A review of dihydroartemisinin as another gift from traditional Chinese medicine not only for malaria control but also for schistosomiasis control

Artemisinin, also known as qinghaosu, is a sesquiterpene lactone endoperoxide extracted from the plant Artemisia annua L, an herb employed in traditional Chinese medicine. Artemisinin and its two main derivatives artemether and artesunate have been shown to be effective against both malaria and schistosomiasis, and therefore, they were described by Liu et al (Parasitol Res 110:2071–2074, 2012b) as the gifts from traditional Chinese medicine not only for malaria control but also for schistosomiasis control. However, another artemisinin derivative dihydroartemisinin (DHA) cannot be neglected. Dihydroartemisinin, a derivative of artemisinin with the C-10 lactone group replaced by hemiacetal and the active metabolite of all artemisinin compounds, was firstly identified as an antimalarial agent, and the dihydroartemisinin-piperaquine combination has been recommended as a first-line treatment of uncomplicated Plasmodium falciparum malaria by the WHO. It has been recently found that administration of dihydroartemisinin at a single dose of 300 mg/kg 2 h or 3, 5, 7, 10, 14, 18, 21, 28, or 35 days post-infection reduces total worm burdens by 1.1–64.8 % and female worm burden reductions by 11.9–90.5 %, and the in vivo activity of dihydroartemisinin against S. japonicum is enhanced by the use of multiple doses. However, a combination of praziquantel and dihydroartemisinin appears no more effective against S. japonicum schistosomulum than treatment with dihydroartemisinin alone. In mice experimentally infected with S. mansoni, administration with dihydroartemisinin at a single dose of 300 mg/kg on days 1, 7, 14, 21, 28, 35, 42, 49, or 56 post-infection results in total worm burden reductions of 13.8–82.1 % and female worm burden reductions of 13–82.8 %, and a clear-cut dose-response relationship of dihydroartemisinin against the schistosomula and adult worms of S. mansoni is observed. In addition, dihydroartemisinin was found to cause damages to the reproductive system of female S. mansoni worms, reduce the oviposition of survival worms, and inhibit the formation of granulomas around tissue-trapped eggs. More interestingly, no reduced sensitivity to dihydroartemisinin is detected in praziquantel non-susceptible S. japonicum, which provides a new option for the treatment of S. japonicum and S. mansoni infections, notably in endemic foci with praziquantel resistance or insensitivity detected. It is therefore considered that dihydroartemisinin is another gift from the traditional Chinese medicine not only for malaria control but also for schistosomiasis control.     

Haemin enhances the in vivo efficacy of artemether against juvenile and adult Schistosoma mansoni in mice

Among the potential alternatives to praziquantel, interestingly, the antimalarial artemether (Art) also exhibits antischistosomal properties. Previous in vitro studies suggested that Art interacts with haemin and together produce a lethal agent against schistosomes. This study investigates the in vivo effect of Art plus haemin on juvenile and adult Schistosoma mansoni worms and on their antioxidant enzymes. Infected mice were allocated into two batches each in four groups (I-IV): (I) untreated control; (II) injected with haemin (ip, 100 mg/kg/day) on days 26, 27, and 28 post-infection (PI) for juvenile stage and on days 47, 48, and 49 PI for adult stage; (III) treated with a single oral dose of Art (300 mg/kg) either after 28 or 49 days PI, respectively; and (IV) received both haemin, as group (II) and Art as group (III). Half of mice for each batch were killed 72 h; meanwhile, the remaining half was killed 3 weeks after Art administration. Parasitological criteria of cure and worms’ antioxidant enzymes were assessed. Glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), and superoxide dismutase (SOD) activities were lower in juvenile worms than adult ones and in females than males. Haemin plus Art at the juvenile and adult stages produced significant inhibition in worms’ GST, GPx, and SOD activities 72 h after Art treatment, compared with Art-treated group, with enhanced killing of females (96.98 and 91.47 % versus 87.04 and 72.97 %, respectively) and total worms (91 and 83.39 % versus 75 and 59.01 %, respectively) 3 weeks posttreatment. In conclusion, Art plus haemin has a higher harmful effect on juvenile and adult schistosomes and antioxidant capacity than Art alone. This gives new insights into the importance of haemin in the antischistosomal properties of artemether.     

Parasitological evaluation of Ro 15-9268, a 9-acridanone-hydrazone derivative against Schistosoma mansoni in mice, and observations on changes in serum enzyme levels

Schistosoma mansoni is one of the major causes of schistosomiasis prevalent in tropical and subtropical areas, especially in poor communities. It is estimated that at least 90 % of those requiring treatment for schistosomiasis live in Africa. The primary control strategy employed for schistosomiasis is mass drug administration (MDA).The aim is to reduce disease through treatments with a single lower dose of Ro 15-9268 as a new antischistosomal drug. In the present search, the efficacy of Ro 15-9268 was studied in mice using a dose of 12.5 mg/kg of body weight (b.wt.) against an Egyptian strain of S. mansoni. This was carried out at 2 days and 3, 4, and 6 weeks post–cercarial exposure of mice. The criteria used were the worm load, oogram pattern and number of ova in the liver and intestine, hepatic enzyme activity, and liver histopathology. The tested agent has led to a significant reduction in worm burden (89.80 %) in liver and portomesenteric veins concurrent with a hepatic shift at the second week posttreatment followed by a complete disappearance of worms, 4 weeks postmedication. The oogram of infected animals treated revealed an increased number of dead ova 2 days posttreatment and complete absence of immature and mature ova 2 weeks later. The hepatic and intestinal egg counts significantly declined by about 96 and 98 %, respectively, 6 weeks after treatment, and the fecal egg count completely disappeared from stool 4 weeks after medication. The hepatic histopathological changes were improved, ova were markedly degenerated, and worms showed fragmentation and degeneration after drug administration. In conclusion, when Ro 15-9268 was administered to mice infected with the Egyptian strain of S. mansoni, at a low dose level (12.5 mg/kg b.wt.), encouraging results were obtained. The drug showed high efficacy against schistosomal worms as well as histopathological inflammatory changes.     

