Population-based, spatiotemporal modeling of social risk factors and mortality from schistosomiasis in Brazil between 1999 and 2018

Schistosomiasis remains a significant public health concern in Brazil. To identify areas at, and social determinants of health (SDH) associated with, high-risk for schistosomiasis-related mortality from Brazil, we conducted a spatial and spatiotemporal modeling assessing all deaths confirmed in Brazil between 1999 and 2018. We used the segmented log-linear regression model to assess temporal trends, and the local empirical Bayesian estimator, the Global and Local Moran Index for spatial analysis. A total of 12,251 schistosomiasis-related deaths were reported in this period. Within the Mortality Information System (SIM) of the Brazilian Ministry of Health, the states of Alagoas (AL), Pernambuco (PE) and Sergipe (SE) recording the highest mortality rates: 2.21, 1.92 and 0.80 deaths/100,000 inhabitants, respectively. Analyses revealed an increase in the mean age of schistosomiasis-related deaths over the time assessed (APC = 0.9; p-value<0.05). Spatial analysis identified a concentration of municipalities presenting high risk of schistosomiasis-related mortality along the coastline of PE and AL. Similarly, we identified the formation of high space-time clusters in municipalities in the states of PE, AL, SE, Bahia, and Minas Gerais. Finally, mortality rates showed a significant correlation with 96.96% of SDH indices. The data reveal additional important changes in schistosomiasis-related deaths in Brazil between 1999 and 2018, such as a slow reduction among males (unlike females that displayed no change). Regardless, our analyses indicates that schistosomiasis continues to have the greatest detrimental impact in poor regions of Brazil and suggest the need for enhancement of current control measures to accelerate progress.

Positive consequences of splenectomy for patients with schistosomiasis-induced variceal bleeding

BACKGROUND

Patients with hepatic schistosomiasis are at high risk of gastroesophageal variceal bleeding, which is highly torrential and life threatening. This study aimed to assess the effects of splenectomy on patients with schistosomiasis-induced variceal bleeding, especially those influences related to overall survival (OS) rate.

METHODS

From January 2005 to December 2018, 112 patients with schistosomiasis-induced varices were enrolled. In that period, all the patients with hepatic schistosomiasis who received endoscopic treatment for primary and secondary prophylaxis of gastroesophageal variceal bleeding were found eligible. The patients were divided into splenectomized group (n = 44, 39.3%) and control group (n = 68, 60.7%).

RESULTS

Multivariate regression analysis of OS showed that splenectomy, hepatic carcinoma, and times of endoscopic treatment were independent prognostic factors for OS. Kaplan-Meier analysis revealed that the 5-year OS rate was 82.7% in splenectomized group versus 53.2% in control group (P = 0.037). The rate of no recurrence of variceal bleeding during 5-year (56.8% vs. 47.7%, P = 0.449) indicated that there was no significant difference between the two groups. Patients who received splenectomy had increased risk of portal vein thrombosis (52.3% vs. 29.4%, P = 0.012) and decreased proportion of severe ascites (20.5% vs 50.0%, P = 0.002).

CONCLUSION

Splenectomy prior to endoscopic treatment provides a superior long-term survival for patients with schistosomiasis-induced variceal bleeding.

Building a global schistosomiasis alliance: an opportunity to join forces to fight inequality and rural poverty

Schistosomiasis, one of the 17 neglected tropical diseases listed by the World Health Organization, presents a substantial public health and economic burden. Of the 261 million people requiring preventive chemotherapy for schistosomiasis in 2013, 92% of them lived in sub-Saharan Africa and only 12.7% received preventive chemotherapy. Moreover, in 2010, the WHO reported that schistosomiasis mortality could be as high as 280 000 per year in Africa alone.In May 2012 delegates to the sixty-fifth World Health Assembly adopted resolution WHA65.21 that called for the elimination of schistosomiasis, and foresees the regular treatment of at least 75% of school age children in at-risk areas. The resolution urged member states to intensify schistosomiasis control programmes and to initiate elimination campaigns where possible.Despite this, in June 2015, schistosomiasis was indicated to have the lowest level of preventive chemotherapy implementation in the spectrum of neglected tropical diseases. It was also highlighted as the disease most lacking in progress. This is perhaps unsurprising, given that it was also the only NTD with access to drug donations but without a coalition of stakeholders that collaborates to boost commitment and implementation.As a consequence, and to ensure that the WHO NTDs Roadmap Targets of 2012 and World Health Assembly Resolution WHA65.21 are met, the Global Schistosomiasis Alliance (GSA) has been set up. Diverse and representative, the GSA aims to be a partnership of endemic countries, academic and research institutions, international development agencies and foundations, international organizations, non-governmental development organizations, private sector companies and advocacy and resource mobilisation partners. Ultimately, the GSA calls for a partnership to work for the benefit of endemic countries by addressing health inequity and rural poverty.

Decline in infection-related morbidities following drug-mediated reductions in the intensity of Schistosoma infection: A systematic review and meta-analysis

Background

Since 1984, WHO has endorsed drug treatment to reduce Schistosoma infection and its consequent morbidity. Cross-sectional studies suggest pre-treatment correlation between infection intensity and risk for Schistosoma-related pathology. However, evidence also suggests that post-treatment reduction in intensity may not reverse morbidity because some morbidities occur at all levels of infection, and some reflect permanent tissue damage. The aim of this project was to systematically review evidence on drug-based control of schistosomiasis and to develop a quantitative estimate of the impact of post-treatment reductions in infection intensity on prevalence of infection-associated morbidity.

Methodology/Principal findings

This review was registered at inception with PROSPERO (CRD42015026080). Studies that evaluated morbidity before and after treatment were identified by online searches and searches of private archives. Post-treatment odds ratios or standardized mean differences were calculated for each outcome, and these were correlated to treatment-related egg count reduction ratios (ERRs) by meta-regression. A greater ERR correlated with greater reduction in odds of most morbidities. Random effects meta-analysis was used to derive summary estimates: after treatment of S. mansoni and S. japonicum, left-sided hepatomegaly was reduced by 54%, right-sided hepatomegaly by 47%, splenomegaly by 37%, periportal fibrosis by 52%, diarrhea by 53%, and blood in stools by 75%. For S. haematobium, hematuria was reduced by 92%, proteinuria by 90%, bladder lesions by 86%, and upper urinary tract lesions by 72%. There were no consistent changes in portal dilation or hemoglobin levels. In sub-group analysis, age, infection status, region, parasite species, and interval to follow-up were associated with meaningful differences in outcome.

