[Can we overcome schistosomiasis? A Senegalese example]. / Peut-on vaincre les bilharzioses ? Un exemple sénégalais.

The authors report the results of controlling schistosomiasis in 53 villages from Ninefecha area-(Kedougou District, East Senegal) within Schistosomiasis National Control Program partnership. The four aims were: i) praziquantel treatment of 3324 children 6-14 years old, ii) installation of a laboratory for children prevalence annual monitoring (random draw one in three), iii) health education of the concerned people ("sensitization"), iiii) construction of latrines. 900 latrines are required and 649 have been built. The initial prevalence (2006) of 44% for S. mansoni and 4% for S. haematobium are now respectively 1.9% and 1.4% (2013). The program must be continuous as shown in the Assoni village: a prevalence study in children 0-5 years old, for which praziquantel is not recommended, reveals an infestation rate for S. mansoni of 78% in 2008 and of 47% in 2012. This age group is an important parasite reservoir and health education of parents is absolutely necessary. A permanent and effective center like Ninefescha hospital for distribution of praziquantel, sensitization meetings and latrines control is essential for the success of the program.

[Can schistosomiasis be defeated? An example from Senegal]. / Peut-on vaincre les bilharzioses ? Un exemple sénégalais.

The authors report the results of actions combatting schistosomiasis since 2008 in 53 villages in eastern Senegal, including the creation of 450 latrines and the distribution of praziquentel. The prevalence of Schistosoma mansoni has fallen from 44% in 2006 to 1.8% today. To succeed in eradicating schistosomiasis, access to non-infected water must be improved to ensure the adhesion of local village communities.

The oxygen concentrator: an appropriate technology for treating hypoxaemic children in developing countries.

The World Health Organization (WHO) recommends supplying oxygen in developing countries by concentrators because cylinders pose considerable logistic and financial problems. This technology was employed to treat children in a hospital in Ndioum, Senegal, who met the WHO oxygenation criteria. There were clear clinical and financial benefits, but neither the nurses' knowledge of the various techniques of oxygen supply nor the maintenance service were satisfactory. The use of concentrators should be encouraged in developing countries. A strategy including technical training, maintenance and monitoring should be adopted. Corrective actions were undertaken in Ndioum, and several concentrators are now being used on a regular basis.

Evaluation of the patterns of Schistosoma mansoni infection and re-infection in Senegal, from faecal egg counts and serum concentrations of circulating anodic antigen.

Infection and re-infection patterns were evaluated in a recent Schistosoma mansoni focus in northern Senegal, by determining concentrations of serum circulating anodic antigen (CAA), as a measure of worm burden, and counting eggs in faeces before, 6 or 12 weeks and 1 year after praziquantel treatment in two subsequent cohorts (cohort A and B). No differences in egg counts and CAA concentrations or their relationship were found between the cohorts, which were examined 2 years apart. Within both cohorts, CAA concentrations showed the same, typical, age-related patterns as egg counts, with a peak in children and a strong decline in adults. These trends were apparent both before and 1 year after treatment. The results indicate that an age-related resistance to infection and to re-infection has been firmly established, at a steady level, in the recent S. mansoni focus investigated, with no indication of a gradual development of immunity or anti-fecundity immunity over a period of 2 years. Both shortly and 1 year after treatment, the decrease in egg counts was stronger than that in CAA concentrations, indicating that that there had been a reduction in worm fecundity after treatment. The possibility that praziquantel may induce anti-fecundity immunity has important implications for the use and interpretation of the results of (egg-count-based) re-infection studies designed to follow the development of naturally acquired immunity.

Dynamics of egg counts and circulating antigen levels in a recent Schistosoma mansoni focus in northern Senegal.

Serum circulating anodic antigen (CAA) levels were compared with faecal egg counts in four subsequent population samples, randomly selected at 8-month intervals, in a recent Schistosoma mansoni focus in northern Senegal. In all four samples, antigen levels showed the same age-intensity profiles as egg counts, with a strong decline in adults. Also across population samples, a consistent relationship was found between egg counts and antigen levels. Assuming the level of CAA to be a direct reflection of worm burden, these findings support the idea that the observed egg count patterns and levels indeed reflect dynamics of worm burdens, and not of egg excretion or worm fecundity. Remarkably similar levels of both egg counts and CAA were observed in the first and last sample, collected in the same season (August--September), but 2 years apart. This suggests that a steady state of S. mansoni infection had already been reached shortly after the onset of the epidemic in this focus (3 years). Significantly lower infection levels were found in the intermediate population samples collected in January and April. The differences in infection levels across the four population samples may be because of seasonal transmission patterns. They would indicate a substantial turnover of worm populations, with an estimated average life span of only 7 months, probably less, in this recently emerged, intense S. mansoni focus.

