Treatment of Schistosoma mekongi with praziquantel: a double-blind study

Rectal carcinoma arising in a patient with intestinal and hepatic schistosomiasis due to Schistosoma mekongi

Schistosomiasis is a parasitic trematode infection spread by snails with multiple species causing human disease. Infection can cause liver disease, including fibrosis and portal hypertension, and has been linked to malignancies such as bladder and colorectal cancer. We describe a case of Schistosoma mekongi, a geographically limited form of schistosomiasis, in a Laotian immigrant who presented with both hepatic fibrosis and rectal cancer, with numerous schistosome eggs present in the patient’s rectal resection. We believe this case is the first report of a rectal carcinoma arising in the setting of S. mekongi infection.

Chronic Schistosoma mekongi in a traveler--a case report and review of the literature

Travel-related schistosomiasis can be detected in patients without symptoms of acute or chronic infection. A case of Schistosoma mekongi acquired in an endemic area of Laos and discovered unexpectedly from colon biopsies taken 5 years after infection is presented here. A literature review of previous cases of S. mekongi infection specifically associated with travelers is then presented.

Efficacy of praziquantel against Schistosoma mekongi and Opisthorchis viverrini: a randomized, single-blinded dose-comparison trial

Background

Schistosomiasis and opisthorchiasis are of public health importance in Southeast Asia. Praziquantel (PZQ) is the drug of choice for morbidity control but few dose comparisons have been made.

Methodology

Ninety-three schoolchildren were enrolled in an area of Lao PDR where Schistosoma mekongi and Opisthorchis viverrini coexist for a PZQ dose-comparison trial. Prevalence and intensity of infections were determined by a rigorous diagnostic effort (3 stool specimens, each examined with triplicate Kato-Katz) before and 28–30 days after treatment. Ninety children with full baseline data were randomized to receive PZQ: the 40 mg/kg standard single dose (n = 45) or a 75 mg/kg total dose (50 mg/kg+25 mg/kg, 4 hours apart; n = 45). Adverse events were assessed at 3 and 24 hours posttreatment.

Principal Findings

Baseline infection prevalence of S. mekongi and O. viverrini were 87.8% and 98.9%, respectively. S. mekongi cure rates were 75.0% (95% confidence interval (CI): 56.6–88.5%) and 80.8% (95% CI: 60.6–93.4%) for 40 mg/kg and 75 mg/kg PZQ, respectively (P = 0.60). O. viverrini cure rates were significantly different at 71.4% (95% CI: 53.4–84.4%) and 96.6% (95% CI: not defined), respectively (P = 0.009). Egg reduction rates (ERRs) against O. viverrini were very high for both doses (>99%), but slightly lower for S. mekongi at 40 mg/kg (96.4% vs. 98.1%) and not influenced by increasing diagnostic effort. O. viverrini cure rates would have been overestimated and no statistical difference between doses found if efficacy was based on a minimum sampling effort (single Kato-Katz before and after treatment). Adverse events were common (96%), mainly mild with no significant differences between the two treatment groups.

Conclusions/Significance

Cure rate from the 75 mg/kg PZQ dose was more efficacious than 40 mg/kg against O. viverrini but not against S. mekongi infections, while ERRs were similar for both doses.

Trial Registration

Controlled-Trials.com ISRCTN57714676

Parasitic worm infections are of public health importance in Southeast Asia. Particularly, the blood-dwelling Schistosoma mekongi worm, which is acquired by skin contact with the infectious cercariae in freshwater, can lead to liver enlargement. An infection with Opisthorchis viverrini is obtained by consumption of undercooked freshwater fish, and this infection increases the risk of developing cholangiocarcinoma. A single oral dose of 40 mg/kg praziquantel is recommended for mass treatment of schistosomiasis and opisthorchiasis, while at the individual level, a total dose of 75 mg/kg divided into three doses, is currently common practice to treat O. viverrini infection. Diagnosis is based on stool examination under a microscope for detection of worm eggs, but is limited by the low sensitivity of the widely used Kato-Katz technique. In this study, we showed that a 75 mg/kg total dose of praziquantel (50 mg/kg+25 mg/kg given 4 hours apart) cleared significantly more O. viverrini infections than a single 40 mg/kg dose, but no difference was observed for S. mekongi. Solicited adverse event profiles were mainly mild and similar in both groups. Repeated stool examination before and after treatment was essential for an accurate assessment of drug efficacy in terms of cure rate, but showed no effect on assessing egg reduction rates.