Structural changes of <Emphasis Type="Italic">Schistosoma mansoni</Emphasis> adult worms recovered from C57BL/6 mice treated with radiation-attenuated vaccine and/or praziquantel against infection

Although the current treatment of schistosomiasis relies largely on praziquantel (PZQ), it has not significantly reduced the overall number of disease cases, perhaps due to inevitable resistance to PZQ. Previous studies showed that radiation-attenuated vaccine gives protection levels for Schistosoma mansoni in host various species. In the present study, we evaluated the effect of various vaccination strategies in C57BL/6 mice, including single or multiple vaccination strategy, subcurative dose (20 mg/kg) of PZQ, and a combination of single vaccination with subcurative dose of PZQ. Groups of five mice were sacrificed postinfection in 42 days and schistosomes were collected by perfusion and examined by scanning electron microscopy. Treatment either with subcurative dose of PZQ or with a single vaccination of attenuated cercariae (500 per mouse), caused significant reduction in total worm burden, hepatic and intestinal ova counts 43.03%, 73.2%, 59.5% and 37.97%, 52.02%, 26.3%, respectively. Furthermore, tegumental changes were observed, including severe swelling, fusion of tegumental folds, vesicle formation, and loss or shortening of the spines on the tubercles. However, multiple vaccination strategy resulted in much higher reduction in total worm burden, hepatic and intestinal ova count. However, multiple vaccination strategy resulted in high reduction of worm burden, hepatic and intestinal ova counts 72.5%, 90.7%, 65.79%, respectively, and further causing swollen, disruption of tubercles teguments and erosion, extensive peeling, fusion of tegumental folds. Our findings suggest that multiple vaccination strategy is the most effective strategy to clear schistosomal infection, indicating its potential in guiding the design of appropriate therapeutic strategy against schistosomes.     

Anthelmintic activity of carvacryl acetate against Schistosoma mansoni

Blood flukes of the genus Schistosoma are the causative agents of human schistosomiasis, a debilitating disease that afflicts over 200 million people worldwide. Praziquantel is the drug of choice but concerns over praziquantel resistance have renewed interest in the search for alternative drug therapies. Carvacrol, a naturally occurring monoterpene phenol and food additive, has been shown high medicinal importance, including antimicrobials activities. The aim of this study was to evaluate in vitro effect of carvacryl acetate, a derivative of carvacrol, on Schistosoma mansoni adult worms. We demonstrated that carvacryl acetate at 6.25 μg/mL has antischistosomal activity, affecting parasite motility and viability. Additionally, confocal laser scanning microscopy pictures revealed morphological alterations on the tegumental surface of worms, where some tubercles appeared to be swollen with numerous small blebs emerging from the tegument around the tubercles. Furthermore, experiments performed using carvacryl acetate at sub-lethal concentrations (ranging from 1.562 to 6.25 μg/mL) showed an inhibitory effect on the daily egg output of paired adult worms. Thus, carvacryl acetate is toxic at high doses, while at sub-lethal doses, it significantly interferes with the reproductive fitness of S. mansoni adult worms. Due to its safety and wide use in the industry, carvacryl acetate is a promising natural product-derived compound and it may represent a step forward in the search for novel anthelmintic agents, at a time when there is an urgent need for novel drugs.     

In vivo schistosomicidal activity of three novels 8-hydroxyquinoline derivatives against adult and immature worms of Schistosoma mansoni

Schistosomiasis control is widely dependent on a single drug, praziquantel (PZQ). The potential for development of resistance to PZQ has justified the search for new alternative chemotherapies. In a previous study, we have been reported that three of 8-hydroxyquinoline derivatives namely: 3-((8-hydroxyquinolin-5-yl) sulfonyl) pentane-2,4-dione (HQSP), 5-((2,4-diphenyl-3H-benzo[b][1,4]diazepin-3-yl) sulfonyl) quinolin-8-ol (HQBD), and 5-((2,4-diphenyl-3H-pyrido[3,4-b][1,4] diazepin-3-yl) sulfonyl) quinolin-8-ol (HQPD) possess a potent anti-schistosomal activity in vitro. The aim of the present study was to evaluate the in vivo schistosomicidal effect of these three compounds on adult and immature worms of Schistosoma mansoni and their induced pathology. Treatment of S. mansoni-infected mice with 1000, 250, 150, and 200 mg/kg body weight of PZQ, HQSP, HQBD, and HQPD, respectively, reduced adult and immature worm burden by 94.63 and 31.32 %, 73.63 and 5.45 %, 76.5 and 28.11 %, and 81.25 and 56.84 %, respectively, compared to infected untreated mice. Moreover, numbers of egg per gram liver and intestine were decreased by 84 and 95.51 %, 47.84 and 46.28 %, 53.18 and 59.37 %, and 54.22 and 67.26 as a result of PZQ, HQSP, HQBD, and HQPD treatment, respectively. Hepatic granuloma volume was also reduced by 40.10, 42.96, 35.72, and 72.09 % due to PZQ, HQSP, HQBD, and HQPD treatment, respectively. In addition, hepatic histopathological alterations and collagen fiber deposition that accompanied with S. mansoni infection were largely retrieved with different treatments, especially HQPD treatment. Furthermore, humoral immune response, especially IgG response against S. mansoni antigens, was augmented with different treatments. This study concluded that among the three tested 8-hydroxyquinoline derivatives, HQPD is the most effective compound against adult and pre-mature worms of S. mansoni and can be used for the development of a new schistosomicidal drug.     