Seasonality in the transmission of schistosomiasis and in populations of its snail intermediate hosts in and around a sugar irrigation scheme at Richard Toll, Senegal.

Irrigation for intensive sugar cultivation started in the early 1980s at Richard Toll, some 100 km from the mouth of the Senegal River. Infections with Schistosoma mansoni were first seen in late 1988. This study records quantitative snail surveys for over 3 years from 1992 at sites representing different habitats in and around the irrigation scheme. Populations of both Biomphalaria pfeifferi (the intermediate host of S. mansoni) and Bulinus spp. (mainly B. truncatus, the local host of S. boris) peaked in late 'spring' or early 'summer', depending on the habitat, and then remained low until the following spring', B. pfeifferi favoured smaller, man-made habitats with most transmission between May and August each year. The less abundant Bulinus spp. favoured larger natural and man-made habitats with most S. bovis transmission between April and July. S. mansoni infections were more, but S. bovis infections were less abundant than other trematodes in their respective snail hosts. Ecological changes in the early 1980s due to sugar irrigation pre-dated similar, more widespread changes in the late 1980s when the completion of dams across the Senegal River prevented seasonal rain fed floods and sea water intrusion. S. mansoni has since spread rapidly around Richard Toll. The incompatibility of the local S. haematobium strains with the dominant bulinid snails has so far prevented an epidemic of urinary schistosomiasis at Richard Toll, but the invasion of similar downstream habitats by susceptible B. globosus is worrying. The principal control measure, chemotherapy, given in the 'winter' would minimise the rate of reinfection. It could be reinforced by judicious mollusciciding within the sugar irrigation scheme but not elsewhere.

Organometric investigations of the spleen and liver by ultrasound in Schistosoma mansoni endemic and nonendemic villages in Senegal.

With the intention of ultrasonographically assessing hepatosplenic morbidity in Schistosoma mansoni infection and of validating the grading system applied (Cairo classification), 191 subjects in a schistosomiasis endemic village and 247 controls from a nonendemic village in northern Senegal underwent sonographic examination of the liver and spleen. Measurements of the diameters of the peripheral periportal vein branches, the main portal vein stem, liver size (left lobe and right lobe), and spleen length in the endemic village were compared with those in the nonendemic village to evaluate the much discussed influence of S. mansoni infection on those variables. To subtract this presumed influence from reference values for the named variables, they are given as measured in the nonendemic village, stratified by body weight, enabling future investigators on schistosomiasis-induced morbidity to refer to these reference values. The 95th percentile regarding peripheral periportal vein branch diameter in the control groups was exceeded in 24% of the subjects in the endemic group. It was exceeded by 6% for the main portal vein stem diameter, 13% for the left liver lobe, 12% for the right liver lobe, and 14% for the spleen length. According to the Cairo classification, 97% of the endemic population and 81% of the controls had periportal thickening of the liver, mostly grade I. We conclude that 1) hepatic morbidity in the S. mansoni endemic area was low, despite strikingly high intensities of infection; 2) the Cairo classification in its present form overestimates periportal thickening, especially in the case of mild morbidity; and 3) body height-dependent reference values, obtained from endemic controls, must be applied for organometric parameters.

Therapeutic evaluation of two different dose regimens of praziquantel in a recent Schistosoma mansoni focus in Northern Senegal.

A therapeutic trial, involving 130 Schistosoma mansoni-infected children, with no previous history of antischistosomal treatment, was carried out to evaluate the efficacy of two different dose regimens of praziquantel. The study was carried out because low cure rates were described in this recently established (1990) S. mansoni focus in northern Senegal, following treatment with a standard dosage of 40 mg/kg. The subjects were randomly allocated into two groups: one group (1) received 40 mg/kg in one oral dose, the other group (2) was treated with two oral doses of 30 mg/kg at a 6-hr interval. Parasitologic examination and circulating anodic antigen (CAA) detection were performed before, 10 days, three, six, and 21 weeks after chemotherapy. No significant differences in cure rates were found between the two groups. Six weeks after treatment, 34% and 44% of the individuals were found to be stool negative in group 1 and group 2, respectively. However, only 10-15% became completely negative according to the serum CAA antigen assay. Mean egg counts were reduced by 99% in both groups. Antigen detection confirmed the parasitologic results. Fewer side effects were observed in the group treated with 2 x 30 mg/kg, which may be explained by split dosage administration. Our study shows that the low cure rates observed in this area could not be improved by using a higher dosage of praziquantel.

