Oxylog studies of energy expenditure and schistosomiasis in the Sudan

The effects of varying intensities of S. mansoni infection on physical work performance in agricultural tasks were studied in 269 male farmers living in the highly endemic Gezira area of the Sudan. The subjects were in the age range 18-50 years, and they were subdivided into four infection groups: non-infected (passing no S. mansoni eggs in their faeces), lightly infected (egg excretion 1-499), moderately infected (egg excretion 500-999), and heavily infected (egg excretion 1000+ eggs g-1 faeces). The Oxylog, a portable oxygen analyser, was used to measure energy expenditure throughout the field studies. The investigations showed that heavy S. mansoni infection significantly lowered oxygen intake by 20-30% during agricultural work tasks. There was a clear relationship between the intensity of S. mansoni infection and both the aerobic power output and morbidity in those populations. Anti-schistosomal treatment (praziquantel) given over a period of 1 year produced a marked improvement in working capacity and reduced morbidity.     

Factors associated with Schistosoma mansoni infection 5 years after selective treatment in a low endemic area in Brazil.

Five years after a single dose treatment, prevalence, intensity and morbidity of schistosomiasis mansoni were evaluated in Agua Branca, a low endemic community in the South East Brazil (cure rate 94%). At community level, prevalence showed a decrease from 38.9 to 24.5% and the intensity of infection dropped from 119.5 to 38.9 eggs per g of faeces (epg). However, after the exclusion of immigrants, newborn children and individuals that had left the area after the first evaluation, the prevalence among the treated and followed population was not significantly affected. Multivariate analysis showed that the 10-29 age group and water contact for agricultural purposes were independently associated with the presence of infection on post treatment evaluation [OR 3.9 and 5.09, respectively]. A previous treatment among subjects older than 15 years was inversely associated [OR 0.58]. The authors wish to draw attention to the fact that mobility may lead to a serious bias in evaluating the impact of the control programme.     

Geographic distribution of schistosomiasis and soil-transmitted helminths in Western Kenya: implications for anthelminthic mass treatment

A survey of 1,246 children 10-12 years old in 32 primary schools in Kenya near Lake Victoria was conducted to determine prevalence and distribution of schistosome and geohelminth infections. Stool and urine samples were collected and examined for eggs of Schistosoma mansoni, S. haematobium, and intestinal helminths. A questionnaire was used to obtain demographic information and to quantify exposure to surface waters. Houses, schools, and water sources were mapped using a geographic information system. The mean school prevalence of S. mansoni infection was 16.3% (range = 0-80%). Proximity to the lake (r = 0.89, P < 0.001) and contact with lake water were associated with infection, as were specific water-related activities including swimming, fishing, and collecting water. Sixty-three percent of students were infected with one or more other geohelminths and these infections were more homogenously distributed. The separate distributions of schistosome and geohelminth infections have important implications for combined mass-treatment programs.     

Emergence of Schistosoma mansoni infection in upper Egypt: the Giza governorate.

We found an unexpectedly high prevalence of Schistosoma mansoni in a village in the Upper Egyptian governorate of Giza. Historically, S. mansoni is endemic in the northern Egyptian Nile Delta rather than in the southern Upper Egypt. This observation was made during an evaluation of a rural health care schistosomiasis surveillance program using a cross sectional survey for S. haematobium and S. mansoni in the village of El-Gezira El-Shakra El-Saf district in the Upper Egypt Giza Governorate. A 10% systematic random sample of households of the village was chosen. All persons in the selected houses were invited to submit urine and stool samples. All students from a primary school were also included in the study. Urine was screened by a polycarbonate filtration method and stool was examined using modified Kato-Katz technique. The prevalence of S. mansoni in the population sample and in the school children was 33.7% and 57.7%, respectively, whereas the prevalence of S. haematobium infection in the population sample and the school children was 7.4% and 10.6%, respectively. The prevalence of infection was highest in the younger age groups, and males were infected more than females. Review of Ministry of Health records showed that both species of vector snails, Bulinus truncatus and Biomphalaria alexandrina, were present from 1991 to 1995, and that B. alexandrina was more abundant than B. truncatus in the canals surrounding this village. The unexpected high prevalence of S. mansoni in this village indicates an urgent need to include training programs for S. mansoni surveillance in the primary health care facilities of Giza and to educate villagers to request examinations for S. mansoni as well as for S. haematobium infection.     