A penta-substituted pyridine alkaloid from the rhizome of Jatropha elliptica (Pohl) Muell. Arg. is active against Schistosoma mansoni and Biomphalaria glabrata

Jatropha elliptica is a shrub distributed throughout the north and west of Brazil and reputedly possesses a wide range of therapeutical properties. The roots of this plant possess molluscicidal activity and contain terpenoids, coumarin, lignoid, steroids and alkaloid. In the present study, we assessed the schistosomicidal, miracicidal and cercaricidal activities (against Schistosoma mansoni) and molluscicidal activities (against adults and egg masses of Biomphalaria glabrata) of the alkaloid diethyl 4-phenyl-2,6-dimethyl-3,5-pyridinedicarboxylate, isolated from the ethanol extract of the rhizome of J. elliptica, have been determined. The alkaloid was 100 % lethal to adult schistosomes within 4 days at a concentration of 50 μg/mL. Alterations were observed in the schistosome tegument occasioned by treatment with the alkaloid, such as formation of vesicles and vacuolisation. The extent of tegumental damage of the worm was proportional to the time of incubation and to the concentration of compound. The alkaloid also exhibited a potent cercaricidal activity (LC₁₀₀?=?2 μg/mL); it was totally ineffective against miracicidal forms of the parasite. Moreover, the alkaloid presented strong activity against adult snails (LC₉₀?=?36.43 μg/mL) but was inactive against their egg masses. It is observed then the potential of this compound for the development of new therapies for the treatment of schistosomiasis.     

Mefloquine, a new type of compound against schistosomes and other helminthes in experimental studies

Up to date, schistosomiasis is still prevalent worldwide. It is estimated that more than 200 million individuals are infected, and 120 million suffer from clinical morbidity. Facing such huge cases of schistosomiasis, only heavy reliance on a single praziquantel for schistosomiasis control does not adapt and may promote the selection and spread of drug-resistant parasites. Therefore, it is an urgent need to develop the new antischistosomal drug. In 2008–2009, the antimalarial drug mefloquine, an arylaminoalcohol compound, has been found to be effective against schistosomes. According to the experimental studies, the deepest impression on the antischistosomal properties of mefloquine can be summarized as following points: (1) single dose of mefloquine possesses potential effect against three major species of schistosomes (Schistosoma mansoni, Schistosoma haematobium, and Schistosoma japonicum) infecting humans; (2) the drug displays similar effects against developing stages of juvenile and adult schistosomes, which are superior to that of artemisinins and praziquantel; (3) in vitro mefloquine exerts direct killing effect on juvenile and adult schistosomes, while in vivo, the efficacy of the drug is independent to host immune response, (4) mefloquine causes extensive and severe morphological, histopathological, and ultrastructural damage to adult and juvenile schistosomes, particularly, the worm tegument, musculature, gut, and vitelline glands of female worms are the key sites attacked by the drug; (5) combined treatment with mefloquine and praziquantel, or artemisinins shows synergistic effect against schistosome in experimental therapy,while in initially clinical trial, mefloquine in combination with artesunate also exhibits higher cure rates against schistosomiasis hematobia and schistosomiasis mansoni, and (6) several mefloquine-related arylmethanols exhibit potential effect against schistosomes in vivo, which is a useful clue helpful for development of new antischistosomal compound. In the present review, we have summarized the major results published in recent years, and the significance as well as the prospect for the future study of mefloquine have been discussed briefly.     

Morphological and morphometric study of cercariae and adult worms of Schistosoma mansoni (SLM strain) isolated from infected mice

In northeastern Brazil, the schistosomiasis is historically endemic and considered as a public health problem. The Schistosoma mansoni São Lourenço da Mata (SLM—PE, Brazil) strain was used in several paper already published; however, morphological and morphometric studies about this strain was never done. In this work, scanning electron microscopy (SEM) was used in morphological and morphometric analysis of cercariae and adult worms. Cercariae were obtained from Biomphalaria glabrata snails and adult worms from mice, both infected by the S. mansoni SLM strain, fixed and prepared for SEM. The results showed that cercariae of S. mansoni measures 254.9 μm of length. The bodies are covered by spines, with a ventral sucker, an oral sucker with sensory receivers, and a pair of penetration glands in the head. The area of tail and body and the distance between suckers were 3,011.77, 1,530.32, and 42.9 μm, respectively. Adult worms of S. mansoni were divided into three main regions: the anterior, medial, and posterior, besides the gynecophoral canal in males. The measure of adult worms of S. mansoni was 4 mm males and 5 mm females. The anterior region length of the male was 470 μm and of the female 271 μm. All the parameters were assayed in ten samples. The morphometric values found in the SLM strain were smaller than other S. mansoni strains described in the literature as well as other helminths. This is the first morphological and morphometric study with the SLM strain of S. mansoni being extremely important for improving control strategies and life quality of the local population.     

