Emerging foodborne trematodiasis

Baseline health situation of communities affected by the Nam Theun 2 hydroelectric project in central Lao PDR and indicators for monitoring

Hydroelectric projects offer opportunities for infrastructure development and economic growth; yet, if not well designed, implemented and operated, they have the potential to negatively affect the health and well-being of local and distant downstream communities. Remote rural populations are particularly vulnerable to the sudden influx of men, materials and money, and associated population mixing that accompany project construction phases. Two large-scale baseline health surveys, carried out in 2001/2002 in two communities that were affected by the Nam Theun 2 hydroelectric project in central Lao PDR, were analysed. For the population to be resettled on the Nakai plateau it was observed that access to clean water and basic sanitation facilities was lacking. Faecal examinations revealed a high infection prevalence for Ascaris lumbricoides (67.7%), but relatively low prevalences for hookworm (9.7%), Taenia spp. (4.8%), Enterobius vermicularis (4.4%), Trichuris trichiura (3.9%), Strongyloides stercoralis (1.4%) and Opisthorchis viverrini (0.9%). For the population in the Xe Bang Fai downstream area, rapid diagnostic tests for malaria carried out in the rainy season found a prevalence below 1%, which might be explained by the complete coverage of households with insecticide-treated nets (99.8%). Anthropometric measurements in both populations suggest that wasting, stunting and underweight in under 5-year-old children were moderate to high; 15.9-17.5%, 40.4-55.7% and 35.8-55.7%, respectively. One out of six individuals aged above 14 years were malnourished, most likely as a result of early childhood wasting. Moderate anaemia, assessed by age- and sex-specific haemoglobin levels, was present in 43.8% (Nakai) and 54.9% of the individuals examined (Xe Bang Fai). Several indicators were extracted that can be utilised for monitoring changes in health, well-being and equity, as the project is implemented and operated.

Cholangiocarcinoma: lessons from Thailand

PURPOSE OF REVIEW

To present the background of liver fluke-associated cholangiocarcinoma in Thailand focusing on recent epidemiological data and pathogenesis of this bile duct cancer.

RECENT FINDINGS

More systematic tumor registration in Thailand nowadays uncovers new high-incidence areas that are confined to not only the northeastern part but also some provinces in northern Thailand. The link between the liver fluke, Opisthorchis viverrini, and cholangiocarcinoma, particularly in terms of cellular and molecular pathogenesis, is further elucidated.

SUMMARY

Thailand is still the country with the highest incidence of cholangiocarcinoma in the world. Liver fluke induces chronic inflammation leading to oxidative DNA damage of the infected biliary epithelium and malignant transformation. Eradication of the fluke and identification of high-risk populations are urgently needed.

Artemether, artesunate, praziquantel and tribendimidine administered singly at different dosages against Clonorchis sinensis: a comparative in vivo study

We comparatively assessed the in vivo efficacy of artemether, artesunate, praziquantel and tribendimidine against different stages of Clonorchis sinensis. Rats were infected with 40-50 C. sinensis metacercariae, and drugs were administered singly by the oral route at different dosages. Rats were dissected 2-4 weeks post-treatment and C. sinensis trematodes were removed from the liver and bile ducts and counted. We used a negative binomial regression model to test the effect of drug and dosage in terms of worm burden reduction. Single 150 mg/kg oral doses of artesunate, artemether, tribendimidine and praziquantel, administered to rats infected with adult C. sinensis, resulted in mean worm burden reductions of 100, 100, 89.5 and 80.7%, respectively (all P<0.001). Halving the dose to 75 mg/kg still resulted in highly significant worm burden reductions for artesunate, artemether and tribendimidine (71.4-100%), but not for praziquantel (20.7%). In the juvenile infection model, a single 150 mg/kg oral dose of tribendimidine and praziquantel resulted in mean worm burden reductions of 99.1 and 90.0%, respectively, whereas considerably lower reductions were observed for artemether (59.2%) and artesunate (57.6%) when used at the same single dose. The in vivo results presented here with the artemisinins and tribendimidine provide further data for clinical investigations to assess the safety and efficacy of these drugs in clonorchiasis patients.

