The efficacy of human schistosomicide treatment may depend on the rate of transmission

The efficacy of different treatment protocols in humans infected with Schistosoma mansoni at sites with different transmission conditions was evaluated by the disappearance of anti-worm intestine IgM antibodies in an indirect fluorescence antibody test (IgM-IFT) and anti-egg antibodies in the circumoval precipitin test (COPT). Patient sera coming from sites of active low transmission (ALT), active high transmission (AHT) and low interrupted transmission (LIT) from Venezuela were studied. Chemotherapy protocols were (1) ALT, 60 mg/kg praziquantel (Pzq60); (2) AHT, one dose of 40 mg/kg Pzq followed by one dose of 20 mg/kg oxamniquine for one group and one dose of 40 mg/kg Pzq alone for the other group; (3) LIT, one dose of 40 mg/kg Pzq repeated every 3 months up to three doses. Cure rates occurred mostly between 3 and 12 months with the exception of Pzq60-ALT where it was evident before 3 months. Higher cure rates were evident in both places of low transmission (ALT and LIT) and the lowest in the AHT regardless of the treatment protocol. Cure was more evident with COPT compared to IgM-IFT. The rate of serological cure appears then to depend on the previous state of transmission. The differential cure rate evaluated by both techniques is probably due to the persistence of antibodies against antigens in different stages of the parasite.

Efficacy of oxamniquine and praziquantel in school children from two Schistosoma mansoni endemic areas

OBJECTIVE

To determine the relative susceptibility of Schistosoma mansoni infections to treatment with the oxamniquine (OXA) and praziquantel (PZQ).

DESIGN AND SETTING

Three separate cross sectional studies were performed in six primary schools located in two Schistosoma mansoni endemic areas in Eastern Kenya: Kangundo (low morbidity) and Kibwezi (high morbidity).

SUBJECTS

One thousand two hundred and fourteen infected children aged 6-20 years were involved.

INTERVENTION

Each child received either 15-mg OXA/kg body weight twice within an interval of six hours or a single dose of 40 or 60 mg PZQ/kg body weight. Three duplicate Kato stool examinations were done before and four or five weeks after treatment to assess treatment efficacy.

RESULTS

The cure rates in different schools with OXA were 71.7-79.7% in Kangundo and 56.7-61.9% in Kibwezi. In children treated with PZQ, the 40-mg/kg-dose regimen achieved cure rates of 77.6-87.2% in Kangundo and 67.1-81.1% in Kibwezi, whereas the 60-mg/kg dose regimen attained cure rates of 93.2% in Kangundo and 76.3% in Kibwezi. Both OXA and PZQ efficacy declined significantly with age in Kangundo, whereas the age effect was not seen in Kibwezi.

CONCLUSION

The poorer cure rates in Kibwezi than in the Kangundo children were not due to known previous drug exposure to either OXA or PZQ. The varying efficacy may be attributed to innate low drug susceptibility, possibly related to schistosome strain differences between the two areas.

Schistosomiasis control based on repeated chemotherapy in a rural village of the sugar-cane zone in northeast Brazil

A schedule of repeated chemotherapy with oxamniquine, consisting of biannual treatment of school-aged (7-13 years) children and annual treatment of all other age groups, was used in a representative rural village from a highly endemic area of schistosomiasis in Pernambuco. Significant reductions in infection were obtained only after two cycles of treatment, as the overall prevalence decreased from 72.6% to 41.7% and the geometric mean egg counts per gram of faeces among positives fell from 188.4 to 76. In a school-aged cohort (n = 29) three treatments at six-month intervals were necessary to significantly reduce the proportion of positives (from 75.9% to 51.7%). In a cohort of children under 7 years of age (n = 20) the proportion of positives actually increased (from 30% to 45%) despite two annual treatments. Water contact was intense and host snail density was relatively high. As there is no short-term perspective of improved sanitation, auxiliary measures such as focal mollusciciding are needed for an adequate control of schistosomiasis in this and alike areas.