Use of wogonin as a cooperative drug with praziquantel to better combat schistosomiasis

BackgroundSchistosomiasis is one of the most devastating tropical diseases in the world. Currently, praziquantel (PZQ) represents the best pharmacological option for the treatment of schistosomiasis as it effectively kills the worm. However, the inability to reverse established liver damages often makes treatment futile. In the current study, we investigate whether combining the use of wogonin, a compound that was found to be liver-protective, with PZQ can attribute to the greatest beneficial effect in Schistosoma mansoni-infected mice.MethodsTo determine the protective effect of PZQ-wogonin treatment on S. manosni-infected mice, histopathological analysis was done to evaluate the granuloma size and fibrotic areas in the liver. Western blotting was performed to analyze several injuries-related markers including fibrotic markers, inflammasomes, and apoptotic markers. Scanning electron microscopy was done to evaluate the effect of wogonin on the worms, and the worm and egg burden was calculated.ResultsOur results showed that PZQ-wogonin treatment significantly improved liver histopathology of S. mansoni-infected mice. Further analysis showed that PZQ-wogonin combinations are more effective in reducing fibrosis, inflammation, and apoptosis in the liver than that of individual drug use. Furthermore, our results revealed that wogonin is anthelmintic; and it works better with PZQ in reducing hepatic egg burden, further lessen the disease progression.ConclusionIn general, this combinatorial strategy may represent a new and effective approach to schistosomiasis treatment.     

Susceptibility or resistance of praziquantel in human schistosomiasis: a review

Since praziquantel was developed in 1970s, it has replaced other antischistosomal drugs to become the only drug of choice for treatment of human schistosomiases, due to high efficacy, excellent tolerability, few and transient side effects, simple administration, and competitive cost. Praziquantel-based chemotherapy has been involved in the global control strategy of the disease and led to the control strategy shifting from disease control to morbidity control, which has greatly reduced the prevalence and intensity of infections. Given that the drug has been widely used for morbidity control in endemic areas for more than three decades, the emergence of resistance of Schistosoma to praziquantel under drug selection pressure has been paid much attention. It is possible to induce resistance of Schistosoma mansoni and Schistosoma japonicum to praziquantel in mice under laboratorial conditions, and a reduced susceptibility to praziquantel in the field isolates of S. mansoni has been found in many foci. In addition, there are several schistosomiasis cases caused by Schistosoma haematobium infections in which repeated standard treatment fails to clear the infection. However, in the absence of exact mechanisms of action of praziquantel, the mechanisms of drug resistance in schistosomes remain unclear. The present review mainly demonstrates the evidence of drug resistance in the laboratory and field and the mechanism of praziquantel resistance and proposes some strategies for control of praziquantel resistance in schistosomes.     

Effect of Mirazid in Schistosoma japonicum-infected mice: parasitological and pathological assessment

Conflicting reports are found in the literature about the antischistosomal efficacy of Mirazid (MZ), which is a special formulation of myrrh obtained from the stem of the plant Commiphora molmol. This initiated the present study to assess this drug for the first time in experimental schistosomiasis japonicum. Mice were divided into four groups: infected untreated control (I); infected treated with MZ, 500 mg/kg (II); infected treated with MZ, 250 mg/kg (III); and infected treated with praziquantel (PZQ), 200 mg/kg (IV). The drugs were given 7 weeks post-infection for five successive days. All animals were killed 3 weeks posttreatment. Results showed no signs of antibilharzial activity of MZ. Total worms, total tissue egg load, egg developmental stages, and granuloma area were not affected by any of the MZ treatment regimens as compared to the infected untreated group (P?>?0.05 for all variables). These results were in contrast to those obtained in PZQ-treated animals in which 82.82 % total worm reduction, 94.62 % egg reduction, and 86.35 % granuloma area reduction were observed. Also, it significantly increased the percentage of dead ova and decreased the percentage of mature ova with complete absence of immature ones in comparison with the control group (P?<?0.01 for all variables). In conclusion, the results of the current study raise serious doubts about the antischistosomal activity of MZ.     

Characterization and localization of ouabain receptors in Schistosoma mansoni

Saturable ouabain binding sites were detected in intact male schistosomes. The K_D for binding of ouabain to Schistosoma mansoni was 2.6 × 10^?7 M and to Schistosoma japonicum 2.9 × 10^?7 M. The binding of ouabain to the receptor demonstrated pharmacological specificity. Binding sites, obtained by differential centrifugation, were associated with fractions containing tegument (58%) and microsomal membranes (33%). Binding sites were concentrated in tegumental membranes, i.e., a 19-fold enrichment of receptors was found in membranes isolated from intact schistosomes exposed to Triton X-100. The antiparasitic drugs praziquantel (IC₅₀ = 9 × 10^?7 M) and Ro-11-3128 (IC₅₀ = 5 × 10^?6 M) inhibit binding of [³H]ouabain to intact parasites in a pharmacologic specific manner. Both praziquantel and Ro-11-3128 are without effect (IC₅₀ > 10^?4 M) on [³H]ouabain binding to homogenates of S. mansoni. These findings indicate that ouabain receptors are present in S. mansoni and that these receptors represent Na⁺-K⁺ pump sites. In addition, the characteristics and location of these receptors are consistent with previous observations on the physiological action of ouabain on the parasite.     