Emerging angiostrongyliasis in Mainland China

Our review of angiostrongyliasis in China found that the disease is emerging as a result of changes in food consumption habits and long-distance transportation of food. Enhanced understanding of angiostrongyliasis epidemiology, increased public awareness about the risks associated with eating raw food, and enhanced food safety measures are needed.

Fishborne zoonotic intestinal trematodes, Vietnam

Although fishborne zoonotic trematodes that infect the liver are well documented in Vietnam, intestinal fishborne zoonotic trematodes are unreported. Recent discoveries of the metacercarial stage of these flukes in wild and farmed fish prompted an assessment of their risk to a community that eats raw fish. A fecal survey of 615 persons showed a trematode egg prevalence of 64.9%. Infected persons were treated to expel liver and intestinal parasites for specific identification. The liver trematode Clonorchis sinensis was recovered from 51.5%, but > or =1 of 4 intestinal species of the family Heterophyidae was recovered from 100%. The most numerous were Haplorchis spp. (90.4% of all worms recovered). These results demonstrate that fishborne intestinal parasites are an unrecognized food safety risk in a country whose people have a strong tradition of eating raw fish.

Artemisinins and synthetic trioxolanes in the treatment of helminth infections

PURPOSE OF REVIEW

Helminthiases, including schistosomiasis and food-borne trematodiasis, affect millions of people. Just a few drugs are used for the treatment and control of these diseases. We review recent in-vitro and in-vivo observations with the artemisinins and synthetic trioxolanes against major trematode infections, update clinical findings, and discuss the potential impact that artemisinin-based combination therapy might have on trematode infections in settings where malaria and helminthiases are co-endemic.

RECENT FINDINGS

The artemisinins and synthetic trioxolanes possess a broad spectrum of activity against trematodes. High worm-burden reductions were obtained with these drugs in rodents with acute or chronic infections of Schistosoma japonicum, S. mansoni, Clonorchis sinensis, Fasciola hepatica and Opisthorchis viverrini. Clinical trials carried out in Africa, utilizing artemether or artesunate singly or as artemisinin-based combination therapies, following recommended malaria treatment schedules, found an effect against schistosomiasis.

SUMMARY

Artemisinin-based combination therapies are increasingly deployed against malaria, and hence there is a need to assess the potential auxiliary effects against schistosomiasis in settings where both diseases are endemic. Also, the effect of artemisinin-based combination therapies on food-borne trematodiasis should be assessed. In-vitro and in-vivo findings with the synthetic trioxolanes provide data to launch preclinical investigations.

Clonorchicidal properties of the synthetic trioxolane OZ78

Because the synthetic trioxolane OZ78 is active against the liver fluke Fasciola hepatica, we were motivated to investigate the in vivo and in vitro activity against another liver fluke, namely Clonorchis sinensis. Rats infected with C. sinensis for 2 and 5 wk were treated orally with single doses of OZ78 (75, 150, or 300 mg/kg). Worm burden reductions were assessed against untreated control rats. Scanning electron microscopy (SEM) was used to observe adult C. sinensis after recovery from rats 1-3 days posttreatment with a single 300 mg/kg oral dose of OZ78 and after in vitro exposure to concentrations of 1, 10, and 100 microg/ml of OZ78. A single 300 mg/kg oral dose of OZ78 resulted in worm burden reductions of 78.5% and 98.5% against juvenile and adult C. sinensis, respectively. SEM observations revealed tegumental surface alterations, including blebbing and sloughing. OZ78 emerges as a new compound with a broad spectrum of activity against major foodborne trematode infections.

Occurrence and species distribution of fishborne zoonotic trematodes in wastewater-fed aquaculture in northern Vietnam

OBJECTIVES

To assess the risk of fishborne zoonotic trematode (FZT) infection in fish reared in wastewater-fed ponds in peri-urban areas of northern Vietnam.

