observed in 2.5% of the sampled children, several of whom presented with particularly severe distensions necessitating hospital referral. ACR scores were highly overdispersed between districts and schools. Multivariate regression analysis revealed that S. mansoni infection accounted for only a small fraction of ACR variation, suggesting that either single point prevalence and intensity measures failed to reflect this more chronically evolved morbidity and/or that other interacting factors were involved, e.g. malnutrition and malaria. At 1-year follow-up, ACR scores showed an overall trend of regression towards the mean, potentially indicative of amelioration following chemotherapy, but geographic overdispersion still remained.     

Schistosoma mansoni infection and cognitive functions of primary school children, in Kafr El Sheikh, Egypt

There is growing concern that parasitic infection may detrimentally affect children's mental function. In this study our main objective was to investigate the effects of schistosoma mansoni infection on cognitive functions of school children aged 9-12 years in Kafr El Sheikh Governorate. Out of 2601 children screened parasitologically, 60.7% were S. mansoni positive. Children recruited for the case-control study were 40 with light S. mansoni infection (<100 epg), 40 with heavy infection (>400 epg) and 40 parasite-free served as control. All children were subjected to the Arabic Version of Wechsler Intelligence Scale for Children (WISC) and the Verbal Fluency Test. Though, the general IQ scores of infected children were insignificantly lower than their controls, yet they recorded a significantly lower performance IQ as well as, poorer performance on comprehension, vocabulary and picture completion subtests. Implications for preventive measures will be discussed.     

Cross sectional study of schistosomiasis among military recruits in Alexandria.

A cross-sectional survey for schistosomiasis infection was carried out among 1170 military recruits in Alexandria. Data on prevalence-intensity of infection-subjective symptoms and history of antischistosomal chemotherapy administration were collected from participants. The results confirmed the endemicity of S. mansoni and the low prevalence of S. haematobium infection in Delta region (33.1% and 1.1%) respectively. Previous antischistosomal chemotherapy administration was associated with decreased geometric mean egg count inspite the increase in prevalence. It is recommended that mass chemotherapy with praziquantel of this young active adult group would be of beneficial effect in decreasing schistosomiasis morbidity among an important large section of the community.     

Differences in the rate of hepatosplenomegaly due to Schistosoma mansoni infection between two areas in Machakos District, Kenya.

The relationship between intensity of Schistosoma mansoni infection and the degree of related morbidity was suspected to differ locally within the Machakos district of Kenya. To test this possibility, prevalences of hepatomegaly and splenomegaly among 1483 school children were compared between 2 areas, Kangundo and Kambu, within this district. These areas, which were similar in many geographical and economic respects and populated by the same tribe (Akamba), had comparable levels of S. mansoni infection and no S. haematobium infection. A relationship was observed between the prevalence of hepatomegaly and intensity of S. mansoni infection, which showed no consistent difference between the 2 areas. In contrast, a relationship between the prevalence of splenomegaly and intensity of S. mansoni infection was observed only in the Kambu schools, and not in the Kangundo schools where the overall prevalence of splenomegaly was much lower. It was possible that part of the splenomegaly observed in Kambu was due to malaria. However, the observation that malaria and schistosomiasis in 2 Kambu schools were not positively correlated allowed approximations to be made of the relative contributions of each to the prevalence of splenomegaly. It was concluded that, in a school close to the river that formed the main transmission site of S. mansoni, schistosomiasis-related hepatosplenomegaly was present in at least 17% of children. The reason for the high prevalence in Kambu of hepatosplenic schistosomiasis remains uncertain, but it could include a synergistic interaction of schistosome infection with malaria.     