A comparison of the susceptibility to praziquantel of Schistosoma haematobium,S. japonicum,S. mansoni,S. intercalatum and S. mattheei in hamsters

Summary Groups of six- to eight-week-old hamsters each experimentally infected with Sudanese and South African strains of S. haematobium, Puerto Rican and Liberian strains of S. mansoni, S. japonicum from mainland China, a Congo strain of S. intercalatum and a Nelspruit South African strain of S. mattheei, were treated with different dosage regimens of a new schistosomicide — praziquantel.The drug is more effective against S. haematobium when administered by the intramuscular route than per os, a complete parasitological cure being obtained following a single intramuscular injection of 200 mg/kg bwt. Per os the best results were obtained using the three highest regimens of 5×100 mg/kg, 5×50 mg/kg and 3×100 mg/kg bwt. It was observed that S. haematobium female worms are more susceptible to the compound than male worms.The results show that S. japonicum in the hamster is very susceptible to the compound, a dosage of 100 mg/kg administered orally for three days resulting in a complete parasitological cure. More than a 90% reduction in adult worms was obtained at all the dosage regimens used except 1×50 mg/kg (73.2%). Female worms were again found to be more susceptible to the drug than male worms. Hatching tests performed on ova in liver tissue of control and treated animals were positive up to four weeks after treatment, thus showing that praziquantel has no ovicidal properties.Immature S. japonicum worms were found to be markedly less susceptible to treatment than the mature schistosomes (5×100 mg/kg reduced mature adults by 99.7%, but immature forms were reduced by only 54.2%).A 100% cure rate was obtained in the hamster infected with the Liberian strain of S. mansoni following treatment with praziquantel at 3×100 mg/kg given on consecutive days, and at 3×50 mg/kg administered in one day. Treatment of the hamsters infected with the Puerto Rican strain of S. mansoni also resulted in substantial reductions of adult worms. Praziquantel was also found to be highly effective against S. intercalatum and S. mattheei.It is noted that the efficacy of the compound against S. haematobium, S. japonicum and S. mattheei in the hamster is significantly greater than that of metrifonate (Bilarcil). Following treatment with praziquantel most S. haematobium and S. japonicum worms undergo a classic hepatic shift and are trapped and killed in the liver tissue.It is considered that the present study shows that this new compound exhibits a high degree of activity against the three major schistosome species S. haematobium, S. japonicum and S. mansoni, against S. intercalatum, and against the cattle schistosome S. mattheei in the hamster, with no apparent significant differences in efficacy against the different geographical strains of the parasites used in the trials.

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Zusammenfassung Gruppen von 6–8 Wochen alten Goldhamstern wurden jeweils mit einem sudanesischen und südafrikanischen Stamm von S. haematobium, mit einem puertoricanischen und liberianischen Stamm von S. mansoni, mit S. japonicum aus Kontinentalchina, S. intercalatum vom Kongo und mit S. mattheei aus Nelspruit, Südafrika, infiziert und mit verschiedenen Dosierungen des neuen Schistosomenmittels Praziquantel behandelt.Praziquantel ist gegen S. haematobium bei intramuskulärer Gabe wirksamer als bei oraler Gabe. Eine parasitologische Heilung konnte durch eine einmalige intramuskuläre Injektion von 200 mg/kg erreicht werden. Bei oraler Gabe ergaben die drei höchsten Dosen 5×100, 5×50 und 3×100 mg/kg die besten Ergebnisse. Es wurde beobachtet, daß die Weibchen von S. haematobium empfindlicher gegen Praziquantel sind als die Männchen.Die Ergebnisse zeigen, daß S. japonicum im Goldhamster sehr empfindlich gegen Praziquantel ist. Eine parasitologische Heilung wird durch 3×100 mg/kg erreicht. Mit allen verabreichten Dosen wurde die Zahl der adulten Parasiten um mehr als 90% reduziert. Nur bei Gabe von 1×50 mg/kg betrug die Parasitenreduktion 73,2%. Wieder waren die Weibchen empfindlicher gegen Praziquantel als die Männchen. Der Miracidienschlüpfversuch wurde an Eiern aus der Leber behandelter und unbehandelter Kontrolltiere durchgeführt. Er war bis zu vier Wochen nach der Behandlung positiv; Praziquantel wirkt also nicht ovizid.Jugendliche S. japonicum waren gegen die Behandlung deutlich unempfindlicher als adulte Schistosomen (5×100 mg/kg bewirkten bei Adulten eine Reduktion um 99,7%, bei den Jugendlichen eine um 54,2%).Eine parasitologische Heilung wurde bei Goldhamstern, die mit einem liberianischen Stamm von S. mansoni infiziert waren, mit 100 mg/kg (verabreicht an drei aufeinanderfolgenden Tagen) und mit 3×50 mg/kg/die erreicht. Die Behandlung von Goldhamstern, die mit einem puertoricanischen S. mansoni-Stamm infiziert waren, ergab ebenfalls eine sehr starke Reduktion der Anzahl adulter Schistosomen. Gegen S. intercalatum und S. mattheei war Praziquantel ebenfalls sehr gut wirksam.Es wurde gefunden, daß die Wirksamkeit von Praziquantel gegen S. haematobium, S. japonicum und S. mattheei im Hamster deutlich besser ist als die von Metrifonat (Bilarcil). Nach Behandlung mit Praziquantel zeigen die meisten S. haematobium- und S. japonicum-Würmer eine klassische liver shift und werden im Lebergewebe festgehalten und abgetötet.Die Untersuchung zeigt, daß Praziquantel gegen alle drei wichtigen Schistosomenarten, S. haematobium, S. japonicum und S. mansoni, und auch gegen S. intercalatum sowie gegen den Rinderparasiten S. mattheei im Hamster hoch wirksam ist. Zwischen den in dieser Untersuchung verwendeten Parasitenstämmen unterschiedlicher geographischer Herkunft bestehen in der Wirksamkeit keine wesentlichen Unterschiede.