METHODS

We collected 1200 fish from aquaculture systems receiving wastewater from the cities of Hanoi and Nam Dinh in northern Vietnam and examined them for zoonotic metacercariae. Collection periods were fall (October-November 2005) and spring (April-June 2006). The fish were digested in pepsin and metacecariae, recovered and identified by light microscopy. Data were expressed as both prevalence and intensity of infection.

RESULTS

FZT metacercariae were recovered from fish samples at both sites and during both sampling periods. The overall prevalence of FZT was 5% (2.0% in fall and 6.5% in spring) in fish from Hanoi and 4.6% (2.4% in fall and 5.7% in spring) in fish from Nam Dinh. The higher prevalence in the warmer months was likely due to ecological factors such as temperatures and population dynamics of the snail vectors. All metacercariae recovered were zoonotic intestinal trematodes of the family Heterophyidae. The infected fish included tilapia (Oreochromis niloticus) and three species of carps, including silver carp (Hypophthalmichthys molitrix), which is commonly used for the preparation of raw fish dishes. Intensities of infection were relatively low.

CONCLUSION

Fish raised in peri-urban wastewater-fed aquaculture systems are at risk of infection with trematode parasites, which can be transmitted to humans through consumption of raw or improperly prepared fish. However, the prevalence was low as compared to previous findings of FZT in non-wastewater fish elsewhere in Vietnam. Studies are needed to assess the relative importance of different risk factors for transmission and control of FZT in wastewater-fed aquaculture.

Abandoning small-scale fish farming in western Kenya leads to higher malaria vector abundance

Fishponds become abandoned due to lack of access to both young fish and technical support and faster economic returns from other activities. Certain conditions found in abandoned fishponds, such as absence of fish and presence of aquatic vegetation, are conducive to the presence of malaria vectors. We conducted a district-wide fishpond census to determine the maintenance status and mosquito populations of fishponds in Kisii Central District in western Kenya. Two hundred and sixty one fishponds were found, 186 active (fish present) and 75 abandoned (fish absent). Vegetation was not significantly associated with the distribution of Anopheles gambiae s.l., Anopheles funestus or culicines (Diptera: Culicidae) in active or abandoned ponds. The presence of fish, however, correlated significantly with the distribution of all mosquito species, with significantly higher mosquito densities in abandoned fishponds. An. gambiae s.l. was the most abundant mosquito species found in both active and abandoned ponds, being proportionally more abundant in the abandoned ponds. The proportion of An. funestus increased with altitude. Following the census the demand for fish to re-stock abandoned ponds rose by 67% when compared to the same time period in the previous year. This study highlights the potential public health problems associated with the abandonment of small-scale fish farming in the highlands of western Kenya.

Human fascioliasis: a case of hyperinfection and an update for clinicians

Fascioliasis is a foodborne trematode infection that affects patients worldwide causing both liver inflammation and biliary obstruction. In developed countries, the disease is rare but a number of focal outbreaks have been reported. Here, we report a case of human fascioliasis in which acute and chronic manifestations coexisted and discuss the newest evidence regarding pathogenesis, diagnostic approach, and treatment, with emphasis on strategies to control the incidence of this emergent disease.

Activity of artemether and OZ78 against triclabendazole-resistant Fasciola hepatica

Triclabendazole is the drug of choice against Fasciola hepatica infections in humans and animals. However, parasite resistance against triclabendazole is spreading in the veterinary field, and there are no drugs of comparable activity currently available for the treatment and control of fascioliasis. We investigated the efficacy of single oral doses of artemether and OZ78 against adult triclabendazole-resistant F. hepatica harboured in rats, and compared the results with triclabendazole administered at two different doses. Single oral doses of 100 mg/kg OZ78 and 200 mg/kg artemether resulted in worm burden reductions of 100%. Whereas a single 10 mg/kg dose of triclabendazole achieved a worm burden reduction of only 4.0%, a five-fold higher dose yielded a significant worm burden reduction of 60.9%. However, the lower dose of triclabendazole administered to rats harbouring a triclabendazole-sensitive F. hepatica isolate resulted in a worm burden reduction of 95.3%. Our findings confirm that artemether and OZ78 possess good fasciocidal properties, even against a triclabendazole-resistant F. hepatica isolate, and hence these drugs might become useful in areas where triclabendazole resistance is common.