O6-methylguanine and O6-methylguanine-DNA [corrected] methyltransferase activity in tissues of BDF-1 mice treated with antiparasitic drugs

Levels of the DNA promutagenic methylation damage, O6-methylguanine (O6-MeG) and the activity of the O6-methylguanine-DNA methyltransferase (MGMT), the enzyme responsible for repairing O6-MeG, were measured at various time intervals in tissues of BDF-I mice administered a single therapeutic dose of the antischistosomal agents hycanthone, oxaminiquine and metrifonate. Hycanthone increased O6-MeG in the liver-DNA after 6 h, then decreased by 3-fold after 48 h. Lower levels of the adduct and a slower rate of formation were found in the intestine and bladder. MGMT activities were significantly lower in the liver (74%) and bladder (25%) compared to control animals after 6 h, then restored by 48 h. Oxaminiquine increased O6-MeG in all tissues, but spleen, after 6 h and persisted only in the bladder after 48 h. Liver and bladder tissues of these animals exhibited a pattern of alteration in the MGMT activity similar to that observed for hycanthone. Metrifonate induced a profile of O6-MeG comparable to that of oxaminiquine but the levels of the adduct were about 2-fold lower. Hepatic MGMT in these animals was significantly lower (approximately 38%) than the control values after 6 h, then restored by 48 h. A significant negative correlation was obtained between O6-MeG and MGMT activity in the liver (r=- 0.85), intestine (r=- 0.62) and bladder (r=- 0.59). These results demonstrate that treatment with antischistosomal agents may lead to the formation of promutagenic alkylation damage in the tissue DNA and alterations in the DNA repair capacity.

Effect of praziquantel and oxamniquine treatment on human isotype responses to Schistosoma mansoni: elevated IgE to adult worm

Pre- and post-treatment antibody isotype responses to Schistosoma mansoni adult worm and soluble egg antigens were compared in a study population previously used to show that IgE against adult worm correlates negatively with intensity of reinfection following chemotherapeutic cure. IgG subclass responses to adult worm were lower after treatment whereas IgM and IgE were higher. The increase in IgE to adult worm was observed with different preparations of adult worm, including the worm tegument, and with both praziquantel and oxamniquine therapy. No significant difference was observed between pre- and post-treatment isotype responses to egg antigens following either praziquantel or oxamniquine therapy.

Evaluation of the schistosomicidal efficacy of liposome-entrapped oxamniquine

Oxamniquine (OXA) was successfully encapsulated in small unilamellar vesicles using a pH gradient method. This procedure led to a high drug encapsulation efficiency (> 85%) at a drug to lipid molar ratio of 1/10. Moreover, these liposomes were found to retain encapsulated OXA efficiently under dialysis conditions at 37 degrees C. Liposome-entrapped OXA (LOXA), OXA, and empty liposomes were tested against Schistosoma mansoni in a murine model. LOXA produced a significant reduction of the worm burden compared to the other preparations, when inoculated by subcutaneous route (s.c.) with 10 mg OXA/kg animal one day before the infection, and 3, 7, and 14 days after. However, LOXA was not effective when given 7 days before, or 35 days after infections. OXA, in the free form, was effective in relation to the untreated group, only when administered 3 days after the infection. Maximum effect of LOXA, with 97% reduction of the parasite number, was observed when the preparation was given s.c. one day before the infection. On the other hand, LOXA inoculated intraperitoneally one day before the infection didn't show any reduction of the parasite count. It can be concluded that LOXA is more effective than OXA for the treatment of experimental schistosomiasis, particularly when administered subcutaneously at a time close to the infection.

Lethal effect of oxamniquine and praziquantel on mice experimentally infected with Schistosoma mansoni

Lethality caused by administration of oxamniquine and praziquantel to mice infected with Schistosoma mansoni, and their respective controls (uninfected), has been studied. As the results indicate, the infected animals clearly showed higher mortality rates when praziquantel was used. Surprisingly, it may be noted that exactly the contrary occurs in relation to the use of oxamniquine, inasmuch as marked higher mortality rates were seen in the control animals (uninfected). These observations lead to the conclusion that further toxicological studies of antischistosomal drugs using. S. mansoni infected animals are needed.