Evaluation of ultrasonographic staging systems for the assessment of Schistosoma mansoni induced hepatic involvement.

For the sonographic assessment and grading of hepatosplenic morbidity induced by Schistosoma mansoni infection, several quantitative and qualitative classification systems have been used. In an attempt to evaluate two staging systems, a study was performed as part of a schistosomiasis research and control programme in Richard Toll, Senegal. A total of 700 residents of the township N'diangué were parasitologically, clinically and sonographically examined in July 1993. Two ultrasound observers (M.D. and E.D.) applied the Cairo and the Managil classification (E.D. only) for the grading of periportal thickening of the liver. In spite of high prevalence and intensity of infection, severe hepatic morbidity was rare. According to the Cairo classification, there was a high percentage of subjects with grade I periportal thickening, with considerable inter-observer variability. In the Cairo classification, which is based on the diameter of peripheral portal vein branches, firm cut-offs are used, independent of body height. We show the relationship between body height and portal vein diameters and recommend the use of body height-dependent reference values to avoid falsely high percentages of periportal thickening, especially in children. To minimize inter-observer variability, a clarification of existing instructions for taking measurements for grading is suggested. These suggestions have been considered during the follow-up expert meeting on the Cairo classification in Niamey under the auspices of the World Health Organization in October 1996.

Ultrasonography in a Senegalese community recently exposed to Schistosoma mansoni infection.

Inhabitants of Ndombo (n = 614), a village in an area recently infected with Schistosoma mansoni in Northern Senegal, were examined clinically, parasitologically, and ultrasonographically to investigate the presence and degree of S. mansoni-related hepatosplenic morbidity after a few years of exposure to schistosomal infection of regional canals. Despite previous praziquantel treatment of 56% of the inhabitants prior to our investigation, the prevalence of S. mansoni infection in 1993 was 90%, and 42% of the villagers excreted more than 1,000 eggs per gram of stool. Previously untreated individuals were found to have significantly higher egg counts than treated ones. Despite the high intensities of infection, ultrasonographically detected severe periportal thickening of the liver was infrequent. Grading according to body length-dependent normal values of cross-section diameter of peripheral portal vein branches of a European control group correlated with intensities of infection. Of the total group of patients, 30% (n = 182) had more severe thickening of portal vein branch diameters above the 97th percentile and 70% of these had a splenomegaly. The highest egg counts and the most frequent development of periportal thickening were found in 11-20 year-old individuals. Periportal thickening was less frequent in praziquantel-treated adolescents than in untreated ones. This suggests that early antischistosomal medication may be useful to limit schistosomiasis-induced hepatic morbidity especially in children, even though reinfection seems inevitable.

Antibody response patterns against Schistosoma mansoni in a recently exposed community in Senegal.

Acquired immune resistance is believed to be largely responsible for age-dependent infection and reinfection patterns in schistosomiasis. In a recently established but intense focus of Schistosoma mansoni in Senegal, the humoral immune response was studied in a random population sample of 289. Antibody levels of various isotypes to schistosome worm and egg antigens were determined by ELISA and related to egg counts (eggs per gram of feces [EPG]), age, and sex. Both IgG1 and IgG4 followed age-related patterns similar to egg counts and strongly correlated with EPG, even after allowing for age. Specific IgE levels increased slowly with age. The humoral immune response patterns in this recently infected population appeared to be largely similar to those in chronically infected communities. Thus far, the observations do not support the current hypothesis that age-related resistance to Schistosoma is determined by IgE-mediated protective immunity acquired during many years of exposure.

Clinical investigation of a population recently infected with Schistosoma mansoni (Richard-Toll, Senegal).

Following the introduction of large-scale irrigation, an exceptional epidemic of intestinal schistosomiasis occurred in northern Senegal when a non-immune population was exposed to massive infection. Subjects infected with Schistosoma mansoni were followed up parasitologically and clinically from the onset of the epidemic. After the initial evaluation, patients received a health education session and were treated with praziquantel in a dose of 30 mg/kg. One year after this treatment, S. mansoni eggs were found in the stools of 227/301 subjects (75%). Twenty-three per cent of subjects excreted > 400 eggs per gram (e.p.g.) and 11% excreted > 1000 e.p.g. of faeces. Overall, the geometric mean was 191 e.p.g. of faeces in infected individuals. The prevalence of diarrhoea was reduced from 55 to 29%, the prevalence of bloody diarrhoea from 44 to 11% and the prevalence of abdominal discomfort from 66 to 41%. No hepatomegaly was found in these patients either before or one year after treatment. Splenomegaly was reduced from 30% (measured by ultrasound) to 3% (on clinical examination). Morbidity associated with S. mansoni infection was considerably reduced one year after treatment with praziquantel (30 mg/kg).

