Praziquantel in the treatment of hepatosplenic schistosomiasis: biochemical disease markers indicate deceleration of fibrogenesis and diminution of portal flow obstruction

Praziquantel and Upper Gastrointestinal Bleeding in Hepatic Schistosomiasis: A Quasi-Experimental Study

Background

There is a general consensus that widespread use of praziquantel in populations where schistosomiasis is endemic prevents development of hepatic schistosomiasis and its complications. However, a few studies have reported discordant findings linking praziquantel to the occurrence of upper gastrointestinal bleeding (UGIB) in some patients with hepatic schistosomiasis and varices.

Objective

We explored if there was any causal association between recent praziquantel use (rPZQ) and upper gastrointestinal bleeding in hepatic schistosomiasis in rural Africa.

Patients and Methods

A quasi-experimental, retrospective case-controlled study was performed. It involved adult patients with past or acute UGIB, varices, periportal fibrosis, and/or cirrhosis. Cases had acute variceal bleeding while controls did not. The outcome was the frequency of lifetime episodes of UGIB and exposure was rPZQ (received praziquantel in the last 11 months from the date of enrollment). The data analysis included 2 × 2 tables, logistic regression, and propensity-score matching. Odds ratios (ORs), average treatment effects (ATEs), and their 95% confidence intervals (CIs) were used for inference.

Results

Over 6 weeks, we enrolled 19 cases with 92 lifetime episodes of UGIB, and 66 controls with 192 lifetime episodes of UGIB. Cases were more likely to experience UGIB than controls following rPZQ (92% vs. 62%; OR 7.6; 95% CI 3.4–17). Factors predictive of more lifetime episodes of UGIB at multivariable analysis included rPZQ (adjusted OR 13; 95% CI 2.9–53), relative leukocytosis (adjusted OR 26; 95% CI 7.6–89), large varices (adjusted OR 5.0; 95% CI 1.7–15), a family member with hepatosplenic schistosomiasis (adjusted OR 19; 95% CI 7.4–51), advanced periportal fibrosis (adjusted OR 8.0; 95% CI 2.6–22), ascites (adjusted OR 14; 95% CI 4.3–47), and jaundice (adjusted OR 32; 95% CI 7.8–128). While the ATE following rPZQ among the treated was 0.40 (95% CI 0.33–0.48).

Conclusions

Our findings suggest the presence of a plausible causal association between recent praziquantel use and increased frequency of UGIB in our study population.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40801-020-00222-7.

Characterising granuloma regression and liver recovery in a murine model of schistosomiasis japonica

For hepatic schistosomiasis the egg-induced granulomatous response and the development of extensive fibrosis are the main pathologies. We used a Schistosoma japonicum-infected mouse model to characterise the multi-cellular pathways associated with the recovery from hepatic fibrosis following clearance of the infection with the anti-schistosomal drug, praziquantel. In the recovering liver splenomegaly, granuloma density and liver fibrosis were all reduced. Inflammatory cell infiltration into the liver was evident, and the numbers of neutrophils, eosinophils and macrophages were significantly decreased. Transcriptomic analysis revealed the up-regulation of fatty acid metabolism genes and the identification of Peroxisome proliferator activated receptor alpha as the upstream regulator of liver recovery. The aryl hydrocarbon receptor signalling pathway which regulates xenobiotic metabolism was also differentially up-regulated. These findings provide a better understanding of the mechanisms associated with the regression of hepatic schistosomiasis.

