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.     

Health implications of chronic hepatosplenomegaly in Kenyan school-aged children chronically exposed to malarial infections and Schistosoma mansoni

Hepatosplenomegaly among school-aged children in sub-Saharan Africa is highly prevalent. Two of the more common aetiological agents of hepatosplenomegaly, namely chronic exposure to malaria and Schistosoma mansoni infection, can result in similar clinical presentation, with the liver and spleen being chronically enlarged and of a firm consistency. Where co-endemic, the two parasites are thought to synergistically exacerbate hepatosplenomegaly. Here, two potential health consequences, i.e. dilation of the portal vein (indicative of increased portal pressure) and stunting of growth, were investigated in a study area where children were chronically exposed to malaria throughout while S. mansoni transmission was geographically restricted. Hepatosplenomegaly was associated with increased portal vein diameters, with enlargement of the spleen rather than the liver being more closely associated with dilation. Dilation of the portal vein was exacerbated by S. mansoni infection in an intensity-dependent manner. The prevalence of growth stunting was not associated with either relative exposure rates to malarial infection or with S. mansoni infection status but was significantly associated with hepatosplenomegaly. Children who presented with hepatosplenomegaly had the lowest height-for-age Z-scores. This study shows that hepatosplenomegaly associated with chronic exposure to malaria and schistosomiasis is not a benign symptom amongst school-aged children but has potential long-term health consequences.     

A prospective study of Plasmodium falciparum multiplicity of infection and morbidity in Tanzanian children

Several studies suggest that in individuals with substantial previous exposure to malaria, co-infection with multiple clones of Plasmodium falciparum can protect against subsequent clinical malaria attacks. Other studies, mainly of individuals with little previous exposure, found the converse relationship. To test whether acquisition of such cross-protection tracks the acquisition of clinical immunity in general, 610 Tanzanian children aged 0-6 years were enrolled in a nine-month prospective study of the risk of morbidity in relation to parasitological status and merozoite surface protein 2 genotypes on enrolment. Prevalence of parasitaemia and multiplicity of infection increased with age. In the first year of life, the incidence of clinical malaria was almost three times higher in children with parasites at baseline than in those without. In older children, baseline P. falciparum infections appeared to protect against both parasitaemic and non-parasitaemic fever episodes. In children aged less than three years, baseline multiple infection tended to be associated with higher prospective risk of clinical malaria than single infection while in children aged more than three years the converse was found, but these effects were not statistically significant. These results provide further evidence that relationships between asymptomatic malaria infections and clinical malaria change with cumulative exposure.     

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.     

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.     

Hepatosplenic morbidity in two neighbouring communities in Uganda with high levels of Schistosoma mansoni infection but very different durations of residence

Peri-portal fibrosis can be a serious sequelae of Schistosoma mansoni infection. Age or duration of exposure have been identified as important risk factors, but their relative importance cannot be easily separated. Here, we have compared two cohorts, aged 6-50 years and resident for ten years or since birth, from two neighbouring villages (Booma and Bugoigo) on the eastern shore of Lake Albert, Uganda. Parasitological measurements were similar, whereas the prevalence of peri-portal fibrosis was 5-fold higher in Booma. Data from the cohorts were pooled to assess the relative contribution of age and duration of residency on the risk of disease. Amongst adults, duration of residency was the critical risk factor--individuals aged 17-31 years resident for more 22 years had an almost 12-fold increased risk of fibrosis than those resident for less than 15 years. Height-standardised Splenic Vein Diameter (SVD), Portal Vein Diameter (PVD), Para-sternal Liver Length (PLL) and Spleen Length (SL) values were all higher in Booma, and each organometric parameter except PLL increased with the severity of fibrosis. Our results clearly demonstrate that duration of exposure is a critical risk factor for the development of peri-portal fibrosis and its sequelae in adults. This parameter should therefore be a routine measurement during epidemiological surveys of S. mansoni.     