Fasciola hepatica: tegumental alterations in adult flukes following in vitro and in vivo administration of artesunate and artemether

The tegumental changes in adult Fasciola hepatica induced by artemether and artesunate were assessed utilizing scanning electron microscopy (SEM). F. hepatica were incubated with artemether and artesunate for 48h at a concentration of 10microg/ml in the absence or presence of haemin. For the latter experiment both, a triclabendazole-resistant and sensitive F. hepatica isolate were used. For the in vivo studies rats were treated with single 200mg/kg oral doses of artemether and artesunate and flukes recovered from the bile ducts after 24-96h. SEM analysis of the flukes incubated in the presence of the drugs without haemin showed only minor and localized damage of the tegument. In the presence of haemin extensive tegumental damage, including sloughing, blebbing and eruptions, particularly in the ventral and dorsal mid-body and tail region, was evident. No difference in the extent of damage could be observed between artemether and artesunate and between the triclabendazole-resistant and non-resistant flukes. After 24h in vivo disruption of the tegument was evident in the artemether-treated flukes, and the damage increased in severity 48-72h post-treatment. Sloughing, swelling and extensive furrowing of the tegument was observed in several flukes, in particular in the tail region and the ventral apical cone region. In the artesunate treatment, tegumental damage was evident after 72h, but seemed slightly less pronounced when compared to the artemether-treated specimens examined at the same time point. Concluding our experiments confirm that artemether and artesunate are potent fasciocidal drugs and the tegument of adult F. hepatica appears to be a target for the action of these drugs.

Survey for zoonotic liver and intestinal trematode metacercariae in cultured and wild fish in An Giang Province, Vietnam

Although Vietnam has a high risk of fishborne zoonotic trematode (FZT) infections for humans, little information exists on the epidemiology of these infections in the country's fish. Because of the importance of cultured catfish and snakehead production in An Giang province, a major production area in the Mekong Delta of Vietnam, a survey for FZTs was carried out in randomly selected fish farms between June 2005 and March 2006. For comparison, wild fish from the same area were also surveyed. A total of 852 cultured fish from 4 districts were collected and examined by pepsin digestion to determine their FZT infection status. In Tra catfish, the prevalence of all types of metacercariae was 2.6%, of which the prevalence of Haplorchis pumilio was 0.7%. The overall prevalence of metacercariae in wild fish was 30.6%, of which 10.3% harbored zoonotic species: H. pumilio (2.8%) and Procerovum sp. (5.6%). The prevalence of Opisthorchis metacercariae, which were diagnosed as O. viverrini, was 1.9%. No metacercariae were found in cultured snakehead fish, although wild-caught snakehead fish had a FZT prevalence of 10.3%: 5.1% were O. viverrini 2.6% H. pumilio and 2.6% were Procerovum sp. These are the first reports of H. pumilio, Procerovum sp., and O. viverrini metacercariae in Vietnamese fish. These results indicate that consumption of improperly prepared fish represents a significant risk of acquiring FZTs in this south Vietnam region.

Prevalence of fishborne zoonotic parasites in important cultured fish species in the Mekong Delta, Vietnam