Conclusion/Significance

While there are challenges to implementing therapy for schistosomiasis, and praziquantel therapy is not fully curative, reductions in egg output are significantly correlated with decreased morbidity and can be used to project diminution in disease burden when contemplating more aggressive strategies to minimize infection intensity.

Schistosomiasis is the disease caused by infection with Schistosoma parasitic flukes. Depending on the infecting species, chronic Schistosoma infection can cause a variety of pathologies including liver and spleen enlargement, fibrosis and hypertension of the portal vein of the liver, or bladder ulceration and deformities and kidney blockage. Infection can also cause anemia, diarrhea, abdominal pain, and decreased physical fitness. In our study, we quantified the reductions in prevalence of infection-related morbidities among populations with Schistosoma infection, as achieved by giving one or more drug treatments. We systematically reviewed 71 available reports of Schistosoma-related morbidity reduction and determined, based on a meta-analysis of the primary data, that the odds of persisting morbidity progressively decrease when greater post-treatment reductions in parasite burden are achieved, as reflected by reduced egg counts in standard diagnostic testing. This suggests that repeated or more effective anti-parasite drug treatment will be a valuable tool for greater reduction of Schistosoma-related patient morbidities in affected areas.

[Dynamic analysis of treatment of advanced schistosomiasis in Qianjiang City]

OBJECTIVE

To understand the dynamics of the treatment and outcomes of advanced schistosomiasis patients in Qianjiang City, so as to provide the evidence for improving the future work.

METHODS

All advanced schistosomiasis patients were investigated in Qianjiang City during the period of 2009-2013.

RESULTS

Totally 1 284 person-times of advanced schistosomiasis patients received the treatment. The rate of clinical improved was 89.88%, and 82 patients were cured. The type of ascites was the majority and the megalosplenia type was the second.

CONCLUSION

The prevalence of advanced schistosomiasis showed a decreasing tendency, but the incidence of new advanced schistosomiasis patients showed a slightly increasing.

[Curative effect of anti-HBV treatment in advanced schistosomiasis patients with ascites and HIBV infection]

OBJECTIVE

To improve the curative effect of advanced schistosomiasis patients with ascites and HBV infection.

METHODS

A total of 27 advanced schistosomiasis patients with ascites and HBV infection were selected as a trial group and given with anti-HBV treatment, and 31 corresponding patients were as the controls and did not received anti-HBV treatment from February 2003 to December 2012.

RESULTS

The incidence of ascites recurrence, spontaneous peritonitis, hepatic encephalopathy, hepatorenal syndrome, upper gastrointestinal bleeding, and primary liver cancer in the trial group were significantly lower than those in the control group. The detection indexes of liver function, renal function and prothrombin time in the trial group were superior to those in the control group. The mortality in the treatment group was also significantly lower than that in the control group.

CONCLUSION

The anti-HBV treatment in the advanced schistosomiasis patients with ascites and HBV infection can obviously improve their physical conditions, the survival rate, and their life qualities.

[Investigation on current status of advanced schistosomiasis in Shanggao County]

OBJECTIVE

To understand the current status of advanced schistosomiasis patients, so as to provide the reference for improving the medical care of them in Shanggao County.

METHODS

The data of advanced patients in Shanggao County were collected from the Information Management System for the Advanced Schistosomiasis Chemotherapy and Assistance in Jiangxi Province, and a field survey including the epidemiological investigation, physical examinations, and B ultrasound examinations was performed in 2014. All the data were analyzed statistically and compared with those in 2010.

RESULTS

Among the 128 advanced schistosomiasis patients, the male:female ratio was 2.46: 1, the average age was 68.02 ± 6.19 years, and the patients older than 65 years contributed to 64.84% for the all. The proportions of clinically types of ascites, splenomegaly, multiple granuloma in the colon, dwarf, general, and haemorrhage were 57.81%, 12.50%, 2.34%, 0, 26.57%, and 0.78%, respectively. The ultrasound examinations revealed the average diameter of the main trunk of portal vein was 12.70 ± 1.91mm in 2014, which was significantly broader than that of 12.05 ± 0.34mm in 2010 (P < 0.01).

CONCLUSIONS

The advanced schistosomiasis patents in Shanggao County decreases with years and shows an aging trend. Some advanced schistosomiasis patients are worse; therefore the chemotherapy and salvation work still should be strengthened.

Urothelial carcinoma of the urinary bladder mixed with squamous differentiation or squamous cell carcinoma in areas with schistosomiasis is showing high risk of recurrence and poor survival

In schistosomiasis haematobium areas endemic, bladder cancer is the first cause of malignancy in men and fourth in women. The chronic schistosomiasis would lead to variant histologic patterns which manifest in squamous cell carcinoma (SCC) or squamous differentiation (SqD). This study evaluated the clinical outcome after radical cystectomy (RC) in patients with urothelial carcinoma (UC) mixed with SCC or SqD, Comparison was done with two arms of pure UC and pure SCC, indication for RC was muscle-invasive-disease, and evaluation included recurrence, metastases, and overall survival. The data of patients treated with RC for muscle-invasive-disease, selection was revised for 127 patients with urothelial carcinoma mixed with SCC/SqD, two comparative arms were 100 patients with pure UC, and 100 patients had pure SCC. Follow up was on 8 months, 3 years, and 5 years to detect recurrence, metastasis, and overall survival in the three groups. The results showed that by comparison of disease aggressiveness in the three groups regarding recurrence, metastasis, and overall survival was analysed. Overall survival with mixed tumours was significantly lower than pure UC or SCC, recurrence and metastases were higher in mixed tumour which was an independent factor for poor prognosis and low survival.

Conflict and diarrheal and related diseases: a global analysis

The purpose of this study was to determine the association between deaths owing to terrorism, civil war and one-sided violence from 1994-2000 and disability-adjusted life years (DALYs) attributable to diarrheal and related diseases, schistosomiasis, trachoma and the nematode infections (DSTN diseases) in 2002 among World Health Organization Member States. Deaths resulting from terrorism, civil war and one-sided violence were significantly related to DSTN DALYs across the majority of sex-age subgroups of the populace, after controlling for baseline levels of improved water/sanitation and a variety of economic measures: overall, a 1.0% increase in deaths owing to terrorism and related violence was associated with an increase of 0.16% in DALYs lost to DSTN diseases. Associations were greatest among 0-to-4-year olds. The results of the present study suggest that DSTN disease control efforts should target conflict-affected populations with particular attention to young children who suffer disproportionately from DSTN diseases in these settings. In view of the evidence that terrorism and related violence may influence DSTN DALYs in the longer term, control strategies should move beyond immediate responses to decrease the incidence and severity of DSTN diseases to seek solutions through bolstering health systems infrastructure development among conflict-affected populations.