Schistosomiasis in a migrating population in the lake region of China and its potential impact on control operation

Coverage of migrating people in schistosomiasis control program is a growing concern in China. Schistosomiasis caused by Schistosoma japonicum is still one of the major infectious diseases of public health importance in China though tremendous efforts have been made to control the transmission over the past decades. Along with the rapid social-economic development, migrant population has been remarkably increasing across the country. The infected migrants may introduce a new souse of infection to endemic areas or the areas where the transmission had been controlled or interrupted but the intermediate host Oncomelania snail is still present. Preliminary studies for surveillance on schistosomiasis prevalence in migrants were reported, but there is little basic information provided. We carried out an investigation on the prevalence in immigrants, emigrants and permanent residents in three villages of Hunan province located in the main endemic area of lake region, and analyzed the potential impact of migration on control practice. In the study villages, the migrant population accounts for 53.6% of the total. Schistosoma infection was detected by modified Kato-Katz method and miracidium hatching test. Questionnaire survey was conducted comprising knowledge of disease and its transmission, water contact, personal protective measures, and whether examined and treated after water contact. The survey indicated that the migrants and permanent residents had similar life style, and the majority of them experienced water contact in agricultural work or routine life activities. However, the infection rate in immigrants was significantly higher than that in permanent residents. It was also found that the migrants had significantly less knowledge about the disease than the permanent residents, and took no personal protective measures. This is due to that the control program could not cover the migrants when they were absent at the time the program being implemented. The present study suggested that the surveillance and intervention for migrants, immigrants in particular, should be included and strengthened in schistosomiasis control program and a feasible scheme be developed.     

Limitations of the intradermal test for schistosomiasis mansoni: experience from epidemiologic studies in a Puerto Rican community

The intradermal reaction with Schistosoma mansoni adult-worm antigen (35-40 microgram/ml nitrogen) was evaluated as an edpidemiologic tool in an endemic Puerto Rican community where the prevalence of S. mansoni infection was 36% and the geometric-mean egg count was 17.6 eggs/g. Subcutaneous injections of antigen were made in forearms, and stool specimens were examined for S. mansoni eggs by a formol-ether concentration method. Of 296 persons tested, 43% had positive intradermal reactions (greater than or equal to 1.0 cm 2 at least twice the area of the control wheal), compared to 48% positive stool examinations. However, sensitivity was low at 36% for children 14 yr old or less, and only 73% to 79% for adults. The test results were very specific for children (96%), but 32% of stool negative adults were positive. Mean wheal area was not directly related to intensity of infection as determined by egg counts in either children or adults, but did increase directly with age. Mean wheal areas were greater for males than females (both children and adults) at all intensities of infection. Because of unsatisfactory sensitivity and specificity the intradermal test may overestimate the prevalence of infection when rates are low, and underestimate prevalence of infection when rates are high. For its proper interpretation, complementary parasitologic data from stool surveys are required.     

A municipal level approach to the management of schistosomiasis control in Peri-Peri, MG, Brazil.

A schistosomiasis control program was implemented between 1974/87 in Peri-Peri, MG (622 inhabitants). Molluscicide (niclosamide) was applied at three monthly intervals in water sources with Biomphalaria glabrata, and individuals eliminating Schistosoma mansoni eggs in the feces were treated annually with oxamniquine. From 1974 to 1983 the control measures were undertaken by staff of the "René Rachou" Research Center FIOCRUZ (CPqRR), and from 1984 to 1987 these measures were included in the Capim Branco basic health network activities. During both periods, the prevalence, incidence, intensity of infection and hepatosplenic form as well as the number of infected snails decreased significantly. The prevalence decreased from 43.5 to 4.4%, the incidence from 19.0 to 2.9%, the overall intensity of S. mansoni from 281 to 87 and of the hepatosplenic form from 5.9 to 0.0%. The results obtained suggest that the municipal management of control measures was as effective as the vertical program conducted by CPqRR staff.     

Comparison of self-reported and observed water contact in an S. mansoni endemic village in Brazil

Estimates of exposure are critical for immuno-epidemiologic and intervention studies in human schistosomiasis. Direct observation of human water contact patterns is both costly and time consuming. To address these issues, we determined whether individuals residing in a Schistosoma mansoni endemic village in Brazil could accurately self-report their water contact patterns. We compared the results of a water contact questionnaire to the present gold standard, direct observation of water contact in 86 volunteers, aged 8--29. We administered a survey to estimate volunteers' frequency and type of water contact and directly measured each volunteers' water contact patterns during 5 weeks of detailed water contact observations. We found a poor correlation between self reported frequency of contact and directly observed exposure (rho=0.119, P=NS). The questionnaire data was supplemented by information about average body surface area of exposure and duration of contact for specific activities derived from observations of this cohort. This 'supplemented questionnaire' data was significantly correlated with their exposure index (rho=0.227, P=0.05). It provides a starting point from which questionnaires may develop to provide a more cost-effective and less labor intensive method of assessing water contact exposure at the level of the individual.     

