Effectiveness of health education in improving knowledge, attitude and practice related to foodborne zoonotic trematodes in Vietnam, with a particular focus on Clonorchis sinensis.

OBJECTIVE: Foodborne zoonotic trematodes (FZT), which infect the liver, lungs and intestines of humans, are an emerging public health concern in tropical countries including Vietnam. In northern Vietnam, Clonorchis sinensis is recognised as the most important species of the FZT. Up to now, small-scale studies conducted in the country have indicated that health education could improve participants' knowledge and practices related to clonorchiasis, however strong evidence is still lacking. We conducted an intervention trial between 2020 and 2021 in four communes in Yen Bai and Thanh Hoa province, aiming to evaluate the impact of an extended educational package on knowledge, attitude and practices related to clonorchiasis, as well as on knowledge on the large liver fluke and minute intestinal flukes. METHODS: To this end, baseline and post-intervention questionnaires were conducted. Generalised estimating equations models were run to analyse the impact of the intervention on knowledge, attitudes and practices over time in the intervention versus control group. Finally, 172 people in the intervention group and 162 in the control group were included for analysis. RESULTS: Results demonstrated that the intervention significantly improved clonorchiasis knowledge, attitudes and practices, with higher odds for a correct knowledge response (odds ratio (OR) = 2.80, 95% confidence interval (CI) = 1.84-4.27, p-value < 0.001), increased average mean attitude score (mean = 0.363, 95%CI = 0.182-0.544, p-value < 0.001), and a reduced odds of consuming raw fish (OR = 0.15, 95%CI = 0.06-0.40, p = 0.002) in the intervention group compared to the control group post-intervention versus baseline. Additionally, participants in the intervention group exhibited enhanced basic knowledge of the large liver fluke and minute intestinal flukes post-intervention. CONCLUSIONS: These findings demonstrate the potential of health education programs in preventing clonorchiasis in endemic areas, emphasising the importance of continued health education as a critical component of integrated control programs for clonorchiasis.

Molecular classification of rumen fluke eggs in fecal specimens from Suphanburi Province, Thailand, based on cytochrome C oxidase subunit 1.

Rumen fluke infections have been known to cause paramphistomiasis in both wild and domestic animals worldwide. Occasionally, coinfections of rumen flukes (Carmyerius, Fischoederius, and Paramphistomum) with liver flukes (Fasciola) have been observed due to the similar life cycles that these two species share. This study involved an alternative approach that was developed to classify and distinguish rumen fluke eggs from other genera by using the polymerase chain reaction (PCR) method based on cytochrome c oxidase subunit 1 (COI). Thirty-eight fecal specimens of Bos taurus from Suphanburi Province, Central Thailand were examined using the formalin-ether sedimentation technique. PCR detection was then performed using COI-specific primers that were developed in this study. The results showed that this primer set can classify and distinguish the egg specimens into a separate clade of the genera comprising Gastrothylax, Carmyerius, Fischoederius, Paramphistomum, Explanatum, and Fasciola. Moreover, epidemiological mapping revealed coinfections of three genera of rumen flukes at some collection sites, leading to the need to further investigate Paramphistomoidea infection along with Fasciolidae infection within the endemic area. This data is important for monitoring the outbreak of these parasites in Suphanburi Province, Thailand. It can be applied for initiating surveillance programs of paramphistomiasis and fascioliasis in veterinary studies.

Form and Function in the Digenea.

This review aims at covering the general aspects of the form and function of the major body systems in digenetic trematodes, with emphasis on the advances that have been made on this topic since the publication of the first edition of this book; this is since 2012. In particular, the advancement in the knowledge of form and function of tegumentary, sensory, neuromuscular, alimentary, respiratory, excretory, and reproductive systems is covered. Furthermore, a brief mention of the current trends in the targeting of trematode body systems for developing novel opportunities of treatment and control is provided.

Intestinal Trematode Infections.

Intestinal trematodes are among the most common types of parasitic worms. About 76 species belonging to 14 families have been recorded infecting humans. Infection commonly occurs when humans eat raw or undercooked foods that contain the infective metacercariae. These parasites are diverse with regard to their morphology, geographical distribution, and life cycle, which make it difficult to study the parasitic diseases that they cause. Many of these intestinal trematodes have been considered as endemic parasites in the past. However, the geographical limits and the population at risk are currently expanding and changing in relation to factors such as growing international markets, improved transportation systems, new eating habits in developed countries and demographic changes. These factors make it necessary to better understand intestinal trematode infections. This chapter describes the main features of human intestinal trematodes in relation to their biology, epidemiology, host-parasite relationships, pathogenicity, clinical aspects, diagnosis, treatment, and control.