[Causes of death of advanced schistosomiasis patients in Huacao Town, Shanghai]

OBJECTIVE

To explore the causes of death of advanced schistosomiasis patients in Huacao Town, Shanghai, so as to improve the relief measures for advanced schistosomiasis patients.

METHODS

The data of advanced schistosomiasis patients from 2007 to 2012 were collected and analyzed statistically.

RESULTS

There were totally 340 advanced schistosomiasis patients, and among them there were 110 deaths and 230 survival cases currently. The deaths of the men were less than those of the female with the gender ratio of 1: 1.08. The average age of deaths of advanced schistosomiasis patients was 77.98 years, while the patients with age older than 70 years accounted for 90.00%. There were 36 advanced schistosomiasis patients died of cancer, accounted for 32.73%, and 34 deaths died of schistosomiasis, accounted for 30.91%.

CONCLUSION

The mortality rate of advanced schistosomiasis patients shows a rising trend in Huacao Town, and they mainly die of cancer and schistosomiasis.

[Survey on advanced schistosomiasis in Jiangyin City]

There were 66 patients with advanced schistosomiasis in Jiangyin City in 2008, among which 88 died, and other 48 cases were all advanced schistosomiasis patients with splenomegaly.

Liver morbidity due to Schistosoma mekongi in Cambodia after seven rounds of mass drug administration

Severe liver disease due to Schistosoma mekongi was frequent in northern Cambodia. Between 1995 and 2002, seven rounds of mass chemotherapy (praziquantel) reduced infection from 50% to below 3%. In 2002, we assessed hepatosplenic morbidity by historical, clinical and ultrasonographic investigations in adults (older than 14 years) from endemic (n=342) and non-endemic (n=103) areas (Kratie province). Clinical hepatomegaly (25 vs. 0%), splenomegaly (55 vs. 0%), reported blood in stool (41 vs. 20%) and abdominal pain (78 vs. 57%) were significantly higher in the endemic area. In this area, significantly more subjects reported a family history of death due to schistosomiasis (12 vs. 0%); 63% (vs. 0%) reported having at least three treatments of praziquantel in previous years; and only 11% (vs. 99%) had normal liver ultrasonographic examination. Periportal fibrosis with portal hypertension was diagnosed in 46% (vs. 0%) of people in this area; 18% (vs. 0%) and 5% (vs. 0%) of portal hypertension was classified as moderate and severe, respectively. People aged between 24 and 35 years were mostly affected. There was no gender difference. The pathology in the endemic district is most probably residual morbidity of S. mekongi infections. Contributions of co-infections (hepatitis) cannot be excluded. Careful monitoring of the affected communities is required.

[Experimental infection of goats with Schistosoma bovis and S. curassoni: comparative pathogenic effects]

Specific mortality and morbidity have been quantified in goats experimentally infected with Schistosoma bovis or S. curassoni strains from Niger. The study involved nine animals followed during 380 days after infection with, respectively, 1,800 or 2,400 cercariae. S. bovis was significatively more pathogenic than S. curossoni in terms of mortality, weight loss and packed cell volume decrease. In addition, the intensity of clinical symptoms was significatively and positively correlated to the levels of fecal egg excretion. Compared to non-infected controls, a growth differential of, respectively, 1,600 and 880 grams per month should incite to consider S. bovis and S. curassoni as parasites of serious economical impact in sahelian countries.

An analysis of the impact of the Schistosomiasis Control Programme in Brazil

The impact of the Schistosomiasis Control Programme (PCE) in Brazil was analyzed, covering the period 1976 to 2003, using the following indicators: percentage of Schistosoma mansoni carriers detected among the population examined in the coproscopic surveys (PPS): mortality rate for schistosomiasis, per 100,000 inhabitants (TME): hospitalization rate for schistosomiasis, per 100,000 inhabitants (TIE): average age of deaths caused by schistosomiasis (IMOE). There was a 38.5% reduction in the PPS after the introduction of the PCE, attributed to the treatment of carriers. Even in hyper-endemic municipalities, such as Conde and Cuitegí, in the state of Paraíba, the PPS fell more than 50% after the first year of treatment. The parasitic burden of the carriers also decreased in the two municipalities. The TME was reduced by 63.4% and the TIE by 77.3%. The mortality rate was highest among the 50-and-above age group. The country's IMOE rose 32.3%. The IMOE was seen to be much lower in the state of Minas Gerais, where the PCE was only initiated in 1983, with very limited coverage.

Long-term follow-up after liver transplantation in Egyptians transplanted abroad

OBJECTIVE

To study the long-term outcome after liver transplantation (LT) in Egyptian patients who underwent LT outside Egypt.

METHODS

Between May 1993 and February 2004, over 150 Egyptians underwent LT outside Egypt. Data of 67 recipients were collected in Egypt through personal communications with the Overseas Liver Transplant Centers and through the records of the Egyptian Liver Transplant Association.

RESULTS

Most patients underwent LT in Europe (73.1%), few in the United State of America (17.9%) and in Japan (9%). Sixty-one patients underwent cadaveric LT and the remaining 6 patients underwent living related liver transplantation (LDLT). The male to female ratio was 58:9. Median age was 45 (3-63 years). Hepatitis C virus (HCV) cirrhosis whether alone or mixed with schistosomiasis was the main indication for LT. Out of those 67 recipients, 52 (77.6%) survived after a median follow-up period of 4.6 years (rang 1-10.5 years). Deaths were due to primary non-function in 3 patients, postoperative bleeding in one patient, recurrent hepatitis C virus (HCV) in 10 patients, and chronic rejection in one patient.

CONCLUSION

Egyptians underwent LT abroad showed a good long-term outcome. Due to the high prevalence of HCV, we expect a growing need for LT in Egypt. Although LDLT has been introduced recently in Egypt, cadaveric liver donation is still not legalized by the government. Efforts should be directed to expanding LDLT, legalizing cadaveric LT and also to the prevention and control of HCV infection in Egypt in order to avoid its devastating effect on the society as well as its enormous negative impact on Egypt's economy and future development.