     

The susceptibility to praziquantel of Schistosoma haematobium in the baboon (Papio anubis) and of S. japonicum in the vervet monkey (Cercopithecus aethiops)

Summary Baboons infected with S. haematobium and vervet monkeys infected with S. japonicum were treated orally with different dosage regimens of praziquantel. The progress of the infections in the primates was followed by weekly faecal and urine egg counts before and after treatment. The response to treatment was also monitored by observing oogram changes in rectal snips. The baboons and vervet monkeys were autopsied and perfused 3–4 months after treatment.The results of the praziquantel treatments of baboons infected with S. haematobium show that a single administration of 100 mg/kg in one day was as effective as 50 mg/kg for five consecutive days in producing a complete cure. A single dose of 30 mg/kg failed to stop egg laying but retreatment with 50 mg/kg administered in one day resulted in cessation of egg laying 12 days after treatment and only one immature female worm and 33 male worms were recovered at autopsy. A baboon treated with 30 mg/kg administered at 10 mg/kg three times in one day was not cured, but when retreated with 75 mg/kg, administered in three separate doses of 25 mg/kg in one day, egg laying stopped 15 days afterwards and only three male worms were recovered at autopsy. The results suggest that a single oral dose of 75–100 mg/kg bwt is likely to be effective against S. haematobium in the baboon. An intramuscular injection of 200 mg/kg bwt was well tolerated by one animal.The results obtained with praziquantel against S. japonicum in the vervet monkey show that a complete cure was obtained in the animal given 50 mg/kg on five consecutive days, but the regimens of a single dose of 20 mg/kg followed by two separate doses of 10 mg/kg during one day, and of 10 mg/kg given three times during one day, resulted in only partial parasitological cures.The results based upon faecal egg output studies and the oograms taken after treatment suggested that praziquantel is more effective against S. japonicum than S. haematobium in the doses given, but the subsequent autopsies showed that some S. japonicum adult worms had survived treatment.A baboon naturally infected with S. mansoni, with a daily egg output of 150 eggs, was completely cured by a single oral dose of 50 mg/kg of praziquantel. This dose however failed to cure another naturally infected animal with a daily egg output of 1,800 eggs.It is considered that a predominant characteristic in the pathology of the animals given a curative dose of praziquantel was the total resolution of cellular reaction and fibrosis in the tissues containing known numbers of dead residual eggs. In the baboons with S. haematobium, the ureters and bladder had recovered their functional integrity and in the vervet monkeys infected with S. japonicum, a similar resolution of pathology in the liver and bowel was apparent.The results show that praziquantel is effective against patent S. haematobium and S. mansoni infections in baboons and against S. japonicum in vervet monkeys, in relatively low dosage regimens (100 mg/kg and < 100 mg/kg) applied in one day, as shown by suppression of egg laying and reduction or complete elimination of adult worms. Female worms of S. haematobium are apparently more susceptible to the compound than male worms. The classic hepatic shift of adult schistosomes was observed in all of the primates treated in the present series, but histopathological studies showed that numerous worms also died in situ, while only a few were found in the lungs.

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Zusammenfassung Mit S. haematobium infizierte Paviane und mit S. japonicum infizierte Meerkatzen wurden mit unterschiedlichen oralen Dosen von Praziquantel behandelt. Der Infektionsverlauf wurde bei den Affen vor und nach der Behandlung durch wöchentliche Eizählungen im Kot und im Urin verfolgt. Die Wirkung der Behandlung wurde anhand der Oogrammveränderung in rectalen Biopsieproben untersucht. Drei bis vier Monate nach der Behandlung wurden die Tiere seziert und perfundiert.Die Behandlung S. haematobium-infizierter Paviane mit Praziquantel erbrachte folgende Ergebnisse: Die orale Verabreichung von 1×100 mg/kg oder von 50 mg/kg/die an fünf aufeinanderfolgenden Tagen führte zur parasitologischen Heilung. 1×30 mg/kg hatte keinen Einfluß auf die Eiausscheidung, diese hörte jedoch 12 Tage nach einer Nachbehandlung mit 1×50 mg/kg auf. Bei der Autopsie dieses Tieres fanden sich lediglich ein junges Weibchen und 33 männliche Würmer. Ein mit 30 mg/kg (3×10 mg/kg an einem Tag) behandelter Pavian wurde nicht geheilt. Die Nachbehandlung mit 75 mg/kg (3×25 mg/kg an einem Tag) bewirkte ein Sistieren der Eiausscheidung nach 15 Tagen. Bei der Sektion fanden sich nur drei männliche Würmer.Die Ergebnisse lassen vermuten, daß eine einmalige orale Gabe von 75–100 mg/kg KW gegen S. haematobium im Pavian wirksam ist. Eine intramuskuläre Injektion von 200 mg/kg wurde von einem Tier gut vertragen.Mit S. japonicum infizierte Meerkatzen erwiesen sich nach der Verabreichung von 50 mg/kg/die an fünf aufeinanderfolgenden Tagen als parasitologisch geheilt. Dagegen bewirkten Gaben von 1×20 mg/kg gefolgt von 2×10 mg/kg an einem Tag oder von 3×10 mg/kg/die lediglich eine Teilwirkung.Die Ergebnisse der Kotuntersuchungen und der Oogramme nach der Behandlung lassen vermuten, daß Praziquantel in den verabreichten Dosen gegen S. japonicum wirksamer ist als gegen S. haematobium. Die anschließenden Sektionen zeigten allerdings, daß einige adulte S. japonicum-Würmer die Behandlung überlebt hatten.Ein natürlich mit S. mansoni infizierter Pavian mit einer Tageseiausscheidung von 150 Eiern wurde durch einmalige orale Gabe von 50 mg/kg geheilt. Diese Dosis war bei einem anderen, ebenfalls natürlich infizierten Tier mit einer täglichen Eiausscheidung von 1.800 Eiern nicht voll wirksam.Bei den mit curativen Dosen von Praziquantel behandelten Tieren kam es zu einer bemerkenswerten Rückbildung der typischen pathologischen Organveränderungen. Die zellulären Reaktionen und die fibrösen Bildungen in den Geweben, die eine bekannte Anzahl abgestorbener Eier enthielten, waren völlig aufgelöst. Bei den mit S. haematobium infizierten Pavianen gewannen die Harnleiter und die Harnblase ihre funktionelle Integrität zurück. Auch bei den mit S. mansoni infizierten Meerkatzen war eine entsprechende Auflösung pathologischer Veränderungen in der Leber und im Darm zu erkennen.Die Ergebnisse zeigen, daß Praziquantel gegen patente Infektionen mit S. haematobium und S. mansoni im Pavian und mit S. japonicum in der Meerkatze in relativ niedrigen, an einem Tag verabreichten Dosierungen (100 mg/kg und < 100 mg/kg) wirksam ist. Die klassische liver shift der adulten Schistosomen wurde bei allen in dieser Untersuchung behandelten Tieren gesehen. Histopathologische Untersuchungen zeigten jedoch, daß zahlreiche Würmer in situ starben, während nur wenige in der Lunge gefunden wurden. Dies äußerte sich in einem Aussetzen der Eiausscheidung und einer Reduktion oder in der quantitativen Elimination der adulten Würmer.Bei S. haematobium sind die Weibchen offensichtlich gegenüber Praziquantel empfindlicher als die Männchen.