Dicrocoeliidae Family: Major Species Causing Veterinary Diseases.

This chapter analyses the taxonomic position of Dicrocoeliidae family and several of its genus and species. The biology of the major species causing veterinary diseases such Dicrocoelium dendriticum, Dicrocoelium hospes, Dicrocoelium chinensis, Eurytrema pancreaticum and Platynosomum fastosum, has been reviewed. All these species have an indirect life cycle, involving two intermediate hosts (molluscs as first and ants, grasshoppers and lizards as second). Dicrocoelium dendriticum is a very widespread hepatic trematode in the ruminants of many countries in Europe, Asia, North Africa and North America, even affecting humans. Dicrocoelium hospes is widely distributed in the savanna areas of Africa south of the Sahara, whilst D. chinensis has mainly been found in ruminants in East Asia and some European countries (probably imported from Asia). Eurytrema pancreaticum is a common parasite whose adults live in ruminant bile ducts, gall bladder, pancreatic ducts and intestines in Europe, Madagascar, Asia and South America. Adult P. fastosum live in the liver, gall bladder and pancreas of birds and mammals in Europe, Africa, Asia, North, Central and South America. Information about the epidemiology, pathology, clinical aspect, diagnosis, treatment, control, prevention and economic impact mainly of Dicrocoeliosis produced by D. dendriticum, as well as of Eurytrematodosis and Platynosomiosis, has been included.

Epidemiology of Trematode Infections: An Update.

Digenetic trematodes infecting humans are more than 91 species which belong to 46 genera all over the world. According to their habitat in definitive hosts, they are classified as blood flukes (Schistosoma japonicum. S. mekongi, S. mansoni, S. haematobium, and S. intercalatum), liver flukes (Clonorchis sinensis, Opisthorchis viverrini, O. felineus, Metorchis conjunctus, M. bilis, M. orientalis, Fasciola hepatica, F. gigantica, Dicrocoelium dendriticum, and D. hospes), lung flukes (Paragonimus westermani, P. heterotremus, P. skrjabini, P. miyazakii, P. kellicoti, P. mexicanus, P. africanus, and P. uterobilateralis), throat fluke (Clinostomum complanatum), pancreatic fluke (Eurytrema pancreaticum), and intestinal flukes (Metagonimus yokogawai, M. miyatai, M. takahashii, Heterophyes nocens, H. heterophyes, Haplorchis taichui, H. pumilio, H. yokogawai, Centrocestus formosanus, Echinostoma revolutum, E. ilocanum, Isthmiophora hortensis, Echinochasmus japonicus, E. lilliputanus, Artyfechinostomum malayanum, A. sufrartyfex, A. oraoni, Fasciolopsis buski, Gymnophalloides seoi, Neodiplostomum seoulense, Caprimolgorchis molenkampi, Phaneropsolus bonnei, and Plagiorchis muris). The mode of transmission to humans includes contact with cercariae contaminated in water (schistosomes) and ingestion of raw or improperly cooked fish (liver and throat flukes, heterophyids, and echinostomes), snails (echinostomes and gymnophallids), amphibia, reptiles (neodiplostomes), aquatic vegetables (amphistomes), or insect larvae or adults (plagiorchiids, lecithodendriids, and pancreatic fluke). Praziquantel has been proved to be highly effective against most species of trematode infections except fascioliasis. Epidemiological surveys and detection of human infections are required for better understanding of the geographical distribution and endemicity of each trematode species.

Evaluation of targeted copper sulfate (CuSO4) application for controlling swimmer's itch at a freshwater recreation site in Michigan.

Swimmer's itch has historically been controlled by applying copper sulfate (CuSO4) to lakes as a way to eliminate snails that serve as the intermediate hosts for swimmer's itch-causing parasites. CuSO4 is still sometimes applied specifically to areas of lakes where swimmer's itch severity is high. It is unclear whether targeted application of chemical molluscicides like CuSO4 is effective for controlling swimmer's itch. Previous research has found that the larval stage of the parasites responsible for swimmer's itch are released from infected snails and are concentrated by onshore and alongshore winds, and thus, may not be affected by such focused applications. In this study, we evaluated the impact of targeted CuSO4 application to a specific recreational swimming area in a lake in Michigan. We measured the effect on snail populations, as well as on the presence/abundance of swimmer's itch-causing parasites using qPCR. Ultimately, while CuSO4 was confirmed to significantly reduce populations of snails within the treatment area, it was found to have no significant impact on swimmer's itch-causing parasites in the water, likely due to the free-swimming larval stages (cercariae) moving into the treatment area from surrounding regions.