Neopterin in Diagnosis and Monitoring of Infectious Diseases

Neopterin is produced by activated monocytes, macrophages, and dendritic cells upon stimulation by interferon gamma produced by T-lymphocytes. Quantification of neopterin in body fluids has been achieved by standard high-performance liquid chromatography, radioimmunoassays, and enzyme-linked immunosorbent assays. Neopterin levels predict HIV-related mortality more efficiently than clinical manifestations. Successful highly active antiretroviral therapy is associated with a decrease in neopterin levels. Elevated neopterin levels were associated with hepatitis by hepatitis A, B, and C viruses. Serum neopterin levels were found to be a predictor of response to treatment of chronic HCV infection with pegylated interferon combined with ribavirin. Neopterin levels of patients with pulmonary tuberculosis were found to be higher in patients with more extensive radiological changes. Elimination of blood donors with elevated neopterin levels to reduce risk of transmission of infections with known and unknown viral pathogens has been undertaken. Neopterin measurement is hereby more cost effective but less sensitive than screening using polymerase chain reaction based assays. In conclusion neopterin is a nonspecific marker of activated T-helper cell 1 dominated immune response. It may be a useful marker for monitoring of infectious disease activity during treatment and for more accurate estimation of extent of disease and prognosis.

Effect of ketoconazole, a cytochrome P450 inhibitor, on the efficacy of quinine and halofantrine against Schistosoma mansoni in mice

The fear that schistosomes will become resistant to praziquantel (PZQ) motivates the search for alternatives to treat schistosomiasis. The antimalarials quinine (QN) and halofantrine (HF) possess moderate antischistosomal properties. The major metabolic pathway of QN and HF is through cytochrome P450 (CYP) 3A4. Accordingly, this study investigates the effects of CYP3A4 inhibitor, ketoconazole (KTZ), on the antischistosomal potential of these quinolines against Schistosoma mansoni infection by evaluating parasitological, histopathological, and biochemical parameters. Mice were classified into 7 groups: uninfected untreated (I), infected untreated (II), infected treated orally with PZQ (1,000 mg/kg) (III), QN (400 mg/kg) (IV), KTZ (10 mg/kg)+QN as group IV (V), HF (400 mg/kg) (VI), and KTZ (as group V)+HF (as group VI) (VII). KTZ plus QN or HF produced more inhibition (P<0.05) in hepatic CYP450 (85.7% and 83.8%) and CYT b5 (75.5% and 73.5%) activities, respectively, than in groups treated with QN or HF alone. This was accompanied with more reduction in female (89.0% and 79.3%), total worms (81.4% and 70.3%), and eggs burden (hepatic; 83.8%, 66.0% and intestinal; 68%, 64.5%), respectively, and encountering the granulomatous reaction to parasite eggs trapped in the liver. QN and HF significantly (P<0.05) elevated malondialdehyde levels when used alone or with KTZ. Meanwhile, KTZ plus QN or HF restored serum levels of ALT, albumin, and reduced hepatic glutathione (KTZ+HF) to their control values. KTZ enhanced the therapeutic antischistosomal potential of QN and HF over each drug alone. Moreover, the effect of KTZ+QN was more evident than KTZ+HF.

Ultrasound versus biological markers in the evaluation of periportal fibrosis in human Schistosoma mansoni

In this paper, the authors review the literature and share their experience of the principal biological markers of fibrosis for the evaluation of periportal fibrosis (PPF) caused by mansoni schistosomiasis. These biological markers are compared to diagnostic ultrasound (US) scans as means of grading PPF. We also review procollagen type I and III, collagen type IV, laminin, hyaluronic acid (HA), immunoglobulin G, platelets, aspartate aminotransferase to platelet ratio index (APRI) and gamma-glutamyl transpeptidase as markers of the disease. Although there are several good markers for evaluating PPF and portal hypertension, such as HA, platelets or APRI, none can yet replace US. These markers may, however, be used to identify patients at greater risk of developing advanced disease in endemic areas and determine who will need further care and US studies.