Schistosoma mansoni in pregnancy and associations with anaemia in northwest Tanzania

Schistosomiasis among pregnant women has been inadequately investigated. In order to determine the importance of Schistosoma mansoni in this subgroup, we conducted a cross-sectional survey of 972 women in Tanzania and investigated the prevalence of Schistosoma mansoni, hookworm and malaria and their associations with anaemia. Overall, 63.5% of women were infected with S. mansoni, with prevalence highest among younger women and decreasing with increasing age. The prevalence of hookworm was 56.3%, and 16.4% of women had malaria parasitaemia. Overall, 66.4% of women were anaemic. Increased risk of anaemia was associated with heavy infection with S. mansoni but not hookworm or Plasmodium falciparum parasitaemia.     

Current status of S. mansoni infection in El-Prince village, Alexandria Governorate

The present work was implemented to determine the current status of Schistosoma mansoni infection in "El-Prince" village, near Alexandria, which was studied before as a control village between 1985 and 1990. Stool examination was performed on 571 of the inhabitants by Kato thick smear technique and intensity of infection was determined. Prevalence was found to be 15.4% with a percentage decrease of 53% from the 1990 survey. The geometric mean egg count (GMEC) ranged from 19.05 eggs/gram of stools in children aged five years or less to 81.86 in the oldest group greater than 50 years of age and averaged 42.26. Age stratified prevalence of infection peaked at 31.4% in the (20 to 25)-year-old age group. High prevalence of 23.6% was also observed in the age group from 36 to 50 years. Infection in males was higher than females (17.8% vs.13.5%). However the difference was not statistically significant (chi2 = 2.2, P = 0.0086). Risk factors significantly associated with the infection were an age more than 5 years, male gender, males with water contact activities and having done a previous laboratory analysis for schistosomiasis. The community category of the village changed from high prevalence in 1990 to moderate prevalence in 2002. Most of the infected individuals (85%) had light intensity of infection (less than 99 eggs /g stools). Active screening and treatment programs should be maintained in the area. More control measures should be directed towards older people who should be included in evaluation of control programs.     

Hookworm infection in a rural community in south India and its association with haemoglobin levels

Faecal samples were obtained from 1113 persons living in a rural area in South India, and the hookworm ova load (Necator americanus) was determined using Kato's thick smear method. Evidence of hookworm infection was present in 92%, 77% having a count of under 100 epg, 11% a count of 1000 to 1999 epg, and 4% having counts between 2000 and 12,000 epg. Females had significantly higher ova counts than males on the average, but age did not appear to have any effect. Haemoglobin was also estimated: 80% of adult males, 87% of adult females and 90% of children were anaemic. There was a significant negative association between ova load and haemoglobin level, and the decrease in haemoglobin for a doubling of the ova load was estimated by regression analysis to be 0.18, 0.29 and 0.16 g/dl in adult males, adult females and children, respectively. There was nearly perfect agreement in the ranking of 10 clusters by mean ova count and mean haemoglobin level or percentage with anaemia.     

The role of hygienic bathing after defecation in the transmission of Schistosoma mansoni

Transmission of Schistosoma mansoni depends on fecal eggs reaching water, but the way this happens is poorly understood. We studied the role of hygienic bathing after defecation in the contamination of water with S. mansoni eggs. Individuals in an endemic community in Northern Senegal (n=991) were examined for S. mansoni infection and a random sample (22%) was interviewed about stool disposal practices and hygienic behavior. We assessed the presence and viability of S. mansoni eggs adhering to the peri-anal region of 13 infected volunteers, by counting the miracidia in the water they had used for hygienic washing; for 10 of them (77%) miracidia were demonstrated. From the population infection distribution, average number of defecations per day, proportion of individuals bathing after defecation, and association between miracidial counts and infection intensity, we calculated a daily population miracidial output of approximately 30,000 through hygienic bathing. For comparison, one complete stool reaching the water was calculated to yield approximately 2500 miracidia. Thus, 12 individuals in this population should defecate into the water every day to produce the same number of miracidia as through hygienic bathing. Our results suggest a major role of hygienic bathing after defecation in the transmission of S. mansoni.     