Efficacy of praziquantel and artemisinin derivatives for the treatment and prevention of human schistosomiasis: a systematic review and meta-analysis

Background

Praziquantel has been used as first-line drug for chemotherapy of schistosomiasis since 1984. Besides praziquantel, artemether and artesunate have also been used for the control of this infectious disease since late 1990s. In this article, we conducted a systematic review and meta-analysis to evaluate the antischistosomal efficacy of different medication strategies including monotherapy or combination therapies of these drugs.

Results

A number of 52 trials from 38 articles published in peer-reviewed journals before July 2011 were selected for analysis after searching the following literature databases: the Cochrane Library, PubMed/Medline, ISI Web of Science, Chinese Biomedicine Literature Database, and China National Knowledge Infrastructure. Our meta-analyses showed that a dosage of 30-60 mg/kg praziquantel compared with placebo produced a protection rate of about 76% (95% CI: 67%-83%) for treating human schistosomiasis, which varied from 70% to 76% with no significant differences among the subspecies S. haematobium, S. japonicum or S. mansoni. Protection rates were higher when praziquantel doses were elevated, as concluded from the nRCTs results: the protection rate of praziquantel at 40 mg/kg was 52% (95% CI: 49%-55%), and it increased to 91% (95% CI: 88%-92%) when the dosages were elevated to 60/80/100 mg/kg divided two or more doses. Multiple doses of artemether or artesunate over 1- or 2-week intervals resulted in protection rates of 65% to 97% for preventing schistosomiasis, and increased doses and shorter medication intervals improved their efficacies. Praziquantel and artemisinin derivatives (artemether or artesunate) in combination resulted in a higher protection rate of 84% (95% CI: 64%-91%) than praziquantel monotherapy for treatment. praziquantel and artesunate in combination had a great protection rate of 96% (95% CI: 78%-99%) for preventing schistosomes infection.

Conclusions

According to the results, praziquantel remains effective in schistosomiasis treatment, and multiple doses would improve its efficacy; meanwhile, praziquantel is also a good drug for preventing acute schistosomiasis morbidity. It's better to use multiple doses of artemether or artesunate with 1- or 2-week intervals for prevention against schistosome infection. Praziquantel and artemether or artesunate in combination perform better in treatment than praziquantel monotherapy, and they are especially suitable for treating the patients with repeated exposure to infected water.

Use of praziquantel for clinical treatment and morbidity control of schistosomiasis japonica in China: a review of 30 years' experience

Chemotherapy is widely acknowledged as the most important, rapid and cost-effective method of reducing morbidity due to schistosome infections. The discovery of praziquantel in the 1970s has been a breakthrough for treatment of patients infected with schistosomes, including Schistosoma japonicum in China, and entire communities at risk of schistosomiasis. Praziquantel is usually administered in a single oral dose and has no or only mild and transient side effects. The drug is highly efficacious against S. japonicum, both in patients with acute and chronic stages of the infection, among subjects with extensive hepatosplenic involvement, and in patients with other complicated diseases. The cost of praziquantel has been reduced significantly over the past years. Hence, praziquantel has become the backbone of the national schistosomiasis control programme in China and in other countries where the disease remains endemic, most notably in sub-Saharan Africa. Chemotherapy with praziquantel also plays a role in transmission control of schistosomiasis, although transmission interruption cannot be reached by chemotherapy alone. Here, I review 30 years' of experiences gained with the use of praziquantel for clinical treatment and larger-scale control of schistosomiasis japonica in China.