Schistosomiasis does not contribute to death or recurrence of nontyphoid Salmonella bacteremia in human immunodeficiency virus-infected Malawian adults

Nontyphoid Salmonella (NTS) bacteremia has a very high mortality and recurrence rate among human immunodeficiency virus (HIV)-infected Malawian adults. Concurrent schistosomal infection might cause persistence of NTS infection and poor response to antibiotic therapy. Therefore, we tested serum samples for Schistosoma-specific circulating anodic antigen to diagnose coinfection with schistosomiasis among consecutive HIV-positive adults with NTS bacteremia. The results suggest that active schistosomiasis is not associated with adverse outcome of NTS bacteremia in this population, in contrast to other groups.

Approximating the long-term behaviour of a model for parasitic infection

In a companion paper two stochastic models, useful for the initial behaviour of a parasitic infection, were introduced. Now we analyse the long term behaviour. First a law of large numbers is proved which allows us to analyse the deterministic analogues of the stochastic models. The behaviour of the deterministic models is analogous to the stochastic models in that again three basic reproduction ratios are necessary to fully describe the information needed to separate growth from extinction. The existence of stationary solutions is shown in the deterministic models, which can be used as a justification for simulation of quasi-equilibria in the stochastic models. Host-mortality is included in all models. The proofs involve martingale and coupling methods.

Stochastic models of a parasitic infection, exhibiting three basic reproduction ratios

Two closely related stochastic models of parasitic infection are investigated: a non-linear model, where density dependent constraints are included, and a linear model appropriate to the initial behaviour of an epidemic. Host-mortality is included in both models. These models are appropriate to transmission between homogeneously mixing hosts, where the amount of infection which is transferred from one host to another at a single contact depends on the number of parasites in the infecting host. In both models, the basic reproduction ratio R0 can be defined to be the lifetime expected number of offspring of an adult parasite under ideal conditions, but it does not necessarily contain the information needed to separate growth from extinction of infection. In fact we find three regions for a certain parameter where different combinations of parameters determine the behavior of the models. The proofs involve martingale and coupling methods.

[Reduced morbidity of schistosomiasis: report from an expert workshop on the control of schistosomiasis held at CERMES (15-18 February 2000, Niamey, Niger)]

Schistosomiasis remains a problem for public health in sub-Saharan Africa. Despite past efforts, cases have not decreased significantly. Schistosoma haematobium and S. mansoni are endemic in all the West African countries. The distribution of both parasites is focal. During a workshop held at CERMES in Niamey, in February 2000, a group of experts recommended that schistosomiasis control be considered as a public health priority in all the endemic West African countries, and National Control Programmes rapidly implemented. The objective of these control programmes would be to reduce schistosomiasis-related morbidity. Case detection should be based on clinical symptoms such as haematuria or bloody diarrhoea, and be carried out at two levels: health care centres and schools, in order to reach patients and school-age children. Health workers should be trained in case detection and community based control of schistosomiasis. The assembled experts advocated the use of praziquantel dosed at 40 mg.kg-1, which therefore must be made available and accessible in outlying areas. Associated measures consist of sanitation, water supply and health education, especially aimed at improving patients' treatment-seeking behaviour. A West African network for schistosomiasis control was created during the workshop. It runs on the Web site of CERMES as network co-ordinator. (http://www.mpl.ird.fr/cermes/).

Foci of Schistosomiasis mekongi, Northern Cambodia: II. Distribution of infection and morbidity

In the province of Kracheh, in Northern Cambodia, a baseline epidemiological survey on Schistosoma mekongi was conducted along the Mekong River between December 1994 and April 1995. The results of household surveys of highly affected villages of the East and the West bank of the river and of school surveys in 20 primary schools are presented. In household surveys 1396 people were examined. An overall prevalence of infection of 49.3% was detected by a single stool examination with the Kato-Katz technique. The overall intensity of infection was 118.2 eggs per gram of stool (epg). There was no difference between the population of the east and west shore of the Mekong for prevalence (P = 0.3) or intensity (P = 0.9) of infection. Severe morbidity was very frequent. Hepatomegaly of the left lobe was detected in 48.7% of the population. Splenomegaly was seen in 26.8% of the study participants. Visible diverted circulation was found in 7.2% of the population, and ascites in 0.1%. Significantly more hepatomegaly (P = 0.001), splenomegaly (P = 0. 001) and patients with diverted circulation (P = 0.001) were present on the west bank of the Mekong. The age group of 10-14 years was most affected. The prevalence of infection in this group was 71.8% and 71.9% in the population of the West and East of the Mekong, respectively. The intensity of infection was 172.4 and 194.2 epg on the West and the East bank, respectively. In the peak age group hepatomegaly reached a prevalence of 88.1% on the west and 82.8% on the east bank. In the 20 schools 2391 children aged 6-16 years were examined. The overall prevalence of infection was 40.0%, ranging from 7.7% to 72.9% per school. The overalls mean intensity of infection was 110.1 epg (range by school: 26.7-187.5 epg). Both prevalence (P = 0.001) and intensity of infection (P = 0.001) were significantly higher in schools on the east side of the Mekong. Hepatomegaly (55.2%), splenomegaly (23.6%), diverted circulation (4. 1%), ascites (0.5%), reported blood (26.7%) and mucus (24.3%) were very frequent. Hepatomegaly (P = 0.001), splenomegaly (P = 0.001), diverted circulation (P = 0.001) and blood in stool (P = 0.001) were significantly more frequent in schools of the east side of the Mekong. Boys suffered more frequently from splenomegaly (P = 0.05), ascites (P = 0.05) and bloody stools (P = 0.004) than girls. No difference in sex was found for the prevalence and intensity of infection and prevalence of hepatomegaly. On the school level prevalence and intensity of infection were highly associated (r = 0. 93, P = 0.0001). The intensity of infection was significantly associated only with the prevalence of hepatomegaly (r = 0.44, P = 0. 05) and blood in stool (r = 0.40, P = 0.02). This comprehensive epidemiological study documents for the first time the public health importance of schistosomiasis mekongi in the Province of Kracheh, Northern Cambodia and points at key epidemiological features of this schistosome species, in particular the high level of morbidity associated with infection.

