Open Source Drug Discovery with the Malaria Box Compound Collection for Neglected Diseases and Beyond.

A major cause of the paucity of new starting points for drug discovery is the lack of interaction between academia and industry. Much of the global resource in biology is present in universities, whereas the focus of medicinal chemistry is still largely within industry. Open source drug discovery, with sharing of information, is clearly a first step towards overcoming this gap. But the interface could especially be bridged through a scale-up of open sharing of physical compounds, which would accelerate the finding of new starting points for drug discovery. The Medicines for Malaria Venture Malaria Box is a collection of over 400 compounds representing families of structures identified in phenotypic screens of pharmaceutical and academic libraries against the Plasmodium falciparum malaria parasite. The set has now been distributed to almost 200 research groups globally in the last two years, with the only stipulation that information from the screens is deposited in the public domain. This paper reports for the first time on 236 screens that have been carried out against the Malaria Box and compares these results with 55 assays that were previously published, in a format that allows a meta-analysis of the combined dataset. The combined biochemical and cellular assays presented here suggest mechanisms of action for 135 (34%) of the compounds active in killing multiple life-cycle stages of the malaria parasite, including asexual blood, liver, gametocyte, gametes and insect ookinete stages. In addition, many compounds demonstrated activity against other pathogens, showing hits in assays with 16 protozoa, 7 helminths, 9 bacterial and mycobacterial species, the dengue fever mosquito vector, and the NCI60 human cancer cell line panel of 60 human tumor cell lines. Toxicological, pharmacokinetic and metabolic properties were collected on all the compounds, assisting in the selection of the most promising candidates for murine proof-of-concept experiments and medicinal chemistry programs. The data for all of these assays are presented and analyzed to show how outstanding leads for many indications can be selected. These results reveal the immense potential for translating the dispersed expertise in biological assays involving human pathogens into drug discovery starting points, by providing open access to new families of molecules, and emphasize how a small additional investment made to help acquire and distribute compounds, and sharing the data, can catalyze drug discovery for dozens of different indications. Another lesson is that when multiple screens from different groups are run on the same library, results can be integrated quickly to select the most valuable starting points for subsequent medicinal chemistry efforts.

Immune system development during early childhood in tropical Latin America: evidence for the age-dependent down regulation of the innate immune response.

The immune response that develops in early childhood underlies the development of inflammatory diseases such as asthma and there are few data from tropical Latin America (LA). This study investigated the effects of age on the development of immunity during the first 5 years of life by comparing innate and adaptive immune responses in Ecuadorian children aged 6-9 months, 22-26 months, and 48-60 months. Percentages of naïve CD4+ T cells declined with age while those of memory CD4(+) and CD8(+) T cells increased indicating active development of the immune system throughout the first five years. Young infants had greater innate immune responses to TLR agonists compared to older children while regulatory responses including SEB-induced IL-10 and percentages of FoxP3(+) T-regulatory cells decreased with age. Enhanced innate immunity in early life may be important for host defense against pathogens but may increase the risk of immunopathology.

Soil-transmitted helminthiasis in rural south-west China: prevalence, intensity and risk factor analysis.

Only few studies in rural China have explored the epidemiology of intestinal helminth infections and identified risk factors for transmission. The study was carried out in Simao and Mengla counties, where single fecal samples were collected from 317 school-aged children and from 94 inhabitants of a single village. Fecal specimens were examined with the Kato-Katz thick smear method and examined for helminth eggs. Data regarding socio-demographic and behavioral risk factors were collected using questionnaires. In Simao County the overall soil-transmitted helminthes (STH) prevalence was 40.2% (2.7, 5.4 and 35.7% for ascariasis, trichuriasis and hookworm infection, respectively). The STH infection rates were significantly higher in Mengla County, with an overall prevalence of 68.3% (19.0, 34.6 and 47.3% for ascariasis, trichuriasis and hookworm infection, respectively). Females were less likely to be infected with Trichuris trichiura (OR 0.29; 95% CI 0.15-0.56) and with hookworms (OR 0.55; 95% CI 0.33-0.93) than males. Hookworm infections were more prevalent among those 12 years of age or older (OR 2.9; 95% CI 1.2-7.1). Children of mothers with educational attainment of secondary school or higher had a protective effect against T. trichiura (OR 0.18; 95% CI 0.06-0.54) and hookworm (OR 0.21; 95% CI 0.09-0.51) infections. In the village survey, hookworm was the most prevalent species (62.8%) with infection seen in those 50 years of age and older. Based on recommended intervention strategies by the World Health Organization, Simao County should opt for school-based deworming once each year, while Mengla County should implement a similar strategy biannually, but should include the elderly population.