Effect of praziquantel prolonged administration on granuloma formation around Schistosoma japonicum eggs in lung of sensitized mice

Schistosomiasis remains a major public health problem and it is an immune disease. The schistosome egg is the primary parasite factor responsible for the overt disease. The eggs release the soluble antigen, which induces intensive tissue reaction, a granulomatous reaction to the eggs. If granuloma formation could be suppressed, overt disease might not develop. Praziquantel is an effective antischistosomal drug especially for adult worms. However, whether praziquantel has a suppressing effect on granuloma formation around schistosome eggs directly remains unclear. The purpose of the present study was to investigate the effect of praziquantel, especially administered persistently, on granuloma formation around Schistosoma japonicum eggs in the lung of sensitized mice. Thirty-six mice were divided into three groups averagely. Group A was a control group. First, the mice were injected with schistosomal eggs hypodermically in abdomen, and 10 days later injected with schistosomal eggs intravenously via a tail vein. Group B was a praziquantel short administration group. In addition to the injections of schistosomal eggs as the same of Group A, the mice were administered with praziquantel in a daily dose of 300 mg/kg for 3 days, from 1 day before the intravenous injection of the eggs. Group C was a praziquantel prolonged administration group. In addition to the injections of schistosomal eggs as the same of Group A, the mice were administered with praziquantel in a daily dose of 150 mg/kg for 5 days weekly until the mice were sacrificed. Three mice of each group were sacrificed on days 7, 14, 28, and 56, respectively after the intravenous injection of the eggs, and the lung tissues were fixed with formalin and the slices were HE stained. The granulomas containing eggs in their centers were selected, and 25-30 granulomas from the animals of each group were measured at each time period. The mean areas of egg granulomas of each group were calculated, and the neutrophilic granulocytes, eosinocytes, lymphocytes, fibroblasts, and macrophages within the egg granulomas were counted. The mean numbers of them of each group were calculated. All the data of each group were analyzed and compared statistically. On day 56 after the intravenous injection of the eggs, the mean area of schistosomal egg granulomas in group B was (227.4 ± 728.0) × 10(3) μm(2), less than that of [(297.9 ± 153.3) × 10(3) μm(2)] in group A, and the suppression rate was 23.7% (P < 0.05). On days 7, 14, 28, and 56, the mean areas of schistosomal egg granulomas in group C were (575.8 ± 155.6) × 10(3) μm(2), (310.5 ± 854.0) × 10(3) μm(2), (267.7 ± 513.3) × 10(3) μm(2), and (214.9 ± 446.4) × 10(3) μm(2), respectively, significantly less than those of [(692.7 ± 232.6) × 10(3) μm(2), (439.4 ± 165.0) × 10(3) μm(2), (385.7 ± 129.3) × 10(3) μm(2), and (297.9 ± 153.3) × 10(3) μm(2)] in group A. The suppression rates were 16.9%, 29.3%, 30.6%, and 27.9%, respectively (P values <0.05). On day 56, the mean numbers of neutrophilic granulocytes were 11.4 ± 5.0 in group A and 5.2 ± 3.1 in group C, respectively, with the suppression rate of 54.4% in group C (P < 0.05). On day 56, the mean numbers of eosinocytes within the egg granulomas were 2.3 ± 2.0, 0.1 ± 0.3, and 0.3 ± 0.6 in groups A, B, and C, respectively, with the suppression rate of 95.7% in group B and 87.0% in group C (P values <0.05). On day 56, the mean numbers of macrophages within egg granulomas were 14.3 ± 6.9 in group C, compared with 18.6 ± 8.2 in group A, the suppression rate was 23.1% (P < 0.05). On day 56, the mean numbers of fibroblasts within the egg granulomas were 6.6 ± 4.4 and 5.8 ± 2.6 in groups B and C, respectively, and compared with 14.3 ± 7.8 in group A, the increasing extents decreased by 53.8% and 59.4%, respectively (P values <0.05). Therefore, the administration of praziquantel, especially the prolonged administration, can suppress the formation of schistosomal egg granulomas, including reduction in the areas of granulomas and suppression of the inflammatory cells and the hyperplasia of fibroblasts within granulomas.

