A research agenda for helminth diseases of humans: intervention for control and elimination

Arthrospira platensis nanoparticles dietary supplementation improves growth performance, steroid hormone balance, and reproductive productivity of Nile tilapia (Oreochromis niloticus) broodstock

This study evaluates the impact of dietary supplementation of the blue-green alga Arthrospira platensis NIOF17/003 nanoparticles (AN) on the growth performance, whole-body biochemical compositions, blood biochemistry, steroid hormonal, and fry production efficiency of Nile tilapia (Oreochromis niloticus) broodstock, during the spawning season. After a 21-day preparation period to equip the females and ensure that their ovaries were filled with eggs, mating between the mature females and males took place in a 3:1 ratio during a 14-day spawning cycle. A total of 384 tilapia broodstock 288 females and 96 males with an initial body weight of 450.53±0.75, were divided into four groups; AN0: a basal diet as a control group with no supplementation of Arthrospira platensis, and the other three groups (AN2, AN4, and AN6) were diets supplemented with nanoparticles of A. platensis at levels of 2, 4, and 6 g kg─1 diet, respectively. The results found that fish-fed group AN6 showed the highest significant differences in weight gain (WG), final weight (FW), feed conversion ratio (FCR), protein efficiency ratio (PER), and feed efficiency ratio (FER). Females fed the AN6 diet showed the highest significant fat content. Compared to the AN0 group, fish fed on the supplemented diets showed significant improvement (p < 0.05) in triglyceride, glucose, and aspartate aminotransferase (AST). A gradual increase in AN inclusion level resulted in a gradual increase in the concentrations of luteinizing hormone (LH), and follicle-stimulating hormone (FSH), testosterone, progesterone, and prolactin. The rates (%) of increase in fry production for females fed supplemented diets were 10.5, 18.6, and 32.2% for AN2, AN4, and AN6, respectively, compared to the control group. This work concluded that the inclusion levels of 6 g kg─1 of A. platensis nanoparticles in the diet of Nile tilapia broodstock significantly improved the growth performances, steroid hormone concentrations, and increased the fry production efficiency by 32.2%, respectively. These findings revealed that A. platensis nanoparticles resulted in a significantly enhanced female' reproductive productivity of Nile tilapia broodstock.

Intestinal parasitic infections in children from marginalised Roma communities: prevalence and risk factors

BACKGROUND

Intestinal parasitic infections remain a significant global health issue, particularly affecting poor and marginalised populations. These infections significantly contribute to children's diseases, malnutrition, poor school performance, cognitive disorders, and future economic losses. This study aimed to explore and compare the occurrence of intestinal parasites in early childhood among the group of infants from the Slovak majority population and from marginalised Roma communities (MRCs). Furthermore, it aimed to explore the health complaints of children with and without intestinal parasitic infection in the past month and assess the effect of various risk factors on the occurrence of intestinal parasitic infection in infants from MRCs.

METHODS

We obtained cross-sectional data from mothers and stool samples of their children aged 13-21 months using the first wave of the longitudinal RomaREACH study. A total of 181 stools from infants were analysed: 105 infants from the Slovak majority population and 76 from MRCs.

RESULTS

Infants from MRCs are significantly more often infected by Ascaris lumbricoides, Trichuris trichiura and Giardia duodenalis than their better-off peers from the majority population. Infection rates are 30% in infants from MRCs vs. 0% in the majority population (p < 0.001). Single and mixed infections were observed in children from MRCs. Infants with intestinal parasitic infections suffer significantly more often from various health complaints, particularly cough, stomach ache, irritability, and diarrhoea. Within MRCs, the risk of parasitic infections in infants is significantly increased by risk factors such as the absence of flushing toilets in households (OR = 4.17, p < 0.05) and contact with un-dewormed animals (OR = 3.61, p < 0.05). Together with the absence of running water in the household, these three factors combined increase the risk more than ten times (p < 0.01).

CONCLUSION

Maintaining hygienic standards in conditions of socioeconomic deprivation in MRCs without running water and sewage in the presence of un-dewormed animals is problematic. These living conditions contribute to the higher prevalence of parasitic infections in children from MRCs, causing various health complaints and thus threatening their health and healthy development.

The response of Anisakis simplex (s. s.) to anthelmintics - Specific changes in xenobiotic metabolic processes

Anisakiasis is a parasitic disease transmitted through the consumption of raw or undercooked fish and cephalopods that are infected with larvae of Anisakis simplex (sensu stricto) or Anisakis pegreffii. The purpose of this study was to investigate how A. simplex (s. s.) responds to the influence of anthelmintics such as ivermectin (IVM) and pyrantel (PYR). In vitro experiments were conducted using larvae at two developmental stages of A. simplex (s. s.) (L3 and L4) obtained from Baltic herring (Clupea harengus membras). Larvae were cultured with different concentrations of IVM or PYR (1.56, 3.125, and 6.25 μg/mL) for various durations (3, 6, 9, and 12 h) under anaerobic conditions (37 °C, 5% CO2). The gene expression of actin, ABC transporter, antioxidant enzymes, γ-aminobutyric acid receptors, and nicotinic acetylcholine receptors, as well as the oxidative status were analyzed. The results showed that A. simplex (s. s.) L3 stage had lower mobility when cultured with PYR compared to IVM. The analysis of relative gene expression revealed significant differences in the mRNA level of ABC transporters after treatment with IVM and PYR, compared to the control group. Similar patterns were observed in the gene expression of antioxidant enzymes in response to both drugs. Furthermore, the total antioxidant capacity (TAC) and glutathione S-transferase (GST) activity were higher in the treatment groups than in the control group. These findings suggest a relationship between the expression of the studied genes, including those related to oxidative metabolism, and the effectiveness of the tested drugs.

Role of cytokines in immunomodulation during malaria clearance

Malaria remains a significant global health challenge, demanding a deeper understanding of host immune responses for effective clearance of the parasitic infection. Cytokines, as crucial mediators of the immune system, orchestrate a complex interplay during the various stages of malaria infection. Throughout the course of the disease, an intricate balance of pro-inflammatory and anti-inflammatory cytokines dictate the immune response's outcome, influencing parasitic clearance and disease severity. During the initial stages, interleukins such as interleukin-12 (IL-12), interferon-gamma (IFN-γ), and tumour necrosis factor-alpha (TNF-α) play pivotal roles in activating innate immune cells, initiating the anti-parasitic response. Simultaneously, regulatory cytokines like interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β) modulate this immune activation, preventing excessive inflammation and tissue damage. As the infection progresses, a delicate shift occurs, characterized by a transition to adaptive immunity, guided by cytokines like interleukin-4 (IL-4), interleukin-5 (IL-5), and interleukin-13 (IL-13), promoting antibody production and T-cell responses. Notably, the resolution of malaria infection crucially relies on a fine-tuned balance of cytokine networks. Dysregulation or imbalances in these mediators often result in immune hyperactivation, contributing to severe manifestations and prolonged infection. Understanding the multi-faceted roles of cytokines in malaria clearance offers promising avenues for therapeutic interventions. Targeting cytokine pathways to restore immune equilibrium or bolster protective responses could potentially enhance treatment strategies and vaccine development. In conclusion, the pivotal role of cytokines in immunomodulation during malaria clearance underscores their significance as potential targets for therapeutic interventions, offering promising prospects in the global fight against this infectious disease.

Repurposed Drugs That Activate Autophagy in Filarial Worms Act as Effective Macrofilaricides

Onchocerciasis and lymphatic filariasis are two neglected tropical diseases caused by filarial nematodes that utilize insect vectors for transmission to their human hosts. Current control strategies are based on annual or biannual mass drug administration (MDA) of the drugs Ivermectin or Ivermectin plus Albendazole, respectively. These drug regimens kill the first-stage larvae of filarial worms (i.e., microfilariae) and interrupt the transmission of infections. MDA programs for these microfilaricidal drugs must be given over the lifetime of the filarial adult worms, which can reach 15 years in the case of Onchocerca volvulus. This is problematic because of suboptimal responses to ivermectin in various endemic regions and inefficient reduction of transmission even after decades of MDA. There is an urgent need for the development of novel alternative treatments to support the 2030 elimination goals of onchocerciasis and lymphatic filariasis. One successful approach has been to target Wolbachia, obligatory endosymbiotic bacteria on which filarial worms are dependent for their survival and reproduction within the human host. A 4-6-week antibiotic therapy with doxycycline, for example, resulted in the loss of Wolbachia that subsequently led to extensive apoptosis of somatic cells, germline, embryos, and microfilariae, as well as inhibition of fourth-stage larval development. However, this long-course regimen has limited use in MDA programs. As an alternative approach to the use of bacteriostatic antibiotics, in this study, we focused on autophagy-inducing compounds, which we hypothesized could disturb various pathways involved in the interdependency between Wolbachia and filarial worms. We demonstrated that several such compounds, including Niclosamide, an FDA-approved drug, Niclosamide ethanolamine (NEN), and Rottlerin, a natural product derived from Kamala trees, significantly reduced the levels of Wolbachia in vitro. Moreover, when these compounds were used in vivo to treat Brugia pahangi-infected gerbils, Niclosamide and NEN significantly decreased adult worm survival, reduced the release of microfilariae, and decreased embryonic development depending on the regimen and dose used. All three drugs given orally significantly reduced Wolbachia loads and induced an increase in levels of lysosome-associated membrane protein in worms from treated animals, suggesting that Niclosamide, NEN, and Rottlerin were effective in causing drug-induced autophagy in these filarial worms. These repurposed drugs provide a new avenue for the clearance of adult worms in filarial infections.