The discovery of a novel series of compounds with single-dose efficacy against juvenile and adult Schistosoma species.

Treatment and control of schistosomiasis depends on a single drug, praziquantel, but this is not ideal for several reasons including lack of potency against the juvenile stage of the parasite, dose size, and risk of resistance. We have optimised the properties of a series of compounds we discovered through high throughput screening and have designed candidates for clinical development. The best compounds demonstrate clearance of both juvenile and adult S. mansoni worms in a mouse model of infection from a single oral dose of < 10 mg/kg. Several compounds in the series are predicted to treat schistosomiasis in humans across a range of species with a single oral dose of less than 5 mg/kg.

Locally up-regulated lymphotoxin alpha, not systemic tumor necrosis factor alpha, is the principle mediator of murine cerebral malaria.

Cerebral malaria (CM) causes death in children and nonimmune adults. TNF-alpha has been thought to play a key role in the development of CM. In contrast, the role of the related cyto-kine lymphotoxin alpha (LTalpha) in CM has been overlooked. Here we show that LTalpha, not TNFalpha, is the principal mediator of murine CM. Mice deficient in TNFalpha (B6.TNFalpha-/-) were as susceptible to CM caused by Plasmodium berghei (ANKA) as C57BL/6 mice, and died 6 to 8 d after infection after developing neurological signs of CM, associated with perivascular brain hemorrhage. Significantly, the development of CM in B6.TNFalpha-/- mice was not associated with increased intracellular adhesion molecule (ICAM)-1 expression on cerebral vasculature and the intraluminal accumulation of complement receptor 3 (CR3)-positive leukocytes was moderate. In contrast, mice deficient in LTalpha (B6.LTalpha-/-) were completely resistant to CM and died 11 to 14 d after infection with severe anemia and hyperparasitemia. No difference in blood parasite burden was found between C57BL/6, B6.TNFalpha-/-, and B6.LTalpha-/- mice at the onset of CM symptoms in the two susceptible strains. In addition, studies in bone marrow (BM) chimeric mice showed the persistence of cerebral LTalpha mRNA after irradiation and engraftment of LTalpha-deficient BM, indicating that LTalpha originated from a radiation-resistant cell population.

Praziquantel analogs with activity against juvenile Schistosoma mansoni.

Six amide and four urea derivatives of praziquantel were synthesized and tested for antischistosomal activity against juvenile and adults stages of Schistosoma mansoni in infected mice. Only one of these had significant activity against adult worms, but, unlike praziquantel, six of these had low to modest activity against juvenile worms. A praziquantel ketone derivative had the best combination of activity against juveniles and adults, but it had no effect on the motility of adult S. mansoni in ex vivo culture. Cytochrome P450 metabolic stability data support the hypothesis that the major trans-cyclohexanol metabolite of praziquantel plays an important role in the antischistosomal activity of this drug.

Antiprotozoal and antihelminthic properties of plants ingested by wild Japanese macaques (Macaca fuscata yakui) in Yakushima Island.