Oxamniquine: a labeling procedure with technetium-99m and a biodistribution study in mice

Oxamniquine (OXY), a tetrahydroquinoline derivative, is used as an antischistosomal drug and generally has been labeled with carbon-14 and tritium. We decided instead to label it with technetium-99 (99mTc). In order to determine the optimal conditions, different concentrations of this drug were incubated with various stannous chloride solutions. We then added 99mTc, and chromatography was performed using 0.9% NaCl solution, acetone and 1.2N HCl as the mobile phase. Using a solution of 1.0 mg/mL stannous chloride and 0.5 mg/mL oxamniquine, over 94% of the radioactivity bound to oxamniquine (99mTc-OXY). In the biodistribution study, 99mTc-OXY was administered in mice intramuscularly, orally and intravenously. When the intramuscular route was used, the main uptake (after 30 minutes) of the labeled drug was in the kidneys, liver and intestines; after 240 minutes the labeled drug was still found in the liver and kidneys, but at increased levels in the intestines. It was also present in the faeces. When the oral route was employed, labeled OXY was mainly found in the stomach after 30 minutes, but there was a decrease after 240 minutes. During this period radioactivity increased in the intestines. When the intravenous route was employed the labeled OXY was found in the liver and spleen. The radioactivity decreased with time in these organs. Using infected animals, radioactivity was found in isolated worms.

[Cardiac arrhythmia with oral oxamniquine use in the schistosomiasis mansoni treatment]

The authors report a case of a patient with schistosomiasis (S. mansoni) treated with one single dose (15 mg/kg/BWT) of oral oxamniquine who presented Mobitz type I second-degree AV block and sinus arrest with ventricular escape as a side-effect. They conclude that in spite of the safety and good activity of oxamniquine it may be a determinant of cardiotoxicity.

Acute schistosomiasis: clinical, diagnostic and therapeutic features

Three distinct syndromes caused by schistosomiasis have been described: cercarial dermatitis or swimmer's itch, acute schistosomiasis or Katayama fever, and chronic schistosomiasis. Complications of acute schistosomiasis have also been reported. The absence of a serological marker for the acute stage has hindered early diagnosis and treatment. Recently, an ELISA test using KLH (keyhole limpet haemocyanin) as antigen, has proved useful in differentiating acute from chronic schistosomiasis mansoni. Clinical and experimental evidence indicate that steroids act synergistically with schistosomicides in the treatment of Katayama syndrome. In this paper, clinical, diagnostic and therapeutic features of acute schistosomiasis are updated.

Stool examination and rectal biopsy in the diagnosis and evaluation of therapy of schistosomiasis mansoni

From each of a group of 217 adult males selected through enzyme-immunoassay or skin-test (Group A), six stool samples were examined by both the Lutz/Hoffman, Pons & Janer (Lutz/HPJ) and Kato/Katz methods. In addition, one oogram of the rectal mucosa was performed. By these methods, schistosomiasis was detected in 44.7%, 47.5% and 40.1% of the individuals respectively. To evaluate the methods in the assessment of cure, the last 40 patients from group A, treated with a single oral dose of oxamniquine at 15 mg/kg were followed up for six months (Group B). The criteria for parasitological cure included three stool examinations by Kato/Katz and Lutz/HPJ methods, one, three and six months post-treatment and a rectal biopsy between the fourth and sixth months post-treatment. The examinations were negative in 87.5%, 90% and 95% of the patients, respectively. The efficacy of oxamniquine was 82.5% when the three methods were considered together and there was no statistically significant difference between the sensitivity of the individual methods.

Effect of praziquantel and oxamniquine on prostacyclin synthesis by the rat arterial and myometrial tissues

1. The influence of the two antischistosomal drugs (+/-) praziquantel and (+/-) oxamniquine on PGI2 synthesis by the male rat thoracic aorta and day-20 pregnant rat myometrium in vitro was investigated using a rat platelet antiaggregatory bioassay method. 2. Pretreatment of the tissues with praziquantel (64-512 microM) or oxamniquine (36-288 microM) for 30 min at 37 degrees C significantly inhibited basal PGI2 synthesis in a concentration-dependent manner (P less than 0.005, n = 5-6). 3. Both drugs failed to inhibit PGI2 synthesis in presence of exogenous arachidonic acid (AA) (16.6 microM). 4. Furthermore, they did not antagonize AA (4 nmol kg-1)-induced hypotension in urethane-anaesthetized rats. Thus, the drugs seemed to act via inhibition of phospholipase A2 enzyme (PLA2). 5. The highly lipophilic drugs may interact with membrane phospholipids resulting in prevention of interaction between the substrates and the enzyme's active site.