Community composition of invasive, outbreak, and non-pest snail species along a source spring-to-fishpond gradient in a spatially structured aquacultural region

Agricultural lands are integrated into and interact with natural areas. Such is the case of Emek HaMa'ayanot, northern Israel, comprising a springs-rich area characterized by multiple land-uses, including spring-water-based aquaculture, recreational springs, and nature reserves. Aquacultural farms suffer from pest snails that carry fish disease; in the study region, these species are invasive (Thiara scabra, Tarebia granifera, Pseudosuccinea columella) and outbreak endemic (Melanoides tuberculata). Previous snail control efforts have focused on individual fishponds without considering management on larger environmental scales in the waterways from the source springs to the fish farms. To broaden our understanding of the status of the pest snail problem in the study area prior to suggesting environmental managerial solutions, we quantified changes in the community composition of snail species along the springs-to-fishponds gradients in a spatially explicit system. We found a remarkable increase in pest snail abundances along these gradients, indicating that pest snails might be invading upstream towards the springs. There were always nearly 100% pest snails in the endpoint sites for water tracks that ended in fishponds. Moreover, pest snails dominated the site when it was used as a fishpond, even though the site was also a spring. In contrast, in a water track that does not end in a fish farm, the relative abundances of non-pest snail species was similar between the source spring and the downstream endpoint, in spite of an increase in pest snail abundance at a midpoint site. These results suggest that invasive pest snails are actively moving upstream and that the fishponds have a marked upstream effect on the ability of non-pest snails to resist pest species invasions. We suggest further investigation of possible strategies for biocontrol of the observed invasion of the snails into natural areas as a basis for environmental management efforts. Finally, the observations made during this study could have practical global implications for snail management in aquaculture and agriculture, and for the control of snails and snail vectors implicated in animal and human diseases.

Identification of key interactions of benzimidazole resistance-associated amino acid mutations in Ascaris β-tubulins by molecular docking simulations

Ascaris species are soil-transmitted helminths that infect humans and livestock mainly in low and middle-income countries. Benzimidazole (BZ) class drugs have predominated for many years in the treatment of Ascaris infections, but persistent use of BZs has already led to widespread resistance in other nematodes, and treatment failure is emerging for Ascaris. Benzimidazoles act by binding to β-tubulin proteins and destabilising microtubules. Three mutations in the β-tubulin protein family are associated with BZ resistance. Seven shared β-tubulin isotypes were identified in Ascaris lumbricoides and A. suum genomes. Benzimidazoles were predicted to bind to all β-tubulin isotypes using in silico docking, demonstrating that the selectivity of BZs to interact with one or two β-tubulin isotypes is likely the result of isotype expression levels affecting the frequency of interaction. Ascaris β-tubulin isotype A clusters with helminth β-tubulins previously shown to interact with BZ. Molecular dynamics simulations using β-tubulin isotype A highlighted the key role of amino acid E198 in BZ-β-tubulin interactions. Simulations indicated that mutations at amino acids E198A and F200Y alter binding of BZ, whereas there was no obvious effect of the F167Y mutation. In conclusion, the key interactions vital for BZ binding with β-tubulins have been identified and show how mutations can lead to resistance in nematodes.

Does a school-based intervention to engage parents change opportunity for handwashing with soap at home? Practical experience from the Mikono Safi trial in Northwestern Tanzania

BACKGROUND

School-based de-worming is advocated as a strategy for reducing the burden of soil-transmitted helminth (STH) infections among children. However, re-infection tends to occur rapidly, suggesting that comprehensive water, sanitation, and hygiene (WASH) improvements may be needed to prevent this. We qualitatively assessed the influence of parental engagement activities on parents' motivation to improve WASH infrastructure and hygiene practices at home in the context of a school-based de-worming programme.

METHODOLOGY

We conducted a longitudinal qualitative study nested within the Mikono Safi trial, designed to assess the effect of a WASH intervention on STH infection prevalence in children. Meetings were organized for parents/guardians at schools where they were given information about STH infection, the role of WASH in STH infection prevention, and actionable steps they could take at home. During the meetings, parents/guardians received information about their own child's STH infection status. Twenty purposively selected households were visited and interviewed 3 times over a period of about 8-months. We employed thematic analysis; findings are reported following the Capability-Opportunity-Motivation and Behaviour (COM-B) framework.

PRINCIPAL FINDINGS

The engagement strategy improved parents'/guardians' knowledge and skills about handwashing with soap and its benefits. Parents/guardians reported that the sessions had motivated them to improve WASH infrastructure at home. Of 20 households included in this study, 17 renovated or built new latrines and 18 installed handwashing facilities. However, only 8 households established and maintained handwashing stations with both soap and water at 8 months.

CONCLUSIONS

The engagement of parents/guardians in a school-based WASH education intervention as part of the Mikono Safi trial resulted in increased knowledge and motivation about handwashing and sanitation. This led to improvements in sanitation facilities and handwashing opportunities at home. However, long-term success in provision of water and soap was limited, indicating that sustained engagement may be required to encourage households to ensure these materials are consistently available at home.

Cost yield of different treatment strategies against Clonorchis sinensis infection

BACKGROUND

Clonorchiasis is attributed to the ingestion of raw freshwater fish harboring Clonorchis sinensis. Morbidity control is targeted through the administration of antihelminthics. This study modelled the cost yield indicated by effectiveness and utility of different treatment strategies against clonorchiasis.

METHODS

About 1000 participants were enrolled from each of 14 counties selected from four provincial-level administrative divisions namely Guangxi, Guangdong, Heilongjiang and Jilin in 2017. Fecal examination was adopted to detect C. sinensis infection, while behavior of ingesting raw freshwater fish was enquired. Counties were grouped into four categories based on prevalence, namely low prevalence group (< 1%), moderate prevalence group (1-9.9%), high prevalence group (10-19.9%) and very high prevalence group (≥ 20%), while population were divided into three subgroups, namely children aged below 14 years old, adult female and adult male both aged over 14 years old. The average of cost effectiveness indicated by the cost to treat single infected cases with C. sinensis and of cost utility indicated by the cost to avoid per disability-adjusted life years (DALYs) caused by C. sinensis infection was calculated. Comparisons were performed between three treatment schedules, namely individual treatment, massive and selective chemotherapy, in which different endemic levels and populations were considered.

RESULTS

In selective chemotherapy strategy, the cost to treat single infected case in very high prevalence group was USD 10.6 in adult male, USD 11.6 in adult female, and USD 13.2 in children. The cost increased followed the decrease of endemic level. In massive chemotherapy strategy, the cost per infected case in very high prevalence group was USD 14.0 in adult male, USD 17.1 in adult female, USD 45.8 in children, which were also increased when the endemic level decreased. In individual treatment strategy, the cost was USD 12.2 in adult male, USD 15.0 in adult female and USD 41.5 in children in very high prevalence group; USD 19.2 in adult male, USD 34.0 in adult female, and USD 90.1 in children in high prevalence group; USD 30.4 in adult male, USD 50.5 in adult female and over USD 100 in children in moderate prevalence group; and over USD 400 in any population in low prevalence group. As to cost utility, the differences by treatment strategies, populations and endemic levels were similar to those in cost effectiveness.

CONCLUSIONS

Both cost effectiveness and cost utility indicators are highly impacted by the prevalence and population, as well as the treatment schedules. Adults especially men in the areas with a prevalence over 10% should be prioritized, in which selective chemotherapy was best and massive chemotherapy was also cost effective. In moderate endemic areas, the yield is not ideal, but selective chemotherapy for adult male may also be adopted. In low endemic areas, all strategies were high costly and new strategies need to be developed.

Treatment of Pregnant Women with Ivermectin during Mass Drug Distribution: Time to Investigate Its Safety and Potential Benefits

To date, pregnant women are excluded from programmes delivering community-directed treatment of ivermectin (CDTI) for onchocerciasis and preventive chemotherapy of other helminthiases because of concerns over ivermectin safety during pregnancy. This systematic exclusion sustains an infection reservoir at the community level and deprives a vulnerable population from known benefits—there are indications that treating O. volvulus infected women may improve pregnancy outcomes and reduce the risk that their children develop onchocerciasis-associated morbidities. Furthermore, teratogenic effects are seen in non-clinical experiments at doses that far exceed those used in CDTI. Lastly, early, undetected and undeclared pregnancies are being systematically exposed to ivermectin in practice. Treatment of this population requires appropriate supporting evidence, for which we propose a three-pronged approach. First, to develop a roadmap defining the key steps needed to obtain regulatory clearance for the safe and effective use of ivermectin in all pregnant women who need it. Second, to conduct a randomised placebo-controlled double-blind clinical trial to evaluate the safety and benefits of ivermectin treatment in O. volvulus infected pregnant women. Such a trial should evaluate the possible effects of ivermectin in reducing adverse pregnancy outcomes and neonatal mortality, as well as in reducing the incidence of onchocerciasis-associated epilepsy. Third, to establish a pregnancy registry for women who inadvertently received ivermectin during pregnancy. This situation is not unique to ivermectin. Access to valuable therapies is often limited, delayed, or denied to pregnant women due to a lack of evidence. Concerns over protecting vulnerable people may result in harming them. We need to find acceptable ways to build robust evidence towards providing essential interventions during pregnancy.