Distribution, prevalence and intensity of Schistosoma bovis infection in cattle in Iringa district, Tanzania

Monthly abattoir, farms and village surveys were carried out to determine the distribution, prevalence and intensity of Schistosoma bovis infection in cattle in Iringa district in the southern highlands of Tanzania between August 1991 to August 1992. Abattoir surveys were conducted at the Iringa regional abattoir and age, sex, live animal grade and livestock market of origin of each of 342 animals examined were recorded. Five grams of the central part of the jejunum were collected from each animal and schistosome egg counting was carried out after tissue digestion. Nine farms and six villages were randomly selected and age, sex and origin of 501 cattle was recorded. Faecal samples were collected from each animal and quantification of schistosome eggs was carried out by means of the Modified Bell filtration technique. Abattoir surveys revealed S. bovis to be present in 116 out of 342 cattle examined in 10 out of the 12 livestock markets surveyed giving a point prevalence of 34%. A high frequency (70.1%) of low tissue egg counts (< 200 eggs per gram) was observed among the infected animals. The prevalence and intensities of infection observed in the slaughtered cattle were not related to the age-group, sex and grade of the animals. Results from faecal egg counts in nine farms and six villages disclosed that the infection was predominant in four farms (Lulanzi, Igumbiro, Ruaha and Mlolo) and three villages (Itunundu, Ibumu and Lulanzi). Egg counts per gram of faeces (EPGF) at Lulanzi dairy farm revealed a peak egg excretion in 1-3 yr old animals which was followed by a decline in the number of EPGF within the age group of 3- to 9-yr old animals. However, the faecal egg excretion tended to rise again in animals over 9 years old. Deaths of four animals which were preceded by signs of intermittent diarrhea, loss of condition, anaemia and high faecal egg counts was observed at Lulanzi farm. Postmortem examination of the dead animals revealed that they had severe schistosomal lesions and higher tissue egg counts than the slaughtered cattle. It was concluded from the present study that S. bovis infection in cattle is very common in foci in Iringa district and possibly the whole of the southern highlands of Tanzania and in some enzootic farms it could be among the major causes of ill-health and lowered productivity.

Schistosoma mattheei infection in cattle: the course of the intestinal syndrome, and an estimate of the lethal dose of cercariae

Three groups of young oxen were infected percutaneously with cercariae of Schistosoma mattheei. Three of five oxen infected with 248 cercariae kg-1 mass died or were killed in extremis 58-70 d after infection, a fourth survived extremely severe clinical schistosomosis and the fifth was only slightly affected. None of seven calves infected with 187 cercariae kg-1 died, while one of seven exposed to 119 cercariae kg-1 was in extremis (possibly not from schistosomosis) when killed after 378 d. The LD50 appears to be in the region of the highest dose tested (248 cercariae kg-1), but depends on variations in the viability of the cercariae used. The clinical syndrome was characterized by a drastic, rapid loss in body mass; a severe diarrhoea containing blood clots; straining, gnashing of the teeth, occasional groaning, and other signs of abdominal pain; and markedly sunken eyes. Lethally infected oxen did not become recumbent until shortly before death. Some severely affected animals made remarkable, but slow, recoveries without treatment. Schistosomes, in close association with granulomata, are described-apparently for the first time-in the omental veins of cattle. Mean worm development in three calves that died or were killed in extremis in the acute stage of the disease, was 55.5%. In contrast to most previous findings with S. mattheei, in two of these animals, more female than male worms developed. The worms were recovered by perfusion and, in one animal, a large number of intestinal veins were dissected open to estimate the efficiency of the perfusion method. Only 1.9% of the total worm burden had not been removed by perfusion in this animal.

Adam's rib awry? Women and schistosomiasis

The present paper reviews the literature to determine whether there are predisposing factors which influence the transmission, prevalence, intensity of infection and morbidity of schistosomiasis in women. The review suggests that: (1) the higher prevalence rates observed in males, in most endemic areas, are not due to sex per se, but to the greater opportunities afforded to males for exposure; (2) cultural and social practices often determine occupational roles and, in some circumstances, these practices may protect women from exposure; (3) when women assume typical 'male' roles, their risk and prevalence of infection increases; (4) in Muslim societies, women's exposure to water is restricted and infection rates are usually lower; (5) morbidity does not appear to be influenced by sex; and (6) the most important impact of schistosomiasis on women is its possible disruption of maternal functions, such as pregnancy, and its role in maternal, infant and child mortality and fetal wastage. Suggestions are also made for expanding existing research and for new studies concerning factors which may influence infection and disease in women.

Public health impact of schistosomiasis: disease and mortality. WHO Expert Committee on the Control of Schistosomiasis

The public health significance of schistosomiasis is often underestimated for two reasons. First, like all helminthic infections, the distribution of worms in any community is widespread but uneven, i.e., few have heavy infections and severe disease, while many have lighter infections and fewer symptoms. Some people with very few worms may have no symptoms. Secondly, severe disease usually follows after many years of silent or mildly symptomatic infection. Even if only 10% of those 200 million infected with schistosomiasis have severe clinical disease, this still represents 20 million seriously ill people. Of the remaining 180 million infected people, an estimated 50-60% also have symptoms--a public health problem of enormous proportions. The impact on public health can be assessed in terms of the frequency and severity of schistosomiasis-related disease, incapacity and premature death. This article presents extracts from the Expert Committee's recently published second report and deals with morbidity and mortality, as well as the links between schistosomiasis and cancer, nutrition and intercurrent infections, and the immune response to schistosomiasis.

Should both schistosomal and nonschistosomal variceal bleeders be disconnected?

Splenopancreatic disconnection (SPD) was conceived and implemented as a technical addition to distal splenorenal shunt (DSRS) to maintain its selectivity and preserve portal perfusion. The proposed hemodynamic and metabolic stability of hepatocytes after DSRS-SPD should improve survival. In this nonrandomized study, 145 consecutive (Child A/B) variceal bleeders were electively subjected to selective shunt with DSRS in 93 and DSRS-SPD in 52 patients. The 2 groups were similar before surgery with a mean follow up of 24 +/- 12 (DSRS) and 27 +/- 14 (DSRS-SPD) months. DSRS-SPD had an operative mortality of 3.8%. Postoperative pancreatitis occurred in 7.7% after DSRS-SPD and 3.2% after DSRS alone, with schistosomal hepatic fibrosis representing 86% of morbid cases. Shunt patency was high and recurrent variceal hemorrhage was low in both groups. Clinical encephalopathy was significantly reduced after DSRS-SPD (p less than 0.05). The addition of SPD significantly reduced both the incidence of chronic hyperbilirubinemia in the schistosomal patients (p less than 0.05) and the difference between the changes in total serum bilirubin in all patients (p = 0.001). Portal perfusion was preserved after DSRS-SPD in all of the angiographically-studied patients. The overall survival was 84% after DSRS and 88% after DSRS-SPD. The schistosomal patients showed an incidence of 95% and 96% survival after DSRS and DSRS-SPD, respectively. DSRS-SPD was able to improve survival (92%) better than DSRS (77%) among well-matched nonschistosomal patients. These data show: (1) DSRS-SPD still has low operative mortality and a high patency rate with a low incidence of recurrent variceal hemorrhage, (2) DSRS-SPD maintains portal perfusion, achieves better survival, and reduces the incidence of encephalopathy, especially in patients with nonalcoholic cirrhosis and mixed liver disease, (3) in the schistosomal population, DSRS-SPD reduces the incidence of chronic hyperbilirubinemia but increases the risk of postoperative pancreatitis.