Comparison of different chemotherapy strategies against Schistosoma mansoni in Machakos District, Kenya: effects on human infection and morbidity

A comparison was made of the long-term impact of different methods of administration of chemotherapy (oxamniquine, 30 mg/kg in divided doses; or praziquantel, 40 mg/kg) on prevalence and intensity of Schistosoma mansoni infection in four areas in Kangundo Location, Machakos District, Kenya. In Area A, treatment was offered in October 1983 and again in April 1985 to all infected individuals. In Area H, treatment was offered in April 1985 to individuals excreting greater than or equal to 100 eggs per gram (epg) of faeces. In Area S, treatment was offered in April 1985 to all infected school children, within the framework of the primary schools. In the witness area, Area W, treatment was given in April 1985, for ethical reasons, to a small number of individuals excreting greater than or equal to 800 epg. Prevalence and intensities of infection were subsequently monitored at yearly intervals for three complete post-treatment years. In the Area S schools, clinical examination was also carried out at yearly intervals. Treatment of all infected individuals on two occasions (Area A) was the most effective and long-lasting way of reducing prevalence and intensity of infection. In this area, however, some earlier interventions had been carried out and pre-treatment intensities were lower than in the other areas. Treatment only of infected schoolchildren (Area S) also had a marked and prolonged effect, comparable to or better than treatment of individuals with heavy infections (Area H). Treatment of infected schoolchildren also caused a persistent reduction in the prevalence of hepatomegaly, and there was suggestive evidence from intensities of infection in community stool surveys (but not from incidence rates) of an effect on transmission. In all study areas, reinfection was most rapid and most intense among children. These findings are discussed in the light of theoretical considerations and of results from other studies, both on schistosomiasis and on intestinal helminths. We conclude that, in areas of low morbidity such as Kangundo, chemotherapy of schoolchildren only, at intervals of up to 3 years, is a satisfactory way of producing a long-term reduction in both intensity of infection and morbidity.

Efficacy of alternating therapy with oxamniquine and praziquantel to treat Schistosoma mansoni in children following failure of first treatment

Two hundred children infected with Schistosoma mansoni were treated with either 20 mg/kg oxamniquine or 60 mg/kg praziquantel. Cure rates (about 85%) were similar as was the percentage reduction (80%) in egg counts in uncured children. Treatment with the alternative drug of children not cured with the first treatment resulted in negative stools in 11 of 12 cases examined one month after the second round of therapy. In order to minimize the risk of the development of drug resistance, our data suggest that infected patients be treated with one drug, and therapeutic failures with another. Evidence from experiments in mice with isolates obtained after failures of one treatment in children suggests that therapeutic failure does not necessarily indicate the presence of drug-resistant schistosomes. The value of using mice to assess drug resistance in schistosomes is questioned.

Oxamniquine pharmacokinetics in healthy Kenyan African volunteers

Oxamniquine pharmacokinetics were studied following oral administration of 750, 1000 mg or 1250 mg (equivalent to approximately 15 mg/kg) to five healthy Kenyan African volunteers. Peak plasma concentrations ranging between 1 and 4.3 mg/1 were achieved 1 to 4 h after dosing. The estimated mean elimination half-life (t1/2) was 2.2 h. Despite the limited number of subjects in the study, it is concluded that the pharmacokinetics of oxamniquine in healthy Kenyan Africans do not markedly differ from those in Africans from other regions of the continent where previous studies have been reported.

Schistosoma mansoni: acquired immunity in mice after the use of oxamniquine at the evolutive skin and pulmonary phases

Mice infected with 350 cercariae of Schistosoma mansoni (LE strain) were treated with oxamniquine, at the dose of 400 mg/kg, 24, 48, 72, and 96 h after infection. Forty days after the treatment, the animals were submitted to a challenge infection with 80 cercariae, through the abdominal and ear skins. The number of immature worms in the animal groups treated 24 and 96 h after the first infection was found to be lower than that in the control group, thus showing that the death of schistosomes by chemotherapy, at the skin and pulmonary phases, causes an acquired resistance state.

Relationship between schistosomicidal drug efficacy, gonadal steroid hormonal changes and state of disease immunopathology in murine schistosomiasis mansoni

The schistosomicidal efficacy of praziquantel (2 x 500 mg/kg), oxamniquine (1 x 100 mg/kg) and combined one-third the curative dose of each of them (333 mg/kg praziquantel + 33 mg/kg oxamniquine), were correlated to gonadal steroid hormonal changes and state of disease immunopathology, in mice infected with 100 Schistosoma mansoni (S. mansoni) cercariae. Maximum efficacy recorded with combination regimen particularly 4 weeks after treatment, was accompanied by maximum reduction in granuloma volume (65%), least fall in testosterone level (-56.2 and -60.2% in male and female mice respectively) and increased progesterone level (+33.9 and +81.5% in male and female mice respectively). These findings revealed a potentiated effect of combination therapy on mature infection and the possible involvement of gonadal steroid hormones in affecting the efficacy of schistosomicidal drugs and state of disease immunopathology.