High serum laminin and type IV collagen levels in schistosomiasis mansoni

BACKGROUND: Fibrosis is the process of excessive deposition of collagen and other extra cellular matrix components and large amounts of these components have been shown in periovular schistosomal granulomas, especially in the liver. Laminin and type IV collagen have been investigated in various hepatic disorders but their accuracy in fibrosis detection and in the evaluation of its progression in schistosomiasis have not been fully explained. AIM: To measure the serum levels of two markers of fibrosis, laminin and type IV collagen in schistosomiasis. PATIENTS AND METHODS: Sixty-four patients with different clinical forms of schistosomiasis mansoni: intestinal (group I), hepatointestinal (group II), compensated (group III) and decompensated hepatosplenic (group IV) and 18 healthy volunteers were included. RESULTS: Serum type IV collagen and laminin levels were significantly increased in patients compared to controls. At about clinical forms, serum type IV collagen was increased in groups II and IV, compared to controls and was significantly higher in group IV than in group I. Serum laminin was significantly increased in groups II, III and IV and was significantly higher in group IV than in group II. Serum type IV collagen was closely correlated with serum laminin in groups II and IV. CONCLUSIONS: Connective tissue marker levels did not correlate with periportal thickness. In schistosomiasis mansoni there is an increase of type IV collagen and laminin levels at the initial stage of the disease, as well as in advanced forms. We also suggest that these markers may be a useful predictor of disease progression.

Prevalence of schistomasiasis lesions detected by ultrasonography in children in Molodo, Mali

AIM

To study schistomasiasis infection in school children in Molodo, an irrigated rice growing region of Mali, by determining the prevalence of schistomasiasis and lesions identified by ultrasonography among children living in this region.

METHODS

This cross sectional study included 346 children aged 7 to 14 years selected at random from five schools in Molodo. We tested for hematuria using urine dipsticks and searched for Schistosoma haematobium eggs in urine and S. mansoni eggs in stools. Ultrasonography of the liver, spleen and urinary tract was performed.

RESULTS

The prevalences of Schistosoma haematobium and S. mansoni infection were 72% (range: 66.9-76.6%) and 68.2% (range: 60.9-71.2%) respectively; 55.1% of the children had co-infection. Ultrasonography of the urinary tract revealed an irregular bladder wall as the most frequent abnormality (3.4% of children). Abdominal ultrasonography demonstrated type B hepatic fibrosis in four children (1.1%), type C in one (0.3%) and type D in one (0.3%).

CONCLUSION

Few schistosomiasis lesions were detected by ultrasonography compared with the prevalence of S. haematobium and S. mansoni infections. This observation is probably related to mass treatment programs conducted during a national anti-schistosomiasis program.

Schistosomiasis mansoni -- clinical features

In the present review, we will discuss the Schistosoma mansoni form, which is the most widely distributed schistosome in humans and is found both in the Old and New Worlds. The main features of the natural history of mansonic schistosomiasis are reviewed, with emphasis on the clinical forms of the disease, their diagnosis and treatment.

The impact of chemotherapy on morbidity due to schistosomiasis

Current knowledge on the impact of chemotherapy on schistosomiasis-related morbidity is still fragmentary. In urinary schistosomiasis, reversal of organ pathology follows cure after 6 months and resurgence takes place after at least another 6 months. Retreatment after less than 1 year is, therefore, unnecessary. Also, intestinal schistosomiasis appears to regress promptly after chemotherapy. For the reversal of hepatic morbidity, more than one chemotherapy round appears necessary at least in foci of intense transmission of schistosomiasis. The earlier chemotherapy is given, the higher the chances of reversal of schistosomal pathology, but pathology may regress to some extent also in adults. The regression and resurgence of periportal fibrosis, as detected by ultrasonography, occurs with a delay of 7 months to more than 2 years after therapy. Retreatment after less than 1 year may not permit full assessment of the impact of the first round on hepatic morbidity. Children and adolescents should be the major target population, taking into account that in many foci, children out-of-school must be covered because they are at the highest risk. Repeated treatment during childhood may prevent the development of urinary tract disease in adulthood. However, no data are available on the prevention of genital pathology. Repeated chemotherapy may have a long term effect on re-infection intensities and the development of severe morbidity, even in foci where control has been interrupted for many years. Severe hepatic fibrosis may be prevented even in foci of intense transmission provided more than two rounds of chemotherapy have been given in childhood and that chemotherapy is available on demand. Chemotherapy has an important impact on child development, physical fitness and working capacity. Its effect on growth and anemia is improved by simultaneous treatment of intestinal parasites and the provision of adequate iron supplementation. The impact of chemotherapy on many of the multifaceted manifestations of schistosomiasis has not been assessed systematically. More data are needed on gallbladder pathology, neuroschistosomiasis, endocrinologic disorders, bladder cancer and co-infections with other pathogens. In areas where control has been achieved, the overall morbidity and mortality has decreased with a delay of many years or even decades.