Multi-intervention integrated deworming strategy for sustained control of soil-transmitted helminths infections: a case study in Jiangsu Province, China

BACKGROUND

Soil-transmitted helminths (STH) infections still present a global health problem. Mass drug administration (MDA) is a widely applied strategy to reduce morbidity and mortality caused by STH. Yet, this approach has some shortcomings. In this study, we analyzed the impact of a multi-intervention integrated deworming approach including MDA, health education (HE), and environmental sanitation improvements (ESI) for sustained STH control in Jiangsu Province of China that was applied from 1989 to 2019.

METHODS

Data, including infection rate of STH, medications used, coverage of the medication, non-hazardous lavatory rate, and household piped-water access rate in rural areas, and actions related to HE and ESI were collected (from archives) and analyzed in this retrospective descriptive study. Pearson's correlation analysis was applied to test correlations.

RESULTS

There was a dramatic decline in the infection rate of STH from 1989 (59.32%) to 2019 (0.12%). From 1995 to 1999, MDA and HE were recommended in rural areas. A negative correlation was observed between infection rate and medication from 1994 to 1998 (r = - 0.882, P = 0.048). From 2000 to 2005, targeted MDA was given to high-risk populations with HE continuously promoting good sanitation behaviors. From 2006 to 2014, targeted MDA + HE and ESI were used to consolidate the control effect. ESI was strengthened from 2006, and a negative correlation was observed between the coverage rate of the non-hazardous lavatory and the infection rate from 2006 to 2019 (r = - 0.95, P < 0.001). The targeted MDA was interrupted in 2015, while continuous efforts like HE and ESI contributed in sustaining STH control.

CONCLUSIONS

Multi-intervention integrated deworming strategy contributes to the reduction of STH infections. This approach is a valuable example of how different interventions can be integrated to promote durable STH control.

Antioxidants resveratrol and SkQ1 attenuate praziquantel adverse effects on the liver in Opisthorchis felineus infected hamsters

Anthelmintic praziquantel (PZQ) is the drug of the choice for opisthorchiasis, schistosomiasis and other trematodiases therapy for several decades. Despite its good therapeutic performance and effective control of trematode infections, PZQ has some shortcomings; its inability to counteract disease sequelae necessitates novel therapeutic strategies. Testing of antioxidants that have proven themselves in clinical practice, in combination with this anthelmintic drug, offers new opportunities for developing alternatives to PZQ monotherapy. The effects of two antioxidants combined with PZQ on histological parameters of liver tissue were evaluated in a hamster model of opisthorchiasis felinea. Liver pathology including the parenchyma state, accumulation of neutral lipids and 4-Hydroxy-2-nonenal as a lipid peroxidation product, biochemical characteristics of hamster blood serum, and mRNA expression of inflammation- and fibrogenesis-associated genes were determined. PZQ and opisthorchiasis caused liver accumulation of lipids and glycogen. The combination of PZQ with resveratrol (RSV) or 10-(6'-plastoquinonyl)decyltriphenylphosphonium (SkQ1) significantly reduced hepatocyte changes (P = 0.009 and P = 0.009, respectively, Mann-Whitney U test) as compared with infected hamsters treated only with PZQ. RSV and SkQ1 significantly reduced cholangiocyte hyperplasia, bile duct proliferation, fibrosis, and lipid droplet and glycogen granule accumulation. The downregulation of 4-hydroxynonenal was also observed. The combinations of the anthelmintic drug with antioxidants RSV and SkQ1 ameliorate host oxidative stress and mitigate adverse effects of PZQ on hepatic parenchyma. The use of drug combinations may improve the action of standard anthelmintic agents, such as PZQ, which still remains the most effective agent against adult trematodes.

Genomics and proteomics of the liver fluke Opisthorchis felineus

The causative agent of opisthorchiasis, the liver fluke Opisthorchis felineus (Rivolta, 1884) is one of the helminths of humans and animals in Russia. Together with closely related species of trematodes O. viverrini (Poirier, 1886) and Clonorchis sinensis (Loos, 1907), O. felineus is a part of a triad of epidemiologically important trematodes in the family Opisthorchiidae. Adult O. felineus worms infest the hepatobiliary system of warm-blooded animals and might provoke the development of severe pathologies, including malignancy of bile duct epithelium. The high medical importance of O. felineus attracts the attention of researchers. This review briefly summarizes the data about O. felineus genomics and proteomics. The review provides a comparative analysis of the number of genes and sizes of nuclear genomes of a number of flatworms, the distribution of intron lengths, as well as results of synteny between the O. felineus, O. viverrini and C. sinensis genomes. Special attention is paid to a particular form of RNA processing known as trans-splicing, widely presented in the opisthorchiid genomes. We also provide the results of a comparative analysis of the xenobiotic metabolizing system between parasitic and free-living flatworms. Moreover, data on parasitic granulins, which are potential promoters of cholangiocyte neoplasia, are also presented. Data on the O. felineus genomics and proteomics provide first insights into the structural and functional organization of the genome of this parasitic flatworm with a complex life cycle as well as provide a significant contribution to our understanding of “host-parasite” interaction and evolution of this group of parasitic flatworms.

Anthelmintic Activity of Antioxidants: In Vitro Effects on the Liver Fluke Opisthorchis felineus

Currently, molecular parasitologists are searching for new agents against trematodiases. Redox metabolism is important for parasites as far as long-lived adult parasites inside a mammalian host are exposed to redox challenges. Antioxidants have been poorly studied as anthelmintic agents, in particular against the foodborne trematodes. Study of in vitro anthelmintic activity of nonenzymatic natural and synthetic antioxidants of various chemical structures was performed using standard motility and mortality assays against juvenile and adult Opisthorchis felineus worms. Promising agents have been found among both natural and synthetic compounds. The mitochondria-targeted antioxidant SkQ1 [10-(6′-plastoquinonyl)decyltriphenylphosphonium] in motility assays was as effective (half-maximal inhibitory concentration [IC₅₀] 0.6–1.4 μM) as praziquantel (IC₅₀ 0.47–1.4 μM), and SkQ1 was significantly more effective than praziquantel in mortality assays. Moreover, extensive tegument damage of the adult fluke was revealed after SkQ1 treatment. Flavonoids manifested potency too, with IC₅₀ values in a micromolar range (5.1–17.4 μM). Other natural and synthetic compounds tested against helminths were significantly less effective than praziquantel. Results of our study indicate that SkQ1 and flavonoids have high anthelmintic activities against the liver flukes. We propose that structure–activity relationship research might be worthwhile based on the structures of the most effective substances.

Effectiveness of a community-based integrated strategy to control soil-transmitted helminthiasis and clonorchiasis in the People's Republic of China

Soil-transmitted helminthiases (STHs) are caused by a group of intestinal nematode infections due to poor hygiene and environments, and clonorchiasis is a food-borne trematode (FBT) infection caused by ingestion of raw freshwater fish. Both are endemic in the People's Republic of China. To explore a suitable control strategy, integrated interventions were applied between 2007 and 2009 in ten pilot counties (eight for the STHs and two for clonorchiasis). Drug administration was used for treatment and complementary efforts to improve the situation based on health education, provision of clean water and sanitation were carried out. Significant achievements were gained as reflected by a drastic decrease in prevalence these infections were demonstrated. The overall prevalence of STHs and clonorchiasis decreased from 35.9% to 7.8% and from 41.4% to 7.0%, respectively. The reduction of prevalence and high cost-effectiveness were documented supporting large-scale application of this integrated intervention in China and elsewhere.

An Integrated Approach to Identify New Anti-Filarial Leads to Treat River Blindness, a Neglected Tropical Disease

Filarial worms cause multiple debilitating diseases in millions of people worldwide, including river blindness. Currently available drugs reduce transmission by killing larvae (microfilariae), but there are no effective cures targeting the adult parasites (macrofilaricides) which survive and reproduce in the host for very long periods. To identify effective macrofilaricides, we carried out phenotypic screening of a library of 2121 approved drugs for clinical use against adult Brugia pahangi and prioritized the hits for further studies by integrating those results with a computational prioritization of drugs and associated targets. This resulted in the identification of 18 hits with anti-macrofilaricidal activity, of which two classes, azoles and aspartic protease inhibitors, were further expanded upon. Follow up screening against Onchocerca spp. (adult Onchocerca ochengi and pre-adult O. volvulus) confirmed activity for 13 drugs (the majority having IC50 < 10 μM), and a counter screen of a subset against L. loa microfilariae showed the potential to identify selective drugs that prevent adverse events when co-infected individuals are treated. Stage specific activity was also observed. Many of these drugs are amenable to structural optimization, and also have known canonical targets, making them promising candidates for further optimization that can lead to identifying and characterizing novel anti-macrofilarial drugs.

Evaluating the impact of biannual school-based and community-wide treatment on urogenital schistosomiasis in Niger

Background

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) coordinated a five-year study implemented in several countries, including Niger, to provide an evidence-base for programmatic decisions regarding cost-effective approaches to preventive chemotherapy for schistosomiasis control.

Methods

This was a cluster-randomised trial investigating six possible combinations of annual or biannual community-wide treatment (CWT), school-based treatment (SBT), and holidays from mass treatment over four years. The most intense arm involved two years of annual CWT followed by 2 years of biannual CWT, while the least intensive arm involved one year of annual SBT followed by a year without treatment and two more years of annual SBT. The primary outcome of interest was prevalence and intensity of Schistosoma haematobium among 100 children aged 9–12 years sampled each year. In addition, 100 children aged 5–8 years in their first year of school and 50 adults (aged 20–55 years) were tested in the first and final fifth year of the study.