洲岛型疫区围垦后居民接触疫水的定量研究

目的 :定量研究洲岛型血吸虫病疫区围垦后居民的疫水接触状况及疫情。方法 :对鄱阳湖一洲岛型血吸虫病疫区村在围垦一年后开展居民疫水接触调查 ,并对普治后居民的血吸虫感染情况进行纵向观察。结果 :围垦后居民主要在堤内活动 ,下田劳动、洗衣菜是主要的疫水接触方式 ,春夏高于秋冬 ;堤外疫水接触很少 ,主要是下湖捕鱼虾和水上运输 ,秋冬高于春夏 ,以男性为主。人群接触疫水随年龄的增长而增长 ,老年后逐渐减少。围垦后试区疫情迅速下降。结论 :围垦后居民生产和生活方式发生了显著变化 ,化疗已能有效地控制疫情。     

江陵县血吸虫感染者行为学调查

2010年底对湖北省血吸虫病重流行区江陵县筛查,发现感染者接触疫水方式以农业生产为主（占92.5%）,且该县居民再感染、重复感染严重。     

Infection with Schistosoma mansoni correlates with altered immune responses to Ascaris lumbricoides and hookworm

Studies were performed on humoral and cellular immune responses of patients from areas in Brazil endemic for hookworm and Ascaris lumbricoides, and either endemic or non-endemic for Schistosoma mansoni. Humoral and cellular responses were evaluated by enzyme-linked immunosorbant assay (ELISA) and peripheral blood mononuclear cell (PBMC) proliferation assays against larval hookworm antigens, A. lumbricoides egg antigens, and soluble egg antigens (SEA) or soluble whole adult antigenic preparation (SWAP) from S. mansoni. Patients from S. mansoni-endemic areas, who currently had only hookworm or Ascaris infections, expressed lower humoral and cellular responses to hookworm or Ascaris antigens, respectively, than did their counterparts from areas not endemic for S. mansoni. Individuals from S. mansoni endemic area, although without detectable S. mansoni infection, do mount humoral and cellular responses to SEA and SWAP. This group of individuals has been probably in contact with S. mansoni antigens, since the groups harboring A. lumbricoides or hookworm infections from non-S. mansoni endemic areas do not have detectable anti-S. mansoni responses. PBMC proliferative responses discriminated well between patients with active hookworm infections versus ascariasis, if they were from areas not endemic for S. mansoni.     

淮南地区曼氏迭宫绦虫病流行的危险因素调查

目的：探讨淮南地区曼氏迭宫绦虫病流行现状及其危险因素,为曼氏迭宫绦虫病的预防提供理论基础。方法：采用现场流行病学调查的方法,对淮南市各辖区水域剑水蚤原尾蚴感染状况、青蛙肌肉曼氏裂头蚴感染状况及各辖区家猫或家犬粪便曼氏迭宫绦虫卵感染状况进行随机抽样,分析剑水蚤原尾蚴感染率、青蛙肌肉曼氏裂头蚴感染率及各辖区家猫或家犬粪便曼氏迭宫绦虫卵感染率,另外采用问卷调查的方法调查曼氏迭宫绦虫病流行的环境及社会因素。结果：淮南地区6个市辖区或县剑水蚤原尾蚴感染率：田家庵区、谢家集区、八公山区、潘集区、大通区及凤台县分别为2%、1%、1%、2%、2%、3%;淮南地区青蛙曼氏裂头蚴总感染率为7.33%;家猫和家犬粪便中虫卵的检获率分别为0%~15%和0%~5%。问卷调查结果显示农民曼氏迭宫绦虫病预防知识知晓率为为0%,受调查农民中,有捕食青蛙的习俗的占14.77%,曾食过半生熟青蛙者占3.13%,曾用蛙喂猫或喂犬者占36.29%。结论：淮南地区剑水蚤原尾蚴感染率和青蛙曼氏裂头蚴总感染率均高,终宿主受到虫卵感染,农民对曼氏迭宫绦虫病预防知识知晓率低,应加强对农民曼氏迭宫绦虫病防治知识的教育,以达到有效控制曼氏迭宫绦虫病的发生、传播和流行的目的。     