Experimental Schistosoma bovis infection in goats: pathological consequences of praziquantel treatment

Schistosoma bovis-infected goats were treated with praziquantel (60 mg/kg) and killed for examination 1, 7 or 28 days later. Infected non-treated goats and parasite-free, treated or non-treated goats were included for comparison. The gross pathological changes seen in the infected non-treated groups were mild to moderate. The liver appeared discoloured and moderately enlarged. The intestinal lesions were most prominent in the small intestines, which showed catarrhal inflammation with numerous tiny corpuscles beneath the luminal surface. The mesenteric lymph nodes were slightly to moderately enlarged. In contrast, on macroscopical examination, the infected treated groups invariably showed pronounced liver changes and marked enlargement of the lymph nodes, whereas the lesions in the intestines were comparatively slight. Histological lesions related to dead worms were seen in the livers of all treated animals. These lesions included pronounced inflammatory cellular infiltrates, thrombophlebitis, necrosis and periportal fibrosis, still severe 4 weeks after treatment. In the intestines, the deposition of new eggs with little cellular reaction had almost completely ceased 1 week after treatment. Four weeks after treatment, only a very few egg-associated lesions were noted in the intestines. The presence of severe lesions attributable to dead worms in the liver indicates the need for caution when treating animals with high worm loads or concomitant liver disease.

Portal hypertension in mansonic schistosomiasis

Mansonic schistosomiasis is an endemic disease in Brazil, with an estimated 10-12 million people infested. Among its clinical manifestations, the hepatosplenic form causes portal hypertension which, in turn, brings about severe digestive hemorrhage, the most serious complication of the disease. Normally, the patients are young, and have hepatosplenomegaly, hypersplenism without clinical manifestations, and slightly reduced hepatic function. The angiographic findings are characteristic, differing from those of hepatic cirrhosis. In Brazil, the definitive treatment for gastrointestinal hemorrhage is surgery, which should be done under elective conditions whenever possible. During a short period of time, known as the "risk period" (the time between the hemorrhagic episode and the surgery), propranolol has been used to prevent further bleeding. Surgical treatment is indicated only after the first episode, and never on a prophylactic basis. In 1977, a prospective, randomized trial was begun in order to assess the delayed results of the 3 surgical operations most widely used in this country. The study was interrupted after 94 patients had been operated on due to the high incidence of encephalopathy in the group who underwent classical splenorenal shunt. After a follow-up of at least 60 months and, at most, 130 months, the results showed that classical splenorenal shunt caused encephalopathy in 39.3% of the cases and distal splenorenal shunt in 14.8%. None of those submitted to esophagogastric devascularization with splenectomy developed encephalopathy. The 3 procedures showed similar rates of hemorrhagic recurrence.

Treatment of Schistosoma mekongi with praziquantel in Cambodian refugees in holding centres in Prachinburi Province, Thailand

Eighty-four cases of schistosomiasis mekongi among Cambodian refugees in holding centres in Thailand received praziquantel at 30 mg/kg body-weight orally twice in one day. Those treated were admitted to hospital in order to observe side effects for 24 hours. Assessment of the efficacy of praziquantel was based on cure rates. Side effects observed consisted primarily of abdominal pain, anorexia, nausea, emesis and headache. These were generally mild and transient. Physical signs revealed mild hepatomegaly and splenomegaly. The cure rate obtained one month after treatment was 97.5% and by 2 to 12 months after treatment reached 100%.

Quantitative determination of praziquantel in serum by high-performance liquid chromatography

A simple method for the quantitation of praziquantel by high-performance liquid chromatography is described. This method has a lower limit of sensitivity of 2.5 ng of drug per ml of human serum and a relative standard deviation of 2.6% at concentrations of 5 ng/ml.