Results

In total, data were collected from 167,500 individuals across 225 villages in nine districts within the Niger River valley, Western Niger. Overall, the prevalence of S. haematobium decreased from baseline to Year 5 across all study arms. The relative reduction of prevalence was greater in biannual compared with annual treatment across all arms; however, the only significant difference was seen in areas with a high starting prevalence. Although adults were not targeted for treatment in SBT arms, a statistically significant decrease in prevalence among adults was seen in moderate prevalence areas receiving biannual (10.7% to 4.8%) SBT (P < 0.001). Adults tested in the annual SBT group also showed a decrease in prevalence between Year 1 and Year 5 (12.2% to 11.0%), but this difference was not significant.

Conclusions

These findings are an important consideration for schistosomiasis control programmes that are considering elimination and support the idea that scaling up the frequency of treatment rounds, particularly in areas of low prevalence, will not eliminate schistosomiasis. Interestingly, the finding that prevalence decreased among adults in SBT arms suggests that transmission in the community can be reduced, even where only school children are being treated, which could have logistical and cost-saving implications for the national control programmes.

A comprehensive research agenda for zero leprosy

BACKGROUND

Leprosy control achieved dramatic success in the 1980s-1990s with the implementation of short course multidrug therapy, which reduced the global prevalence of leprosy to less than 1 in 10 000 population. However, a period of relative stagnation in leprosy control followed this achievement, and only limited further declines in the global number of new cases reported have been achieved over the past decade.

MAIN TEXT

In 2016, major stakeholders called for the development of an innovative and comprehensive leprosy strategy aimed at reducing the incidence of leprosy, lowering the burden of disability and discrimination, and interrupting transmission. This led to the establishment of the Global Partnership for Zero Leprosy (GPZL) in 2018, with partners aligned around a shared Action Framework committed to achieving the WHO targets by 2030 through national leprosy program capacity-building, resource mobilisation and an enabling research agenda. GPZL convened over 140 experts from more than 20 countries to develop a research agenda to achieve zero leprosy. The result is a detailed research agenda focusing on diagnostics, mapping, digital technology and innovation, disability, epidemiological modelling and investment case, implementation research, stigma, post exposure prophylaxis and transmission, and vaccines. This research agenda is aligned with the research priorities identified by other stakeholders.

CONCLUSIONS

Developing and achieving consensus on the research agenda for zero leprosy is a significant step forward for the leprosy community. In a next step, research programmes must be developed, with individual components of the research agenda requiring distinct expertise, varying in resource needs, and operating over different timescales. Moving toward zero leprosy now requires partner alignment and new investments at all stages of the research process, from discovery to implementation.

Caenorhabditis elegans in anthelmintic research - Old model, new perspectives

For more than four decades, the free-living nematode Caenorhabditis elegans has been extensively used in anthelmintic research. Classic genetic screens and heterologous expression in the C. elegans model enormously contributed to the identification and characterization of molecular targets of all major anthelmintic drug classes. Although these findings provided substantial insights into common anthelmintic mechanisms, a breakthrough in the treatment and control of parasitic nematodes is still not in sight. Instead, we are facing increasing evidence that the enormous diversity within the phylum Nematoda cannot be recapitulated by any single free-living or parasitic species and the development of novel broad-spectrum anthelmintics is not be a simple goal. In the present review, we summarize certain milestones and challenges of the C. elegans model with focus on drug target identification, anthelmintic drug discovery and identification of resistance mechanisms. Furthermore, we present new perspectives and strategies on how current progress in C. elegans research will support future anthelmintic research.

Integrated community-based intervention for urinary schistosomiasis and soil-transmitted helminthiasis in children from Caxito, Angola

BACKGROUND

Schistosomiasis and soil-transmitted helminths (STH) infections are major public health problems. We aimed to study the 6-mo impact of mass drug administration with praziquantel and albendazole on urinary schistosomiasis and STH.

METHODS

We examined children (aged 2-15 y) from one hamlet, who provided urine and faeces samples at baseline (n=197), 1 mo (n=102) and 6 mo (n=92); 67 completed the protocol.

RESULTS

At baseline, 47/67 (70.1%) children presented Schistosoma haematobium (75.8% in the baseline total sample) and 12/67 (17.9%) with STH (30.5% in the initial sample, p=0.010). Among the children, 47.3% had heavy Schistosoma haematobium infection. The most frequent STH was Trichuris trichiura in 9.0%. We also found Hymenolepis nana (13.2%) and Plasmodium falciparum (9.1%) infections and anaemia (82.1%). One mo after chemotherapy there was a significant (p=0.013) reduction of Schistosoma haematobium prevalence (23.5%) and a high egg reduction rate (86.9%). Considering the sample of 67 children, the mean egg concentration was 498 at baseline, 65 at 1 mo and 252 at 6 mo (p<0.05). We also observed a reduction in STH infections, 50% in Ascaris lumbricoides, 33.3% in T. trichiura and 50% in hookworms. At 6 mo, the prevalence of Schistosoma haematobium (76.1%) was similar to the baseline and the STH reduction was not significant.

CONCLUSIONS

Longitudinal studies have reported many losses in these settings, but we were able to show that mass drug administration for control of schistosomiasis and STH present low effectiveness, that reinfections occur rapidly and that stand alone anthelmintic therapy is not a sustainable choice.

Recent advances in functional genomics for parasitic nematodes of mammals

Human-parasitic nematodes infect over a quarter of the world's population and are a major cause of morbidity in low-resource settings. Currently available treatments have not been sufficient to eliminate infections in endemic areas, and drug resistance is an increasing concern, making new treatment options a priority. The development of new treatments requires an improved understanding of the basic biology of these nematodes. Specifically, a better understanding of parasitic nematode development, reproduction and behavior may yield novel drug targets or new opportunities for intervention such as repellents or traps. Until recently, our ability to study parasitic nematode biology was limited because few tools were available for their genetic manipulation. This is now changing as a result of recent advances in the large-scale sequencing of nematode genomes and the development of new techniques for their genetic manipulation. Notably, skin-penetrating gastrointestinal nematodes in the genus Strongyloides are now amenable to transgenesis, RNAi and CRISPR/Cas9-mediated targeted mutagenesis, positioning the Strongyloides species as model parasitic nematode systems. A number of other mammalian-parasitic nematodes, including the giant roundworm Ascaris suum and the tissue-dwelling filarial nematode Brugia malayi, are also now amenable to transgenesis and/or RNAi in some contexts. Using these tools, recent studies of Strongyloides species have already provided insight into the molecular pathways that control the developmental decision to form infective larvae and that drive the host-seeking behaviors of infective larvae. Ultimately, a mechanistic understanding of these processes could lead to the development of new avenues for nematode control.

Efficacy of Anthelminthic Drugs and Drug Combinations Against Soil-transmitted Helminths: A Systematic Review and Network Meta-analysis

Background

Periodic mass distribution of benzimidazole anthelminthic drugs is the key strategy to control soil-transmitted helminths (STHs) globally. However, benzimidazoles have low efficacy against Trichuris trichiura, and there are concerns about benzimidazole resistance potentially emerging in humans. Therefore, identifying alternative drug regimens is a pressing priority. We present a systematic review and network meta-analysis comparing the efficacy of 21 different anthelminthic drug regimens, including standard, novel, and combination treatments.

Methods

We searched PubMed, Medline, Embase, Web of Science, and Cochrane databases and identified studies comparing anthelminthic treatments to each other or placebo. The outcomes calculated were relative risk (RR) of cure and difference in egg reduction rates (dERR). We used an automated generalized pairwise modeling framework to generate mixed treatment effects against a common comparator, the current standard treatment (single-dose albendazole).

Results

Our search identified 4876 studies, of which 114 were included in the meta-analysis. Results identified several drug combinations with higher efficacy than single-dose albendazole for T. trichiura, including albendazole-ivermectin (RR of cure, 3.22 [95% confidence interval {CI}, 1.84-5.63]; dERR, 0.97 [95% CI, .21-1.74]), albendazole-oxantel pamoate (RR, 5.07 [95% CI, 1.65-15.59]; dERR, 0.51 [95% CI, .50-.52]), mebendazole-ivermectin (RR, 3.37 [95% CI, 2.20-5.16]), and tribendimidine-oxantel pamoate (RR, 4.06 [95% CI, 1.30-12.64]).

Conclusions

There are several promising drug combinations that may enhance the impact of STH control programs on T. trichiura, without compromising efficacy against Ascaris lumbricoides and hookworm. We suggest further, large-scale trials of these drug combinations and consideration of their use in STH control programs where T. trichiura is present.

International Prospective Register of Systematic Reviews Registration

CRD42016050739.

Preventive chemotherapy and anthelmintic resistance of soil-transmitted helminths - Can we learn nothing from veterinary medicine?

Current parasite control programs in veterinary species have moved away from mass anthelmintic treatment approaches due to the emergence of significant anthelmintic resistance (AR), and the availability of few classes of anthelmintics. A number of parallels between livestock and human helminths exist that warn of the risk of AR in human soil-transmitted helminthiases, yet current public health interventions continue to prioritize mass treatment strategies, a known risk factor for AR. This review discusses the existing parallels between human and animal helminth biology and management, along with current public health recommendations and strategies for helminth control in humans. The effectiveness of current recommendations and alternative management strategies are considered.