The incidence of clinical malaria detected by active case detection in children in Ifakara, southern Tanzania

Between July 2000 and June 2001, we used weekly active case detection (ACD) of clinical malaria episodes in 618 children aged < 5 years to describe the epidemiology of malaria in Ifakara, southern Tanzania. Plasmodium falciparum-positive blood slides prepared from children with axillary temperature 37.5 degrees C were used to define clinical malaria and a rolling cross-sectional survey documented the prevalences of parasitaemia and anaemia. A random subsample of children was visited daily for 1 month at the end of the study to assess the effect of more frequent visits on estimated incidence rates. Only 50 (8%) children had 1 or more episodes of clinical malaria during the year, an overall incidence of 0.275 episodes/100 child-weeks-at-risk, with no age dependence. The maximum parasite prevalence of 25% was reached in children aged 4 years. The incidence of illness was significantly lower in children visited daily than in those visited weekly, suggesting a marked effect of frequent visits on estimated incidence rates. We conclude that the age pattern of malaria detected through ACD is a more robust epidemiological indicator than absolute incidence rate estimates and that, in contrast to the surrounding area, Ifakara town is subject to only moderate perennial malaria transmission.     

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 effects of untreated bednets on malaria infection and morbidity on the Kenyan coast

A study was conducted in order to determine whether children that slept under untreated bednets were protected against both malaria infection and clinical disease compared with children not sleeping under bednets. The study was conducted in Kilifi District, Kenya, during the malaria season (June-August, 2000) and involved 416 children aged < or = 10 years. Data collected from a cross-sectional survey showed evidence of protection against malaria infection among children sleeping under untreated bednets in good condition compared with those not using nets (adjusted odds ratio [AOR] = 0.4, 95% CI 0.22-0.72, P = 0.002). There was no evidence of a protective effect against infection when comparing those that used untreated bednets that were worn and those not using nets (AOR = 0.75, 95% CI 0.34-1.63, P = 0.47). When these same children were followed-up during the malaria season, there was evidence of a lower rate of clinical malaria among those that used untreated nets in good condition (adjusted incidence rate ratio = 0.65, 95% CI 0.45-0.94, P = 0.022), while the rate of clinical malaria among those that used untreated bednets that were worn was similar to that of those that did not use bednets. In the face of persistent failure of communities to take up net retreatment, there is hope that untreated nets will offer some protection against malaria infection and disease compared with not using nets at all.     

Lead poisoning associated with malaria in children of urban areas of Nigeria

The principal objectives of this study are to (a) investigate the prevalence of elevated blood lead levels (EBLLs) in children of three major cities of Nigeria with different levels of industrial pollution; (b) identify the environmental, social and behavioral risk factors for the EBLLs in the children; and (c) explore the association between malaria (endemic in the study areas) and EBLLs in the pediatric population. The study involved 653 children aged 2-9 years (average, 3.7 years). The mean blood lead level (BLL) for the children was 8.9+/-4.8mug/dL, the median value was 7.8mug/dL, and the range was 1-52mug/dL. About 25% of the children had BLL greater than 10mug/dL. There were important differences in BLLs across the three cities, with the average value in Ibadan (9.9+/-5.2mug/dL) and Nnewi (8.3+/-3.5mug/dL) being higher than that in Port Harcourt (4.7+/-2.2mug/dL). Significant positive associations were found between BLL and a child's town of residence (p<0.001), age of the child (p=0.004), length of time the child played outside (p<0.001), presence of pets in a child's home (p=0.023), but negatively with educational level of caregiver (p<0.001). This study is one of the first to find a significant negative association between BLL and malaria in a pediatric population, and this association remained significant after controlling for confounding diseases and symptoms. The shared environmental and socio-demographic risks factors for lead exposure and Plasmodium (most common malaria parasites) infection in urban areas of Nigeria are discussed along with possible ways that lead exposure may influence the host response to infection with malarial parasites.     

Schistosoma haematobium infection in Egyptian schoolchildren: demonstration of both hepatic and urinary tract morbidity by ultrasonography.

Parasitological, clinical and ultrasonographical studies were performed upon 422 schoolchildren aged 12-16 years living in a village in the Fayoum where Schistosoma haematobium, but not S. mansoni, was transmitted. Over half of the children gave a history of receiving praziquantel therapy during the preceding 2 years. Symptoms (e.g., haematuria, burning micturition), signs (e.g., hepatomegaly, splenomegaly) and urinary findings (e.g., haematuria, proteinuria) correlated better with the presence and intensity of S. haematobium infection after correcting for this variable. Renal obstructive lesions detected by ultrasound were 2 and 3 times as common in those with moderate and heavy infections as in those with no or light infections, and urinary bladder wall lesions were far more frequent in those with moderate and heavy infections. A mild grade of periportal fibrosis, hepatomegaly and splenomegaly were present in some children in all groups. However, the prevalence of splenomegaly correlated directly with the intensity of infection; liver lesions occurred much more frequently in children with infection or a history of treated infection than in non-infected children denying recent treatment; and no child had hepatomegaly or splenomegaly in the absence of periportal fibrosis.     

