Epidemiology and morbidity of Schistosoma mansoni infection in a fishing community along Lake Albert in Uganda

Schistosoma mansoni infection, associated morbidity and symptoms were studied in Piida fishing community at Butiaba, along Lake Albert, Uganda, from November 1996 to January 1997. The study revealed that S. mansoni is highly endemic with an overall prevalence of 72%, a mean intensity of 419.4 eggs per gram (epg) faeces (geometric mean for positives only), with 37.8% of males and 33.0% of females excreting over 1000 epg. Prevalence and intensity peaked in the 10-14 year old age group and decreased with increasing age. Females were less heavily infected than males. Differences were also shown between tribes. Diarrhoea and abdominal pain were commonly reported in Piida. However, no clear-cut correlation between intensity of S. mansoni infection and these conditions could be demonstrated, indicating that retrospective questionnaires concerning S. mansoni related-symptomatology are of limited value. Organomegaly, as assessed by ultrasonography, was frequent and hepatomegaly was associated with heavy S. mansoni infection. No correlation was demonstrated between splenomegaly and infection. This study emphasizes that schistosomiasis mansoni is a major public health problem in Piida fishing community and presumably also in many similar fishing communities. These observations call for immediate intervention and can help in planning long-term strategies for sustainable morbidity control.     

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)     

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.     

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.     

IgM-ELISA for diagnosis of schistosomiasis mansoni in low endemic areas

An immunoenzymatic method for the detection of IgM antibodies (IgM-ELISA) against a fraction of Schistosoma mansoni adult worm antigen, soluble in trichloroacetic acid (TCA-soluble fraction), was evaluated for epidemiological purposes in low endemic areas for schistosomiasis. Blood samples on filter paper were collected from a population living in the municipality of Pedro de Toledo, S?o Paulo State, and submitted to IgM-ELISA. The results were compared to those obtained by the IgM-immunofluorescence test (IgM-IFT) and the Kato-Katz parasitological method. Positive rates of 36.8%, 33.5%, and 1.6% were obtained respectively by the IgM-ELISA, IgM-IFT, and Kato-Katz methods. The geometric mean obtained by the parasitological method was 40.9 eggs per gram of feces (epg). The nearly perfect agreement observed between the two serological tests (Kappa index of 0,89) indicates good diagnostic performance by the evaluated test. IgM-ELISA is a potentially useful method for diagnosis of schistosomiasis in individuals with low worm burden.     

Current status of schistosomiasis and soil-transmitted helminthiasis in Beyla and Macenta Prefectures, Forest Guinea

A cross-sectional survey was undertaken in children aged 9-14 years in Beyla and Macenta Prefectures, Forest Guinea. Stool samples were examined by Kato-Katz and urine samples were examined by the centrifugation method. The overall prevalence and intensity of infection was 66.2% and 462.4 eggs per gram of faeces (epg) for Schistosoma mansoni, 21.0% and 17.8 eggs per 10 ml of urine for S. haematobium, 51.2% and 507.5 epg for hookworm, 8.1% and 89.1 epg for Ascaris lumbricoides and 2.4% and 16.7 epg for Trichuris trichiura. The overall prevalence of schistosomiasis (S. mansoni and/or S. haematobium) was 70.7%. The prevalence of schistosomiasis was similar to those reported in the 1990s in the region; however, the prevalence of soil-transmitted helminths has since fallen. These findings illustrate the need for schistosomiasis control in Guinea.     

Schistosoma hematobium and S. mansoni among children, Southern Sudan

We conducted a survey of schistosomiasis among schoolchildren in 2 villages in Southern Sudan. In Lui (West Equatoria region), prevalence of Schistosoma mansoni infection was 51.5%; no cases of S. hematobium infection were detected. In Nyal (Upper Nile region), prevalence of S. hematobium infection was 73% and S. mansoni infection, 70%.     

Studies on schistosomiasis in the Niger Delta: Schistosoma intercalatum in the urban city of Port Harcourt, Nigeria

Ova of S. intercalatum have been found in the urban city of Port Harcourt in the Niger Delta area of Nigeria, following examination of stool and urine samples from 1,709 persons (5-15 years of age) resident in various parts of the city. The ova occurred only in urine, with prevalence ranging from 1.0% to 9.8% with an overall prevalence of 5.7%. The intensity of the infection was low. Most infected individuals had counts of less than 500 ova in total bladder content. There was no significant difference in either the prevalence or intensity of the infection among the sexes (Male; prevalence 6.1%, intensity 527.3 vs Female; prevalence 5.4%, intensity 500.9). No case of infection with either S. haematobium or S. mansoni was encountered in the study. Malacological surveys in the gutters, creeks, streams and stagnant waterbodies within the city showed the presence of Lymnaea natalensis, Bulinus forskalii, Pila ovata, Melanoides tuberculata, Physa sp., Lanistes ovum and Segmentorbis sp. B. forskalii is indicated as the probable vector of S. intercalatum in the city. The growing problem of urban schistosomiasis in tropical Africa is discussed. Further studies on urban transmission and epidemiology of schistosomiasis in the Niger Delta area of Nigeria is also indicated.     