The role of carbon dioxide in nematode behaviour and physiology

Carbon dioxide (CO2) is an important sensory cue for many animals, including both parasitic and free-living nematodes. Many nematodes show context-dependent, experience-dependent and/or life-stage-dependent behavioural responses to CO2, suggesting that CO2 plays crucial roles throughout the nematode life cycle in multiple ethological contexts. Nematodes also show a wide range of physiological responses to CO2. Here, we review the diverse responses of parasitic and free-living nematodes to CO2. We also discuss the molecular, cellular and neural circuit mechanisms that mediate CO2 detection in nematodes, and that drive context-dependent and experience-dependent responses of nematodes to CO2.

The antioxidants resveratrol and N-acetylcysteine enhance anthelmintic activity of praziquantel and artesunate against Schistosoma mansoni

Background

Treatment of schistosomiasis has relied on the anthelmintic drug praziquantel (PZQ) for more than a generation. Despite its celebrated performance for treatment and control of schistosomiasis and other platyhelminth infections, praziquantel has some shortcomings and the inability of this drug to counteract disease sequelae prompts the need for novel therapeutic strategies.

Methods

Using a host-parasite model involving Biomphalaria glabrata and Schistosoma mansoni we established mechanical transformation of S. mansoni cercariae into newly transformed schistosomula (NTS) and characterized optimal culture conditions. Thereafter, we investigated the antischistosomal activity and ability of the antioxidants N-acetylcysteine (NAC) and resveratrol (RESV) to augment the performance of praziquantel and/or artesunate (AS) against larval stages of the parasite. Drug effects were evaluated by using an automated microscopical system to study live and fixed parasites and by transmission electron microscopy (TEM).

Results

Transformation rates of cercariae to schistosomula reached ~ 70% when the manipulation process was optimized. Several culture media were tested, with M199 supplemented with HEPES found to be suitable for S. mansoni NTS. Among the antioxidants studied, RESV alone or combined with anthelminthic drugs achieved better results rather N-acetylcysteine (NAC). TEM observations demonstrated that the combination of AS + RESV induced severe, extensive alterations to the tegument and subtegument of NTS when compared to the constituent compounds alone. Two anthelmintic–antioxidant combinations, praziquantel-resveratrol [combination index (CI) = 0.74] and artesunate-resveratrol (CI = 0.34) displayed moderate and strong synergy, respectively.

Conclusions

The use of viability markers including staining with propidium iodide increased the accuracy of drug screening assays against S. mansoni NTS. The synergies observed might be the consequence of increased action by RESV on targets of AS and PZQ and/or they may act through concomitantly on discrete targets to enhance overall antischistosomal action. Combinations of active agents, preferably with discrete modes of action including activity against developmental stages and/or the potential to ameliorate infection-associated pathology, might be pursued in order to identify novel therapeutic interventions.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3566-9) contains supplementary material, which is available to authorized users.

Pharmacological and molecular dynamics analyses of differences in inhibitor binding to human and nematode PDE4: Implications for management of parasitic nematodes

Novel chemical controls are needed that selectively target human, animal, and plant parasitic nematodes with reduced adverse effects on the host or the environment. We hypothesize that the phosphodiesterase (PDE) enzyme family represents a potential target for development of novel nematicides and anthelmintics. To test this, we identified six PDE families present in the nematode phylum that are orthologous to six of the eleven human PDE families. We characterized the binding interactions of family-selective PDE inhibitors with human and C. elegans PDE4 in conjunction with molecular dynamics (MD) simulations to evaluate differences in binding interactions of these inhibitors within the PDE4 catalytic domain. We observed that roflumilast (human PDE4-selective inhibitor) and zardaverine (selective for human PDE3 and PDE4) were 159- and 77-fold less potent, respectively, in inhibiting C. elegans PDE4. The pan-specific PDE inhibitor isobutyl methyl xanthine (IBMX) had similar affinity for nematode and human PDE4. Of 32 residues within 5 Å of the ligand binding site, five revealed significant differences in non-bonded interaction energies (van der Waals and electrostatic interaction energies) that could account for the differential binding affinities of roflumilast and zardaverine. One site (Phe506 in the human PDE4D3 amino acid sequence corresponding to Tyr253 in C. elegans PDE4) is predicted to alter the binding conformation of roflumilast and zardaverine (but not IBMX) into a less energetically favorable state for the nematode enzyme. The pharmacological differences in sensitivity to PDE4 inhibitors in conjunction with differences in the amino acids comprising the inhibitor binding sites of human and C. elegans PDE4 catalytic domains together support the feasibility of designing the next generation of anthelmintics/nematicides that could selectively bind to nematode PDEs.

Efficacy and safety of ivermectin and albendazole co-administration in school-aged children and adults infected with Trichuris trichiura: study protocol for a multi-country randomized controlled double-blind trial

BACKGROUND

Soil-transmitted helminthiasis affects almost 2 billion people worldwide in tropical climates. Preventive chemotherapy, using the benzimidazoles (albendazole and mebendazole) is the current main recommended control strategy. Nevertheless, there is limited efficacy of these drugs against hookworm infection and, to a greater extent, against trichuriasis. We describe a protocol for a trial investigating the efficacy and safety of the co-administration of ivermectin and albendazole against trichuriasis.

METHODS

A double-blind, placebo-controlled randomized controlled trial will be conducted in three countries (Côte d'Ivoire, Tanzania and Lao PDR) with the aim to determine the efficacy, safety and extended effects of co-administered ivermectin and albendazole compared to standard albendazole monotherapy. We will enroll 600 participants aged 6-60 years in each setting. The primary outcome is cure rate (CR) against Trichuris trichiura infection as assessed by Kato-Katz 14-21 days after treatment. Secondary outcomes include CRs against concomitant soil-transmitted helminth (STH) infections (Ascaris lumbricoides, hookworm and Strongyloides stercoralis) and egg reduction rates (ERRs) against STH at 14-21 days, 180 days and 360 days. Tolerability of treatment, infection status assessed by polymerase chain reaction (PCR), and potential benefits of deworming on nutritional and morbidity indicators will be assessed. The primary analysis will include an available-case set and use logistic regression models adjusted for age, sex and weight.

DISCUSSION

This trial will provide robust results on the efficacy and safety of co-administration of ivermectin and albendazole with the aim to better inform WHO recommendations on control of STHs. Furthermore, secondary and explanatory outcomes will provide direct evidence on the extended effects of combination therapy and insight on the relationship between nutrition and morbidity parameters and infection status and intensity.

TRIAL REGISTRATION

NCT03527732 (date assigned: 17 May 2018).

Results of a national school-based deworming programme on soil-transmitted helminths infections and schistosomiasis in Kenya: 2012-2017

Background

Soil-transmitted helminth (STH) and schistosome infections are among the most prevalent neglected tropical diseases (NTDs) in the world. School-aged children are particularly vulnerable to these chronic infections that can impair growth, nutritional status and cognitive ability. Mass drug administration (MDA) delivered either once or twice annually is a safe and effective approach recommended by the World Health Organization (WHO) to reduce worm burden. In 2012, Kenya began a national school-based deworming programme (NSBDP) aimed at reducing infection and associated morbidity. The change in prevalence and intensity of these infections was monitored over five years (2012–2017). Here, we present the changes in STH and schistosome infections between baseline and endline assessments, as well as explore the yearly patterns of infection reductions.

Methods

We used series of pre- and post-MDA intervention, repeat cross-sectional surveys in a representative, stratified, two-stage sample of schools in 16 counties of Kenya. The programme consisted of two tiers of monitoring; a national baseline, midterm and endline surveys consisting of 200 schools, and pre- and post-MDA surveys conducted yearly consisting of 60 schools. Stool and urine samples were collected from randomly selected school children and examined for STH and schistosome infections using Kato-Katz and urine filtration techniques respectively.

Results

Overall, 32.3%, 16.4% and 13.5% of the children were infected with any STH species during baseline, midterm and endline assessment, respectively, with a relative reduction of 58.2% over the five-year period. The overall prevalence of S. mansoni was 2.1%, 1.5% and 1.7% and of S. haematobium was 14.8%, 6.8% and 2.4%, respectively, for baseline, midterm and endline surveys. We observed inter-region and inter-county heterogeneity variation in the infection levels.

Conclusions

The analysis provided robust assessment of the programme and outlined the current prevalence, mean intensity and re-infection pattern of these infections. Our findings will allow the Government of Kenya to make informed decisions on the strategy to control and eliminate these NTDs. Our results suggest that complimentary interventions may have to be introduced to sustain the chemotherapeutic gains of MDA and accelerate attainment of elimination of these NTDs as a public health problem in Kenya.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3322-1) contains supplementary material, which is available to authorized users.

Aminoacyl tRNA synthetases as malarial drug targets: a comparative bioinformatics study

BACKGROUND

Treatment of parasitic diseases has been challenging due to evolution of drug resistant parasites, and thus there is need to identify new class of drugs and drug targets. Protein translation is important for survival of malarial parasite, Plasmodium, and the pathway is present in all of its life cycle stages. Aminoacyl tRNA synthetases are primary enzymes in protein translation as they catalyse amino acid addition to the cognate tRNA. This study sought to understand differences between Plasmodium and human aminoacyl tRNA synthetases through bioinformatics analysis.