ETHNOPHARMACOLOGICAL RELEVANCE: Primates forage on a variety of plant parts to balance their dietary intake to meet requirements of energy, nutrition and maintenance, however the reason(s) leading them to ingest some plants which have no nutritional value and/or contain bioactive or even toxic secondary metabolites is recently gaining closer attention. The growing literature suggests that primates consume plants for medicinal purposes (self-medication) as well, particularly when infected with parasites and pathogens (bacteria, viruses, microbes). Interestingly, some of the plants they consume are also used by humans for similar purposes or may have potential uses for humans. MATERIALS AND METHODS: As part of a 16-month study of the parasite ecology of a sub-species of Japanese macaques (Macaca fuscata yakui) on the island of Yakushima, we surveyed their feeding habits and collected a subset of plants and plant parts observed being ingested by macaques. The ethnomedicinal value of these plants was surveyed and methanolic extracts of 45 plant parts were tested in vitro against important parasites of humans, including four protozoan parasites Plasmodium falciparum, Trypanosoma brucei rhodesiense, T. cruzi and Leishmania donovani, and the trematode flatworm Schistosoma mansoni. Potential toxicity of the extracts was also assessed on mammalian cells. RESULTS: A wide range of ethnomedicinal uses in Asia for these plants is noted, with 37% associated with the treatment of parasites, pathogens and related symptoms. Additionally, the 45 extracts tested showed broad and significant activity against our test organisms. All extracts were active against T. b. rhodesiense. The majority (over 80%) inhibited the growth of P. falciparum and L. donovani. Half of the extracts also displayed antiprotozoal potential against T. cruzi while only several extracts were active against both larval and adult stages of S. mansoni. Cytotoxicity was generally low, although several extracts lacked specific toxicity to test parasites. CONCLUSIONS: Our results indicated a number of plants and their parts to have antiparasitic activity not previously reported in the ethnopharmacological literature. Enhanced understanding of the primate diets, particularly during periods of intensified parasite infection risk may help to further narrow down plants of interest for lead compound development. The study of animal self-medication is a complementary approach, with precedence, to drug discovery of new lead drug compounds against human parasitic diseases.

Adjusting for the acute phase response is essential to interpret iron status indicators among young Zanzibari children prone to chronic malaria and helminth infections.

The extent to which the acute phase response (APR) influences iron status indicators in chronic infections is not well documented. We investigated this relationship using reported recent fever and 2 acute phase proteins (APP), C-reactive protein (CRP), and alpha-1-acid glycoprotein (AGP). In a sample of 690 children matched on age and helminth infection status at baseline, we measured plasma for AGP, CRP, ferritin, transferrin receptor (TfR), and erythropoietin (EPO) and whole blood for hemoglobin (Hb) concentration, zinc protoporphyrin (ZPP), and malaria parasite density, and we obtained maternal reports of recent fever. We then examined the influence of the APR on each iron status indicator using regression analysis with Hb as the outcome variable. Ferritin was inversely related to Hb in the APR-unadjusted model. Adjusting for the APR using reported recent fever alone was not sufficient to reverse the inverse Hb-ferritin relationship. However, using CRP and/or AGP resulted in the expected positive relationship. The best fit model included reported recent fever, AGP and CRP (R(2) = 0.241; P < 0.001). The best fit Hb-ZPP, Hb-TfR, and Hb-EPO models included reported recent fever and AGP but not CRP (R(2) = 0.253, 0.310, and 0.292, respectively; P < 0.001). ZPP, TfR, and EPO were minimally influenced by the APR, whereas ferritin was immensely affected. Reported recent fever alone cannot be used as a marker for the APR. Either AGP or CRP is useful for adjusting if only 1 APP can be measured. However, AGP best predicted the APR in this population.

Chronic intestinal nematode infection exacerbates experimental Schistosoma mansoni infection.