A seasonal investigation on the occurrence of fishborne zoonotic trematodes (FZT) in economically important mono-cultured hybrid catfish and giant gouramy was conducted in the Mekong Delta of Vietnam. Fish from carp poly-culture and intensive small-scale integrated vegetable-aquaculture-animal husbandry farming (VAC) systems were also examined. No FZT metacercariae were found in any mono-cultured hybrid catfish. FZT metacercariae were common, however, in fish from the other three systems: All metacercariae belonged to the Heterophyidae family of trematodes, Haplorchis pumilio, H. taichui, Centrocestus formosanus and Stellantchasmus falcatus. The FZT prevalence was 1.7% in mono-cultured giant gouramy, 6.6% in carp from the poly-culture and 3.0% in fish raised in the VAC system. H. pumilio was the most common FZT species constituting more than 58.0% of all metacercariae recovered. The prevalence of infection was significantly higher in the flooding season compared to the non-flooding season for both giant gouramy and fish reared in the VAC system. FZT intensity was greatest in fish from carp poly-culture, particularly in the flooding season. The results indicate that certain fish production systems are at risk for FZT, and control approaches will benefit from understanding these risk factors.

Liver fluke induces cholangiocarcinoma

The authors discuss the molecular pathogenesis of opisthorchiasis and associated cholangiocarcinogenesis, particularly nitrative and oxidative DNA damage and the clinical manifestations of cholangiocarcinoma.

Identification of a platyhelminth neuropeptide receptor

We report the characterisation of the first neuropeptide receptor from the phylum Platyhelminthes, an early-diverging phylum which includes a number of important human and veterinary parasites. The G protein-coupled receptor (GPCR) was identified from the model flatworm Girardia tigrina (Tricladida: Dugesiidae) based on the presence of motifs widely conserved amongst GPCRs. In two different assays utilising heterologous expression in Chinese hamster ovary cells, the Girardia GPCR was most potently activated by neuropeptides from the FMRFamide-like peptide class. The most potent platyhelminth neuropeptide in both assays was GYIRFamide, a FMRFamide-like peptide known to be present in G. tigrina. There was no activation by neuropeptide Fs, another class of flatworm neuropeptides. Also active were FMRFamide-like peptides derived from other phyla but not known to be present in any platyhelminth. Most potent among these were nematode neuropeptides encoded by the Caenorhabditis elegans flp-1 gene which share a PNFLRFamide carboxy terminal motif. The ability of nematode peptides to stimulate a platyhelminth receptor demonstrates a degree of structural conservation between FMRFamide-like peptide receptors from these two distinct, distant phyla which contain parasitic worms.

Prevention, control, and elimination of neglected diseases in the Americas: pathways to integrated, inter-programmatic, inter-sectoral action for health and development

Background

In the Latin America and Caribbean region over 210 million people live below the poverty line. These impoverished and marginalized populations are heavily burdened with neglected communicable diseases. These diseases continue to enact a toll, not only on families and communities, but on the economically constrained countries themselves.

Discussion

As national public health priorities, neglected communicable diseases typically maintain a low profile and are often left out when public health agendas are formulated. While many of the neglected diseases do not directly cause high rates of mortality, they contribute to an enormous rate of morbidity and a drastic reduction in income for the most poverty-stricken families and communities. The persistence of this "vicious cycle" between poverty and poor health demonstrates the importance of linking the activities of the health sector with those of other sectors such as education, housing, water and sanitation, labor, public works, transportation, agriculture, industry, and economic development.

Summary

The purpose of this paper is three fold. First, it focuses on a need for integrated "pro-poor" approaches and policies to be developed in order to more adequately address the multi-faceted nature of neglected diseases. This represents a move away from traditional disease-centered approaches to a holistic approach that looks at the overarching causes and mechanisms that influence the health and well being of communities. The second objective of the paper outlines the need for a specific strategy for addressing these diseases and offers several programmatic entry points in the context of broad public health measures involving multiple sectors. Finally, the paper presents several current Pan American Health Organization and other institutional initiatives that already document the importance of integrated, inter-programmatic, and inter-sectoral approaches. They provide the framework for a renewed effort toward the efficient use of resources and the development of a comprehensive integrated solution to neglected communicable diseases found in the context of poverty, and tailored to the needs of local communities.