Reliability of clinical diagnosis in identifying infectious trachoma in a low-prevalence area of Nepal.

The WHO Alliance for Global Elimination of Trachoma by 2020 has increased the need to identify ocular chlamydial infections by clinical examination in areas of both high and low prevalence. The relationship between clinically active trachoma (as defined by clinical examination) and chlamydial infection is known for areas with hyperendemic trachoma, but not for areas with a low prevalence of the clinical disease. In the present study, we examined, photographed, and DNA tested the conjunctivae of children in the Surkhet district of mid-western Nepal, an area known to have a low prevalence of clinically active trachoma. Although 6% of the children aged 10 years and under were found to have clinically active trachoma, none were found to have chlamydia infection by the most sensitive DNA amplification tests available. A very low prevalence of clinically active trachoma is not necessarily evidence of the presence of chlamydial infection. Therefore, the WHO policy of not recommending an intensive trachoma control effort when the prevalence of clinically active trachoma is less than 10% in children is appropriate for this area of Nepal.     

Human fascioliasis infection: gender differences within school-age children from endemic areas of the Nile Delta, Egypt

Several studies have reported a higher prevalence of infection for human fascioliasis among girls than among boys. To investigate this aspect further a sufficiently large data set was assembled comprising of 21,477 subjects with 932 positive cases. Subjects were primary school children covered by a control programme implemented by the Egyptian Ministry of Health and Population in the Nile Delta from 1988 to 2002. Stool analyses were performed by the Kato-Katz thick smear technique for a quantitative diagnosis on the intensity of infection. Both prevalence and intensity of infection, indirectly measured as mean number of eggs per gram of faeces, were significantly higher among girls than boys. The higher level of infection in girls was consistent across different years and in different survey areas. Co-infection with Schistosoma mansoni was present and associated with fascioliasis, but schistosomiasis was significantly more prevalent among boys. In Egypt rural girls are often involved in household and farm work and are exposed more than boys to infected foci. The lower school attendance for girls in rural areas appears to be an important factor increasing risk of infection. The precise mode of transmission and behavioural risk factors for human infection need to be investigated further to identify those related to gender.     

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.     

Impact of drainage and sewerage on intestinal nematode infections in poor urban areas in Salvador, Brazil

This cross-sectional study was conducted in 1989 among children aged between 5 and 14 years old living in nine poor urban areas of the city of Salvador (pop. 2.44 million), capital of Bahia State, in Northeast Brazil. Three of these areas had benefited from both drainage and sewerage, 3 from improved drainage only, and 3 from neither. The children studied thus belonged to 3 exposure groups regarding their level of sanitation infrastructure. An extensive questionnaire was applied to collect information on each child and on the conditions of the household, and stool examinations of the children 5-14 years old were performed to measure nematode infection. Comparison of the sewerage group with the drainage-only group and the latter with the control (no sewerage or drainage) group showed that, when the level of community sanitation was better, the prevalence of infection among children was less, but risk factors identified for infection were more numerous and more significant. Intensity of infection with Trichuris, but not with Ascaris or hookworm, was also less. The results suggest that sewerage and drainage can have a significant effect on intestinal nematode infections, by reducing transmission occurring in the public domain.     

Evaluating a malaria intervention strategy using knowledge, practices and coverage surveys in rural Bolifamba, southwest Cameroon

We evaluated the impact of a malaria intervention in Bolifamba in rural Cameroon. The intervention consisted of educating the community on management of malaria and provision of a dispensary for early diagnosis and treatment. In July 2001, prior to the intervention, a questionnaire was used to obtain information on knowledge of and practices toward childhood malaria of 185 mothers of children aged 0-5 years. The same questionnaire was administered to 120 of the 185 mothers, one-year post-intervention. Clinical and laboratory investigations were carried out on children whose mothers were interviewed. A comparison of pre- and post-intervention data indicated significant changes in (i) the use of appropriate malaria treatment (from 50% to 81.7%); (ii) recognition of splenomegaly as a feature of malaria (from 18.4% to 80.8%); (iii) prevalence of splenomegaly (from 26.5% to 13.3%); (iv) prevalence of fever (from 27.8% to 13.3%); (v) parasite prevalence (from 60.5% to 44.2%) and (vi) severe malaria anaemia (from 2.6% to 0.0%). These findings revealed that proper education of villagers, particularly mothers, on malaria and the presence of health facilities, where treatment is readily available at affordable cost, close to villages, are important strategies that would reduce malaria morbidity and mortality significantly.     