Selective shunt versus nonshunt surgery for management of both schistosomal and nonschistosomal variceal bleeders

This clinical study included 219 (Child A/B) consecutive variceal bleeders. Electively 123 had distal splenorenal shunt (DSRS) and 96 had splenectomy with gastroesophageal devascularization (S&GD). Liver pathology was documented in 73% of patients, with schistosomal fibrosis in 41% and nonalcoholic cirrhosis or mixed pattern (fibrosis and cirrhosis) in 59%. The surgical groups were similar before operation, with a mean follow-up of 82 +/- 13 and 78 +/- 18 months, respectively (range, 60 to 120 months). The two pathologic populations were also similar before each and both procedures. The operative mortality rates were low, with incidences of 3.3% (DSRS) and 3.1% (S&GD). Rebleeding occurred significantly (p less than 0.05) more frequently after S&GD (27%) compared to DSRS (5.7%). Sclerotherapy salvaged 65% of S&GD rebleeders. Encephalopathy developed significantly (p less than 0.05) more after DSRS (18.7%) compared to S&GD (7.3%), with no significant difference among the current survivors. The difference in overall rebleeding and encephalopathy rates between both procedures was statistically related to patients with cirrhosis and mixed lesions (p less than 0.05). Distal splenorenal shunt significantly reduced the endoscopic variceal size more than S&GD (p less than 0.05). Prograde portal perfusion was documented in 94% of patients in each group, with a variable distinct pattern of portaprival collaterals in 91% (DSRS) and 65% (S&GD). The total population cumulative survival was similar with 80% for DSRS and 79% for S&GD (plus sclerosis in 23%), with hepatic cell failure the cause of death in 46% and 50%, respectively. However, in the schistosomal patients, survival was better improved after DSRS (90%) compared to S&GD (75%), with no difference among the cirrhotic and mixed group (DSRS 73%, S&GD 72%). In conclusion (1) both DSRS and S&GD have low operative mortality rates, (2) DSRS is superior to S&GD in the schistosomal patients, and (3) S&GD backed by endosclerosis for rebleeding is a good surgical alternative to selective shunt in the nonalcoholic cirrhotic and mixed population.

[Mortality caused by schistosomiasis in Brazil, 1977-1986]

The authors present schistosomiasis mortality data in the country, in macrozones and in the federal units during the period of 1977-86. They relate mortality average to the control program. Its impact seems to be evident, especially concerning the population that underwent treatment. Here the reinfection risk has been decreased or eliminated. Data referring to the proportional mortality and distribution by age are also presented.

Results of sclerotherapy in 100 patients comparison of the outcome between schistosomiasis and hepatitis B

One hundred patients received sclerotherapy for acutely bleeding esophageal varices. Seventy per cent of these patients had chronic liver disease due to schistosomiasis or hepatitis B. The remaining 30% had chronic liver disease of other etiology, including alcohol in 2%. Our study shows a favorable outcome of sclerotherapy in the schistosomal group during a mean follow-up period of 39 months. Esophageal varices were completely sclerosed in 53.3% of schistosoma patients, in 37.5% of hepatitis B, and in 42.3% of other groups. The rebleeding rate was 11.1% in schistosomiasis, 43.8% in hepatitis B and 33.3% in other groups. The overall mortality rate was 4.4% in the schistosomal group, 50.0% in the hepatitis B, and 40% in other groups. Rebleeding from gastric varices occurred in 17 patients, 13 of whom died, including 11 who were operated on for bleeding gastric varices and died following surgery.

Postoperative radiotherapy of carcinoma in bilharzial bladder using a three-fractions per day regimen

Patients with T3 bladder cancer who survived surgery and proved to have P3a, P3b or P4a tumors were randomized to either no further treatment (61 patients) or postoperative total pelvic irradiation (55 patients). A three-fraction per day regime was adopted with a dose per fraction of 125 cGy and an interval of 3 h between fractions. The total dose amounted to 3750 cGy divided into 30 fractions over 12 days. Patients of the postoperative radiotherapy group were re-randomized to radiotherapy alone or radiotherapy plus misonidazole (MISO) in a daily dose of 1 g/m2 given orally 2 h before the first daily fraction. The 2-year disease-free survival rate in the cystectomy alone group was 33 +/- 6% compared to 65 +/- 6% in the postoperative radiotherapy group. The therapeutic benefit applied to the two cell types, all histological grades and stages and to patients with or without nodal metastases. The benefit of postoperative irradiation was also verified by the Cox's multivariant analysis which adjusts for the relative representation of the important prognostic factors particularly pathological stage and nodal involvement. MISO did not seem to add to the therapeutic gain. No late complications were encountered in the wall of the rectum, small bowel or uretero-intestinal anastomotic sites. This is suggested to be due to the small dose per fraction used. However, early small bowel reactions were dose-limiting.

Data management in schistosomiasis control programmes

Adequate data recording, processing, analysis and evaluation are all components of data management within schistosomiasis control programmes oriented towards reduction of morbidity. Without data management, the response to operational questions will remain subjective and vague. Different types of data related to the population and the environment are reviewed. Examples of data format and presentation are given. The importance of data management for proper short and long term evaluation of control measures is emphasized.