Mixed-parasite infections are common in many parts of the world, but little is known of the effects of concomitant parasite infections on the immune response or on disease progression. We have investigated the in vivo effects of a chronic gastrointestinal nematode infection on the infectivity and development of the immune response against the common trematode helminth Schistosoma mansoni. The data show that mice carrying an established chronic Trichuris muris infection and coinfected with S. mansoni, had significantly higher S. mansoni worm burdens than mice without coinfection. The increase in S. mansoni worm burden was accompanied by a higher egg burden in the liver. Kinetic analysis of S. mansoni establishment indicate reduced trapping of S. mansoni larvae during skin-to-lung migration, with T. muris-induced alterations in lung cytokine expression and inflammatory foci surrounding lung-stage schistosomula, suggesting that the immunomodulatory effects of chronic T. muris infection elicited at the gut mucosal surface extend to other organs and perhaps specifically to other mucosal surfaces. The data show that a preexisting chronic gastrointestinal nematode infection facilitates the survival and migration of S. mansoni schistosomula to the portal system, and as a result, increases the egg burden and associated pathology of S. mansoni infection.

Meclonazepam analogues as potential new antihelmintic agents.

New analogues of the potent antihelmintic meclonazepam were prepared and evaluated against Schistosoma mansoni. The biological data suggests substitution at positions 2 and 4 of meclonazepam could provide promising analogues for prophylactic and therapeutic activity against S. mansoni.

Characterization of beta-tubulin genes in hookworms and investigation of resistance-associated mutations using real-time PCR.

Human hookworms (Ancylostoma duodenale, Necator americanus) are a major cause of malnutrition and anemia, particularly in children, and high worm burdens can lead to stunted growth and mental retardation. Mass drug administration (MDA) with benzimidazole (BZ) anthelmintics has the potential to greatly reduce morbidity and infection prevalence. However, such treatment strategies may apply significant selection pressure on resistance alleles. In several Strongylid parasites of livestock, resistance to BZ drugs is associated with single nucleotide polymorphisms (SNPs) in the beta-tubulin isotype-1 gene at codons 167 and 200. As an initial investigation into the possible development of BZ resistance in hookworms, we have cloned and sequenced the beta-tubulin isotype-1 genes of the canine hookworm Ancylostoma caninum and the two human hookworm species A. duodenale and N. americanus. The genomic sequences are highly conserved as evidenced by a similar structure of exons and introns; the 10 exons are of the same length in all three species and code for the same amino acids. The genomic sequences were then used to develop a real-time PCR assay for detecting polymorphisms in codons 167 and 200 in all three species. Hookworm specimens previously obtained from Pemba Island school children who had demonstrated a reduced response to treatment with mebendazole were then examined using the real-time PCR assay. None of the samples revealed significant levels of polymorphisms at these loci. If BZ resistance is present in the hookworm populations examined, the results do not support the hypothesis that changes in codons 167 and 200 of beta-tubulin isotype-1 are responsible for any resistance.

A comparison of methods for detecting the eggs of Ascaris, Trichuris, and hookworm in infant stool, and the epidemiology of infection in Zanzibari infants.

This study compared five methods for detecting the eggs of the human parasitic geohelminths Ascaris, Trichuris, and hookworm in infant stool, and describes the epidemiology of infection in infants from a parasite-endemic area. A total of 424 infants 5-11 months old were enrolled from three villages on Pemba Island, Zanzibar. Methods used included the Kato-Katz technique, formol ethyl acetate sedimentation, modified formol ethyl acetate sedimentation, modified Wisconsin floatation, and simple gravity sedimentation. Of methods used alone, Wisconsin floatation and simple gravity sedimentation each provided the highest sensitivity for detecting eggs of these three geohelminths (89.6%). Of methods used in combination, the Kato-Katz technique/simple gravity sedimentation and Wisconsin floatation/simple gravity sedimentation each provided the highest sensitivity (99.0%). Prevalence of geohelminth infection was 26.5%. Between five and nine months of age the mean prevalence was 9.4%, while at 10 and 11 months of age the mean prevalence was 43.4%. Village prevalence varied from 3.6% to 43.8%. Infant geohelminth infection can occur at a high prevalence, and what method is best depends on research specifics.

Gastrointestinal nematode infection is associated with variation in innate immune responsiveness.