     

Propolis enhances the effectiveness of praziquantel in experimental schistosomiasis: biochemical and histopathological study

Despite the wide current use of praziquantel (PZQ) in treatment of schistosomiasis, low cure rates have been recorded in many studies. The aim of this study was directed to evaluate the curative effect of propolis (Pps) alone or in combination with PZQ on biochemical, immunological, parasitological, and histological changes associated with experimental schistosomiasis in mice. Schistosoma mansoni-infected mice were divided into two experimental sets, each with four subgroups: (i) untreated, (ii) treated with Pps/day p.o for 4 weeks, (iii) treated with PZQ p.o 2?×?500 mg/kg bd wt, and (iv) treated with Pps?+?PZQ as in group ii and iii; all treatments started on the 8th week postinfection, in addition to uninfected group as control for the previous groups. Treatment of infected mice with Pps, although failed to eradicate the worm, significantly reduced the hepatic granuloma number, their lymphocytic infiltration and aggregation, hepatic and splenic myeloperoxidase (MPO) activity and plasma, and liver and thymus nitric oxide (NOx) levels together with normalization of plasma proteins and alleviation of oxidative stress in the examined tissues as evidenced by reduction of malondialdehyde (MDA) and normalization of glutathione (GSH). Promising results were obtained when Pps was given in combination with PZQ, where the anti-schistosomal activity of PZQ was markedly potentiated with complete alleviation and amelioration of the histological and biochemical alteration associated with schistosomiasis. This study highlights the potential usefulness of Pps as an adjunct to PZQ in schistosomiasis.     

Schistosoma japonicum-infected hamsters (Mesocricetus auratus) used as a model in experimental chemotherapy with praziquantel, artemether, and OZ compounds

The purpose of the study is to better understand the antischistosomal properties of artemether, praziquantel, and ozonide (OZ) compounds (synthetic trioxolanes, secondary ozonides) in hamster (Mesocricetus auratus) model. A total of 230 male hamsters infected each with 100 Schistosoma japonicum cercariae were used in the study. Groups of five to ten hamsters were treated orally with artemether, praziquantel, and OZ78 or OZ277 7-35 days post-infection at single doses of 50, 100, 150, or 200 mg/kg. Untreated but infected hamsters in each batch of test served as the control. All treated hamsters were sacrificed 4 weeks post-treatment for collection of residual worms using perfusion technique. Nonparametric method (Mann-Whitney test) was used to analyze the data. In groups of five hamsters treated with artemether 7, 14, 21, 28, and 35 days post-infection at single doses of 150 and 200 mg/kg, the difference of mean worm burden between each treated group and control group was statistically significant (P<0.01). Apart from individual group, no difference in mean worm burden between each two groups of them was seen (P>0.05). Further test with various single doses of 50-200 mg/kg confirmed the similar susceptibility of 7-day-old juvenile and 35-day-old adult schistosomes to artemether. After administration of praziquantel 100 mg/kg to groups of five hamsters 7, 21, and 35 days post-infection, higher worm burden reduction of 95.5% was seen in the group with 35-day-old adult schistosomes while in the groups with 7- and 21-day-old juvenile schistosomes, poor efficacy was seen with mean worm burden reductions of 36.6% and 35.6%. In the same batch of hamster treated with praziquantel 200 mg/kg, the moderate effect of the drug against 7- and 21-day-old worms was seen, but their mean worm burden was significantly higher than that of the group with adult schistosomes. In comparison of artemether and praziquantel against various stages of schistosomes, the results further demonstrated that artemether possessed similar effect against juvenile and adult schistosomes in hamsters, while praziquantel was more effective against adult schistosomes than the juvenile ones in the same host. Finally, after administration of OZ78 and OZ277 to the groups of four to six hamsters with 14- and 35-day-old schistosomes at a single dose of 200 mg/kg, promising effect against juvenile and adult schistosome was observed with the mean worm burden and female worm burden reductions of 69.6-94.2% and 64.2-100% as well as 73.3-80.7% and 68.3-81.1%, respectively. The results indicate that in hamster model, praziquantel exhibits higher effect against adult schistosomes than the juvenile ones, while artemether and OZ compound display similar effect against both juvenile and adult schistosomes.     