Schistosomiasis haematobium and the mortality occurring in an endemic community at Bujashi, Tanzania

A population of 4516 inhabitants of an area endemic for schistosomiasis haematobium at Bujashi, Tanzania, was investigated in 1983 seven years after a baseline study for a pilot control project to determine the disease mortality risk. The distribution of the 238 deaths occurring in the population, when analysed by the Mantel Haenszel test, showed similar age and sex specific mortality rates among the 2309 non-cases and 2109 cases found excreting schistosome eggs at the baseline urine examinations. Furthermore, the respective follow up 36 and 57 cases with and without urological sequelae on the baseline excretion urograms, also showed similar age adjusted mortality rates as did the 1663 and 446 metrifonate treated and untreated cases respectively. The findings suggested, therefore, that neither the disease nor its treatment affected the mortality occurring in the population.

The application of a quantitative approach to the assessment of the relative importance of vector and soil transmitted diseases in Ghana

The vector and soil transmitted parasitic infections produce a highly diverse group of diseases in terms of the importance of their impact upon human populations and in terms of the control methods that might limit that impact. In Ghana a method was developed for quantitatively assessing the relative importance of different disease problems by estimating the amount of healthy life lost through illness, disability and death as a result of each disease. The quantitative assessment is derived from information on incidence rate, case fatality rate and the extent and duration of disability produced by the disease. The method may be used to help decide the priorities for the allocation of resources to alternative procedures or programmes by calculating the amount of healthy days of life which may be saved by different approaches and then relating these savings to the costs of the approaches. Each of the vector and soil transmitted parasitic diseases in Ghana had special characteristics that influenced the estimates of their relative importance. Attribution of death due to malaria posed special problems, but even with the most conservative estimate malaria was the single most important cause of loss of healthy life of all diseases in Ghana. For schistosomiasis there is such great uncertainty concerning how much disability or mortality that results from infection that the relative importance of schistosomiasis could not be usefully estimated; thus research into the extent of disability and death caused by schistosomiasis should have a very high priority if rational allocation of resources for its control is to be achieved. Onchocerciasis, though not generally considered an important cause of mortality, is an important cause of chronic severe disability. The importance of ascariasis and hookworm remain uncertain both because of the lack of information as to the extent of disability and mortality that they produce and the lack of data in Ghana as to their prevalence and intensity of infection. Guinea worm was of little importance from the national point of view, but was highly important in focal areas. Trypanosomiasis would appear to be of minor importance because its incidence was quite low, but for an epidemic disease such as trypanosomiasis the importance must be estimated based on what would occur if there were not effective surveillance and control methods. Diverse though this group of parasitic diseases is a common thesis is that each has been relatively neglected in relation to its importance and for each a considerable reduction in loss of healthy life should be achievable at reasonable cost.

Studies on experimental mixed infections of Schistosoma mansoni and S. haematobium in hamsters

Golden hamsters were superinfected simultaneously with 100 Schistosoma haematobium cercariae, 1 and 3 weeks after initial infection with 100 S. mansoni cercariae. Results indicate that there was a higher degree of resistance to superinfection with S. haematobium at 1 week following initial infection with S. mansoni than that produced in the other two superinfections. This resistance was evidenced by a reduction in the number and size of worms of both species, decrease in S. haematobium egg extrusion per female and by a striking deviation in the egg distribution pattern of both species. Such an early host resistance was not recorded in previous works. Cross-mating was observed but no hybridization took place and the eggs produced were hatchable and typical of their species.

Owner survey of schistosomiasis mortality in Sudanese cattle

The estimated mortality in six- to 30-month-old cattle due to presumptive schistosomiasis was 7.1% for 155 interviews conducted in the White Nile Province in 1981. This mortality was higher for those herds under sedentary management than for migratory herds (9.4% vs 3.6%). The interviews were done through an informal visit technique by a veterinarian living in the area. The approximate number (19,000) of cattle over six months old estimated to be owned by those interviewed represents about 1% of the population in that province. The mortality from all causes in the six- to 30-month age group was 9.2%; in the over 30-month age group it was 1.8%. The authors judge the schistosomiasis mortality to be somewhat upwardly biased but the mortality due to all causes (9.2%) is consistent with the few reports available.

Relationship between acquired resistance, portal hypertension, and lung granulomas in ten strains of mice infected with Schistosoma mansoni

Pronounced differences in resistance to reinfection and pathology were observed among various strains of mice infected with Schistosoma mansoni. When comparing strains, the level of resistance induced by a 12-week infection correlated closely with the degree of portal blood pressure elevation and number of lung egg granulomas, but did not correlate with other pathological parameters or with the number of worms or tissue eggs. Among individual mice of the same strain, however, resistance was proportional to the number of worms and tissue eggs. Nmri strain mice infected for more than a year remained highly resistant to reinfection and continued to shunt eggs into the lungs, but showed considerable resolution of portal hypertension, hepatomegaly and splenomegaly. No association was observed among mouse strains between the mortality resulting from a primary infection and the severity of any of the pathological parameters which were measured.

Observations on cattle schistosomiasis in the Sudan, a study in comparative medicine. III. Field testing of an irradiated Schistosoma bovis vaccine

Previous work has shown that cattle can acquire a strong resistance to Schistosoma bovis infection following repeated natural exposure. Partial resistance to a laboratory challenge with S. bovis has also been demonstrated in calves after immunization with an irradiated schistosomular or cercarial vaccine. The aim of the present study was to see whether this type of vaccine could protect calves under the very different conditions of natural exposure to S. bovis in the field. Thirty 6- to 9-month-old calves were each immunized with 10,000 irradiated S. bovis schistosomula by intramuscular injection and 8 weeks later were released into an enzootic area along with 30 unvaccinated animals. The calves were followed up for 10 months, during which period protection was evidenced by a lower mortality rate, a slower rate of acquisition of infection, and lower fecal egg counts in the vaccinated calves. Necropsy of the survivors showed 60--70% reductions in worm and tissue egg counts of the vaccinated calves as compared to those not vaccinated.

Sustained release of niridazole from silicone rubber implants for the treatment of Schistosoma mansoni infections

Niridazole was incorporated into silicone rubber implants to investigate the potential of a sustained release of the drug in the therapy of murine schistosomiasis mansoni. The infected animals (200 cercariae for 6 weeks) were randomly divided into three groups: one group received silicone rubber implants containing 50% by weight niridazole; a second group received blank silicone rubber implants with no drug; and the third group received no implants. Mortality 4 weeks later was in excess of 80% for animals with no implants or with the blank silicone rubber implants. In contrast, 10% mortality was observed in the mice receiving the niridazole-silicone rubber implants over a 10-week period. The worm burden in the niridazole-silicone rubber implant group was reduced at 10 weeks post implantation by 77%.