Ex vivo monocyte cytokine responses (IL-1beta, TNF-alpha, IL-12p70, IL-10, TGF-beta) to bacterial TLR2 and TLR4 ligands were quantified in 47 gastrointestinal (GI) nematode-exposed children in Pemba Island, Tanzania. Worminess (estimated by faecal egg counts (FEC)) had a positive relationship with pro-inflammatory TNF-alpha and IL-1beta responsiveness to the TLR ligands. In particular, there was a strong significant relationship with TNF-alpha response to TLR4 ligand (LPS). There were no significant associations between regulatory responses (IL-10, TGF-beta) and worminess. These results are consistent with the possibility that GI nematodes modulate innate responses and may indicate a potential mechanism for interactions between GI nematodiasis and important bystander pathogens.

High Throughput Screening Identifies Novel Lead Compounds with Activity against Larval, Juvenile and Adult Schistosoma mansoni.

An estimated 600 million people are affected by the helminth disease schistosomiasis caused by parasites of the genus Schistosoma. There is currently only one drug recommended for treating schistosomiasis, praziquantel (PZQ), which is effective against adult worms but not against the juvenile stage. In an attempt to identify improved drugs for treating the disease, we have carried out high throughput screening of a number of small molecule libraries with the aim of identifying lead compounds with balanced activity against all life stages of Schistosoma. A total of almost 300,000 compounds were screened using a high throughput assay based on motility of worm larvae and image analysis of assay plates. Hits were screened against juvenile and adult worms to identify broadly active compounds and against a mammalian cell line to assess cytotoxicity. A number of compounds were identified as promising leads for further chemical optimization.

Development of the egg hatch assay for detection of anthelminthic resistance in human hookworms.

Evidence of development and rapid spread of anthelminthic resistance in veterinary nematodes raises concern that the increasingly frequent treatments used in chemotherapy-based programmes to control human soil-transmitted helminths may select resistant worms. The aim of this study was to adapt, refine, and evaluate the Egg Hatch Assay (EHA) test, which has been used for veterinary nematodes, for field testing of benzimidazole (BZ) susceptibility/resistance in human hookworms. A second objective was to use this EHA to assess whether a population of worms resistant to mebendazole (MBZ) has built up in a sub-population of frequently treated children in Pemba Island. Stools from 470 school children enrolled in the first (Standard 1) and in the fifth (Standard 5) class were examined at baseline and at 21 days after treatment with 500 mg MBZ or placebo tablets. Standard 1 children had never received any MBZ treatment whilst Standard 5 children had received a total of 13 rounds of treatment. The EHA, involving culture of purified eggs with increasing drug concentrations showed that, for thiabendazole (TBZ), the mean ED(50)s (concentrations required to prevent 50% of the viable eggs from hatching) for all children at baseline were 0.079 microg/ml at 48h and 0.120 microg/ml at 72h (P<0.001). For MBZ, the mean ED(50)s for all children at baseline were 0.895 microg/ml at 48h and 1.50 microg/ml at 72h (P<0.001). For TBZ and for MBZ the ED(50) from Standard 1 were similar to those from Standard 5 children both at 48 and at 72h. At the follow-up for TBZ and for MBZ, there was no significant difference between the ED(50) from children who had received MBZ and children treated with placebo. In Pemba, TBZ ED(50) values of children non-exposed (Standard 1) and of children exposed (Standard 5) to MBZ treatment, and data from children treated with MBZ and placebo indicate that a drug-resistant worm population has not built up within treated individuals, and that periodic treatment has not yet selected for widespread BZ resistance, at least at the threshold detectable by the EHA in this study. However, ED(50) values for strains isolated from Mafia island, an area never exposed to BZ treatment were lower than for Pemba, suggesting lowered sensitivity of hookworm eggs recovered from Pembian children towards BZ.

Application of RNAi to Genomic Drug Target Validation in Schistosomes.

