Effects of praziquantel and artesunate on the tegument of adult Schistosoma mekongi harboured in mice

Biogenic silver nanoparticle exhibits schistosomicidal activity in vitro and reduces the parasitic burden in experimental schistosomiasis mansoni

Schistosomiasis is a neglected tropical parasitic disease that affects millions of people, being the second most prevalent parasitic disease worldwide. The current treatment has limited effectiveness, drug-resistant strains, and is not effective in different stages of the disease. This study investigated the antischistosomal activity of biogenic silver nanoparticles (Bio-AgNp) against Schistosoma mansoni. Bio-AgNp presented direct schistosomicidal activity on newly transformed schistosomula causing plasma membrane permeabilization. In S. mansoni adult worms, reduced the viability and affected the motility, increasing oxidative stress parameters, and inducing plasma membrane permeabilization, loss of mitochondrial membrane potential, lipid bodies accumulation, and autophagic vacuoles formation. During the experimental schistosomiasis mansoni model, Bio AgNp restored body weight, reduced hepatosplenomegaly, and decrease the number of eggs and worms in feces and liver tissue. The treatment also ameliorates liver damage and reduces macrophage and neutrophil infiltrates. A reduction in count and size was evaluated in the granulomas, as well as a change to an exudative-proliferative phase, with a local increase of IFN-γ. Together our results showed that Bio-AgNp is a promising therapeutic candidate for studies of new therapeutic strategies against schistosomiasis.

Bisphenol A effects on the host Biomphalaria alexandrina and its parasite Schistosoma mansoni

Bisphenol A (BPA) is one of the most potent endocrine-disrupting chemicals (EDCs) that adversely affect aquatic organisms. The present investigation explored the effects of exposure to BPA at 0.1 and 1 mgL-1 concentrations on the fecundity of Biomphalaria alexandrina, snail's infection with Schistosoma mansoni, and histology of the ovotestis and topographical structure of S. mansoni cercariae emerged from exposed snails. The 24 h LC50 and LC90 values of BPA against B. alexandrina were 8.31 and 10.88 mgL-1 BPA, respectively. The exposure of snails to 0.1 or 1 mgL-1 BPA did not affect the snail's survival. However, these concentrations caused an increase in the reproductive rate (Ro) of infected snails. A slight decrease in egg production was observed in snails exposed to 0.1 mgL-1 BPA after being infected (infected then exposed). However, a significant increase in egg production was noted in snails exposed to 1 mgL-1 BPA after infection with S. mansoni. Histopathological investigations indicated a clear alteration in the ovotestis tissue structure of exposed and infected-exposed groups compared to the control snails. Chronic exposure to BPA caused pathological alterations in the gametogenic cells. SEM preparations of S. mansoni cercariae emerged from infected-exposed snails showed obvious body malformations. From a public health perspective, BPA pollution may negatively impact schistosomiasis transmission, as indicated by the disturbance in cercarial production and morphology. However, it has adverse effects on the reproduction and architecture of reproductive organs of exposed snails, indicating that B. alexandrina snails are sensitive to sublethal BPA exposure.

In Vivo Evaluation of the Anti-Schistosomal Potential of Ginger-Loaded Chitosan Nanoparticles on Schistosoma mansoni: Histopathological, Ultrastructural, and Immunological Changes

Chemotherapy is the most widely advocated method of Schistosome control. However, repeated chemotherapy leads to the emergence of drug-resistant Schistosoma strains. Therefore, efforts to find alternative drugs, especially those of natural origin, have risen globally. Nanoparticles (NPs) have received special interest as efficient drug delivery systems. This work aimed to investigate the anti-schistosomal potential of Zingiber officinale (ginger, Zingiberaceae)-loaded chitosan nanoparticles (GCsNPs) on Schistosoma mansoni experimentally infected mice that were exposed to 80 ± 10 cercariae/mouse. The study groups are: (G1) negative control; (G2) positive control; (G3) praziquantel in a dose of 500 mg/kg/day for two consecutive days; (G4) ginger in a dose of 500 mg/kg treated; (G5) chitosan nanoparticles in a dose 3 mg/kg (G6) GCsNPs in a dose 250 mg/kg; and (G7) GCsNPs in a dose 500 mg/kg. The anti-schistosome potential was assessed using histopathological scanning electron microscopically and immunological parameters. The results showed that there was a significant decrease in cellular granuloma count (p < 0.05) and granuloma diameter (p < 0.001) in all infected treated mice groups, in comparison to the infected non-treated group with the highest reduction in both G3 and G7. SEM of S. mansoni adult worm recovered from G3 showed mild edema of oral and ventral suckers with some peeling and blebs around them, while that recovered from G7 showed abnormal oedematous oral and retracted ventral sucker, edema of the tegument, rupture of many tubercles with vacuolation and complete loss of spines. All infected treated mice groups, in comparison to positive control G2, showed a significant reduction in IL-4, IL-10, and TNF-α levels (p-value < 0.001), especially groups G6 and G7 (p-value < 0.05); both G6 and G7 values were nearer to the normal that indicated recovery of the liver tissue.

Advances in the pharmacological treatment of hepatic alveolar echinococcosis: From laboratory to clinic

Hepatic alveolar echinococcosis (HAE) is a zoonotic parasitic disease caused by the larvae of Echinococcus multilocularis. Because of its characteristics of diffuse infiltration and growth similar to tumors, the disability rate and mortality rate are high among patients. Although surgery (including hepatectomy, liver transplantation, and autologous liver transplantation) is the first choice for the treatment of hepatic alveolar echinococcosis in clinic, drug treatment still plays an important and irreplaceable role in patients with end-stage echinococcosis, including patients with multiple organ metastasis, patients with inferior vena cava invasion, or patients with surgical contraindications, etc. However, Albendazole is the only recommended clinical drug which could exhibit a parasitostatic rather than a parasitocidal effect. Novel drugs are needed but few investment was made in the field because the rarity of the cases. Drug repurposing might be a solution. In this review, FDA-approved drugs that have a potential curative effect on hepatic alveolar echinococcosis in animal models are summarized. Further, nano drug delivery systems boosting the therapeutic effect on hepatic alveolar echinococcosis are also reviewed. Taken together, these might contribute to the development of novel strategy for advanced hepatic alveolar echinococcosis.