METHODS

Plasmodium berghei, Plasmodium falciparum, Plasmodium fragile, Plasmodium knowlesi, Plasmodium malariae, Plasmodium ovale, Plasmodium vivax, Plasmodium yoelii and human aminoacyl tRNA synthetase sequences were retrieved from UniProt database and grouped into 20 families based on amino acid specificity. These families were further divided into two classes. Both families and classes were analysed. Motif discovery was carried out using the MEME software, sequence identity calculation was done using an in-house Python script, multiple sequence alignments were performed using PROMALS3D and TCOFFEE tools, and phylogenetic tree calculations were performed using MEGA vs 7.0 tool. Possible alternative binding sites were predicted using FTMap webserver and SiteMap tool.

RESULTS

Motif discovery revealed Plasmodium-specific motifs while phylogenetic tree calculations showed that Plasmodium proteins have different evolutionary history to the human homologues. Human aaRSs sequences showed low sequence identity (below 40%) compared to Plasmodium sequences. Prediction of alternative binding sites revealed potential druggable sites in PfArgRS, PfMetRS and PfProRS at regions that are weakly conserved when compared to the human homologues. Multiple sequence analysis, motif discovery, pairwise sequence identity calculations and phylogenetic tree analysis showed significant differences between parasite and human aaRSs proteins despite functional and structural conservation. These differences may provide a basis for further exploration of Plasmodium aminoacyl tRNA synthetases as potential drug targets.

CONCLUSION

This study showed that, despite, functional and structural conservation, Plasmodium aaRSs have key differences from the human homologues. These differences in Plasmodium aaRSs can be targeted to develop anti-malarial drugs with less toxicity to the host.

Albendazole resistance induced in Ancylostoma ceylanicum is not due to single-nucleotide polymorphisms (SNPs) at codons 167, 198, or 200 of the beta-tubulin gene, indicating another resistance mechanism

Mass drug administration has been implicated as the major cause of drug resistance in nematodes of ruminants. Single-nucleotide polymorphisms (SNPs) at codons 167, 198, and 200 of the beta-tubulin isotype 1 gene are associated with albendazole resistance mechanisms. Although drug resistance is suspected to occur in nematodes of the same order, at present, there is no evidence of a strong correlation between these canonical SNPs and albendazole resistance in hookworms. In the absence of a hookworm strain that is naturally resistant to albendazole, we produced an albendazole-resistant Ancylostoma ceylanicum strain by selective drug pressure. Restriction fragment length polymorphism-PCR (RFLP-PCR) was employed to identify the presence of SNPs previously associated with drug resistance in other nematodes. However, none of the benzimidazole resistance-associated SNPs known in other nematodes were found. A beta-tubulin isotype 1 gene mini-cDNA library was constructed to obtain the complete cDNA gene sequence for the analysis of the entire gene to identify distinct SNPs associated with resistance. Some SNPs were found, but the resulting sequences were not reproducibly detected among the different clones, preventing their association with the resistance mechanism. The parasitological and hematological parameters of the albendazole-resistant strain were characterized and compared to those of the sensitive strain. Although the albendazole-resistant strain was less adapted to its host, with fewer worms recovered, all other parameters analyzed were similar between both strains. The results of the present study indicate that the mechanism of albendazole resistance of the resistant strain described herein must differ from those that have previously been characterized. Thus, new mechanistic studies are needed in the future.

A Biomphalaria glabrata peptide that stimulates significant behaviour modifications in aquatic free-living Schistosoma mansoni miracidia

The human disease schistosomiasis (or bilharzia) is caused by the helminth blood fluke parasite Schistosoma mansoni, which requires an intermediate host, the freshwater gastropod snail Biomphalaria glabrata (the most common intermediate host). The free-swimming parasite miracidia utilise an excellent chemosensory sense to detect and locate an appropriate host. This study investigated the biomolecules released by the snail that stimulate changes in the behaviour of the aquatic S. mansoni miracidia. To achieve this, we have performed an integrated analysis of the snail-conditioned water, through chromatography and bioassay-guided behaviour observations, followed by mass spectrometry. A single fraction containing multiple putative peptides could stimulate extreme swimming behaviour modifications (e.g. velocity, angular variation) similar to those observed in response to crude snail mucus. One peptide (P12;—R-DITSGLDPEVADD-KR—) could replicate the stimulation of miracidia behaviour changes. P12 is derived from a larger precursor protein with a signal peptide and multiple dibasic cleavage sites, which is synthesised in various tissues of the snail, including the central nervous system and foot. P12 consists of an alpha helix secondary structure as indicated by circular dichroism spectroscopy. This information will be helpful for the development of approaches to manipulate this parasites life cycle, and opens up new avenues for exploring other parasitic diseases which have an aquatic phase using methods detailed in this investigation.

In aquatic environments, where the vast majority of animals live in darkness, key relationships are often formed and maintained by chemical communication (including smell and taste). Parasites with an aquatic life phase rely on an exquisite sense of chemosensation to detect host biomolecules (kairomones), allowing them to locate and infect their host. Our study identifies the first kairomone released by the freshwater gastropod snail Biomphalaria glabrata, an intermediate host for the helminth blood fluke parasite Schistosoma mansoni. This is a key aspect of the S. mansoni life-cycle that ultimately leads to human infection, causing the disease schistosomiasis (or bilharzia), which is considered the most devastating human helminth infection in terms of global morbidity and mortality. The kairomone we identify is a peptide that does not appear to share any similarity with any other known animal peptide. This information will be helpful as we explore methods to interrupt parasite infection, and therefore break the cycle of infection that causes a major human disease.

A study of tribendimidine effects in vitro and in vivo on the liver fluke Opisthorchis felineus

Background

The food-borne liver fluke Opisthorchis felineus is an epidemiologically important species and the causative agent of opisthorchiasis across an extensive territory of Eurasia. For decades, treatment of opisthorchiasis has been based on praziquantel. Tribendimidine could be an alternative drug that has been successfully tested for Opisthorchis viverrini and Clonorchis sinensis infections. We aimed to assess tribendimidine effects in comparison with praziquantel in vivo and in vitro against the liver fluke Opisthorchis felineus.

Results

In this study we (i) calculated half-maximal inhibitory concentrations (IC₅₀) by motility tests against O. felineus adults and newly excysted metacercarie after tribendimidine treatment in vitro; (ii) determined whether tribendimidine and PZQ effects on adult liver flukes are dependent on or mediated by white blood cells; and (iii) tested in vivo the anthelmintic activity of tribendimidine on juvenile and adult worms. We found that the efficiency of tribendimidine in vitro was similar (IC₅₀ = 0.23 μM for newly excysted metacercariae and 0.19 μM for adult worms) to that of praziquantel (IC₅₀ 0.98 μM for newly excysted metacercariae and 0.47 μM for adult worms). The treatment of adult worms in vivo with praziquantel or tribendimidine at 400 mg/kg resulted in a 76% and 77.2% reduction, respectively, in the worm burden during chronic infection.

Conclusions

The differences between WBR values after PZQ and TBN treatment were not significant, thus tribendimidine was as effective as praziquantel against O. felineus liver flukes. Given the broad-spectrum activity of tribendimidine and efficacy against O. felineus, this drug may be a promising candidate for the treatment of opisthorchiasis felinea and other liver fluke infections.

Paragonimiasis

Paragonimiasis is a zoonotic disease caused by lung flukes of the genus Paragonimus. Humans usually become infected by eating freshwater crabs or crayfish containing encysted metacercariae of these worms. However, an alternative route of infection exists: ingestion of raw meat from a mammalian paratenic host. Adult worms normally occur in pairs in cysts in the lungs from which they void their eggs via air passages. The pulmonary form is typical in cases of human infection due to P. westermani, P. heterotremus, and a few other species (Table 5.1). Worms may occupy other sites in the body, notably the brain, but lung flukes have made their presence felt in almost every organ. Ectopic paragonimiasis is particularly common when infection is due to members of the P. skrjabini complex (Table 5.1). Human paragonimiasis occurs primarily in the tropics and subtropics of Asia, Africa, and the Americas, with different species being responsible in different areas (Table 5.1).

Efficacy of subcutaneous doses and a new oral amorphous solid dispersion formulation of flubendazole on male jirds (Meriones unguiculatus) infected with the filarial nematode Brugia pahangi

River blindness and lymphatic filariasis are two filarial diseases that globally affect millions of people mostly in impoverished countries. Current mass drug administration programs rely on drugs that primarily target the microfilariae, which are released from adult female worms. The female worms can live for several years, releasing millions of microfilariae throughout the course of infection. Thus, to stop transmission of infection and shorten the time to elimination of these diseases, a safe and effective drug that kills the adult stage is needed. The benzimidazole anthelmintic flubendazole (FBZ) is 100% efficacious as a macrofilaricide in experimental filarial rodent models but it must be administered subcutaneously (SC) due to its low oral bioavailability. Studies were undertaken to assess the efficacy of a new oral amorphous solid dispersion (ASD) formulation of FBZ on Brugia pahangi infected jirds (Meriones unguiculatus) and compare it to a single or multiple doses of FBZ given subcutaneously. Results showed that worm burden was not significantly decreased in animals given oral doses of ASD FBZ (0.2-15 mg/kg). Regardless, doses as low as 1.5 mg/kg caused extensive ultrastructural damage to developing embryos and microfilariae (mf). SC injections of FBZ in suspension (10 mg/kg) given for 5 days however, eliminated all worms in all animals, and a single SC injection reduced worm burden by 63% compared to the control group. In summary, oral doses of ASD formulated FBZ did not significantly reduce total worm burden but longer treatments, extended takedown times or a second dosing regimen, may decrease female fecundity and the number of mf shed by female worms.