The impact of schistosomiasis among rural populations in Liberia

Human infection with Schistosoma haematobium and/or Schistosoma mansoni is known to be widespread in central Liberia, but no information is available about its clinical manifestations or its significance for public health. Details of a cross-sectional morbidity study are reported. A sample from hospital out-patients and samples from 3 villages situated in areas with different transmission patterns (lack of transmission, transmission of only S. haematobium and transmission of both S. haematobium and S. mansoni) were examined. All 184 individuals were examined by standardized case history, clinical and parasitological investigations, including a skin snip for onchocerciasis and a count of schistosomal and other intestinal worm eggs from stool and urine. A complete blood count, urine analysis, urine cultures, hepatitis-B surface antigen determination and abdominal X-rays were also carried out. Schistosomal egg counts ranged from 1 to 6200/10 ml urine for S. haematobium and from 1 to 228/g stool for S. mansoni. Difficulties for the definition of accurate morbidity indices are discussed. Except for haematuria and dysuria, the overall morbidity in the study area was not striking, neither for S. haematobium nor for S. mansoni infection. No cumulative pathology was observed in patients with mixed infection. The frequency of hypertension, hepato- and splenomegaly, ascites and bacteriuria was low and no relationship to schistosomiasis could be established. Bladder calcifications were found in 10% of people living in an area of transmission of S. haematobium. Although the intensity of infection is low for both S. haematobium and S. mansoni, long-term follow-up studies are essential for a more accurate assessment of the public health importance of these parasites.     

Reduction in prevalence, intensity of infection and morbidity due to Schistosoma mansoni infection in a community following treatment with praziquantel

Five hundred and twenty-three individuals from an area endemic for Schistosoma mansoni infection were followed for a 16 month period in a population-based study in rural Zambia. Those found infected in each of five surveys were treated with praziquantel (40 mg kg-1 body weight). Data on prevalence, intensity of infection and morbidity (intestinal symptoms and liver and spleen enlargements) were also gathered. At the end of the study, prevalence had fallen from 64.8% to 11.5%, intensity of infection had dropped from 28.2 to 0.5 eggs per gram of stool (geometric means) and morbidity showed marked reduction.     

Impact of Schistosoma haematobium infection on urinary tract pathology, nutritional status and anaemia in school-aged children in two different endemic areas of the Niger River Basin, Mali

The aim of the present study was to contribute to define urinary schistosomiasis-related morbidity indicators and to understand the relationship between infection intensity and disease burden among school-aged children in different endemic areas of Mali. A cross sectional study was undertaken in two different endemic settings: Koulikoro district, along the river and Selingué dam area in the Niger River Basin in order to compare and describe morbidity related to Schistosoma haematobium infection. A total of 667 children aged 7-14 were enrolled in the study. Among these, 333 were from Koulikoro district (175 boys and 158 girls) and 334 from Selingué dam area (169 boys and 165 girls). The overall prevalence of S. haematobium in the two areas was 91.5%; Koulikoro (97.0%) and Selingué (85.9%) and this difference was significant after adjusting for age, sex and clustering within villages. Prevalence of heavy infection (≥ 50 eggs per 10 ml of urine), 57.6% in Koulikoro and 43.8% in Selingué, did not differ significantly after adjusting for age, sex and clustering within villages. The transmission of Schistosoma mansoni was mainly confined to Selingué dam area (12.5%) and was nearly absent in Koulikoro district (1.1%). Blood in urine was the most frequently reported clinical symptom, more common in Koulikoro (76.8%) than in Selingué (57.6%). In a multivariable logistic regression model adjusting for sex, age group, egg intensity category and clustering within villages, Selingué had higher prevalence of macro-haematuria, urinary tract pathology, upper urinary tract pathology and total pathology than Koulikoro, while micro-haematuria did not differ between the two areas. Morbidity measures increased to some extent with egg intensity category, especially micro-haematuria. The results obtained from this study are of importance for planning intervention as for monitoring and evaluation of control in different endemic settings in Mali.     

The epidemiology of a recent focus of mixed Schistosoma haematobium and Schistosoma mansoni infections around the 'Lac de Guiers' in the Senegal River Basin, Senegal

A village with mixed Schistosoma mansoni and S. haematobium infections (probably in a early endemic phase) was identified around the Lac de Guiers in the Senegal River Basin. In documenting the epidemiology of both schistosomes, we focused on prevalence and intensity of infection, transmission patterns and the impact of treatment. S. mansoni prevalences (near 100%) and egg counts (overall geometric mean eggs per gram of faeces (epg) of 589 were high in all age groups, with 35% of individuals excreting > 1000 epg, and showing a slow decline in egg output only after the age of 30 years. The overall prevalence (28%) and egg counts (2% > 50 eggs/10 ml) of S. haematobium were low, with mean counts of 6.3 eggs/10 ml. Maximal mean S. mansoni egg counts were found in 5-9 year-old boys and in 15-19 year-old girls; S. haematobium maximal counts in 1-4 year-old boys and in girls aged 5-9. Extremely high Biomphalaria pfeifferi infection ratios were recorded over the whole year. Following a single treatment, re-infection was rapid with prevalences and mean egg counts of both Schistosoma species reaching pretreatment levels within 7 months.     