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.     

High endemicity of human fascioliasis between Lake Titicaca and La Paz valley, Bolivia.

Over a 6-year period, an epidemiological study of human infection by Fasciola hepatica in the Northern Bolivian Altiplano was carried out. Prevalences and intensities were analysed from coprological results obtained in 31 surveys performed in 24 localities and proved to be the highest known so far. The global prevalence was 15.4%, with local prevalences ranging from 0% to 68.2%. Significant differences between prevalence rates were detected and the highest prevalences were in subjects aged < 20 years. However, prevalences showed no gender difference. The global intensity (eggs per gram of faeces, epg) ranged from 24 to 5064 epg and showed arithmetic and geometric means respectively of 446 and 191 epg, with highest local arithmetic and geometric means of 1345 and 678 epg. Significant differences in mean egg output were detected between localities. The significantly higher F. hepatica egg counts shown by girls in school surveys is worth mentioning. Although the distributions of intensities according to age-groups did not show any significant difference, a decrease of egg output counts with an increase of age was detected. It is concluded that fascioliasis is a very important human health problem in this region.     

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.     

Environmental and social determinants in schistosomiasis mansoni in Ravena, Minas Gerais, Brazil

This study identified the role of biological and social determinants in the transmission of schistosomiasis mansoni in Ravena, Minas Gerais, Brazil, in 1980. This data was used to characterize the clinical and epidemiological profiles of the endemic desease in the population, allowing for the determination of the efficacy of the potable water supply and the specific treatment of those infected with S. mansoni. The district contains three locations, Ravenopolis, Ravena and Lavapes, where the prevalence of the endemic disease was, 20.1%, 42.6% and 63.9%, respectively. The prevalence in the district was statistically higher in men. The age brackets that displayed differences by gender were 10-14 and 15-19 years. Severity of infection was statistically different among individuals within the 10-14 year bracket in ali three locations, and in the 15-19 year bracket among individuals from Ravenopolis and Ravena. The hepatointestinal form was associated with age, and individuals under 15 years of age presented risk of infection 8.85 times higher than adults. Multivariable analysis of the factors involved in transmission of the disease showed that Lavapes was independently associated with infection. In that area, poor sanitary conditions and the proximity of houses to streams infested with S. marsoni cercariae facilitated infection of neighborhood women while performing domestic activities, as well as men digging sand from the streams for construction. These results show the focal nature of transmission of the endemic requiring specific intervention for effective control of disease.     

An outbreak of acute schistosomiasis at Porto de Galinhas beach, Pernambuco, Brazil

We recently confirmed several cases of acute schistosomiasis in Porto de Galinhas beach, Northeast Brazil. A total of 662 patients were diagnosed by parasitological and clinical examinations. The infection likely occurred during the September 7 national holiday, when heavy rainfall flooded the Ipojuca River and people were infected when the water covered their yards. Families were continuously exposed to infection for a period of three weeks until the water had completely dried up. Previous investigation suggests that snail vectors were introduced as a result of landfill in marshy areas. The swamp-flooding of such areas facilitated the emergence of slums surrounded by snail breeding sites. Heavy rainfall caused open-air sewage ditches to overflow, allowing for infection of snails by Schistosoma mansoni. Thus, continuous floods were responsible for the spread of human infection. Clinical and laboratory results identified 62% of acute cases of S. mansoni. Complementary studies are being conducted to define the impact and epidemiological meaning of the acute schistosomiasis outbreak.     

The development of an age structured model for schistosomiasis transmission dynamics and control and its validation for Schistosoma mansoni.

Mathematical models are potentially useful tools to aid in the design of control programmes for parasitic diseases. In this paper, a fully age structured epidemiological model of human schistosomiasis is developed and parameterized, and used to predict trends in infection prevalence, intensity and prevalence of heavy infections over age and time during several rounds of mass and age targeted treatment. The model is validated against data from a Schistosoma mansoni control programme in Kenya.     

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.     