Effects of praziquantel and oxamniquine on a Saudi Arabian strain of Schistosoma mansoni in mice

The prophylactic and curative effects of praziquantel and oxamniquine on a Saudi Arabian strain of Schistosoma mansoni in MF-1 mice were assessed. The drugs were administered orally. At 240 mg/kg praziquantel, there was a reduction of 89.1% in adult worm recovery and a marked reduction in tissue deposited eggs. The reduction in adult worm recovery after dosing with 50 mg/kg oxamniquine was 89.2%. At low doses (40 mg/kg praziquantel and 30 mg/kg oxamniquine) administered at 11 days, 5 days and 3 h before and 5, 21 and 49 days after infection, the reduction in adult worm recovery was 0.0%, 65.1%, 58.8%, 33.6%, 0.0% and 76.0% for praziquantel and 0.0%, 66.0%, 60.0%, 41.3%, 10.8% and 79.0% for oxamniquine. Numbers of lung schistosomula and the size of hepatic granulomata were also reduced.

Partitioning of oxaminiquine into brain tissue following intravenous administration to female Wistar rats

Brain and plasma concentrations of oxaminiquine were determined following intravenous dosing (15 mg kg-1) in female Wistar rats. Maximum brain concentrations were achieved one hour after dosing and at all sampling times oxamniquine levels were higher in brain tissues compared to the corresponding plasma samples. It is concluded that the reported adverse neurological effects associated with the clinical use of oxaminiquine in man may be due to the passage of sufficiently large quantities of this drug into the CNS.

[Treatment of Schistosomiasis mansoni with a combination oxamniquine and praziquantel. II. Experimental observations during the patent phase]

The efficacy of an association of oxamniquine and praziquantel in the patent phase of experimental schistosomiasis was studied. The mice were infected and divided in four groups in accordance to the following schedules with the use of single oral doses: I--Oxaminiquine (50 mg/kg); II--praziquantel (75 mg/kg); III--association of oxamniquine (50 mg/kg) and praziquantel (75 mg/kg); and IV--no drug. Efficacy was assessed by the oogram technique, studying and classifying the evolution of the output of eggs in fragments of the small intestine, and also by recovery of the worms by portal vein perfusion. In the animals of groups I and II, the drugs had a partial effect while in the group III sinergism was evident.

Effect of combined low dose praziquantel and oxamniquine on different stages of schistosome maturity

Combined low doses of praziquantel and oxamniquine were tested against different stages of Schistosoma mansoni in infected Swiss albino mice. The effect of combination therapy (1/3 the curative dose of praziquantel plus 1/3 the curative dose of oxamniquine) was compared with the effect of each drug alone, in reduced or full dose. Comparison with infected untreated controls was also made. Drug effects were evaluated on different growth stages of schistosomes by administering the drugs 24 h before infection and 4 h, 1, 2, 3, 4 and 5 weeks after infection. Animals were killed 8 weeks after infection. Worm burden, distribution, tissue egg load and oogram pattern were used in assessing drug efficacy. A potentiating effect was observed in animals receiving combination therapy. The combination regimen was most effective 4 h after infection, producing 96% worm reduction; eggs were not detected in the liver or intestine. Five weeks after infection the same regimen resulted in 98% reduction in the tissue egg load.

Repeated mass treatment of schistosomiasis mansoni: experience in hyperendemic areas of Brazil. II. Micro-level evaluation of results

As shown by a recent survey in northeast Brazil, an overall (macro-level) assessment of control campaigns for schistosomiasis mansoni will tend to ignore localized variations in endemicity, thus resulting in misleading information. Evaluation on a micro-level, on the other hand, allows the identification of individuals who, despite repeated courses of chemotherapy, continue to present substantial reinfection rates. Such cases occur in a definite spatial pattern, which in turn points to the localization of residual foci of transmission. It is believed that in the absence of wide-reaching social investments the control of schistosomiasis by means of mass treatment will not be successful, unless a policy of targeted action, both in chemotherapy as well as snail control, is adopted. Obviously, the search for these reinfection clusters will require the development of sampling techniques suitable for wide-scale use.