Concerns over the possibility of resistance developing to praziquantel (PZQ), has stimulated efforts to develop new drugs for schistosomiasis. In addition to the development of improved whole organism screens, the success of RNA interference (RNAi) in schistosomes offers great promise for the identification of potential drug targets to initiate drug discovery. In this study we set out to contribute to RNAi based validation of putative drug targets. Initially a list of 24 target candidates was compiled based on the identification of putative essential genes in schistosomes orthologous of C. elegans essential genes. Knockdown of Calmodulin (Smp_026560.2) (Sm-Calm), that topped this list, produced a phenotype characterised by waves of contraction in adult worms but no phenotype in schistosomula. Knockdown of the atypical Protein Kinase C (Smp_096310) (Sm-aPKC) resulted in loss of viability in both schistosomula and adults and led us to focus our attention on other kinase genes that were identified in the above list and through whole organism screening of known kinase inhibitor sets followed by chemogenomic evaluation. RNAi knockdown of these kinase genes failed to affect adult worm viability but, like Sm-aPKC, knockdown of Polo-like kinase 1, Sm-PLK1 (Smp_009600) and p38-MAPK, Sm-MAPK p38 (Smp_133020) resulted in an increased mortality of schistosomula after 2-3 weeks, an effect more marked in the presence of human red blood cells (hRBC). For Sm-PLK-1 the same effects were seen with the specific inhibitor, BI2536, which also affected viable egg production in adult worms. For Sm-PLK-1 and Sm-aPKC the in vitro effects were reflected in lower recoveries in vivo. We conclude that the use of RNAi combined with culture with hRBC is a reliable method for evaluating genes important for larval development. However, in view of the slow manifestation of the effects of Sm-aPKC knockdown in adults and the lack of effects of Sm-PLK-1 and Sm-MAPK p38 on adult viability, these kinases may not represent suitable drug targets.

Evaluation of the efficacy of pyrantel-oxantel for the treatment of soil-transmitted nematode infections.

A randomized controlled trial comparing the efficacy of pyrantel-oxantel (10 mg/kg) with mebendazole (500 mg) was performed on 1329 schoolchildren aged 6-9 years on Pemba Island in September-October 2000 to evaluate alternative single-dose drugs for regular treatment of intestinal nematode infections. Both mebendazole and pyrantel-oxantel were very effective in eliminating Ascaris lumbricoides infection, inducing cure rates of more than 96% and reducing the mean egg counts by more than 95%. Both drugs had a moderate efficacy against Trichuris trichiura infection, but pyrantel-oxantel had a higher cure rate (31.5% vs. 23.3%, P < 0.01), though the reductions in egg counts did not differ significantly and were more than 80%. Pyrantel-oxantel and mebendazole had a similar, poor efficacy in curing hookworm infections and had a moderate effect in reducing the egg counts by 67% and 68%, respectively. Pyrantel-oxantel (10 mg/kg) offers a valuable alternative to mebendazole as a single-dose treatment for the control of intestinal nematode infections in children in endemic areas of sub-Saharan Africa, due to its comparable efficacy, its low cost and its suitability for use in young children.

Do shoes reduce hookworm infection in school-aged children on Pemba Island, Zanzibar? A pragmatic trial.

BACKGROUND: A non-blinded, cluster randomised controlled trial to test whether footwear reduces prevalence and intensity of hookworm infection in school-aged children on Pemba Island, Zanzibar. METHODS: Six schools were randomised to receive shoes and standard care (deworming with albendazole and health education) and six control schools to receive standard care only. Children provided a stool sample to assess prevalence and intensity of infection with soil transmitted helminthiases (Ascaris lumbricoides, Trichuris trichiura and hookworm). Shoes were then distributed to pupils in the intervention schools; deworming took place as part of the government's mass drug administration programme and a further round of stool samples were collected six months later. RESULTS: Nine hundred and fifteen children were traced at follow-up (1056 at baseline). As many children wore shoes in the control arm as the intervention arm. There was no difference in hookworm prevalence (23.4% for intervention schools, 21.3% for control schools, p=0.48), and no difference in mean hookworm infection in eggs/gram of stool (18, 1-36 in intervention schools, 18, 7-29 in control schools, p=0.23). Shoe-wearing increased across all schools, from 47.4 to 82.4%. If a child wore shoes at the end of the study, the relative risk of hookworm infection was 0.7 (CI 0.53-0.91). CONCLUSION: Due to contamination, the trial could not conclude that shoes were protective against hookworm infection but the intervention led to behavioural change, and observational data suggest that shoes are protective against hookworm. This trial is registered at ClinicalTrials.gov, NCT01869127.