Differentiating snail intermediate hosts of Schistosoma spp. using molecular approaches: fundamental to successful integrated control mechanism in Africa.

BACKGROUND: Snail intermediate hosts play active roles in the transmission of snail-borne trematode infections in Africa. A good knowledge of snail-borne diseases epidemiology particularly snail intermediate host populations would provide the necessary impetus to complementing existing control strategy. MAIN BODY: This review highlights the importance of molecular approaches in differentiating snail hosts population structure and the need to provide adequate information on snail host populations by updating snail hosts genome database for Africa, in order to equip different stakeholders with adequate information on the ecology of snail intermediate hosts and their roles in the transmission of different diseases. Also, we identify the gaps and areas where there is need for urgent intervention to facilitate effective integrated control of schistosomiasis and other snail-borne trematode infections. CONCLUSIONS: Prioritizing snail studies, especially snail differentiation using molecular tools will boost disease surveillance and also enhance efficient schistosomaisis control programme in Africa.

Monogenean parasites infect ornamental fish imported to Australia.

The ornamental fish trade provides a pathway for the global translocation of aquatic parasites. We examined a total of 1020 fish imported from Singapore, Malaysia, Thailand, or Sri Lanka to Australia (including freshwater and marine fish species) for monogenean ectoparasites. Fish were received following veterinary certification that they showed no clinical signs of pests and diseases from the exporting country and visual inspection at Australian border control. Australian import conditions require mandatory treatment for goldfish with parasiticides (e.g. trichlorfon, formaldehyde, sodium chloride) for the presence of gill flukes (Dactylogyrus vastator Nybelin, 1924 and Dactylogyrus extensus Mueller and Van Cleave, 1932) prior to export. Over 950 individual parasites were detected in five imported fish species, representing 14 monogenean species. Seven Dactylogyrus spp. including D. vastator and three Gyrodactylus spp. infected goldfish, Carassius auratus Linnaeus, 1758, from Malaysia, Singapore, and Thailand. Dactylogyrus ostraviensis Rehulka, 1988, infected rosy barb, Pethia conchonius Hamilton, 1822, from Singapore, Sri Lanka, and Thailand while two Trianchoratus spp. infected three spot gourami, Trichopodus trichopterus Pallas, 1970 and pearl gourami Trichopodus leerii Bleeker, 1852, from Sri Lanka. Urocleidoides reticulatus Mizelle & Price, 1964, infected guppy, Poecilia reticulata Peters, 1859, from Sri Lanka. The discovery of D. vastator in goldfish, as well as 13 other monogenean species, shows that pre-export health requirements, which include chemical treatment of goldfish, and inspection of all ornamental fish species did not prevent infection by monogeneans. Inspection prior to exportation and at border control must account for the highly cryptic nature of monogenean parasites and consider alternatives to current pre-export conditions and visual inspection at border control.

Efficacy and toxicity of praziquantel in helminth-infected barbel (Barbus barbus L.).

This study evaluated efficacy and toxicity of the pyrazinoisoquinoline anthelmintic praziquantel (PZQ) in barbel infected with metacercariae of Diplostomum spathaceum and adult Pomphorhynchus laevis, and assessed antioxidant biomarkers and the lipid peroxidation response in juvenile barbel post-treatment. The estimated 96-hr LC50 of PZQ was 28.6 mg/L. For evaluation of efficacy, barbel naturally infected with D. spathaceum were exposed to a 10 and 20 mg/L PZQ 4-day bath treatment. Both concentrations were 100% effective against D. spathaceum and significantly (p < .01) affected the activity of catalase, superoxide dismutase, glutathione reductase and glutathione-S-transferase as well as levels of reduced glutathione in liver and muscle. The efficacy of orally administered PZQ was assessed in adult barbel naturally infected with P. laevis. Fish were administered 10, 30 and 50 mg/kg of body weight and examined via gut dissection after 6 days. The 50 mg/kg dose significantly decreased the intensity of infection. Praziquantel is a feasible bath treatment for barbel infected with D. spathaceum and has potential for oral treatment of broodfish infected with P. laevis.