Susceptibility of Schistosoma mansoni prevalent in Saudi Arabia to oxamniquine in experimentally infected mice

The therapeutic efficiency of oxamniquine against the local strain of Schistosoma mansoni was investigated in experimentally infected mice. The drug was administered orally using a human-equivalent dose of 20 mg kg-1 day-1 for 3 consecutive days (total dose of 60 mg kg-1). Oxamniquine proved to be very effective as indicated by hepatic shift, oogram changes, complete elimination of adult worms and eradication of faecal eggs.

Field study of different oxamniquine dose for Schistosoma mansoni in Gezira, Sudan

Two hundred and ninety-six individuals of whom 126 were children and 170 adults with positive stool for Schistosoma mansoni were randomly given oxamniquine treatment in a dose of either 20, 40 or 60 mg/kg body wt. They were followed in the field for ova excretion at 1, 3 and 6 months for adults and at 1, 3, 6 and 8 months for children. The cure rates in adults at 6 months are 93%, 87% and 73% for the 60, 40, 20 mg/kg-1 treatments in order. For children the cure rates at 6 months are 36%, 58% and 63% and at 8 months are 16%, 21% and 26% for corresponding doses. There is no difference in egg reduction for those not cured between the three treatments at 6 months. It is concluded that oxamniquine need not be given in the previously recommended 60 mg/kg body wt. A choice between 40 and 20 mg/kg body wt is suggested with the 40 mg/kg body wt to be reserved for individuals leaving the endemic area, and the 20 mg/kg body wt for those continuing to stay there with substantial exposure for reinfection. The overall proper cure rates for children with a possible advantage of the low treatment in the long term for this age group is noted.

Comparison between the efficacy of oxamniquine and praziquantel in the treatment of Schistosoma mansoni infections on a sugar estate in Ethiopia

The efficacy of the antischistosomal drugs praziquantel and oxamniquine was tested on four groups of Ethiopian sugar estate workers. The cure rates, determined by the absence of eggs in stools, were 96, 93 and 74% at one, three and six months post-treatment for patients receiving a single dose (40 mg kg-1 body weight) of praziquantel, and 82, 78 and 78% for patients on a single dose (15 mg kg-1 body weight) of oxamniquine. When split doses of these drugs were used, praziquantel achieved cure rates of 96, 95 and 89%, while the corresponding cure rates for oxamniquine were 98, 96 and 88% at one, three and six months post-treatment. In general, there were no statistically significant differences within the single and split doses of each drug, nor between the two drugs except that single doses of praziquantel had significantly higher cure rates than oxamniquine at one and three months post-treatment. Although both drugs produced mild and transient side-effects such as dizziness, abdominal discomfort and diarrhoea, serious side-effects such as seizures were seen only among patients on oxamniquine. As praziquantel is also effective against other forms of schistosomiasis as well as against cestodes, we recommended the use of this drug in mass chemotherapy and in the ambulatory treatment of schistosomiasis in Ethiopia.

Efficacy of oxamniquine, praziquantel and a combination of both drugs in schistosomiasis mansoni in Brazil

A randomized clinical trial was carried out to compare the efficacy of a low-dosage combination of oxamniquine (7.5 mg/kg) plus praziquantel (20 mg/kg) against either agent, oxamniquine (15 mg/kg) or praziquantel (40 mg/kg) alone, in the treatment of schistosomiasis mansoni in the Brazilian north-east. The drugs were randomly administered per os to 91 patients. Six and twelve months after treatment 89% of those admitted to the trial were reexamined by Kato-Katz method (ten slides) and MIF technique (one gram of stool) The achieved cure rates, as defined by absence of S. mansoni eggs in the faeces of individual patients at all points during the parasitological follow-up, were 81.8%, 81.2% and 67.6% for praziquantel, oxamniquine and the combination respectively. The reduction of eggs excretion in non cured patients six months after therapy ranged from 93.8-96.8% with praziquantel, 32.5-97% with oxamniquine and 76.9-99.5% with the combination. It is concluded that, at the used dosages, the three therapeutical regimens give similar and satisfactory results in the treatment of uncomplicated S. mansoni infection in Brazil.