Diagnostic value of connective tissue metabolites in Schistosoma mansoni related liver disease

Reliable non-invasive markers of hepatosplenic involvement in schistosomiasis are needed for determination of morbidity levels in endemic populations and for diagnosis and follow-up of affected individuals. Serum levels of connective tissue metabolites have been investigated as fibrosis markers in various hepatic disorders, but their accuracy in the detection of hepatosplenic schistosomiasis under endemic conditions has not been fully elucidated. 206 adult inhabitants of a Tanzanian village highly endemic for schistosomiasis mansoni (prevalence 88%) underwent clinical, parasitological and sonographic work-up; sera were tested for aminoterminal procollagen III-peptide (PIIIP), carboxyterminal procollagen IV peptide (NC1) and laminin. Connective tissue marker levels did not correlate with the presence or intensity of infection. NC1 levels were significantly correlated with periportal liver fibrosis (P < 0.001), splenomegaly (P < 0.002), portal vein dilatation (P < 0.004) and the presence of portosystemic collaterals (P < 0.001); for PIIIP and laminin, none of the respective relationships was significant. Due to wide overlap of NC1 levels between individuals with normal sonography findings and those with advanced periportal fibrosis and portal hypertension, the sensitivity and positive predictive value of this markers to detect these individuals were low (< 40%), although specificity and overall accuracy in the given setting were good (80-90%). It is concluded that PIIIP and laminin are not useful as diagnostic serum markers of hepatosplenic schistosomiasis at the community level; NC1 was significantly related to various indices of hepatosplenic involvement, but its low sensitivity precludes its use as a screening tool under endemic conditions.

Effect of skin colour and selected physical characteristics on Schistosoma mansoni dependent morbidity

The effect of the colour group on the morbidity due to Schistosoma mansoni was examined in two endemic areas situated in the State of Minas Gerais, Brazil. Of the 2773 eligible inhabitants, 1971 (71.1%) participated in the study: 545 (27.6%) were classified as white, 719 (36.5%) as intermediate and 707 (35.9%) as black. For each colour group, signs and symptoms of individuals who eliminated S.mansoni eggs (cases) were compared to those who did not present eggs in the faeces (controls). The odds ratios were adjusted by age, gender, previous treatment for schistosomiasis, endemic area and quality of the household. There was no evidence of a modifier effect of colour on diarrhea, bloody faeces or abdominal pain. A modifier effect of colour on hepatomegaly was evident among those heaviest infected (> or = 400 epg): the adjusted odds ratios for palpable liver at the middle clavicular and the middle sternal lines were smaller among blacks (5.4 and 6.5, respectively) and higher among whites (10.6 and 12.9) and intermediates (10.4 and 10.1, respectively). These results point out the existence of some degree of protection against hepatomegaly among blacks heaviest infected in the studied areas.

Um modelo hierárquico de análise das variáveis sócio-econômicas e dos padrões de contatos com águas associados à forma hepatoesplênica da esquistossomose