Evaluation of Antischistosomal Activities of Crude Aqueous Extracts of Artemisia annua, Nigella sativa, and Allium sativum against Schistosoma mansoni in Hamsters

Schistosomiasis is a neglected disease, as the World Health Organization classified it in the second category after malaria. World Health Organization approved praziquantel (PZQ) as the only chemotherapy to treat schistosomiasis. Over the years, some problems have arisen with PZQ, as it showed poor efficacy in the early stages of infection as well as the emergence of some resistance to it. In searching for new alternative drugs to treat schistosomiasis, the researchers intensified their efforts to find a new drug. The present study focuses on evaluating the effect of three plant extracts Artemisia annua, Nigella sativa, and Allium sativum at different doses of 31.25, 62.5, 125, 250, and, 500 μg/ml; in vitro study was accomplished on the Schistosoma mansoni adult worms. The results declared that the concentration of 500, 250, and 125 of Artemisia annua was more effective on adult worms, and the same concentrations of Nigella sativa and Allium sativum gave less effect on the adult worms than the previous plant. In vivo study was accomplished on the hamster's tissue after exposing it to doses of the plants' extracts with different concentrations; it showed the presence of calcifications and damage to the worm eggs in the liver and spleen, as well as reducing the size of granulomas. After conducting many confirmatory studies Artemisia annua extract can be used as an effective and safe treatment for Schistosoma disease.

Schistosomiasis mansoni: A new therapeutic target for ubiquinol, a natural inhibitor of neutral magnesium-dependent sphingomyelinase in murine model

Constituting the host-parasite interface and playing a censorious role in host immune response modulation and parasite survival, tegument represents a crucial target for many antischistosomal drugs. Sphingomyelin forms a stable outer leaflet of tegumental membrane-lipid bilayer. Neutral magnesium‏-dependent sphingomyelinase (Mg²⁺-nSMase) is a key enzyme in sphingomyelin breakdown was identified in schistosomes. We investigated the in vivo efficacy of ubiquinol, a natural inhibitor of Mg²⁺-nSMase, in free and niosomes-encapsulated forms, through five-day and 15-day regimens on the early and late Schistosoma mansoni parasitic stages, respectively, compared to PZQ. Oral administration of 300 mg/kg/day ubiquinol-encapsulated niosomes (U-N) showed significant deterioration of the parasitic growth and development in the term of reduction of lung schistosomula burden (39.12%), adult worm burden (50.81%), hepatic and intestinal tissue-egg counts (80.89% and 75.54%, respectively). PZQ and free ubiquinol regimens reported reductions in lung schistosomula counts (45.36% and 22.90%, respectively) and total worm burdens of 86.28% and 24.58%, respectively. U-N therapy revealed worms de-pairing and remarkable diminution in female worms' perimeters and fecundity. Scanning electron microscope revealed disruption of tegumental ridges with excessive longitudinal corrugation. Transmission electron microscope showed testicular and ovarian parenchymal degeneration, signs of immaturity and cell apoptosis. Indirect immunofluorescence assay approved parasite's tegumental changes. Remarkable reduction of granulomas size with amelioration of hepatic pathology and fibrosis were assumed to be attributed to the anti-inflammatory and anti-oxidant properties of ubiquinol. These findings with the drug safety profile suggest that U-N could be a promising candidate for a new antischistosomal drug development.

A Novel Treatment of Schistosomiasis: Nano-Calcium Silicate Incorporating 5% Copper Oxide

Purpose: Praziquantel (PZQ) is a well-known drug accredited by the World Health Organization (WHO) for the treatment of schistosomiasis. It shows poor efficiency in patients during the earliest infection phases. Therefore, the search for new alternative drugs was the intention of many researchers. Methods: In the current study, the effect of different concentrations (ranging from 0.07-10 μg∕mL) of calcium silicate (CS) containing 5% copper oxide [CS-5%CuO] on golden hamster infected by Schistosoma mansoni and Schistosoma haematobium (Egyptian strains) was evaluated in both in vitro and in vivo. To the best of our knowledge, this is a novel study in investigating the efficiency of CS-5%CuO against both strains of schistosomes. The worms of S. mansoni and S. haematobium were tested in RPMI-1640 medium in vitro. Results: The results declare that CS-5% CuO exhibited excellent anti-schistosomal activities on both in vitro and in vivo experiments for both Egyptians Schistosoma strains. The most potential effect of the CS-5% CuO was exhibited after 6 h by 10 μg∕mL with significant activity of (P value = 0.001). Conclusion: Therefore, CS-5%CuO may become an innovative treatment for the schistosomiasis.

Antischistosomal Activity of Zingiber officinale, Piper nigrum, and Coriandrum sativum Aqueous Plant Extracts on Hamster Infected with Schistosoma mansoni

Schistosomiasis continues to affect the health and quality of life of millions of people around the world. Schistosomiasis has been ranked the second disease after malaria in terms of importance as a targeted tropical disease. Praziquantel (PZQ) is the only drug approved by the World Health Organization (WHO) for the treatment of schistosomiasis. Being the only drug, parasite resistance to this drug has developed. Therefore, the search for new alternatives has been the goal of many researchers. In this study, the effects of aqueous extracts of Zingiber officinale, Piper nigrum, and Coriandrum sativum on Schistosoma mansoni infected golden hamsters (Egyptian strain) were evaluated in vitro and in vivo at different doses of 500, 250, 125, 62.5, and 31.25 μg/ml. In vitro, adult worms of S. mansoni were tested in RPMI-1640 medium for 48 hrs. The results showed that the concentrations 500, 250, and 125 μg/ml of Zingiber officinale and Piper nigrum caused dead of 100% of adult worms within 6 and 12 hrs of incubation, respectively. Although, aqueous extract of Coriandrum sativum at concentrations 500, 250, and 125 μg/ml resulted dead of 100% parasites after 12 to 24 hrs of incubation. In conclusion, Zingiber officinale and Piper nigrum showed efficacy against schistosomiasis in both in vitro and biological experiments of Egyptian schistosome strain, while Coriandrum sativum gave less effective results than the previous ones. Therefore, Zingiber officinale and Piper nigrum may become an innovative treatment for schistosomiasis.