Cross-sectional study of specific antibodies to a polymorphic Plasmodium falciparum antigen and of parasite antigen genotypes in school children on the slope of Mount Cameroon

To investigate relationships between Plasmodium falciparum parasitaemia, parasite genotypes, and specific anti-parasite antibodies, 244 school children (aged 4 to 16 years) were studied in April/May 2002, the peak malaria transmission season in Buea, Cameroon. Antibody reactivities were analysed by ELISA using an array of recombinant antigens representing different sequences from the polymorphic block 2 region of the merozoite surface protein 1 (MSP1), and the blood samples that were slide-positive for P. falciparum were genotyped for msp1 block 2 alleles. The prevalence of antibodies to the specific MSP1 block 2 antigens was significantly higher in children at one particular school (situated at the lowest altitude) compared to the others, although the prevalence of infection or particular parasite genotypes did not differ. Thus, at a population level, the prevalence of these antibodies does not simply reflect prevalence of parasites, but rather may be due to differences in the incidence of past infections. However, there were weak positive associations between specific antibody reactivity and the presence of the corresponding allele in the blood of individuals (statistically significant for the MAD20-type allele of block 2), indicating that antibody specificities are to some extent determined by current parasite infections.     

Morbidity from malaria and immune responses to defined Plasmodium falciparum antigens in children with sickle cell trait in The Gambia.

Morbidity from Plasmodium falciparum malaria and humoral and in vitro cellular immune responses to defined malaria antigens were measured in rural Gambian children with haemoglobin phenotype AS (HbAS) and in those with a normal haemoglobin (HbAA). In a survey undertaken during the dry season, HbAS children had a higher parasite rate than HbAA children but a lower prevalence of parasitaemia at a level of 500/microliters or greater. Malariometric indices measured during a rainy season survey were similar in the 2 groups of children. During the rainy season, the incidence of infection with P. falciparum did not vary with haemoglobin phenotype. However, in children aged 6 years or less, a significantly smaller proportion of HbAS children who acquired infection developed clinical symptoms than did HbAA children. During both the dry season and rainy season surveys, humoral and in vitro cellular immune responses to defined antigens from the sporozoite and merozoite stages of P. falciparum were similar in the 2 groups of children. Thus, despite the differences in parasite indices and morbidity from malaria between the 2 groups of children, we found no evidence of an enhanced immune response to malaria infection amongst HbAS children compared with normal children.     

Evaluation of the antibody response to Anopheles salivary antigens as a potential marker of risk of malaria

The evaluation of human immune responses to arthropod bites may be a useful marker of exposure to vector-borne diseases, with applications to malaria, the most serious parasitic infection in humans. The specific antibody (Ab) IgG response to saliva obtained from Anopheles gambiae mosquitoes was evaluated in young children from an area of seasonal malaria transmission in Senegal. Specific IgG was higher in children who developed clinical Plasmodium falciparum malaria within the 3 months that followed than in those who did not (P<0.05), and it increased significantly (P<0.0001) with the level of Anopheles exposure, as evaluated by conventional entomological methods. These results suggest that evaluation of antisalivary Ab responses could be a useful approach for identifying a marker for the risk of malaria transmission.     

Seroprevalence of zoonotic toxocariasis in the United States: 1971-1973

Demographic characteristics associated with human Toxocara canis infection in children aged one to 11 years were investigated using data from the Health and Nutrition Examination Survey of 1971 to 1973. An enzyme-linked immunosorbent assay with larval stage antigen was used to measure the concentration of antibodies to T. canis in 1,409 available sera. From 4.6 to 7.3% of the children in different geographic regions of the United States have been infected, with serologic prevalence approaching 30% among black children of lower socioeconomic status aged six to 11 years. For both blacks and whites, higher seroprevalence was associated with a rural residence, increased age in children and number of persons in the household, and with decreased income, education, and number of rooms in the house. Multivariate logistic regression models indicated that blacks had higher infection rates than whites, even when socioeconomic factors were controlled. Certain critical variables, however, such as exposure to dogs or reliable pica histories, were not available for analysis.