Um estudo dos fatores associados à forma hepatoesplênica foi desenvolvido em uma área endêmica (Comercinho, Minas Gerais), onde a prevalência da infecção pelo Schistosoma mansoni era 70,4%. Dos 1408 habitantes com > 2 anos de idade, 1162 (82,5%) participaram do estudo. As características sócio-demográficas e os motivos de contatos com águas dos pacientes com forma hepatoesplênica (n = 73) foram comparados aos daqueles sem esplenomegalia que apresentavam (controles positivos; n = 804) ou não (controles negativos; n = 285) ovos de S. mansoni nas fezes. A análise multivariada foi feita, considerando a existência de colinearidade entre a situação sócio-econômica da família, a fonte de água do domicílio e o tomar banho nos córregos. Os resultados mostram que a presença da forma hepatoesplênica em crianças estava fortemente associada à ocupação do chefe de família (trabalhadores manuais) (OR = 11,4; IC 95% = 1,4-91,8), à ausência de água encanada (OR = 7,7; IC 95% = 2,6-23,1) e ao hábito de tomar banho nos córregos (OR e IC 95% = 7,6); 2,5-22,9 e 5,7; 1,3-25,5 para contatos mais (> uma vez/semana) e menos freqüentes, respectivamente esse hábito implicava contatos mais intensos e era conseqüência dos primeiros fatores. Os resultados são sugestivos de que o abastecimento de água no domicílio pode reduzir a morbidade da esquistossomose por diminuir a necessidade de contatos intensos com águas naturais.

Environmental intervention as a tool for control of schistosomiasis: suggestions from a field study in Northeast Brazil

The present survey from the State of Alagoas (Brazil) emphasized, once again, the importance of peridomestic or neighbourhood foci in the transmission of schistosomiasis mansoni. Although the study area consisted of a compact and densely populated urban community (Bairro Frio, União dos Palmares county), prevalence as well as the distribution of high egg counts was quite patchy, exhibiting a spatial pattern correlated with the distribution of ditches and other small-sized collections of surface water. Despite the availability of satisfactory water supply in most households, as well as the absence of any major body of water capable of furthering transmission, egg counts in Bairro Frio exceeded any other in our previous experience. Morbidity, however, appeared to be insignificant, a trend which has been observed over the last decade in several other highly endemic areas. It appears clear to the authors that the control of transmission requires investment in environmental intervention and that this proposal, far from being utopic, can be furthered by quite modest means and through the participation of community or neighbourhood groups.

The physical fitness and work performance of agricultural workers infected with Schistosoma mansoni in Zimbabwe

Stool specimens were collected from 1995 sugarcane cutters on the Hippo Valley and Triangle sugar estates, Zimbabwe, in order to determine the prevalence and intensity of Schistosoma mansoni infection. Pathological changes normally ascribed to S. mansoni infection were assessed in the infected cutters, by ultrasonography before treatment. The height, weight, age, haemoglobin levels, blood pressure and body fat of the infected and uninfected control study subjects, standardized by age, were determined. Those with elevated blood pressure were excluded from the study. Physical fitness and work performances were assessed in 287 infected and 210 uninfected cane cutters aged (mean +/- S.D.) 36.5 +/- 7.5 years. Despite the finding that all the subjects were of good nutritional status and generally physically fit, a t-test showed a significant improvement (P < 0.01) in the performance of the infected cutters following treatment; age-related physical performance, measured by the Harvard Step Test, increased by 4.3% and work output, measured as the amount of cane cut in a given time, rose by 16.6%. Although the physical and work performances of the uninfected control subjects also increased over the same period, this trend, attributed to occupational physical exercise, was not statistically significant (P > 0.05). Significant correlations were found between both infection intensity-related pre-treatment physical fitness (P < 0.05) and work performance (P < 0.01) and prevalence of Symmers' peri-portal fibrosis.

A synoptic inventory of needs for research on women and tropical parasitic diseases. I. Application to urinary and intestinal schistosomiasis

The determinants of major parasitic infections in women have never been studied systematically. Much work remains to be done before vital gaps in our knowledge will be filled. The protocol presented here categorizes the determinants of parasitic diseases, and functions as an inventory for research needs and priorities. In this paper, the synoptic inventory is tested by matching it against the scientific knowledge of schistosomiasis that is at hand. Available data and existing lacunae are discussed. We conclude that the environmental, economic, socio-cultural, nutritional, genetic, biological and immunological factors which determine schistosomiasis in women are largely unknown. There is an urgent need for systematic and interdisciplinary investigations before appropriate and sustainable interventions can be initiated.