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.     

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.     

Changes in human schistosomiasis levels after the construction of two large hydroelectric dams in central C?te d'Ivoire.

The construction of large dams has been shown to increase the prevalence and intensity of human schistosomiasis. However, until now no study had been carried out to assess the impact of such a project in Côte d''Ivoire. For Kossou and Taabo, two large dams which became operational in the 1970s, baseline data are available on schistosomiasis prevalence in the surrounding area before dam construction, so that the changes in schistosomiasis levels can be assessed. We re-evaluated the prevalence of Schistosoma haematobium and S. mansoni in November 1992, by analysing 548 urine and 255 stool samples, respectively, from schoolchildren from five villages around each lake. A marked increase in the overall prevalence of S. haematobium was observed, from 14% to 53% around Lake Kossou and from 0 to 73% around Lake Taabo. Baseline data for S. mansoni are only available for Lake Taabo, where a prevalence of 3% was found in 1979 and where the prevalence in 1992 was still low at 2%. The construction of these two large dams therefore led to little change in S. mansoni prevalence but to a significant increase in that of S. haematobium.     

Schistosomiasis in Ethiopia

The literature on schistosomiasis in Ethiopia is reviewed with the objective of bringing together in one paper diverse sources which may not be available to those interested in schistosomiasis. Particular attention is given to the influence of altitude and climate, snail ecology and government economic programs on the distribution of schistosomiasis. Out of 365 communities studied between 1961 and 1986 for Schistosomiasis mansoni, cases were reported from 225 (62%), and in 85 (23%) the prevalence ranged from 10 to 92%. Most transmission sites and S. mansoni infections are in agricultural communities along streams between 1300 and 2000 m altitude infested with Biomphalaria pfeifferi, the major snail intermediate host. S. mansoni transmission above 2200 m and below 800 m is precluded in many parts of Ethiopia by low and high water temperatures, respectively. Schistosomiasis haematobium cases have been reported from 30 of the 54 communities studied, 17 of them with infection rates between 14 and 75%. Endemic S. haematobium appears to be confined in its distribution to lowlands below 800 m altitude. The highly focal distribution of S. haematobium transmission is largely due to the nonsusceptibility of most bulinine snails to the Ethiopian strain of the parasite and low water temperatures in the highlands. Water resources development, resettlement programs, refugee migration and other population movements may result in the spread of endemic S. mansoni. Lack of information on snail host/parasite relationships and the ecology of proven and suspected snail hosts does not permit predictions on the spread of endemic S. haematobium. Past and present schistosomiasis control programs in Ethiopia are reviewed and recommendations made for the national control program.     

Prevalence of schistosoma mansoni and intestinal parasites with evaluation of hepatic schistosomiasis in a rural area after governmental efforts (Gharbia governorate)

The study was carried out on 2136 individuals from Abo El-Gohoor village. Their ages ranged from 1-72 years with a mean of 28.3 +/- 22.4 years. They were 46.7% males and 53.3% females. The village was divided into sectors. The inhabitants of each sector were examined clinically with history taking through home visits. Three successive stool samples for each individual were examined by the concentration technique. Abdominal ultrasound was done for hepatic and splenic assessment. Rectal biopsy was done for 200 subjects with negative stool samples for Schistosoma mansoni (S. mansoni) ova. Sex distribution was equal in this group. Their ages ranged from 18 to 45 years with a mean of 30.1 +/- 9.5 years. S. mansoni prevalence was 19.3% of individuals through stool examination and 12.5% out of 200 individuals with active schistosomiasis after rectal biopsy (the total prevalence was approximately 29.4%). Hepatic schistosomiasis was 18.8%. Hepatomegaly, hepatosplenomegaly, hepatic fibrosis without and with ascites were 6.0%, 8.8%, 2.5% and 1.5% of examined patients, respectively. The prevalence of intestinal parasites was 37.5% and 27.8% for E. histolytica and G. lamblia, respectively, 9.2% for H. nana, 6.2%, 9.6%, 2.4% and 1.5% for A. lumbricoides, E. vermicularis, T. trichura and A. duodenale, respectively and F. gigantica was 0.4%. A total of 84.6% of examined subjects had parasitic infestations, 60.2% had one parasite, 19.6% had 2 parasites, 4.2% had 3 parasites and 0.7% had 4 parasites. The study revealed some success of governmental efforts for control of schistosomiasis. The prevalence of S. mansoni through stool examination showed a prevalence lower than that reported before but which does not represent the actual prevalence of S. mansoni and rectal biopsy in addition gave more accurate results.