In vitro Effects of Punica granatum Ellagitannins on Adult Worms of Schistosoma mansoni

Schistosomiasis ranks second behind malaria in terms of overall morbidity and mortality. We evaluated the lethal effect of Punica granatum ellagitannins, extracted from the fruit rind, placenta and barks of the root and stem, on adult worms of Schistosoma mansoni (S. mansoni). All four ellagitannins were lethal to S. mansoni adult worms. However, while the rind ellagitannins were the most potent, placental ellagitannins were the least. Rind ellagitannins were capable of killing 40% of adult worms at a concentration of 25µg/mL after 5 days. The killing of 100% of the worms was achievable by rind ellagitannins at a concentration of 50µg/mL after 5 days. The LD_50S of the rind ellagitannins after 96h and 120h were 41.25 µg/mL and 28.73 respectively. Ellagitannins-treated worms suffered from erosions, wrinkles, swellings and losses, degenerations of the surface tubercles and tegument. In addition, ellagitannins induced deformation and degradation of oral and ventral suckers and degenerations in the muscles of worms. Ellagitannins also caused a separation of coupled worms and reduction of their motility. Data obtained suggest that ellagitannins of pomegranate could be considered as a cheap candidate for the treatment of schistosomiasis.

Prophylactic versus therapeutic role of the transplanted CD34+ Umbilical Cord Blood Stem Cells and Wharton Jelly Mesenchymal Stem Cells in early / acute hepatic S. mansoni granulomas reversal in mice; a novel approach

PURPOSE

Praziquantel (PZQ) is the conventional antibilharzial agent. Nevertheless, no antibilharzial prophylactic agents or 100% curable therapy approved and no reported data about use of human CD34⁺ Umbilical Cord Blood Stem Cells (CD34⁺UCBSCs) or Wharton Jelly Mesenchymal Stem Cells (WJMSCs) in prevention and/or complete eradication of acute S.mansoni granulomas in liver. We aimed to study possible prophylactic vs therapeutic role of human CD34⁺UCBSCs and WJMSCs in acute hepatic bilharzial granulomas in pre vs post-infected mice.

METHODS

Seventy mice were divided into 7 groups (10 mice each): Normal, S.mansoni-infected, post-infected PZQ-treated, CD34⁺UCBSCs pre and post-infected, WJMSCs pre and post-infected. Serological, parasitological, histopathological evaluation using OCT4 & TGFB immunohistochemistry and quantitative image analysis assessment of TGFB-stained fibrogenesis in liver granulomas performed.

RESULTS

Histopathologically, surprisingly and significantly, the prophylactic pre-infection stem cells (CD34⁺UCBSCs and WJMSCs) & similarly the post-infection CD34⁺UCBSCs treatment revealed eradication/reversal of the entire granulomas and no fibrosis. Moreover, post-infection PZQ treatment showed fewer and significantly smaller granulomas than post-infection WJMSCs treatment. Nevertheless, post-infection WJMSCs exhibited non-significant less TGFB-stained fibrogenesis.

CONCLUSION

CD34⁺UCBSCs exerted the best prophylactic and therapeutic roles in prevention and complete cure of acute hepatic S.mansoni granulomas over WJMSCs and PZQ. In contrast, only pre-infection WJMSCs exhibited similar preventive (prophylactic) effect. On the contrary, post-infection WJMSCs were the worst (incompletely reversed granulomas). Post-infection Praziquantel was overall better therapeutically than WJMSCs in this regard. Accordingly, when it comes to WJMSCs application, WJMSCs are better used as a pre-infection prophylactic and preventive tool rather than a post-infection therapy. Further studies are needed.

Opisthorchis felineus genes differentially expressed under praziquantel shed light on the nature of tegument disruption and indicate the adaptive role of cGMP-dependent protein kinase

Opisthorchis felineus is a trematode flatworm that parasitises mammals, including humans, and is mainly spread throughout Eastern Europe and Western Siberia. The main drug used in treatment of opisthorchiasis and other trematode and cestode infestations is praziquantel (PZQ). We provide a possible explanation of PZQ-mediated tegument disruption. The idea is that the nature of tegument disruption is related to failure of surface renovation due to insufficiency of microtubule transport of vesicles. This insufficiency arises from microtubule destabilisation, which in the medium term leads to the decrease in tubulins alpha, beta and dynein mRNA amounts and deficiency of the corresponding proteins. We also found the upregulation of cGMP-dependent protein kinase gene, and we concluded that its protein product helped to overcome the effect of praziquantel and might be a promising target for combined anthelmintic therapy with PZQ. We concluded that function of saposin-like protein 2 (SAP2) is unlikely associated with membrane fusion, and SAP2 is probably able to bind some type of hydrophobic compounds including praziquantel.

Schistosomicidal and prophylactic activities of phthalimido-thiazoles derivatives on schistosomula and adult worms

Schistosomiasis is a major public health problem worldwide, especially in poor communities. Praziquantel is currently the only drug available to treat schistosomiasis and it shows low efficacy against schistosomula and juveniles stages of Schistosoma mansoni, allowing lower cure rate in areas with high endemicity. There is an urgent need to identify new antischistosomal drugs. Previous works identified phthalimido-thiazoles as privileged structures acting as schistossomicidal agent. In this way, a phthalimido-thiosemicarbazide intermediate and eight phthalimido-thiazoles derivatives were evaluated concerning the in vitro antischistosomal activity compounds in adult phase of Schistosoma mansoni and examined alterations on the tegumental surface. The results revealed that compounds 2f, 2 l and 2 m caused significant mortality in adult worms at concentrations range of 20 μg/mL to 100 μg/mL. These compounds were also selected in view to verify the activity against the schistosomula. Compound 2 m promoted 100% of mortality of larval forms until doses of 2.5 μg/mL within 48 h. In addition, when compound 2 m was administered orally at dose of 200 mg/kg for 5 consecutive days to the infected mouse with adult schistosomes, a reduction in the parasite burden was observed. Furthermore, scanning electron microscopy revealed that compound 2 m kill the parasite by tegumental damage and bubbles generation.