Increased hepatotoxicity of bacterial lipopolysaccharide in mice infected with Schistosoma mansoni

Mice infected with Schistosoma mansoni were highly sensitive to the lethal effects of bacterial lipopolysaccharide (LPS). The hyper-reactive state of LPS coincided with the development around the parasite eggs of multiple granulomas in the liver. Elevated aspartate transaminase levels in blood and severe hypoglycaemia in LPS-challenged animals indicated extensive liver parenchymal cell damage. There was also a complete depletion of glycogen in hepatocytes of these animals. From this work and studies on other hepatitis models, it is suggested that individuals affected with granulomatous disorders may be at risk because of everyday exposure to LPS from the gut.

Estimating the duration of latency and survival time of snails with schistosomiasis

By means of techniques of analyses of survival data developed for cancer trials it is possible to study aspects of the natural history of the infection of schistosomiasis on the intermediate host of transmission, the snail. The simultaneous study of three response variables is largely based on a model of Lagakos (1976). When using this approach in the schistosomiasis setting it seems inappropriate to assume that one process, the duration of latency, follows an exponential distribution. Thus this stage is modified to follow a normal distribution and the derivatives required to obtain maximum-likelihood estimates and approximate variances of all parameters are provided. Simple graphical tools for assessing the validity of distributional assumptions in survival data are available from industrial research. The reader's attention is drawn to a paper by Nelson (1972). The relevance and application of these methods to the current problem are described in Section 4. In the event that the times to death of prepatent and patent snails do not follow exponential distributions as assumed in the primary model, a further modification is introduced to enable either or both to follow Weibull densities. Lastly it is possible to adapt both the primary model of Section Three and the modified model of Section Five to allow for the inclusion of auxiliary variables or covariates. Again the required derivatives to obtain maximum likelihood estimates and approximate variances are provided.

Factors affecting the acquisition of resistance against Schistosoma mansoni in the mouse. I. Demonstration of resistance to reinfection using a model system that involves perfusion of mice within three weeks of challenge

The degree of resistance acquired by Schistosoma mansoni-infected mice against homologous challenge has been determined by perfusion of the animals within three weeks of the challenge, at which time the challenge-derived organisms were morphologically distinguishable from the primary infection which induced the resistance. The method has been compared with assays based on determination of the number of organisms migrating through the lung, and with perfusions at a later time when the challenge has matured. The results obtained with the three week perfusion method, showing that resistance was acquired by eight weeks after a primary infection, were confirmed by the longer survival of, and reduced egg excretion rates and tissue egg burdens in the experimental animals relative to respective challenge control animals. However, some discrepancy in challenge-derived worm numbers was found between animals perfused three weeks after challenge and those autopsied at later times. The possible reasons for this difference are discussed. The degree of resistance that was acquired was to some extent dependent on the size of the challenge infection.

[Influence of the cryopreservation at nitrogen temperature on the vaccinic ability of the "PF" strain of Trypanosoma cruzi (author's transl)]

The cryopeservation of the "PF" strain of T. cruzi at -196 degree C has not changed its effectiveness in protecting mice against a posterior infection with a virulent Trypanosoma cruzi strain. The cryopeservation technique utilized seems to be efficient and of practical and rapid examination.

Mortality and other parameters of concomitant infections in albino mice: the Schistosoma-Toxoplasma model

Inocula of S. mansoni and T. gondii well tolerated by albino mice when given singly, were given concomitantly to groups of animals. Few notable effects were observed when toxoplasmosis preceded schistosomiasis, but the S. mansoni leads to T. gondii model, with an interval of 59 days between infections, led to massive mortality, great weight loss and a striking splenomegaly. These findings are very similar to data from previous work on the S. mansoni leads to Trypanosoma cruzi model. The authors believe that other examples of such a type of potentialization should be searched for in human schistosomiasis also.

Toxoplasmosis and the host-parasite relationship in murine schistosomiasis mansoni

Infection with Toxoplasma gondii has been shown to suppress markedly the in vitro splenic lymphocyte response to nonspecific mitogens and the in vivo antibody response to sheep red blood cells. The effect of toxoplasmosis on an in vivo cell-mediated response, granuloma formation around Schistosoma mansoni eggs, was examined in the present study. The granulomas were markedly suppressed from two to 20 weeks after infection with T. gondii. In subsequent experiments the effect of toxoplasmosis-induced immunosuppression on the development of hepatosplenic schistosomiasis was evaluated. Mice with the combined infections had markedly smaller hepatic granulomas and lower mean portal pressures than those infected with S. mansoni alone. Although the prevalence of esophageal varices in the mice with schistosomiasis alone was 60%, there was no visible collateral circulation in the animals with both infections.

Schistosomiasis in the congenitally athymic (nude) mouse. I. Thymic dependency of eosinophilia, granuloma formation, and host morbidity

Athymic nude mice (Nu/Nu), heterozygous littermates (Nu/+), and thymus reconstituted homozygous animals (Nu/Nu TXR) were exposed to Schistosoma mansoni cercariae. A marked impairment in the development of peripheral blood eosinophilia and hepatic granuloma was observed in the Nu/Nu animal. In addition, host morbidity judged by organ weight, portal pressures and reticuloendothelial activity were less in the Nu/Nu animal. Thymus-reconstituted animals demonstrated eosinophilia, increased granuloma size, and morbidity equivalent to that shown by the Nu/+ heterozygous littermates. These studies indicate that the eosinophilia, granulomatous hypersensitivity, and ultimate host morbidity, associated with murine schistosomiasis, is dependent on thymic dependent lymphocyte function.

Schistosomiasis: its significance in a changing human ecology

Schistosomiasis is a man-made disease. Evaluation of the current status of schistosomiasis requires knowledge of the intensity of infection, a measure now dependent on quantitative egg counts and applied to data only on a limited scale. The determinants of intensity of infection are as yet ill-defined. Morbidity and mortality associated with schistosomiasis are difficult to assess in indigenous populations saddled with a multiplicity of diseases. However, the problem of schistosomiasis and its deleterious consequences will rapidly worsen as an expanding population creates new aquatic habitats favorable for the snail intermediate hosts and as people have increased contact with infected water. Moreover, the number of children is increasing fastest in the developing regions of the world. Children and young adolescents are the age groups primarily responsible for the transmission of schistosomiasis. We are in an era when a predominantly young population will increasingly contaminate a finite environment.