Nanoemulsion from essential oil of Pterodon emarginatus (Fabaceae) shows in vitro efficacy against monogeneans of Colossoma macropomum (Pisces: Serrasalmidae).

Outbreaks of diseases pose a major threat to sustainable aquaculture development worldwide. Application of herbal products to combat parasitic diseases provides an alternative approach for sustainable aquaculture. This study investigated the in vitro antiparasitic effects of an oil-in-water nanoemulsion prepared using the essential oil from Pterodon emarginatus, against monogeneans infesting Colossoma macropomum. Gill arches from C. macropomum (47.6 ± 14.5 g and 13.5 ± 1.4 cm) that were naturally parasitized by Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri were immersed in different dispersions of the P. emarginatus nanoemulsions (0, 50, 100, 200, 400 and 600 mg/L). The major compounds presented in the essential oil of P. emarginatus were ß-elemene, ß-caryophyllene and α-humulene. Characterization of these nanoemulsions showed that they have a small mean droplet size and low polydispersity index, which is concordant with stable systems. In this in vitro trial, the P. emarginatus nanoemulsion concentrations of 100, 200, 400 and 600 mg/L presented 100% helminthic efficacy against monogeneans of the gills of C. macropomum. The highest two concentrations used (400 and 600 mg/L) were seen to immobilize the parasites after only 15 min. Therefore, it would be worthwhile testing these concentrations in therapeutic baths against monogeneans of C. macropomum.

Paramphistomosis of Ruminants: An Emerging Parasitic Disease in Europe.

Whilst historically regarded as being of minor importance in European livestock, recent evidence suggests that the prevalence of paramphistomosis is greater than that of fasciolosis in parts of the UK. In order to address this emerging threat to ruminant farming systems, and associated risks for food security posed by rumen fluke infection, it is imperative that we develop a better understanding of the basic biology of this parasite and how it interacts with its ruminant host. In this Opinion article we review recent progress in tracking the spread of rumen fluke infection in Europe, and propose some research questions that should be addressed if we are to develop tools to diagnose and treat paramphistomosis more effectively in the future.

Rumen fluke in Irish sheep: prevalence, risk factors and molecular identification of two paramphistome species.

BACKGROUND: Rumen flukes are trematode parasites found globally; in tropical and sub-tropical climates, infection can result in paramphistomosis, which can have a deleterious impact on livestock. In Europe, rumen fluke is not regarded as a clinically significant parasite, recently however, the prevalence of rumen fluke has sharply increased and several outbreaks of clinical paramphistomosis have been reported. Gaining a better understanding of rumen fluke transmission and identification of risk factors is crucial to improve the control of this parasitic disease. In this regard, a national prevalence study of rumen fluke infection and an investigation of associated risk factors were conducted in Irish sheep flocks between November 2014 and January 2015. In addition, a molecular identification of the rumen fluke species present in Ireland was carried out using an isolation method of individual eggs from faecal material coupled with a PCR. After the DNA extraction of 54 individual eggs, the nuclear fragment ITS-2 was amplified and sequenced using the same primers. RESULTS: An apparent herd prevalence of 77.3 % was determined. Several risk factors were identified including type of pasture grazed, regional variation, and sharing of the paddocks with other livestock species. A novel relationship between the Suffolk breed and higher FEC was reported for the first time. The predominant rumen fluke species found was C. daubneyi. Nevertheless, P. leydeni was unexpectedly identified infecting sheep in Ireland for the first time. CONCLUSIONS: An exceptionally high prevalence of rumen fluke among Irish sheep flocks has been highlighted in this study and a more thorough investigation is necessary to analyse its economic impact. The isolation of individual eggs coupled with the PCR technique used here has proven a reliable tool for discrimination of Paramphistomum spp. This technique may facilitate forthcoming studies of the effects of paramphistomosis on livestock production. The most noteworthy finding was the identification of P. leydeni affecting sheep in Ireland, however further studies are required to clarify its implications. Also, a significant relationship between Suffolk breed and a heavier infection was found, which can be used as a starting point for future research on control strategies of rumen fluke infection.

The importance of recognising parasite cryptic diversity for research programmes on foodborne trematodiases.