Epidemiology of Opisthorchis viverrini in a rural district of southern Lao PDR

In Lao PDR, detailed investigations on Opisthorchis viverrini are scarce. The objective was to document epidemiological features of O. viverrini infections in a highly endemic district. A random sample was selected (13 villages, 15 households/village, all household members aged >6 months). Clinical examinations, short interviews and stool examinations (Kato-Katz technique) were performed. Fish samples were dissected for the presence of metacercaria. In total, 814 persons were enrolled (median age 16 years, 51.5% women). The prevalence was 58.5%. Infection rates increased with age (from 20.0 to 85.5%; P<0.001). Intensity of infection and the habit of consuming insufficiently cooked fish also increased with age. Of the study participants, 75.2% reported cooking fish insufficiently. Of the 23 different species of cyprinoid fish consumed in the study villages, 20 species were infected. At the village level, the prevalence of raw fish consumption was strongly associated with the infection status of O. viverrini (r=0.76, P=0.003). At individual level, age, the consumption of insufficiently cooked fish, and the absence of sanitation were strongly associated. The disease associated with O. viverrini infection needs to be assessed in order to develop and conduct adequate interventions.

Evidence of a species complex within the food-borne trematode Opisthorchis viverrini and possible co-evolution with their first intermediate hosts

The food-borne trematodes, Opisthorchis viverrini, O. felineus and Clonorchis sinensis, have long been recognized as the cause of major human health problems, with an estimated 40 million infected persons. Of the three species of liver fluke, only O. viverrini is classified as a type 1 carcinogen because of its role as an initiator of chronic inflammation and the subsequent development of cholangiocarcinoma. At present, there are no techniques for the early diagnosis of cholangiocarcinoma and it is fatal for most patients. There is considerable variation in parasite prevalence and disease presentation in different geographical areas, the latter of which may be associated with genetic differences among parasites. In the present study, multilocus enzyme electrophoresis was used to provide a comprehensive genetic characterization of O. viverrini from different geographical localities in Thailand and the Peoples’ Democratic Republic of Laos. Parasites from different localities were compared genetically at 32 enzyme loci. The results of the genetic analyses are sufficient to reject the null hypothesis that O. viverrini represents a single species. Therefore, O. viverrini consists of at least two genetically distinct, yet morphologically similar (i.e. cryptic) species. Moreover, there was also separation of the different populations of snails (i.e. the first intermediate hosts) into two distinct genetic groups that corresponded with the delineation of O. viverrini into two species. This suggests that there may be a history of co-evolution in this host–parasite lineage. Additionally, five distinct genetic groups of parasites were detected, each of which occurred within a different and independent river wetland system. Our findings have major implications for the implementation of effective control and surveillance programs targeted to these medically important food-borne parasites.

Evaluation of the in vivo activity of tribendimidine against Schistosoma mansoni, Fasciola hepatica, Clonorchis sinensis, and Opisthorchis viverrini

We examined the in vivo activity of tribendimidine against selected trematodes. A single 150-mg/kg dose of tribendimidine achieved a 99.1% reduction of Clonorchis sinensis in rats. A 400-mg/kg dose of tribendimidine reduced Opisthorchis viverrini in hamsters by 95.7%. High doses of tribendimidine showed no activity against Schistosoma mansoni and Fasciola hepatica.

Cross-sectional parasitological survey for helminth infections among fish farmers in Nghe An province, Vietnam

A total of 964 adult fish farmers in five eastern districts in Nghe An province, Vietnam were investigated in late 2004 for food-borne trematodes and other helminth infections using duplicate Kato-Katz thick smears prepared from single stool samples. Eggs of fish-borne trematodes and of Fasciolopsis buski were found in 0.6 and 0.7% of farmers, respectively. Infection prevalences with soil-transmitted helminths (STHs), namely Ascaris lumbricoides, Trichuris trichiura and hookworm, were 34.8, 50.7 and 51.3%, respectively, and 81.8% were infected with at least one of the three STHs. While A. lumbricoides and T. trichiura were more prevalent in the eastern districts compared to the more western districts, the opposite was true for hookworm infections. The widespread prevalence of STH infections in fish farmers suggests that control of these infections in school-age children only may be inadequate. Identification of the human behavioural factors and environmental features responsible for the distribution and frequency of STHs among adults is needed as well as a sensitive diagnostic test of fish-borne trematodes at species level.