Anthropometric measures in relation to Schistosomiasis mansoni and socioeconomic variables

A cross-sectional study of anthropometric measures and their association with socioeconomic variables, infection by Schistosoma mansoni, intensity of infection and splenomegaly was carried out in an endemic area for schistosomiasis in Brazil (Comercinho), using multiple logistic regression methods. Eighty-seven per cent of all 1.5-14.4 year-old children in the area participated in the study. Children below the 5th percentile (USA Ten State Survey) for height-for-age, weight-for-age and arm muscle area-for-age were compared to those greater than the 5th percentile. There was no association between low anthropometric measures and schistosomiasis or socioeconomic variables in children under five years of age. For the 4.4-14.4 year-old children, poor condition of the heads of family and poorer housing were independently associated with low height and arm muscle area. Heavy excretion of S. mansoni eggs (greater than or equal to 500 epg) was related to low height, and splenomegaly was the variable which showed the strongest association with low height, weight and arm muscle area (odds ratios adjusted for socioeconomic variables were 6.4, 3.5 and 3.7 respectively). This indicates that there is a biological component for low anthropometric measures in the severe form of schistosomiasis and this reinforces the need for public health measures to prevent the development of splenomegalies in endemic areas.     

Status of Schistosoma Mansoni Prevalence and Intensity of Infection in Geographically Apart Endemic Localities of Ethiopia: A Comparison

Background

Schistosomiasis is one of the chronic and neglected tropical diseases affecting rural communities. Heavy infections contribute to anemia and can retard children''s growth, physical activity and cognitive function. This study was conducted in order to determine the prevalence, intensity and variation of Schistosoma mansoni infection among human subjects in geographically apart localities. The prevalence and intensity of Schistosoma mansoni infection was assessed in three geographically apart endemic areas of Ethiopia from May to August 2010 through cross-sectional approach.

Methods

A total of 1073 individuals (528 males and 545 females) were found eligible for the study. Their age ranged from 5–60 years with mean age of 11 years in Wondo Genet, 22 years in Kemissie and 24 years in Sille-Elgo. Small plastic sheets were distributed to the study participants and sizable stool specimens were collected and examined using Kato-Katz method (41.7mg template).

Result

The prevalence of Schistosoma mansoni infection among the study participants in Kemissie, Wondo Genet and Sille-Elgo was 89.6%, 59.9%, and 31.6%, respectively. The highest geometric mean of egg per gram of stool for Kemissie, Wondo Genet and Sille-Elgo was, 5208 and 346, 8472 and 252, 3960 and 91, respectively.

Conclusion

It was observed that there was comparable variation in the prevalence and intensity of infection among the study localities. Moreover, it is indicated that S. mansoni is still an ongoing public health problem which requires integrated intervention activities in the country.     

Predisposition of individuals and families in Mexico to heavy infection with Ascaris lumbricoides and Trichuris trichiura

Stool specimens from 90% of the population of 2 marginal communities in Coatzacoalcos, Mexico, were examined by the Kato-Katz technique for the estimation of eggs per gram of faeces (epg). Average epg values for Ascaris lumbricoides and Trichuris trichiura were calculated for each family in the community, based on the arithmetic mean epg of family members for each parasite. 39 families were classified as either lightly or heavily infected with A. lumbricoides and infected members were treated with mebendazole. A. lumbricoides expelled following treatment were collected from the children 2-10 years of age, and reinfection was monitored monthly for 6 months. At the end of the reinfection interval, a final stool specimen was collected from all family members and those infected were treated. Again, A. lumbricoides expelled by the children 2-10 years of age were collected. There was a significant correlation between the number of A. lumbricoides expelled by the children at the first and second treatments as well as in epg values before the first and second treatments for both A. lumbricoides and T. trichiura in children (2-10 years) and adults (greater than 19 years). At the family level, there were significant correlations between the values of family mean epg before each treatment for both A. lumbricoides and T. trichiura.