Orally active antischistosomal early leads identified from the open access malaria box.

BACKGROUND: Worldwide hundreds of millions of schistosomiasis patients rely on treatment with a single drug, praziquantel. Therapeutic limitations and the threat of praziquantel resistance underline the need to discover and develop next generation drugs. METHODOLOGY: We studied the antischistosomal properties of the Medicines for Malaria Venture (MMV) malaria box containing 200 diverse drug-like and 200 probe-like compounds with confirmed in vitro activity against Plasmodium falciparum. Compounds were tested against schistosomula and adult Schistosoma mansoni in vitro. Based on in vitro performance, available pharmacokinetic profiles and toxicity data, selected compounds were investigated in vivo. PRINCIPAL FINDINGS: Promising antischistosomal activity (IC50: 1.4-9.5 µM) was observed for 34 compounds against schistosomula. Three compounds presented IC50 values between 0.8 and 1.3 µM against adult S. mansoni. Two promising early leads were identified, namely a N,N'-diarylurea and a 2,3-dianilinoquinoxaline. Treatment of S. mansoni infected mice with a single oral 400 mg/kg dose of these drugs resulted in significant worm burden reductions of 52.5% and 40.8%, respectively. CONCLUSIONS/SIGNIFICANCE: The two candidates identified by investigating the MMV malaria box are characterized by good pharmacokinetic profiles, low cytotoxic potential and easy chemistry and therefore offer an excellent starting point for antischistosomal drug discovery and development.

Performance and safety of praziquantel for treatment of intestinal schistosomiasis in infants and preschool children.

BACKGROUND: In 2012 the WHO formally recognised that infants and preschool children are at significant risk of schistosomiasis and qualify for treatment with praziquantel (PZQ). Targeted surveys determining both the performance and safety of this drug are now needed in endemic areas. We have formally assessed parasitological cure and putative side-effects in a prospective cohort of Schistosoma mansoni-infected children (aged 5 months-7 years old) in lakeshore settings of Uganda. METHODOLOGY/PRINCIPAL FINDINGS: From a total of 369 children found to be egg-patent for intestinal schistosomiasis, 305 were followed-up three to four weeks after PZQ treatment and infection status re-assessed. Separately, a previously tested side-effect questionnaire was employed before and 24 hours after PZQ treatment to assess incidence and amelioration of symptoms in young children and their mothers. While the overall observed parasitological cure was 56.4%, a significant difference was found between a sub-set of children who had a history of multiple PZQ treatments (between one and four in an 18 month period), where cure rate was 41.7%, and those who had never received treatment (cure rate was 77·6%). PZQ proved to be safe, with only mild reported side effects which cleared within a month after treatment. Prevalence of reported symptoms was significantly lower in children than in mothers, and fewer side-effects were reported upon subsequent rounds of PZQ treatment. CONCLUSION/SIGNIFICANCE: Our findings show that PZQ treatment of young children resulted in satisfactory cure rates, and marked reduction in egg-output, with only mild and transient reported side-effects. However, the cure rate is clearly lower in younger children and those with history of previous treatment. Cure rate, but not egg reduction rate, was also lower in children with heavier pre-intervention infection intensity. With chemotherapy now recommended as a long-term strategy for disease control in young children, research into optimising the periodicity of targeted treatment strategies is now crucial.