PCR-RFLP screening of polymorphisms associated with benzimidazole resistance in Necator americanus and Ascaris lumbricoides from different geographical regions in Brazil

Ascaris lumbricoides and Necator americanus are soil-transmitted parasites with global geographic distribution, and they represent some of the most common and neglected infections in the world. Periodic treatment with mass drug administration (MDA) in endemic areas is the recommended action put forth by the World Health Organization. However, MDA can cause the selection of subpopulations that possess the genetic ability to overcome the mechanism of drug action. In fact, beta-tubulin gene mutations (codons 167, 198 and 200) are correlated with benzimidazole resistance in nematodes of veterinary importance. It is possible that these SNPs also have strong correlation with treatment resistance in the human geohelminths A. lumbricoides, Trichuris trichiura and hookworms. Here, we aimed to investigate the presence of some of these canonical molecular markers associated with parasite resistance to benzimidazole in N. americanus and A. lumbricoides collected from six Brazilian states. Nested-PCR and PCR-RFLP were used to detect mutations at codons 167 and 198 in 601 individual eggs of A. lumbricoides collected from 62 human stool samples; however, no mutations were found. Codons 198 and 200 were tested in 552 N. americanus eggs collected from 48 patients using the same methodology, which presented a relative frequency of 1.4% and 1.1%, respectively. The presence of these SNPs in N. americanus eggs is an important finding, indicating that with high benzimidazole drug pressure there is potential for benzimidazole resistance to be selected in this hookworm. However, at these low frequencies it does not indicate that there is at present any benzimidazole resistance problem. This is the first systematic study performed in South America, and the study yielded a landscape of the genetic variants in the beta-tubulin gene and anthelmintic resistance to soil-transmitted parasites detected by a simple, rapid and affordable genotyping assay of individual eggs.

A Critical Role for Thermosensation in Host Seeking by Skin-Penetrating Nematodes

Skin-penetrating parasitic nematodes infect approximately one billion people worldwide and are a major source of neglected tropical disease [1-6]. Their life cycle includes an infective third-larval (iL3) stage that searches for hosts to infect in a poorly understood process that involves both thermal and olfactory cues. Here, we investigate the temperature-driven behaviors of skin-penetrating iL3s, including the human-parasitic threadworm Strongyloides stercoralis and the human-parasitic hookworm Ancylostoma ceylanicum. We show that human-parasitic iL3s respond robustly to thermal gradients. Like the free-living nematode Caenorhabditis elegans, human-parasitic iL3s show both positive and negative thermotaxis, and the switch between them is regulated by recent cultivation temperature [7]. When engaging in positive thermotaxis, iL3s migrate toward temperatures approximating mammalian body temperature. Exposing iL3s to a new cultivation temperature alters the thermal switch point between positive and negative thermotaxis within hours, similar to the timescale of thermal plasticity in C. elegans [7]. Thermal plasticity in iL3s may enable them to optimize host finding on a diurnal temperature cycle. We show that temperature-driven responses can be dominant in multisensory contexts such that, when thermal drive is strong, iL3s preferentially engage in temperature-driven behaviors despite the presence of an attractive host odorant. Finally, targeted mutagenesis of the S. stercoralis tax-4 homolog abolishes heat seeking, providing the first evidence that parasitic host-seeking behaviors are generated through an adaptation of sensory cascades that drive environmental navigation in C. elegans [7-10]. Together, our results provide insight into the behavioral strategies and molecular mechanisms that allow skin-penetrating nematodes to target humans.

Nanomedicine Approaches Against Parasitic Worm Infections

Nanomedicine approaches have the potential to transform the battle against parasitic worm (helminth) infections, a major global health scourge from which billions are currently suffering. It is anticipated that the intersection of two currently disparate fields, nanomedicine and helminth biology, will constitute a new frontier in science and technology. This progress report surveys current innovations in these research fields and discusses research opportunities. In particular, the focus is on: (1) major challenges that helminth infections impose on mankind; (2) key aspects of helminth biology that inform future research directions; (3) efforts to construct nanodelivery platforms to target drugs and genes to helminths hidden in their hosts; (4) attempts in applying nanotechnology to enable vaccination against helminth infections; (5) outlooks in utilizing nanoparticles to enhance immunomodulatory activities of worm-derived factors to cure allergy and autoimmune diseases. In each section, achievements are summarized, limitations are explored, and future directions are assessed.

Schistosoma egg-induced liver pathology resolution by Sm-p80-based schistosomiasis vaccine in baboons

Schistosomiasis remains a serious chronic debilitating hepato-intestinal disease. Current control measures based on mass drug administration are inadequate due to sustained re-infection rates, low treatment coverage and emergence of drug resistance. Hence, there is an urgent need for a schistosomiasis vaccine for disease control. In this study, we assessed the anti-pathology efficacy of Schistosoma mansoni large subunit of calpain (Sm-p80)-based vaccine against schistosomiasis caused by infections with Schistosoma mansoni in baboons. We also evaluated the disease transmission-blocking potential of Sm-p80 vaccine. Immunisations with Sm-p80-based vaccine resulted in significant reduction of hepatic egg load in vaccinated baboons (67.7% reduction, p = 0.0032) when compared to the control animals, indicative of reduction in pathology. There was also a significant reduction in sizes of egg-induced granulomas in baboons immunised with Sm-p80 vaccine compared to their control counterparts. Egg hatching rate analysis revealed an overall 85.6% reduction (p = 0.0018) in vaccinated animals compared to the controls, highlighting the potential role of Sm-p80 vaccine in disease transmission. The findings on anti-pathology efficacy and transmission-blocking potential presented in this study have formed the basis for a large-scale double-blinded baboon experiment that is currently underway.

Effects of miconazole/clotrimazole and praziquantel combinations against the liver fluke Opisthorchis felineus in vivo and in vitro

The liver fluke Opisthorchis felineus (Rivolta, 1884) is the causative agent of opisthorchiasis felinea in Eurasia. Opisthorchiasis is a serious human and fish-eating animal's disease affecting bile ducts and the gall bladder. Currently, the main drug for specific therapy of opisthorchiasis is praziquantel. We have previously shown that azole inhibitors of O. felineus cytochrome P450 significantly reduced survival of the worms in vitro. Here, we studied in vitro anthelmintic effects of drug combinations involving azole substances approved by the US Food and Drug Administration together with praziquantel against adult or juvenile O. felineus liver flukes. A synergistic interaction was shown for praziquantel-clotrimazole (CI = 0.68) combination and for praziquantel-miconazole (CI = 0.68) combination against adult helminths in vitro. Praziquantel-miconazole (CI = 0.30) had a strongly synergistic effect against newly excysted metacercariae. We also tested anthelmintic effects of azole substances and their combinations with praziquantel in vivo in an animal model of chemotherapy. The treatment of juvenile worms (1 day postinfection) with 100 mg/kg miconazole resulted in a worm burden reduction (WBR) of 37.5% (P = 0.049), with 100 mg/kg clotrimazole causing a WBR of 31.25% (P = 0.025). The treatment of adult worms (5-6 weeks postinfection) with 100 mg/kg or 200 mg/kg miconazole yielded a WBR of 23.8% (P = 0.01) and 21.4% (P = 0.006), respectively. When praziquantel was administered together with clotrimazole or with miconazole, a WBR slightly greater than the effect of ED₅₀ praziquantel was observed (WBR of 59.5 and 54.7%, respectively).In conclusion, the synergistic effect of the praziquantel-clotrimazole and praziquantel-miconazole combinations observed in vitro was not confirmed in vivo. Thus, this combination chemotherapy revealed no benefits over praziquantel monotherapy in the treatment of opisthorchiasis felinea.

Advances in kinome research of parasitic worms - implications for fundamental research and applied biotechnological outcomes

Protein kinases are enzymes that play essential roles in the regulation of many cellular processes. Despite expansions in the fields of genomics, transcriptomics and bioinformatics, there is limited information on the kinase complements (kinomes) of most eukaryotic organisms, including parasitic worms that cause serious diseases of humans and animals. The biological uniqueness of these worms and the draft status of their genomes pose challenges for the identification and classification of protein kinases using established tools. In this article, we provide an account of kinase biology, the roles of kinases in diseases and their importance as drug targets, and drug discovery efforts in key socioeconomically important parasitic worms. In this context, we summarise methods and resources commonly used for the curation, identification, classification and functional annotation of protein kinase sequences from draft genomes; review recent advances made in the characterisation of the worm kinomes; and discuss the implications of these advances for investigating kinase signalling and developing small-molecule inhibitors as new anti-parasitic drugs.

Strongyloides stercoralis and hookworm co-infection: spatial distribution and determinants in Preah Vihear Province, Cambodia

BACKGROUND

Strongyloides stercoralis and hookworm are two soil-transmitted helminths (STH) that are highly prevalent in Cambodia. Strongyloides stercoralis causes long-lasting infections and significant morbidity but is largely neglected, while hookworm causes the highest public health burden among STH. The two parasites have the same infection route, i.e. skin penetration. The extent of co-distribution, which could result in potential high co-morbidities, is unknown in highly endemic settings like Cambodia. The aim of this study was to predict the spatial distribution of S. stercoralis-hookworm co-infection risk and to investigate determinants of co-infection in Preah Vihear Province, North Cambodia.