Antischistosomal activity of ginger (<Emphasis Type="Italic">Zingiber officinale</Emphasis>) against <Emphasis Type="Italic">Schistosoma mansoni</Emphasis> harbored in C57 mice

The repeated chemotherapy of schistosomiasis has resulted in the emergence of drug-resistant schistosome strains. The development of such resistance has drawn the attention of many authors to alternative drugs. Many medicinal plants were studied to investigate their antischistosomal potency. The present work aimed to evaluate antischistosomal activity of crude aqueous extract of ginger against Schistosoma mansoni. Sixteen mice of C57 strain were exposed to 100 ± 10 cercariae per mouse by the tail immersion method; the mice were divided into two groups: untreated group and ginger-treated one. All mice were sacrificed at the end of 10th week post-infection. Worm recovery and egg counting in the hepatic tissues and faeces were determined. Surface topography of the recovered worms was studied by scanning electron microscopy. Histopathological examination of liver and intestine was done using routine histological procedures. The worm burden and the egg density in liver and faeces of mice treated with ginger were fewer than in non-treated ones. Scanning electron microscopical examination revealed that male worms recovered from mice treated with ginger lost their normal surface architecture, since its surface showed partial loss of tubercles’ spines, extensive erosion in inter-tubercle tegumental regions and numerous small blebs around tubercles. Histopathological data indicated a reduction in the number and size of granulomatous inflammatory infiltrations in the liver and intestine of treated mice compared to non-treated mice. The results of the present work suggested that ginger has antischistosomal activities and provided a basis for subsequent experimental and clinical trials.     

Efficacy of artemether and artesunate in mice infected with praziquantel non-susceptible isolate of Schistosoma japonicum

Praziquantel is currently the only drug of choice for the treatment of human Schistosoma japonicum infections, and praziquantel-based chemotherapy has been proved to be generally effective to control the morbidity and reduce the prevalence and intensity of S. japonicum infections. However, the potential emergence of praziquantel resistance in S. japonicum seriously threatens the elimination of this neglected tropical disease in China. The purpose of this study was designed, in mouse animals, to evaluate the in vivo efficacy of artemether and artesunate against praziquantel non-susceptible S. japonicum. Mice infected with a praziquantel non-susceptible isolate and a praziquantel-susceptible isolate of S. japonicum were treated with artemether and artesunate at a single oral dose of 300 mg/kg given once on each of days 7–8 and 35–36 post-infection to assess the efficacy against juvenile and adult worms. Administration with artemether and artesunate at a single oral dose of 300 mg/kg on each of days 7–8 post-infection resulted in total worm burden reductions of 72.8 and 73.5 % in mice infected with praziquantel-susceptible S. japonicum, and 77.9 and 74.1 % in mice infected with the non-susceptible isolate (both P values >0.05), while the same treatments given on days 35–36 post-infection reduced total worm burdens by 71.4 and 69.6 % in mice infected with the susceptible isolate, and 75.3 and 69.6 % in mice infected with the non-susceptible parasite (both P values >0.05). It is concluded that there is no evidence for reduced susceptibility of artemether and artesunate in praziquantel non-susceptible S. japonicum.     

Effect of mefloquine administered orally at single, multiple, or combined with artemether, artesunate, or praziquantel in treatment of mice infected with Schistosoma japonicum

The purpose of the study is to better understand the antischistosomal properties of artemether, praziquantel, and ozonide (OZ) compounds (synthetic trioxolanes, secondary ozonides) in hamster (Mesocricetus auratus) model. A total of 230 male hamsters infected each with 100 Schistosoma japonicum cercariae were used in the study. Groups of five to ten hamsters were treated orally with artemether, praziquantel, and OZ78 or OZ277 7–35 days post-infection at single doses of 50, 100, 150, or 200 mg/kg. Untreated but infected hamsters in each batch of test served as the control. All treated hamsters were sacrificed 4 weeks post-treatment for collection of residual worms using perfusion technique. Nonparametric method (Mann–Whitney test) was used to analyze the data. In groups of five hamsters treated with artemether 7, 14, 21, 28, and 35 days post-infection at single doses of 150 and 200 mg/kg, the difference of mean worm burden between each treated group and control group was statistically significant (P < 0.01). Apart from individual group, no difference in mean worm burden between each two groups of them was seen (P > 0.05). Further test with various single doses of 50–200 mg/kg confirmed the similar susceptibility of 7-day-old juvenile and 35-day-old adult schistosomes to artemether. After administration of praziquantel 100 mg/kg to groups of five hamsters 7, 21, and 35 days post-infection, higher worm burden reduction of 95.5% was seen in the group with 35-day-old adult schistosomes while in the groups with 7- and 21-day-old juvenile schistosomes, poor efficacy was seen with mean worm burden reductions of 36.6% and 35.6%. In the same batch of hamster treated with praziquantel 200 mg/kg, the moderate effect of the drug against 7- and 21-day-old worms was seen, but their mean worm burden was significantly higher than that of the group with adult schistosomes. In comparison of artemether and praziquantel against various stages of schistosomes, the results further demonstrated that artemether possessed similar effect against juvenile and adult schistosomes in hamsters, while praziquantel was more effective against adult schistosomes than the juvenile ones in the same host. Finally, after administration of OZ78 and OZ277 to the groups of four to six hamsters with 14- and 35-day-old schistosomes at a single dose of 200 mg/kg, promising effect against juvenile and adult schistosome was observed with the mean worm burden and female worm burden reductions of 69.6–94.2% and 64.2–100% as well as 73.3–80.7% and 68.3–81.1%, respectively. The results indicate that in hamster model, praziquantel exhibits higher effect against adult schistosomes than the juvenile ones, while artemether and OZ compound display similar effect against both juvenile and adult schistosomes.