The development of molecular tools in the last two decades enhanced our capacity to accurately describe biodiversity on Earth. Analysis of molecular data may lead to the discovery of cryptic species (morphologically indistinguishable, genetically distinct species lineages). As cryptic species are discovered with increasing frequency among parasites, we must consider their potential implications, especially for the epidemiology, diagnostics and control of parasitic diseases that affect humans. Investigators that conduct research on different aspects of infectious diseases, for example, on foodborne trematodiases, must remain aware of the possibility for undiscovered cryptic species and how this could impact their conclusions.

Discovery of intermediate hosts for two species of blood flukes Cardicola orientalis and Cardicola forsteri (Trematoda: Aporocotylidae) infecting Pacific bluefin tuna in Japan.

Fish blood flukes (Aporocotylidae) are important pathogens of farmed finfish around the world. Among them, Cardicola spp. infecting farmed tuna are considered to be serious threats to tuna farming and have received tremendous attention. We conducted periodical samplings at a tuna farming site in Japan between January and May, 2015 to determine the life cycle of Cardicola spp. We collected over 4700 terebellid polychaetes from ropes, floats and frames of tuna culture cages and found nearly 400 infected worms. Sporocysts and cercariae found in Nicolea gracilibranchis were genetically identified as Cardicola orientalis by 28S and ITS2 ribosomal DNA sequences. This was the first discovery of the intermediate host for this parasite species. Infection prevalence and the abundance of N. gracilibranchis significantly varied between sampling points and the highest number of infected terebellids were collected from ropes. We also demonstrated morphologically and molecularly that asexual stages found in a single Amphitrite sp. (Terebellidae) and adult worms isolated from farmed juvenile tuna were Cardicola forsteri. This is the first report of C. forsteri in Pacific bluefin tuna (PBT) Thunnus orientalis in Japan. Our results demonstrated that all three species of Cardicola orientalis, C. forsteri and Cardicola opisthorchis exist in Japanese farmed PBTs and that they all use terebellid polychaetes as the intermediate hosts.

Two-year intervention trial to control of fish-borne zoonotic trematodes in giant gourami (Osphronemus goramy) and striped catfish (Pangasianodon hypophthalmus) in nursery ponds in the Mekong Delta, Vietnam.

Fish-borne zoonotic trematode parasites (FZT) pose a food safety and public health problem in Vietnam. The transmission cycle is complex as domestic animals, especially dogs, cats, fish-eating birds and pigs together with humans serve as reservoir hosts and contribute to FZT egg contamination of aquaculture ponds and the environment. This intervention trial was conducted to determine the effectiveness of various on-farm interventions, including reduction in FZT egg contamination through treatment of infected people and domestic animals, reduction in snail density through mud removal from aquaculture ponds prior to fish stocking, and various other measures in reducing FZT infection in juvenile striped catfish (Pangasianodon hypophthalmus) and giant gourami (Osphronemus goramy). Interventions were implemented on 5 farms for each fish species during production cycles in 2009 and 2010 while 5 similar farms for each species served as control. For both fish species, both prevalence and intensity of infection did not differ significantly between intervention and non-intervention farms prior to the interventions. The interventions significantly reduced both prevalence and intensity of FZT infection in the juvenile fish compared to control ponds. For giant gourami, odds of infection in intervention ponds was 0.13 (95% CL: 0.09-0.20; p<0.001) of that in non-intervention ponds after the 2009 trial and 0.07 (0.03-0.14; p<0.001) after the 2010 trial. For striped catfish, these figures were 0.17 (0.08-0.35; p<0.001) after the 2009 trial while after the 2010 trial all ponds with interventions were free from infection. Metacercariae intensity (no. of metacercariae/fish) in giant gourami from intervention ponds was 0.16 (0.11-0.23; p<0.001) of that in fish from non-intervention ponds after the 2009 trial and 0.07 (0.04-0.15; p<0.001) after the 2010 trial; for striped catfish these figures were 0.18 (0.09-0.36; p<0.001) and 0.00 (confidence limits not estimated), respectively. The aquaculture farm pond intervention approaches taken in this trial have the potential to reduce or eliminate FZT infections in fish and may be implemented across the entire region if adjusted to local conditions and fish species.

[Investigation of natural foci of Metorchis taiwanensis in Wuhu area].