Tolerance of Kenyan Schistosoma mansoni to oxamniquine

Although 30 mg/kg oxamniquine produced high levels (85.5 to 99.5%) of egg reduction in Kenyan children infected with Schistosoma mansoni after a single oral treatment, cure rates from children at Mwea in Kirinyaga district were lower than those from Machakos (58% v. 74%). Redosing uncured children confirmed this lower cure rate (36% v. 83%). Isolates from infected children were passaged into mice and dosed with oxamniquine. Lower than expected reductions in worm numbers were obtained, suggesting that oxaminiquine tolerant S. mansoni are present in the normal worm population in Kenya. It is concluded that mass use of oxamniquine at 30 mg/kg may produce problems of drug resistance.

[Low effectiveness of an oxamniquine and praziquantel combination in the therapy of schistosomiasis mansoni]

Em uma área endêmica onde havia interrupção da transmissão, foram tratados 164 esquistossomóticos com a associação oxamniquine e praziquantel em doses reduzidas. Cada indivíduo tomou de uma só vez uma cápsula de 250mg de oxamniquine e um comprimido de 300mg de praziquantel, ingeridos na nossa presença. As doses de oxamniquine variaram de 3,5 a 16,6mg/kg de peso corporal e as de praziquantel de 4,2 a 20mg. O controle de cura constou de oito exames parasitológicos de fezes de cada paciente, pelo método de Kato-Katz, num período de 6 meses. Os índices de cura variaram de 30% a 56,6%. A percentagem total de cura foi de 39,6%. A tolerância à associação foi boa. Nossos resultados mostraram baixo percentual de cura e aparente ausência de sinergismo da associação oxamniquine epraziquantel em doses reduzidas no tratamento da esquistossomose mansônica no Brasil.

Treatment of Schistosoma mansoni infection with oxamniquine in Riyadh, Saudi Arabia

Single dose therapy with oral oxamniquine was given to 107 Saudi patients suffering from schistosomiasis due to Schistosoma mansoni and they were followed for a period of six months. Clinical cure judged by symptomatic improvement and negative stool counts for S. mansoni eggs was achieved in 88.8%. Side effects were minimal and reversible and it is concluded that this form of treatment is successful for the control of S. mansoni infection.

Effects of chemotherapy on mice submitted to multiple Schistosoma mansoni infections. A controlled randomized prospective study

In an attempt to reproduce experimentally as close a possible the conditions found in endemic areas of mansonian schistosomiasis, a controlled trial in mice submitted to weakly infections with cercariae of S. mansoni was performed. One group (I) was not treated, the other (II) was treated with a single oral doses (100 mg/kg) of oxamniquine at the 13th week. After treatment infections were maintained bi-weekly. Mortality was significantly higher in group I (p less than 0.0001). A comparative morphological and immunoenzymatic study of the liver in the two groups was also carried out, showing a tendency to smaller granulomas and to more efficient antigen restriction in the treated group.

Randomized comparative trials of single doses of the newer antischistosomal drugs at Mwanza, Tanzania. I. Praziquantel and oxamniquine for the treatment of schistosomiasis mansoni

Randomized single-blind comparative trials of the newer antischistosomal drugs praziquantel and oxamniquine were undertaken at Mwanza, Tanzania, an area coendemic for schistosomiasis mansoni and haematobium. The objective was to compare praziquantel, having broad-spectrum activity, with oxamniquine when administered in single doses for levels of tolerance, symptomatic relief, and reduction in schistosome egg output in schistosomiasis mansoni. Whereas the single oral doses of 40 mg/kg and 15 mg/kg for praziquantel and oxamniquine respectively were nearly equally well tolerated, praziquantel showed significantly better efficiency to commend it as a drug of choice for chemotherapy for control programmes, besides its acknowledged place in the clinical management of individual patients.

Effects of certain antibilharzial and contraceptive drugs on liver functions in rats

Effects of single and combined administration of contraceptive drug (microvlar-30) and anti-urinary bilharzial drug (metriphonate) as well as anti-intestinal bilharzial drug (oxamniquine) on the liver functions of female albino rats were studied. Metriphonate increased serum globulin content and caused no change in the hepatic cells. Oxamniquine significantly increased the activities of serum transaminases and alkaline phosphatase and caused necrosis in some liver cells. Microvlar-30 exhibited no change on the serum enzymes, while marked increase was found in serum triglyceride and protein levels. The combined administration of metriphonate or oxamniquine with microvlar-30 prevented the increase in the levels of serum triglycerides and proteins. Histopathological examination confirmed the results obtained by chemical analysis.