Sonographic organometry in Brazilian and Sudanese patients with hepatosplenic schistosomiasis mansoni and its relation to the risk of bleeding from oesophageal varices

Fifty-nine patients with hepatosplenic schistosomiasis mansoni were investigated by sonography in Northeast Brazil and Central Sudan. The sizes of the organs usually involved in this disease were quantitatively assessed according to a standardized protocol, and measurements were adjusted to the body height of the individual. The results were compared with those of healthy controls matched by sex, age, geographical origin and socio-economic status. Considerable differences were found between patients and controls as well as between residents from the two areas. The liver of both patients and controls from the Sudan was significantly smaller than that of patients and controls from Brazil. Only in Brazil, but not in the Sudan, was the left liver lobe larger in patients than in the controls. The diameter of the portal and the splenic vein, the spleen size and the thickness of the gallbladder wall were significantly increased in patients from both areas. The increase of the portal and splenic vein diameter was significantly correlated with the degree of hepatic periportal fibrosis and the frequency of bleeding from endoscopically proven oesophageal varices in the patients, irrespective of their geographic origin. In contrast, such correlations were not found for the degree of splenomegaly nor for the degree of gallbladder-wall thickening. It is concluded that standardized sonographic organometry permits the assessment of morbidity in hepatosplenic schistosomiasis mansoni under different endemic conditions. Especially the measurement of the portal vein diameter may allow estimation of the risk of gastrointestinal haemorrhage in these patients.

A review of the literature on the use of ultrasonography in schistosomiasis with special reference to its use in field studies

This review presents an outline of the pathology resulting from Schistosoma mansoni infections, and the ways in which it can be investigated. The use of ultrasonography is covered in detail. Ultrasonography can provide direct information about lesions in internal organs, and thus provide information about patterns of morbidity and about the regression of pathological changes after treatment. The method is non-invasive, and can be used under field conditions. Ultrasonography is valuable for the study of hepatosplenic pathology, to detect lesions such as the development of periportal fibrosis and the enlargement of the portal vein, which can indicate the development of portal hypertension. This may lead to a severe outcome, including bleeding from oesophageal varices, which is a principal cause of death from S. mansoni infection. A problem with the use of ultrasonography is that the mild lesions likely to be observed in population surveys are not always easy to assess. Ultrasonography has already been used in a number of epidemiological studies of S. mansoni infection, and has proved to be feasible and useful. However, the methodology used for ultrasound studies has varied considerably, so that it is difficult to make valid comparisons between results obtained in different places or at different times. A standardized methodology for making observations and recording the results is needed if the full potential benefit of using ultrasound in the monitoring of schistosomiasis control projects is to be realised.

Re-infection in human schistosomiasis mansoni: a prospective field study 18 months after praziquantel therapy

Twenty-eight Zairean patients with Schistosoma mansoni infection were investigated and treated with praziquantel. Of these, 22 were re-examined 18 months later and 13 were found to be re-infected. Eighteen uninfected Zaireans were monitored concurrently to control for variations unrelated to schistosomiasis. Pathophysiological changes related to liver fibrosis were assessed by the determination of serum cholylglycine and procollagen-III-peptide. Circulating T-cell subsets were quantitated, and shedded T-cell antigens were measured in sera. In patients initially presenting with hepatomegaly, the biochemical indicators for egg-induced immunopathology became normal after therapy and remained normal even after re-infection, when the parasite load attained about 50% of the pretreatment level. Among T-cell phenotypes, CD4+ cells transiently increased by three months after treatment, but after 18 months the CD4/CD8 ratios both in patients then re-infected and in those not re-infected had reverted to the respective balances which had been observed at the start of the investigation. Both soluble CD8 antigen and interleukin 2 receptor in patients' sera were significantly elevated throughout the study period. The results indicate a dissociation of factors regulating fibrogenesis and immunomodulation after treatment and re-infected.