METHODS

A cross-sectional survey was conducted in 2010 in 60 villages of Preah Vihear Province. Diagnosis was performed on two stool samples, using combined Baermann technique and Koga agar culture plate for S. stercoralis and Kato-Katz technique for hookworm. Bayesian multinomial geostatistical models were used to assess demographic, socioeconomic, and behavioural determinants of S. stercoralis-hookworm co-infection and to predict co-infection risk at non-surveyed locations.

RESULTS

Of the 2576 participants included in the study, 48.6% and 49.0% were infected with S. stercoralis and hookworm, respectively; 43.8% of the cases were co-infections. Females, preschool aged children, adults aged 19-49 years, and participants who reported regularly defecating in toilets, systematically boiling drinking water and having been treated with anthelmintic drugs had lower odds of co-infection. While S. stercoralis infection risk did not appear to be spatially structured, hookworm mono-infection and co-infection exhibited spatial correlation at about 20 km. Co-infection risk was positively associated with longer walking distances to a health centre and exhibited a small clustering tendency. The association was only partly explained by climatic variables, suggesting a role for underlying factors, such as living conditions and remoteness.

CONCLUSIONS

Both parasites were ubiquitous in the province, with co-infections accounting for almost half of all cases. The high prevalence of S. stercoralis calls for control measures. Despite several years of school-based de-worming programmes, hookworm infection levels remain high. Mebendazole efficacy, as well as coverage of and compliance to STH control programmes should be investigated.

The self-curing phenomenon of schistosome infection in rhesus macaques: insight from in vitro studies

A reduction in the burden of schistosomiasis is potentially achievable by integrating a schistosomiasis vaccine with current control measures. Here, we determine parasite-specific in vitro responses of B, T, and NK cells from naive uninfected rhesus macaques to Schistosoma mansoni (Sm) egg (SmEA) and worm antigen (SmWA) preparations isolated from infected baboons. Pronounced B cell responses to SmEA and NK cell responses to both SmEA and SmWA were observed. High levels of IL-2 and IL-21 responses against Sm antigens were observed in T and non-T cells of lymph nodes (LNs) and gut lamina propria-derived lymphocytes (LPLs). Data analysis showed multifunctionality of LN-derived CD4⁺ , CD8⁺ , and CD4⁺ CD8⁺ double positive T cells against either SmWA or SmWA+SmEA antigen preparations. Distinct SmEA-specific multifunctional responses were observed in gut LPLs, suggesting simultaneous responses against egg antigens. These data provide insight into the immune effectors involved in schistosome responses by rhesus macaques.

An automated high-throughput system for phenotypic screening of chemical libraries on C. elegans and parasitic nematodes

Parasitic nematodes infect hundreds of millions of people and farmed livestock. Further, plant parasitic nematodes result in major crop damage. The pipeline of therapeutic compounds is limited and parasite resistance to the existing anthelmintic compounds is a global threat. We have developed an INVertebrate Automated Phenotyping Platform (INVAPP) for high-throughput, plate-based chemical screening, and an algorithm (Paragon) which allows screening for compounds that have an effect on motility and development of parasitic worms. We have validated its utility by determining the efficacy of a panel of known anthelmintics against model and parasitic nematodes: Caenorhabditis elegans, Haemonchus contortus, Teladorsagia circumcincta, and Trichuris muris. We then applied the system to screen the Pathogen Box chemical library in a blinded fashion and identified compounds already known to have anthelmintic or anti-parasitic activity, including tolfenpyrad, auranofin, and mebendazole; and 14 compounds previously undescribed as anthelmintics, including benzoxaborole and isoxazole chemotypes. This system offers an effective, high-throughput system for the discovery of novel anthelmintics.

A method for single pair mating in an obligate parasitic nematode

Parasitic nematode species have extremely high levels of genetic diversity, presenting a number of experimental challenges for genomic and genetic work. Consequently, there is a need to develop inbred laboratory strains with reduced levels of polymorphism. The most efficient approach to inbred line development is single pair mating, but this is challenging for obligate parasites where the adult sexual reproductive stages are inside the host, and thus difficult to experimentally manipulate. This paper describes a successful approach to single pair mating of a parasitic nematode, Haemonchus contortus. The method allows for polyandrous mating behaviour and involves the surgical transplantation of a single adult male worm with multiple immature adult females directly into the sheep abomasum. We used a panel of microsatellite markers to monitor and validate the single pair mating crosses and to ensure that the genotypes of progeny and subsequent filial generations were consistent with those expected from a mating between a single female parent of known genotype and a single male parent of unknown genotype. We have established two inbred lines that both show a significant overall reduction in genetic diversity based on microsatellite genotyping and genome-wide single nucleotide polymorphism. There was an approximately 50% reduction in heterozygous SNP sites across the genome in the MHco3.N1 line compared with the MoHco3(ISE) parental strain. The MHco3.N1 inbred line has subsequently been used to provide DNA template for whole genome sequencing of H. contortus. This work provides proof of concept and methodologies for forward genetic analysis of obligate parasitic nematodes.

Isothermal diagnostic assays for the detection of soil-transmitted helminths based on the SmartAmp2 method

Background

Diagnosis of soil-transmitted helminths (STHs) has traditionally relied on stool microscopy, which has a number of critical deficiencies. Molecular diagnostics are powerful tools to identify closely related species, but the requirement for costly equipment makes their implementation difficult in low-resource or field settings. Rapid, sensitive and cost-effective diagnostic tools are crucial for accurate estimation of STH infection intensity in MDA programmes in which the goal is to reduce morbidity following repeated rounds of chemotherapy.

Results

In this study, colourimetric isothermal assays were developed using SmartAmp2 primer sets and reagents in loop-mediated amplification (LAMP) assays. Species-specific primer sets, designed on a specific target sequence in the β-tubulin gene, were used to identify Necator americanus, Trichuris trichiura and Ascaris lumbricoides. After initial optimization on control plasmids and genomic DNA from adult worms, assays were evaluated on field samples. Assays showed high sensitivity and demonstrated high tolerance to inhibitors in spiked faecal samples. Rapid and sensitive colourimetric assays were successfully developed to identify the STHs in field samples using hydroxy napthol blue (HNB) dye.

Conclusions

Rapid and simple colourimetric diagnostic assays, using the SmartAmp2 method, were developed, with the potential to be applied in the field for detection of STH infections and the estimation of response to treatment. However, further validation on large numbers of field samples is needed.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2420-1) contains supplementary material, which is available to authorized users.

Mining Filarial Genomes for Diagnostic and Therapeutic Targets

Filarial infections of humans cause some of the most important neglected tropical diseases. The global efforts for eliminating filarial infections by mass drug administration programs may require additional tools (safe macrofilaricidal drugs, vaccines, and diagnostic biomarkers). The accurate and sensitive detection of viable parasites is essential for diagnosis and for surveillance programs. Current community-wide treatment modalities do not kill the adult filarial worms effectively; hence, there is a need to identify and develop safe macrofilaricidal drugs. High-throughput sequencing, mass spectroscopy methods and advances in computational biology have greatly accelerated the discovery process. Here, we describe post-genomic developments toward the identification of diagnostic biomarkers and drug targets for the filarial infection of humans.

Effective drug combination for Caenorhabditis elegans nematodes discovered by output-driven feedback system control technique

Infections from parasitic nematodes (or roundworms) contribute to a significant disease burden and productivity losses for humans and livestock. The limited number of anthelmintics (or antinematode drugs) available today to treat these infections are rapidly losing their efficacy as multidrug resistance in parasites becomes a global health challenge. We propose an engineering approach to discover an anthelmintic drug combination that is more potent at killing wild-type Caenorhabditis elegans worms than four individual drugs. In the experiment, freely swimming single worms are enclosed in microfluidic drug environments to assess the centroid velocity and track curvature of worm movements. After analyzing the behavioral data in every iteration, the feedback system control (FSC) scheme is used to predict new drug combinations to test. Through a differential evolutionary search, the winning drug combination is reached that produces minimal centroid velocity and high track curvature, while requiring each drug in less than their EC₅₀ concentrations. The FSC approach is model-less and does not need any information on the drug pharmacology, signaling pathways, or animal biology. Toward combating multidrug resistance, the method presented here is applicable to the discovery of new potent combinations of available anthelmintics on C. elegans, parasitic nematodes, and other small model organisms.

Working towards New Drugs against Parasitic Worms in a Public-Development Partnership

There is a clear need to develop new and inexpensive drugs to alleviate diseases caused by parasitic worms in animals and humans worldwide. In this article we discuss the roles and advantages of working in public-private partnerships (PPPs) - among academia, industry, and philanthropy - to enable anthelmintic drug discovery.

The Global State of Helminth Control and Elimination in Children

Helminth infections, including soil-transmitted helminths and schistosomiasis, remain one of the most common infections in the world with over 1 billion people infected. These infections cause significant morbidity, particularly in young children, that may last a lifetime, including growth and cognitive stunting. There is an urgent need for the control and elimination of helminth infections from areas of poverty to reduce morbidity in children. Mass drug administration programs were adopted by the World Health Assembly in 2001 and have evolved to provide coverage with multiple anthelmintic medications in a single rapid impact package and more extensive coverage within a community.