The impact of cinnarizine and griseofulvin on juvenile and adult stages of Schistosoma mansoni

Schistosomiasis affects millions globally. There is no vaccine, and treatment depends entirely on praziquantel (PZQ). Field isolates exhibit reduced susceptibility to PZQ, and resistance has been experimentally induced, suggesting that reliance on a single treatment is particularly dangerous. The present study investigated the value of cinnarizine and griseofulvin against Schistosoma mansoni through their in vitro effects on adult worms and oviposition as well as in vivo evaluation in early and late infection, compared to PZQ, in a preliminary experimental model. In vitro, both cinnarizine and griseofulvin showed uncoupling, sluggish worm movement and complete absence of ova at 100 μg/ml. In early infection, cinnarizine showed a significant reduction in the number of porto-mesenteric couples compared to the griseofulvin and control groups, a finding similar to PZQ. Remarkably, cinnarizine significantly exceeded PZQ and griseofulvin in reducing the total worm burden. In late infection, cinnarizine and griseofulvin showed results similar to PZQ by significantly reducing the numbers of hepatic and porto-mesenteric couples and total worm burden compared to controls. Cinnarizine performed better than griseofulvin by reducing hepatic and intestinal ovum counts, and it led to complete disappearance of the first two immature stages. The current work suggests the possibility of using cinnarizine and griseofulvin, mainly in late S. mansoni infection, especially cinnarizine, which showed similar results to PZQ and surpassed it in early infection. Further studies are required to elucidate their exact mechanisms of action and particularly their synergistic effect with PZQ.

The anthelmintic drug praziquantel promotes human Tr1 differentiation

Praziquantel (PZQ) is an anthelminthic human and veterinary drug used to treat trematode and cestode worms. Changes in immune responses have been demonstrated in humans following curative PZQ treatment of schistosome infections. These changes have been attributed to the removal of immunosupressive worms and immune responses to parasite antigens exposed from dying worms. To date, there has been no study investigating the potential direct effect of PZQ on the host immune cells. Herein, we analyzed the effect of PZQ on human CD4⁺ T cells classically costimulated by CD3/CD28 or costimulated by the complement regulator CD46 to induce Type 1 regulatory T cells (Tr1). Our results show that PZQ enhanced T-cell proliferation, increased secretion of IL-17 and IL-10 but had no effect on secretion of GM-CSF or IFNγ. Moreover, PZQ increased the coexpression of CD49b and LAG-3, a hallmark of Tr1 cells, suggesting increased Tr1 differentiation. Indeed, supernatants from PZQ-treated cells were able to decrease bystander T-cell activation, and this was partly reduced when blocking IL-10. Hence, our study demonstrates that PZQ directly modulates human T-cell activation and promotes Tr1 differentiation, suggesting that PZQ may have immunomodulatory functions in parasite-unrelated human inflammatory diseases.

Paeoniflorin in experimental BALB/c mansoniasis: A novel anti-angiogenic therapy

Chronic hepatic schistosomiasis causes portal hypertension, fibrosis and lethal hepatosplenic complications. Previous studies focused mainly on schistosomicidal drugs and neglected the therapeutic approaches against the vascular complications after portal hypertension. Investigating a novel anti-angiogenic therapy is an urgent. The current study is to evaluate the performance of Paeoniflorin (PAE) as an anti-angiogenic therapy, being a powerful anti-fibrotic, compared to artemether (ART) and praziqantel (PZQ) in schistosomiasis mansoni BALB/c mice. Thirty two laboratory bred male BALB/c Swiss albino mice. The mice were classified into four groups (8 mice each), control infected (CI), PZQ (300 mg/kg/12 h), ART (0.1 ml/mg/d) and PAE (50 mg/kg/d) treated groups for one month. All mice groups were sacrificed 15 weeks post infection for assessment of the drugs' efficacy by parasitological, histopathological and immunohistochemical studies. Our results in PAE group showed marked reduction in the mean egg count/gram stool, worm burden, egg count/gram liver tissue, granuloma diameter and pro-angiogenic factors as vascular endothelial growth factor (VEGF), Proliferating cell nuclear antigen (PCNA), alpha-smooth muscle actin (α-SMA) and CD34; conversely, there was an augmentation of the tissue inhibitor metalloproteinases-2 (TIMP-2) as an anti-angiogenic expression that was exceeded ART and PZQ treated groups compared to CI group (p˂0.001). Conclusively, PAE has an anti-angiogenic impact with no vascular proliferative activity or recanalization, no micro-vessel density (MVD) changes, granuloma resolution and fibrosis regression. PAE is predicted to be a potential therapy for chronic hepatic diseases associated with fibrosis and angiogenesis, hopeful in protecting from advanced serious complications; cancer and metastasis.

Antischistosomal Properties of Hederacolchiside A1 Isolated from Pulsatilla chinensis

Background: Schistosomiasis is a major neglected disease for which the current control strategy involves mass treatment with praziquantel, the only available drug. Hence, there is an urgent need to develop new antischistosomal compounds. Methods: The antischistosomal activity of hederacolchiside A1 (HSA) were determined by total or female worm burden reductions in mice harboring Schistosoma japonicum or S. mansoni. Pathology parameters were detected on HSA against 1-day-old S. japonicum-harboring mice. Moreover, we confirmed the antischistosomal effect of HSA on newly transformed schistosomula (NTS) of S. japonicum in vitro. Results: HSA, a natural product isolated from Pulsatilla chinensis (Bunge) Regel, was initially corroborated to possess promising antischistosomal properties. We demonstrated that HSA had high activity against S. japonicum and S. mansoni less in 11 days old parasites harbored in mice. The antischistosomal effect was even more than the currently used drugs, praziquantel, and artesunate. Furthermore, HSA could ameliorate the pathology parameters in mice harboring 1-day-old juvenile S. japonicum. We also confirmed that HSA-mediated antischistosomal activity is partly due to the morphological changes in the tegument system when NTS are exposed to HSA. Conclusions: HSA may have great potential to be an antischistosomal agent for further research.