Effect of tribendimidine on adult Echinostoma caproni harbored in mice, including scanning electron microscopic observations

Food-borne trematodiasis is an emerging public health problem with more than 10% of the world's population at risk of infection, yet there are only 2 drugs available for treatment and morbidity control. We assessed the effect of a promising broad-spectrum anthelmintic drug, i.e., tribendimidine, with an experimental focus on adult Echinostoma caproni. Female NMRI mice were infected with 30 E. caproni for 2 wk and then administered single oral doses of tribendimidine ranging between 25 and 500 mg/kg. Three days post-treatment, mice were necropsied, and adult worms were recovered from their intestines. Worm burden reductions were assessed against untreated control mice. In addition, scanning electron microscopic observations were done on adult E. caproni recovered from mice given a single dose of 150 mg/kg tribendimidine intragastrically 2, 4, and 8 hr post-treatment. Worm burden reductions of 100% were achieved at doses of 125 mg/kg and above. Severe damage of the tegument, including extensive peeling, formation of blebs, and structural loss of the definition of collar and tegumentary spines already occurred within 2 hr after drug administration. Our findings call for further investigations using tribendimidine in other trematode-animal models, because this compound shows promising trematocidal activity.

Effect of artesunate and artemether against Clonorchis sinensis and Opisthorchis viverrini in rodent models

Food-borne trematodiasis is an emerging public health problem and there is a need to develop novel treatment options. We examined the in vivo efficacy of single oral doses of artesunate and artemether administered to rodents experimentally infected with either Clonorchis sinensis or Opisthorchis viverrini. Rats infected with adult C. sinensis were administered artesunate or artemether at doses of 75, 150 or 300 mg/kg. Hamsters infected with adult O. viverrini were administered artesunate or artemether at doses of 200, 400 or 600 mg/kg. Treatment efficacy was assessed according to reductions in worm burden compared with infected but untreated control animals. Worm burden reductions of 98.6-100% were found in C. sinensis-infected rats after a single dose of artesunate and artemether at 150 mg/kg. Administration of artesunate and artemether at a dose of 400mg/kg to O. viverrini-infected hamsters resulted in worm burden reductions of 77.6% and 65.5%, respectively. However, both drugs showed toxic effects when administered to O. viverrini-infected hamsters at a dose > or =400mg/kg. Our study demonstrates that artesunate and artemether possess excellent clonorchicidal activities in vivo. These findings provide a foundation for subsequent clinical trials. More laboratory investigations are warranted to investigate further the opisthorchicidal properties of the artemisinins.

Trematocidal activity of praziquantel and artemisinin derivatives: in vitro and in vivo investigations with adult Echinostoma caproni

We examined the effects of praziquantel and the artemisinins on adult Echinostoma caproni. In vitro, both praziquantel and the artemisinins exhibited exposure-response relationships. In vivo, worm burden reductions of 100% were achieved with single oral doses of praziquantel, artesunate, and artemether at 50, 700, and 1,100 mg/kg of body weight, respectively.