Epidemiologic application of circulating antigen detection in a recent Schistosoma mansoni focus in northern Senegal.

Quantitative enzyme-linked immunosorbent assays (ELISAs) for the detection of circulating anodic antigen (CAA) and circulating cathodic antigen (CCA) in serum and urine were applied as an epidemiologic tool in a recent, intense focus of Schistosoma mansoni in Senegal. Both CAA and CCA in serum and CCA in urine were found in 94%, 83%, and 95%, respectively, of the population, of which 91% were positive on stool examination. Circulating antigens were also detectable in sera and urines of most egg-negative individuals. The sensitivities of the urine CCA and serum CAA ELISA were substantially higher than that of a single egg count, and increased with egg output. The CAA and CCA levels correlated well with egg counts and with each other. The age-related evolution of antigen levels followed a similar pattern as egg counts, providing supplementary evidence for a genuine reduction of worm burdens in adults in spite of the supposed absence of acquired immunity in this recently exposed community. The antigen:egg ratios decreased in adults, suggesting lower worm fecundity in children. This would be compatible with a density-dependent reduction of fecundity, but not with anti-fecundity immunity in adults that perhaps has not yet developed in this new focus.

Efficacy and side effects of praziquantel in an epidemic focus of Schistosoma mansoni.

Schistosoma mansoni was first reported in the area of Richard Toll (Senegal) in 1988 and spread rapidly in the community, after a series of human-engineered ecologic changes. A random population sample (n = 422) from Ndombo, a village near Richard-Toll, was studied in 1991 by stool examination (four Kato slides from two stool samples) and antigen detection in urine and blood. Stool-positive individuals were treated with 40 mg/kg of praziquantel. A house-to-house interview regarding side effects was conducted 24 hr after treatment. Two hundred ninety-eight subjects were re-examined 10 days (antigen detection) and 12 weeks (egg counts, antigen detection) after treatment. Before treatment, positive egg counts were found in 91% of the subjects, with 41% excreting more than 1,000 eggs per gram (epg) of feces. Treatment of 352 individuals caused serious but transient side effects (colic, vomiting, urticaria, and edema), the frequency of which increased with increasing egg counts. The parasitologic cure rate 12 weeks after treatment was only 18%, the frequency of egg counts with more than 1,000 epg decreased to 5%, and the mean egg count of those remaining positive was reduced by 86%. Antigen detection in serum 10 days and 12 weeks after treatment remained positive in 90% of the subjects, although titers decreased sharply. The low cure rates may be due to intense transmission and/or undeveloped immune responses in this recently exposed population. However, reduced drug susceptibility of the parasite strain has now been confirmed in one local isolate.

Immuno-epidemiology of Schistosoma mansoni infections in a recently exposed community in Senegal.

Schistosoma mansoni was introduced in the Senegal basin around 1988, due to man-made ecological changes. Since 1991, we investigate a recent but very intense focus, Ndombo, a village near the city of Richard Toll where the outbreak was first described. Four cohorts, each a random sample (+/- 400 subjects each) from this community, were examined and followed up after treatment, starting at 8 month intervals over a 2-year period. Each cohort is examined parasitologically (Kato-Katz), clinically, serologically (circulating antigen and antibody profiles); treated with praziquantel 40 mg/kg; followed up 6-10 weeks, one and two years after treatment; and monitored for water contact patterns and local snail densities. In the first cohort, the prevalence was 91%, with a mean egg count of 663 epg. Prevalences are near 100% in all age groups, but egg counts decline strongly in adults. Antigen detection in serum and urine confirmed that the egg counts genuinely reflect variations of worm burdens, not e.g. of worm fecundity. This is surprising, as in this focus acquired immunity in adults should not have yet developed according to current hypothesis. The antigen detection assays (CAA/CCA) showed high sensitivity and quantitative power, and promising perspectives as a research tool and possibly as a method for non-invasive diagnosis and screening in urine. Epidemiological in subsequent cohorts were highly similar, although seasonal variations were observed possibly due to transmission fluctuations. Anti-AWA and anti-SEA IgE levels increased with age, while IgG4 peaked in the age-group 10 years and correlated well with egg counts.(ABSTRACT TRUNCATED AT 250 WORDS)