Anti-angiogenic and anti-lymphangiogenic role of praziquantel and artemether in experimental mansoniasis

Angiogenesis is one of the pillars of neoplasia. Lymphangiogenesis in context of granulomas is not yet understood. This study aimed to evaluate the role of praziquantel (PZQ) and artemether (ART) as anti-angiogenic and anti-lymphangiogenic drugs in Schistosoma mansoni induced experimental hepatic model through immunohistochemical and serological studies, this can be used as a potential novel prophylactic approach in hepatic malignancy prevention and possible management. Forty female CD-1 Swiss albino mice were used divided into 4 groups (10 mice each); control healthy, control infected untreated, PZQ-treated and ART-treated. Angiogenic and lymphangiogenic effect of the drugs assessed pathologically through counting of the newly formed capillaries and lymphatics that immunohistochemically expressed by vascular Endothelial Growth Factor (VEGF), CD34 and D2-40 in liver sections using Cell Image Analyzer and serologically by evaluation of serum level of Tumor Necrosis Factor-Alpha (TNF-α). Our results showed significant decrease in serum TNF-α in ART-treated group compared to control infected and PZQ treated groups. ART exhibited significant anti-angiogenic role on granulomas illustrated by remarkable milder intensity and significantly lower expression values of VEGF and CD34 immunostaining compared to PZQ and non-treated groups. Also, ART treated group exhibited negative D2-40 expression in the granulomas in contrast to the other groups, supporting the potent ART' anti-lymphangiogenic role that exceeded PZQ. In conclusion, ART showed not only anti-angiogenic effect but also prominent anti-lymphangiogenic effect on hepatic S. mansoni granulomas compared to PZQ. Our study supports the potential use of ART as a potential novel prophylactic approach in hepatic malignancy prevention and possible management.

In vivo study of schistosomicidal action of 1-benzyl-4-[(4-fluoro-phenyl)-hydrazono]-5-thioxo-imidazolidin-2-one

Praziquantel has been the drug most widely used therapy against different forms of schistosomiasis around the world. However, this treatment has shown ineffective in humans and in experimental models of Schistosoma mansoni. New therapeutic alternatives have been tested, including the imidazolidine derivative LPSF/PT-09, which has shown high therapeutic potential in vitro. In this work, we tested the schistosomal activity of this derivative in doses of 250mg/kg and 200mg/kg in mice experimentally infected with a high parasite load of S. mansoni. Parasitological evaluations related to the number of S. mansoni worms and their oviposition were performed during the acute phase of the disease and have demonstrated moderate effectiveness of 30-54,4%. However, LPSF/PT-09 did not influence oviposition of the parasites or the embryonic development of the eggs. The results obtained in this model showed that the imidazolidine derivative LPSF/PT-09 presented significant antischistosomal activity in vivo, posing as a potential candidate for this class of drugs. However, a better understanding of the pharmacokinetics and pharmacodynamics of the imidazolidine derivative LPSF/PT-09 is needed.

Effect of Praziquantel on the Tegument and Digestive Epithelium Ultrastructure of Brachylaima sp. Metacercariae Parasitizing the Edible Land Snail Cornu aspersum

The edible land snail Cornu aspersum (Pulmonata: Stylommatophora) acts as second intermediate host in the cycle of Brachylaima sp. trematode, harboring free metacercariae in its kidney. The ingestion of undercooked infected snails by humans allows metacercariae to develop to adult stage in the intestine, causing brachylaimiasis. Praziquantel (PZQ) is the drug of choice to treat trematodiasis and it is effective against Brachylaima sp. metacercariae. The objective of this work was to assess, by transmission electron microscopy (TEM), the ultrastructural changes produced on the tegument and gastrodermis of the Brachylaima metacercariae recovered from C. aspersum treated with PZQ in comparison with untreated ones. Snails naturally infected by Brachylaima sp. metacercariae were treated by PZQ both individually and in groups. Metacercariae recovered from treated and control snails were processed for TEM. The tegument of untreated metacercariae was covered by a regular and thick glycocalyx. The syncytial epithelium contained abundant T2 secretory bodies appearing as membrane-bound biconcave disk-vesicles with high electron-dense and uniform content. The T2 secretory bodies located along the external area of the syncytium were mainly arranged at right angles to the apical plasma membrane. In treated metacercariae, the content of the T2 secretory bodies appeared altered, degenerating from high to low electron density, losing its uniform appearance and forming high electron-dense accumulations scattered around the periphery of the vesicle and separated by low electron-dense spaces. The presence of clusters was detectable in the central area. The characteristic arrangement of the T2 secretory bodies observed in untreated metacercariae was lost in treated ones. Vesicles near the apical area of the tegument no longer maintained their arrangement perpendicular to the apical plasma membrane. The characteristic arrangement of T2 secretory bodies and mitochondria was lost. The T2 secretory bodies were also found altered in the tegumental cell bodies, suggesting that the alterations started at the production stage. Mitochondria were severely degenerated and located in the apical area of the tegument. The digestive system displayed a strong contraction, which included the disappearance of the intracecal lumen.

Dose-response relationship in Schistosoma mansoni juvenile and adult stages following limonin treatment in experimentally infected mice

Preventive chemotherapy with praziquantel is the mainstay of schistosomiasis control. However, drug resistance is an imminent threat, particularly with large-scale administration of praziquantel, in addition to much less efficacy against young schistosomes. Several biological activities of limonin have been explored such as insecticidal, insect antifeedant, and growth-regulating activity on insects as well as antimalarial, antiviral, anticancer, cholesterol-lowering, and antioxidant activities. This study investigates limonin as an alternative antischistosomal compound using two novel, single, oral dose regimens. In the current work, the therapeutic efficacy of different limonin dosing protocols was evaluated in experimentally infected mice harboring Schistosoma mansoni (Egyptian strain) juvenile or adult stages. Oral administration of limonin in a single dose of 50 or 100 mg/kg on day 21 post-infection (p.i.) resulted in a significant worm burden reduction of 70.0 and 83.33 %, respectively. The same dose given on day 56 p.i. reduced total worm burdens by 41.09 and 60.27 %, respectively. In addition, significant reductions of 34.90 and 47.16 % in the hepatic and 46.67 and 56.1 % in the intestinal tissue egg loads, respectively, associated with significant alterations in the oogram pattern with elevated dead egg levels. Limonin produced ameliorations of hepatic pathology with reduction in dimensions and number of granulomas. Limonin also produced a variety of tegumental alterations in treated worms including tubercular disruption, edema, blebbing, and ulcerations. Results obtained by this work elucidated promising limonin bioactivity against S. mansoni juvenile and adult stages and provided a basis for subsequent experimental and clinical trials.