OBJECTIVE: To explore the existence of natural foci of Metorchis taiwanensis in Wuhu area. METHODS: The ecological environment and daily living habits of residents were investigated; the eggs of M. taiwanensis in the dung of ducks in local region were collected by the sedimentation method; the Parafossarulus striatulus were disposed by the tabletting method and examined with a microscope to isolate the rediae and cercariae; the metacercariae in Pseudorasbora parve were isolated by using the homogenation. The duckling were fed directively by metacercaria of M. taiwanensis or by P. parve infected with metacercaria of M. taiwanensis for artificial infection, and M. taiwanensis were separated from ducks by dissecting the gallbladder and bile ducts. RESULTS: The survey revealed that there were staggered lake river, rich vegetation, overgrown shrubs, aquatic plants, rich variety of freshwater snails and fish resources in Wuhu area, and it was home to a variety of waterfowl and duck. The average detection rate of eggs of M. tanwanensis in stool of ducks was 33.33% (10/30); that of rediae and cercarriae in P. striatulus was 1.17%(7/600); and that of encysted metacercaria in P. parve was 13.33% (8/60); the number of M. taiwanensis detected in the infected ducklings in 3 groups were 31, 8 and 0, respectively, the natural M. tanwanensis infection rate of ducks was 23.33% (7/30). CONCLUSION: We have confirmed the existence of natural foci of M. tanwanensis in Wuhu area.

China's sustained drive to eliminate neglected tropical diseases.

Non-communicable diseases dominate the public health arena in China, yet neglected tropical diseases (NTDs) are still widespread and create a substantial burden. We review the geographical distribution, prevalence, and epidemic characteristics of NTDs identified in China caused by helminths, protozoa, bacteria, and viruses. Lymphatic filariasis was eliminated in 2007, but schistosomiasis still affects up to 5% of local village residents in some endemic counties with around 300 000 people infected. China harbours more than 90% of the world's burden of alveolar echinococcosis and food-borne zoonoses are emerging. In 2010, the overall prevalence of soil-transmitted helminth infections caused by Ascaris lumbricoides, Trichuris trichiura, and hookworm was 11·4%, with 6·8% of these infections caused by A lumbricoides. Corresponding figures for food-borne trematodiasis, echinococcosis, and cysticercosis are more than 5%. Dengue, leishmaniasis, leprosy, rabies, and trachoma exist in many areas and should not be overlooked. Transmission of vector-borne diseases can be interrupted; nevertheless, epidemics occur in remote areas, creating a challenge for surveillance and control. Rigorous surveillance, followed by immediate and integrated response packages tailored to specific social and ecological systems, is essential for progress towards the elimination of NTDs in China.

Habitat of in vivo transformation influences the levels of free radical scavengers in Clinostomum complanatum: implications for free radical scavenger based vaccines against trematode infections.

BACKGROUND: Since free radical scavengers of parasite origin like glutathione-S-transferase and superoxide dismutase are being explored as prospective vaccine targets, availability of these molecules within the parasite infecting different hosts as well as different sites of infection is of considerable importance. Using Clinostomum complanatum, as a model helminth parasite, we analysed the effects of habitat of in vivo transformation on free radical scavengers of this trematode parasite. METHODS: Using three different animal models for in vivo transformation and markedly different sites of infection, progenetic metacercaria of C. complanatum were transformed to adult ovigerous worms. Whole worm homogenates were used to estimate the levels of lipid peroxidation, a marker of oxidative stress and free radical scavengers. RESULTS: Site of in vivo transformation was found to drastically affect the levels of free radical scavengers in this model trematode parasite. It was observed that oxygen availability at the site of infection probably influences levels of free radical scavengers in trematode parasites. CONCLUSION: This is the first report showing that habitat of in vivo transformation affects levels of free radical scavengers in trematode parasites. Since free radical scavengers are prospective vaccine targets and parasite infection at ectopic sites is common, we propose that infections at different sites, may respond differently to free radical scavenger based vaccines.

The worm turns: trematodes steering the course of co-infections.

A reductionist approach to the study of infection does not lend itself to an appraisal of the interactions that occur between 2 or more organisms that infect a host simultaneously. In reality, hosts are subject to multiple simultaneous influences from multiple pathogens along the spectrum from symbiotic microflora to virulent pathogen. In this review, we draw from our own work on Fasciola hepatica and that of others studying helminth co-infection to give examples of how such interactions can influence not only the outcome of infection but also its diagnosis and control. The new tools of systems biology, including both the "omics" approaches and mathematical biology, have significant promise in unraveling the as yet largely unexplored complexities of co-infection.