Hamadryas baboons Papio hamadryas as maintenance hosts of Schistosoma mansoni in Saudi Arabia

Free ranging hamadryas baboons ( Papio hamadryas ) in four localities in the west and north of Saudi Arabia were examined for natural infection with Schistosoma mansoni . Faecal examination revealed infection with S. mansoni on four occasions within one year (at a prevalence rate of 2.5–4.0%) in only one locality, the Al‐Baha area. The eggs were viable, as shown by miracidial hatching tests, and were recorded at a density of 140–280 eggs/g of faeces (7000–14 000 eggs/day). Post‐mortem examination of 13–24 baboons from each locality revealed infection with S. mansoni (adult worms and eggs in tissue) in only one locality, the Al‐Baha area, at a prevalence rate of 4.16%. Viable eggs were found in the faeces and tissue of the infected baboons. The low prevalence rate of S. mansoni in hamadryas baboons in Saudi Arabia is in accordance with the low prevalence rate of S. mansoni in humans in the area. This natural baboon isolate was highly infective to snail intermediate hosts and mammalian hosts under experimental conditions. The epidemiological significance of the role of P. hamadryas (considering their large overall population of 250 000) as maintenance hosts of S. mansoni in Saudi Arabia is discussed.     

洲岛型疫区围垦后居民接触疫水的定量研究

目的 :定量研究洲岛型血吸虫病疫区围垦后居民的疫水接触状况及疫情。方法 : 对鄱阳湖一洲岛型血吸虫病疫区村在围垦一年后开展居民疫水接触调查 ,并对普治后居民的血吸虫感染情况进行纵向观察。结果 :围垦后居民主要在堤内活动 ,下田劳动、洗衣菜是主要的疫水接触方式 ,春夏高于秋冬 ;堤外疫水接触很少 ,主要是下湖捕鱼虾和水上运输 ,秋冬高于春夏 ,以男性为主。人群接触疫水随年龄的增长而增长 ,老年后逐渐减少。围垦后试区疫情迅速下降。结论 :围垦后居民生产和生活方式发生了显著变化 ,化疗已能有效地控制疫情。     

Schistosomiasis mansoni in the municipality of Pedro de Toledo (S?o Paulo, Brazil) where the Biomphalaria tenagophila is the snail host. I--Prevalence in human population

Due to the scarce information about the epidemiological features of schistosomiasis in which the vector is Biomphalaria tenagophila, an investigation was carried in Pedro de Toledo in 1980 where such peculiarity is observed. Stool examinations (Kato-Katz method) were performed in 4,741 individuals (22.8% positive to Schistosoma mansoni eggs) of this 583 had previously received chemotherapy and 4,158 remainders, untreated. The schistosomiasis prevalence in those two groups where respectively 31.7% and 21.6%. Epidemiological investigation showed that 83.6% were autochthonous cases from the studied area: the autochthonous prevalence rate, and the intensity of infection in the untreated autochthonous cases were higher in males than in females; the intensity in the latter untreated group was low, 58.5 eggs/g feces (geometric mean). Moreover, according to the age groups the intensity of infections correlated well (rs = 0.745) with the prevalence rates. Schistosomiasis was verified to occur mostly during the leisure time and by the use of water streams for housework in rural zone. Only 0.4% out of 1,137 snails was positive for S. mansoni cercariae, apparently unchanged from the 1978 study when the human prevalence was 12.0%. The studied area presented differences and similarities in relation to the other Brazilian areas were the main intermediate host is B. glabrata.     

The global status of schistosomiasis and its control

Schistosomiasis is being successfully controlled in many countries but remains a major public health problem, with an estimated 200 million people infected, mostly in Africa. Few countries in this region have undertaken successful and sustainable control programmes. The construction of water schemes to meet the power and agricultural requirements for development have lead to increasing transmission, especially of Schistosoma mansoni. Increasing population and movement have contributed to increased transmission and introduction of schistosomiasis to new areas. Most endemic countries are among the least developed whose health systems face difficulties to provide basic care at the primary health level. Constraints to control include, the lack of political commitment and infrastructure for public health interventions. Another constraint is that available anti-schistosomal drugs are expensive and the cost of individual treatment is a high proportion of the per capita drug budgets. There is need for increased support for schistosomiasis control in the most severely affected countries.