Efficacy of Synriam™, a new antimalarial combination of OZ277 and piperaquine, against different developmental stages of Schistosoma mansoni

Control of schistosomiasis relies on a single drug, praziquantel (PZQ). Given the rising concerns about the potential emergence of PZQ-resistant strains, it has now become necessary to search for novel therapeutics. However, the current pace for anti-schistosomal drug discovery is slow; hence, repositioning of existing approved drugs can offer a safe, rapid and cost-effective solution. The anti-malarial synthetic artemisinin-derivatives trioxolanes demonstrated anti-schistosomal efficacies against the three major species infecting humans and, unlike PZQ, showed activities against both juvenile and adult worm stages. The 1,2,4-trioxolane/OZ277 (arterolane maleate) in combination with a partner drug: piperaquine phosphate was recently developed as an anti-malarial drug and manufactured by Ranbaxy (India) as Synriam™ (SYN). Herein, the in vivo activities of SYN were investigated in a mouse model of Schistosoma mansoni (S. mansoni), compared to PZQ. We show that a single fixed dose of 240mg/kg SYN (40mg/kg arterolane and 200mg/kg piperaqine) induced significant protective effects in mice, in terms of reduction in worm and tissue egg burdens, which were evident against all schistosome developmental stages. Extensive alterations in the tegument and subtegumental tissues of SYN-exposed worms were revealed by both scanning and transmission electron microscopes. Progressive decrease in worm activity and occurrence of death were noticed in vitro upon exposure to the drug - more pronounced in the presence of haemin. This report provides the first evidence of the efficacy of a combination of 1,2,4-trioxolane and piperaquine against S. mansoni in mice. Being effective against young stages, SYN could be used to prevent early Schistosoma infection.

Transmission electron microscopic observations on ultrastructural alterations in Schistosoma mansoni adult worms recovered from C57BL/6 mice treated with radiation-attenuated vaccine and/or praziquantel in addition to passive immunization with normal and vaccinated rabbit sera against infection

Although the current treatment of schistosomiasis relies largely on praziquantel (PZQ), it has not been successful in significantly reducing the overall rate of disease cases, one of the suggested reasons being the inevitable resistance to PZQ. Previous studies showed that radiation-attenuated vaccine provides protection against Schistosoma mansoni in a host of 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. 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 of 43.03, 73.2, and 59.5 and 37.97, 52.02, and 26.3%, respectively. Furthermore, tegumental changes were observed. In multiple vaccinated group, there was an extensive lysis in tegumental layers. High deformations in gastrodermis, testis cells, vitelline cells, and oocytes were recorded. Also, this study is to explore the role of humoral immunity using highly resistant rabbits that had been exposed to three immunizations with ultraviolet (UV)-irradiated cercariae (8000 per rabbit in each immunization), and their sera were tested for their ability to transfer protection. The reduction in challenge worm burden had reached 32.76-43.64% when compared with recipients of normal serum or no serum. The reduction in hepatic and intestinal ova counts reached to 74.4 and 71.08% in group immunized with vaccinated rabbit sera. Swelling and extensive lysis of tegumental layers, gastrodermis lumen, spermatocytes, and deformation of oocytes were recorded with more severity than that recorded in normal rabbit sera group. Our findings recorded that multiple vaccination strategy is the most effective strategy then passive transfer of vaccinated rabbit. This gives guiding in the design the appropriate therapeutic strategy.

Natural products as leads in schistosome drug discovery

Schistosomiasis is a neglected parasitic tropical disease that claims around 200,000 human lives every year. Praziquantel (PZQ), the only drug recommended by the World Health Organization for the treatment and control of human schistosomiasis, is now facing the threat of drug resistance, indicating the urgent need for new effective compounds to treat this disease. Therefore, globally, there is renewed interest in natural products (NPs) as a starting point for drug discovery and development for schistosomiasis. Recent advances in genomics, proteomics, bioinformatics, and cheminformatics have brought about unprecedented opportunities for the rapid and more cost-effective discovery of new bioactive compounds against neglected tropical diseases. This review highlights the main contributions that NP drug discovery and development have made in the treatment of schistosomiasis and it discusses how integration with virtual screening (VS) strategies may contribute to accelerating the development of new schistosomidal leads, especially through the identification of unexplored, biologically active chemical scaffolds and structural optimization of NPs with previously established activity.

Phytol, a diterpene alcohol from chlorophyll, as a drug against neglected tropical disease Schistosomiasis mansoni

BACKGROUND

Schistosomiasis is a major endemic disease that affects hundreds of millions worldwide. Since the treatment and control of this parasitic disease rely on a single drug, praziquantel, it is imperative that new effective drugs are developed. Here, we report that phytol, a diterpene alcohol from chlorophyll widely used as a food additive and in medicinal fields, possesses promising antischistosomal properties in vitro and in a mouse model of schistosomiasis mansoni.

METHODS AND FINDINGS

In vitro, phytol reduced the motor activity of worms, caused their death and confocal laser scanning microscopy analysis showed extensive tegumental alterations in a concentration-dependent manner (50 to 100 µg/mL). Additionally, phytol at sublethal doses (25 µg/mL) reduced the number of Schistosoma mansoni eggs. In vivo, a single dose of phytol (40 mg/kg) administered orally to mice infected with adult S. mansoni resulted in total and female worm burden reductions of 51.2% and 70.3%, respectively. Moreover, phytol reduced the number of eggs in faeces (76.6%) and the frequency of immature eggs (oogram pattern) was significantly reduced. The oogram also showed increases in the proportion of dead eggs. Confocal microcopy studies revealed tegumental damage in adult S. mansoni recovered from mice, especially in female worms.