PIP: A cohort analysis was performed in Ndombo, Senegal, a community of about 4000, in the epicenter of the schistosomiasis outbreak. Four randomly selected cohorts of +or- 400 subjects were surveyed. Each cohort was examined parasitologically, clinically, and serologically (circulating antigen and antibody profiles); treated with praziquantel 40 mg/kg; and followed up at 6-12 weeks and at 1 and 2 years after treatment. The first cohort numbered 422 individuals, of which 91% had positive egg counts, with a mean egg count of 663 eggs per gram feces (epg). Quantitative egg counts in those aged 10-14 were 1409 epg and then declined to 632 epg in the age group 20-29 and to 266 epg in the age group over 40. In cohorts 2 and 3, examined in the spring and autumn, egg counts were substantially lower, particularly in adults, as compared with cohorts 1 and 4, which were both examined in the summer season. 94% of the subjects were positive in the serum circulating anodic antigen (CAA) ELISA, 83% in the serum CAA ELISA, and 95% in the urine circulating cathodic antigen (CCA) ELISA; CAA in urine was less sensitive, and was negative in half of the urine samples. Positivity rates for all assays increased with rising egg counts, and circulating antigen concentrations in both serum and urine correlated well with egg counts. IgE showed a significant increase with age, while IgG4 peaked in the age groups 10-15 and/or 15-19 years. A strong correlation between IgG, IgGl, and IgG4 against both crude antigens with pretreatment egg load was observed. Of the subjects in the first cohort, 61% reported abdominal pain, 33% diarrhea; only 16% showed mild hepatomegaly and only a few children had mild splenomegaly. In the first cohort, 82% of 298 reexamined subjects were still positive for S. mansoni 12 weeks after treatment with praziquantel 40 mg/kg. One year after treatment, cohort 1 showed mean egg counts in children (5-19 years) at 358 epg as compared with 1188 epg pretreatment.

Epidemic schistosomiasis in the delta of the Senegal River Basin, Senegal: responses of the health care system.

Since 1988, the delta of the Senegal River Basin has experienced an exceptional epidemic of intestinal schistosomiasis, following the development of large irrigation projects. Urinary schistosomiasis was also rapidly spreading. The response of the health care system to the epidemics is described. Control was integrated in the existing health care system, according to the general health policy of Senegal. Control was based on passive detection, treatment, health education and information. The availability of praziquantel was assured. Priority was given to the development of health services in general. Initial reports have also attracted different research groups to the area. The variety of epidemiological situations made this area unique for research. Researchers would like to observe untreated communities to study the development of immune mechanisms. Inevitably such approach must lead to confrontation with local health services which should offer ethically and medically correct management of infected individuals and affected communities.

Preliminary study of urinary schistosomiasis in a village in the delta of the Senegal river basin, Senegal.

Three years after the first cases of urinary schistosomiasis infection were reported in the village of Mbodiene, Senegal, Schistosoma haematobium eggs were found in 87% of the inhabitants of this village; 30% were heavily infected (> 50 eggs per 10 mL urine). The prevalence of infection was very high in all age groups, but children showed more intense infections. No difference between sexes was found. In the special situation of a very high prevalence, test strips for proteinuria and haematuria are not very useful for the individual diagnosis of S. haematobium infection. Six and 12 weeks after treatment with a single dose of praziquantel (40 mg/kg), S. haematobium eggs were found in 25% and 30% of the treated subjects, respectively. Bulinus globosus was identified as intermediate host, but other snail vectors may also play a role. S. mansoni eggs were found in 1% of the population. Both S. haematobium and S. mansoni are spreading in the delta of the Senegal river.

Morbidity due to heavy Schistosoma mansoni infections in a recently established focus in northern Senegal.

A study of morbidity due to Schistosoma mansoni infection was carried out in Ndombo, a recently established but intense focus in northern Senegal. A random population sample (n = 422) was examined by repeated egg counts, standardized interviews, and clinical examinations. Egg counts were positive in 91%, with more than 1,000 eggs per gram of feces in 41% of the subjects. Abdominal discomfort was reported by 60% of the subjects, diarrhea by 33%; 17% of the stools were liquid upon inspection. Hepatomegaly was mostly mild and found in 7% of the subjects, mainly in males less than 20 years of age. Splenomegaly was detected in only 0.5% of the people examined. There was no significant correlation between the frequency of complaints or symptoms and egg counts. The remarkably mild morbidity in spite of the intense level of many infections may be explained by the recent nature of the focus; more severe chronic morbidity may develop in the future.