Control of Human Parasitic Diseases: Context and Overview

The control of parasitic diseases of humans has been undertaken since the aetiology and natural history of the infections was recognized and the deleterious effects on human health and well-being appreciated by policy makers, medical practitioners and public health specialists. However, while some parasitic infections such as malaria have proved difficult to control, as defined by a sustained reduction in incidence, others, particularly helminth infections can be effectively controlled. The different approaches to control from diagnosis, to treatment and cure of the clinically sick patient, to control the transmission within the community by preventative chemotherapy and vector control are outlined. The concepts of eradication, elimination and control are defined and examples of success summarized. Overviews of the health policy and financing environment in which programmes to control or eliminate parasitic diseases are positioned and the development of public-private partnerships as vehicles for product development or access to drugs for parasite disease control are discussed. Failure to sustain control of parasites may be due to development of drug resistance or the failure to implement proven strategies as a result of decreased resources within the health system, decentralization of health management through health-sector reform and the lack of financial and human resources in settings where per capita government expenditure on health may be less than $US 5 per year. However, success has been achieved in several large-scale programmes through sustained national government investment and/or committed donor support. It is also widely accepted that the level of investment in drug development for the parasitic diseases of poor populations is an unattractive option for pharmaceutical companies. The development of partnerships to specifically address this need provides some hope that the intractable problems of the treatment regimens for the trypanosomiases and leishmaniases can be solved in the not too distant future. However, it will be difficult to implement and sustain such interventions in fragile health services often in settings where resources are limited but also in unstable, conflict-affected or post-conflict countries. Emphasis is placed on the importance of co-endemicity and polyparasitism and the opportunity to control parasites susceptible to cost-effective and proven chemotherapeutic interventions for a package of diseases which can be implemented at low cost and which would benefit the poorest and most marginalized groups. The ecology of parasitic diseases is discussed in the context of changing ecology, environment, sociopolitical developments and climate change. These drivers of global change will affect the epidemiology of parasites over the coming decades, while in many of the most endemic and impoverished countries parasitic infections will be accorded lower priority as resourced stressed health systems cope with the burden of the higher-profile killing diseases viz., HIV/AIDS, TB and malaria. There is a need for more holistic thinking about the interactions between parasites and other infections. It is clear that as the prevalence and awareness of HIV has increased, there is a growing recognition of a host of complex interactions that determine disease outcome in individual patients. The competition for resources in the health as well as other social sectors will be a continuing challenge; effective parasite control will be dependent on how such resources are accessed and deployed to effectively address well-defined problems some of which are readily amenable to successful interventions with proven methods. In the health sector, the problems of the HIV/AIDS and TB pandemics and the problem of the emerging burden of chronic non-communicable diseases will be significant competitors for these limited resources as parasitic infections aside from malaria tend to be chronic disabling problems of the poorest who have limited access to scarce health services and are representative of the poorest quintile. Prioritization and advocacy for parasite control in the national and international political environments is the challenge.

Incorporating a rapid-impact package for neglected tropical diseases with programs for HIV/AIDS, tuberculosis, and malaria

Hotez et al. argue that achieving success in the global fight against HIV/AIDS, tuberculosis, and malaria may well require a concurrent attack on the neglected tropical diseases.

Control of neglected tropical diseases: integrated chemotherapy and beyond

Utzinger and de Savigny discuss the implications of a new policy paper, which argues that the control of "the big three" diseases (HIV, TB, and malaria) should be integrated with control of the neglected tropical diseases.

Triclabendazole for the treatment of fascioliasis and paragonimiasis

Fascioliasis and paragonimiasis, which are caused by liver flukes (Fasciola) and lung flukes (Paragonimus), are emerging public health problems. Several hundred millions of people are at risk of the two diseases that cause considerable morbidity and delay socio-economic development. Triclabendazole, a benzimidazole derivative, has been routinely used since 1983 in veterinary medicine to control infections with Fasciola spp. in domestic herbivorous animals. In 1986, a veterinary formulation of triclabendazole was first administered to two human patients with fascioliasis. Clinical data obtained thus far suggest that triclabendazole is the most efficacious and best tolerated drug for the treatment of fascioliasis. Moreover, the drug holds promise as a useful therapeutic alternative to praziquantel in the treatment of paragonimiasis. This review of triclabendazole includes an overview of the pharmacodynamics and pharmacokinetics, toxicology and efficacy against the major food-borne trematodes in laboratory animals. Data from case reports and clinical trials in humans infected with Fasciola spp. and Paragonimus spp. are summarised and the current state of triclabendazole regarding treatment of human fascioliasis and paragonimiasis is described. Efforts to facilitate broader registration of this drug should go hand-in-hand with research and development on novel drugs against food-borne trematodiasis, better access to improved sanitation, sound health education and the development of new technologies for assuring food safety.