CONCLUSIONS

The significant reduction in parasite burden by this chlorophyll molecule validates phytol as a promising drug and offers the potential of a new direction for chemotherapy of human schistosomiasis. Phytol is a common food additive and nonmutagenic, with satisfactory safety. Thus, phytol has potential as a safe and cost-effective addition to antischistosomal therapy.

Fasciola gigantica: the in vitro effects of artesunate as compared to triclabendazole on the 3-weeks-old juvenile

The in vitro effect of artesunate (ATS) on the 3-week-old juveniles of Fasciola gigantica was compared with triclabendazole (TCZ) by incubating the parasites in M-199 medium containing the drugs at concentrations of 20, 40, and 80 μg/ml for 1, 3, 6, 12, and 24h. The anthelmintic activities of these drugs were evaluated based on the relative motility value (RM) and the alterations of the tegument as observed by scanning (SEM) and transmission (TEM) electron microscopy. The RM values of TCZ-treated flukes decreased significantly from 6 to 24h for all dosages. For ATS-treated flukes, RM value decreased markedly from 12 to 24h, but the rates of decline were less than TCZ at the same doses. When observed by SEM, the tegument showed similar sequence of morphological changes after treatments with both drugs, comprising of swelling of tegumental ridges, followed by blebbing and later rupturing of the blebs, leading to erosion and lesion, and disruption of the tegument. When examined by TEM, ultrastructural changes in the tegument and associated structures after treatments with TCZ and ATS were similar which comprised of swelling, blebbing of the tegument, dilation of basal infoldings, and depolymerization of the microtrabecular network. After a longer incubation time, the tegument was completely sloughed off and the tegument cell bodies became necrotic. Additionally, in ATS-treated flukes, mitochondria showed severe swelling, rupturing of outer membrane, and their interior filled with flocculent materials.

Structural changes of Schistosoma mansoni 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.

Antischistosomal activity of ginger (Zingiber officinale) against Schistosoma mansoni 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.

Bioactivity of miltefosine against aquatic stages of Schistosoma mansoni, Schistosoma haematobium and their snail hosts, supported by scanning electron microscopy

Background

Miltefosine, which is the first oral drug licensed for the treatment of leishmaniasis, was recently reported to be a promising lead compound for the synthesis of novel antischistosomal derivatives with potent activity in vivo against different developmental stages of Schistosoma mansoni. In this paper an in vitro study was carried out to investigate whether it has a biocidal activity against the aquatic stages of Schistosoma mansoni and its snail intermediate host, Biomphalaria alexandrina , thus being also a molluscicide. Additionally, to see whether miltefosine can have a broad spectrum antischistosomal activity, a similar in vitro study was carried out on the adult stage of Schistosoma haematobium, the second major human species, its larval stages and snail intermediate host, Bulinus truncutes. This was checked by scanning electron microscopy.

Results

Miltefosine proved to have in vitro ovicidal, schistolarvicidal and lethal activity on adult worms of both Schistosoma species and has considerable molluscicidal activity on their snail hosts. Scanning electron microscopy revealed several morphological changes on the different stages of the parasite and on the soft body of the snail, which further strengthens the current evidence of miltefosine's activity. This is the first report of mollusicidal activity of miltefosine and its in vitro schistosomicidal activity against S.haematobium.

Conclusions

This study highlights miltefosine not only as a potential promising lead compound for the synthesis of novel broad spectrum schistosomicidal derivatives, but also for molluscicidals.

Morphological effects and tegumental alterations induced by mefloquine on schistosomula and adult flukes of Schistosoma mansoni

There is a pressing need to develop novel anti-schistosomal drugs, as current treatment relies largely on praziquantel (PZQ). To further strengthen current evidence of the anti-schistosomal properties of mefloquine (MQ), we studied the temporal effect of this compound in vitro and in vivo, and examined alterations on the tegumental surface of schistosomula and adults of S. mansoni by means of scanning electron microscopy (SEM). Schistosomula and adults were each incubated in vitro using MQ over a wide concentration range (1-100 microg/ml). In addition, mice infected with adult S. mansoni were treated with a single oral dose of 400 mg/kg MQ, and worms were recovered 24, 48, 72, 96 and 120 h following treatment. MQ showed a rapid onset of action on schistosomula in vitro; 100 and 75 microg/ml of MQ killed schistosomula immediately; the minimal lethal and effective concentrations of MQ on schistosomula after 1 h were 25 and 5 microg/ml, respectively. Adult worms incubated with 100 and 10 microg/ml of MQ were dead after 1 h and 24 h of incubation, respectively. A hepatic shift of adult schistosomes was observed in mice already 24 h after treatment, and 120 h following treatment >98% of all worms had translocated to the liver. SEM observations revealed extensive tegumental destruction, including blebbing, shrinking and sloughing, particularly following in vitro incubation and on the tegument of female worms.

Prodrugs for the treatment of neglected diseases

Recently, World Health Organization (WHO) and Medicins San Frontieres (MSF) proposed a classification of diseases as global, neglected and extremely neglected. Global diseases, such as cancer, cardiovascular and mental (CNS) diseases represent the targets of the majority of the R&D efforts of pharmaceutical companies. Neglected diseases affect millions of people in the world yet existing drug therapy is limited and often inappropriate. Furthermore, extremely neglected diseases affect people living under miserable conditions who barely have access to the bare necessities for survival. Most of these diseases are excluded from the goals of the R&D programs in the pharmaceutical industry and therefore fall outside the pharmaceutical market. About 14 million people,mainly in developing countries, die each year from infectious diseases. From 1975 to 1999,1393 new drugs were approved yet only 1% were for the treatment of neglected diseases[3]. These numbers have not changed until now, so in those countries there is an urgent need for the design and synthesis of new drugs and in this area the prodrug approach is a very interesting field. It provides, among other effects, activity improvements and toxicity decreases for current and new drugs, improving market availability. It is worth noting that it is essential in drug design to save time and money, and prodrug approaches can be considered of high interest in this respect. The present review covers 20 years of research on the design of prodrugs for the treatment of neglected and extremely neglected diseases such as Chagas' disease (American trypanosomiasis), sleeping sickness (African trypanosomiasis), malaria, sickle cell disease, tuberculosis, leishmaniasis and schistosomiasis.

Schistosoma mekongi: the in vitro effect of praziquantel and artesunate on the adult fluke

The efficacy and tolerance of 80 microg/ml praziquantel (PZQ) and 40 microg/ml artesunate (ATS) against adult stage Schistosoma mekongi in vitro were investigated after 3, 6, 12, and 24h incubation by monitoring worm motility and compared tegumental changes using scanning electron microscopy (SEM). Thirty mice were infected with S. mekongi cercaria for 49 days. Adult worms were collected by perfusion method and prepared for in vitro study. Contraction and decreased motor activity were observed after as little as 3h incubation with PZQ and ATS. Some of the worms were immobile 12h after exposure, and died within 24h. The tegument of S. mekongi showed severe swelling, vacuolization and disruption, fusion of the tegumental ridges, collapse and peeling. After 12-24h incubation, PZQ induced similar but they less severe, tegumental changes to those observed after exposure to ATS. The direct observation of the fluke motility and SEM study suggest that ATS is more effective than PZQ in causing tegumental damage in adult S. mekongi, and provides a basis for subsequent clinical trials.

Praziquantel and albendazole damaging action on in vitro developing Mesocestoides corti (Platyhelminthes: Cestoda)

Parasitic flatworms present several steps of body architecture rearrangement during their fast transition from one developmental stage to another, which are, at least in part, responsible for their evasion from host immune response. Besides, different developmental stages present different degrees of susceptibility to drug action, and the identification of more susceptible stages is of importance for the definition of therapeutical approaches. Mesocestoides corti (syn. Mesocestoides vogae) is considered a good model to study cestode biology because it can be easily manipulated both in vivo and in vitro and due to its relatively close relationship to cestodes of medical relevance, such as those from genera Echinococcus or Taenia. We have analyzed the damaging action of two broad spectrum anthelmintic drugs (praziquantel and albendazole) throughout the in vitro strobilization process of M. corti in order to identify developmental stages or body structures more susceptible to these drugs. Tetrathyridia (larval stage) and segmented-induced worms were cultivated and treated with praziquantel and albendazole. Whole mounted samples, taken from different developmental stages, were fixed and stained with fluorophore-labeled WGA lectin and phalloidin for the analysis of tegument and muscles, respectively. Confocal laser scanning microscopy was used to identify anatomical changes and lesions caused by each anthelmintic drug in a 3D view. We demonstrated that both praziquantel and albendazole cause extensive tissue damage, especially on tegument, and that adult forms were the most susceptible to drug exposure.

Evaluation of the anthelmintic effects of artesunate against experimental Schistosoma mansoni infection in mice using different treatment protocols

The therapeutic effects of artesunate against experimental Schistosoma mansoni infection in mice were analyzed. Previous studies showed that artesunate is highly effective against S. japonicum infection, but the action of this drug against S. mansoni remained uncovered. The present study examines the optical conditions for artesunate against S. mansoni and evaluates the effects of inhibiting the sexual maturation of adult worms. Mice infected with S. mansoni were orally administered with artesunate according to different schedules. Four consecutive administrations of 300 mg/kg of artesunate at 2-week intervals conferred almost total protection without the development of pathological lesions in the liver. The significant reduction in the number of eggs produced by surviving worms and the status of egg maturation suggested that artesunate inhibits sexual maturation. Electron microscopy revealed that artesunate caused morphological damage, especially on the worm tegument. Artesunate was also very effective in iron-deficient mice. Furthermore, the efficacy of artesunate was equal to or better than that of artemether against S. japonicum infection. Considering that artemether is more toxic, artesunate is currently one of the most efficient drugs against immature S. mansoni.

Development of antischistosomal drugs in China, with particular consideration to praziquantel and the artemisinins

Remarkable achievements have been made in the control of schistosomiasis in China, with chemotherapy playing a seminal role. From the early 1950s through the early 1980s, Chinese scientists made considerable progress in discovery and development of compounds with antischistosomal properties, including antimonials, non-antimonials and various effective principles stemming from traditional herbs. However, only few compounds entered clinical testing, while others were abandoned mainly due to their toxicity and poor efficacy. The advent of praziquantel in the 1970s changed the landscape of research and development of drugs for treatment and morbidity control of schistosomiasis. The main Chinese contributions to enhance the understanding of the antischistosomal drug praziquantel are reviewed here, including issues of metabolism, antibody-dependency, host immune factors, stage-specific susceptibility and resistance. Over the past 25 years, researchers from China successfully developed artemether and artesunate, two derivatives from the antimalarial artemisinin, as promising drugs against Schistosoma japonicum. Laboratory investigations showed that the artemisinins display their highest activity against the juvenile stages of the parasite. These findings were consistently confirmed in randomised controlled trials; repeated oral administration of artemether or artesunate was safe and efficacious in the prevention of patent S. japonicum infections. The key findings are reviewed here, and emphasis is placed on how it stimulated research outside of China on other human schistosome species.

Eurytrema pancreaticum: the in vitro effect of praziquantel and triclabendazole on the adult fluke

The efficacy and tolerance of the 80 microg/ml praziquantel (PZQ) and 40 microg/ml triclabendazole (TCZ) against adult stage Eurytrema pancreaticum in vitro were investigated at 3, 12, and 15 h incubation. Motility of the flukes and histopathological changes were studied. Sudden paralysis and death were observed after exposed to PZQ as early as 3h incubation. In contrast, the TCZ treated flukes showed active mobility at all intervals. By light microscopic examination, severe damages in various organs such as tegument, muscle, and testes were observed early at 12h incubation of these drugs. PZQ caused more severe damage to flukes than TCZ. There were vigorous contraction of musculature, progressive shrinkage of circular and longitudinal muscles, vacuolization and disintegration of the tegument disrupting the worms' outer surface including detachment of spines in the PZQ treatment. The cells in testes were slightly increased in size and followed by degeneration leaving several hollow spaces. The uterus and vitelline glands remained unaffected. The direct observation of the fluke motility and light microscopic study highly suggested that PZQ was more effective than TCZ treatment for the eurytremiasis infection.