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.

The battle against the introduced pathogenic monogenean Gyrodactylus salaris in Norwegian Atlantic salmon rivers and fish farms.

The introduced salmonid ectoparasite Gyrodactylus salaris has been detected on Atlantic salmon in 53 Norwegian rivers and in 39 Norwegian fish farms. In affected rivers, the mortality of Atlantic salmon juveniles is very high, estimated to a mean of 86%. G. salaris has been considered one of the biggest threats to wild Norwegian Atlantic salmon stocks. With various measures, the authorities have reduced the potential for further spread of the parasite to new rivers and fish farms, and G. salaris has been eradicated from 43 rivers and all fish farms. Furthermore, the eradication process is almost completed in five affected rivers located at the Norwegian west coast, while preparations for the eradication in the remaining five rivers in the southeastern part of Norway have begun. The goal of Norwegian management is to eradicate the introduced pathogenic G. salaris strains from all occurrences in Norway. In fish farms, the parasite has been removed by mandatory slaughter of infected fish. In rivers, G. salaris has mostly been removed by killing all the fish hosts with rotenone. The indigenous genetic Atlantic salmon stocks are re-established after eradication of the parasite. New methods are developed using chemicals that kill the parasite without killing fish in the rivers. Norwegian authorities have so far used more than NOK 1.5 billion on research, monitoring and combating G. salaris. However, the benefits are considered many times greater than the spending. Without control measures, G. salaris would likely have spread to new Atlantic salmon rivers where the same catastrophic outcome had to be expected. The Norwegian authorities seem to meet the goal in their long-term work to halt the spread of G. salaris and to eradicate the parasite in affected rivers.

Biodiversity decreases disease through predictable changes in host community competence.

Accelerating rates of species extinctions and disease emergence underscore the importance of understanding how changes in biodiversity affect disease outcomes. Over the past decade, a growing number of studies have reported negative correlations between host biodiversity and disease risk, prompting suggestions that biodiversity conservation could promote human and wildlife health. Yet the generality of the diversity-disease linkage remains conjectural, in part because empirical evidence of a relationship between host competence (the ability to maintain and transmit infections) and the order in which communities assemble has proven elusive. Here we integrate high-resolution field data with multi-scale experiments to show that host diversity inhibits transmission of the virulent pathogen Ribeiroia ondatrae and reduces amphibian disease as a result of consistent linkages among species richness, host composition and community competence. Surveys of 345 wetlands indicated that community composition changed nonrandomly with species richness, such that highly competent hosts dominated in species-poor assemblages whereas more resistant species became progressively more common in diverse assemblages. As a result, amphibian species richness strongly moderated pathogen transmission and disease pathology among 24,215 examined hosts, with a 78.4% decline in realized transmission in richer assemblages. Laboratory and mesocosm manipulations revealed an approximately 50% decrease in pathogen transmission and host pathology across a realistic diversity gradient while controlling for host density, helping to establish mechanisms underlying the diversity-disease relationship and their consequences for host fitness. By revealing a consistent link between species richness and community competence, these findings highlight the influence of biodiversity on infection risk and emphasize the benefit of a community-based approach to understanding infectious diseases.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

[The prevalence and prevention of alariosis].

High Alaria alata infestation rates were found in the animals of the Kirov Region. The functioning of alariosis foci is maintained by a wide range of primary and intermediate hosts. The purpose of this article was to evaluate the activity of disinfectants against A. alata trematode eggs and their effects on soil microbiocenoses.

Prevention and control of fish-borne zoonotic trematodes in fish nurseries, Vietnam.

Worldwide, >18 million persons were infected with fish-borne zoonotic trematodes in 2002. To evaluate the effectiveness of interventions for reducing prevalence and intensity of fish-borne zoonotic trematode infections in juvenile fish, we compared transmission rates at nurseries in the Red River Delta, northern Vietnam. Rates were significantly lower for nurseries that reduced snail populations and trematode egg contamination in ponds than for nurseries that did not. These interventions can be used in the development of programs for sustained control of zoonotic trematodes in farmed fish.

Models of macroparasitic infections in domestic ruminants: a conceptual review and critique.

A mathematical model is just a means of representing and manipulating something that would not otherwise be accessible. Decision theorists argue that a right decision is one that makes the best use of the available information and using mathematical models of infectious and parasitic disease can help make sure the decision-makers do just that. Seen in this light, models are simply aids to thought--and thus, by definition, good models are useful. This paper deals with the history of mathematical models of parasitic infections of domestic ruminants. It is argued that the early simple forecasting models were very successful, and, although the more complicated models that were constructed to improve the resolution of the forecasts were mostly failures, the experience gained generated a slew of useful, robust models that are still valuable decision-making tools.

Snails and trematode infection after Indian Ocean tsunami in Phang-Nga Province, southern Thailand.

The tsunami and non-tsunami affected areas of Takua Pa District, Phang-Nga Province were investigated for fresh- and brackish-water snails that transmit human parasitic diseases during 2006 and 2007. Among 46 snail species found, 17 species of 8 families were freshwater snails, 28 species of another 7 families were brackish-water snails, and 1 species was a land snail. Of these species, 11 freshwater snails, 4 brackish-water snails and 1 land snail were of medical importance. The fresh-water snails were Pomacea canaliculata, Pila angelica, P. gracilis, P. polita, Filopaludina (S.) martensi, F. (F.) s. polygramma, Melanoides tuberculata, Indoplanorbis exuxtus, Radix rubiginosa, Helicorbis umbilicalis, Gyraulus convexiusculus. Four brackish-water snails were Cerithidea cingulata, C. djadjarensis, C. alata, Sermyla riqueti and Achatina fulica was the land snail. I. exutus, M. tuberculata and F. (F.) s. polygramma harbored Xiphidio, Microcercus, Furocercus, Echinostome cercariae, and cercaria without eyespots or tail with hair. Three species of brackish-water snails, Cerithidia cingulata, C. djadjariensis, and C. alata presented with 6 types of trematode cercariae and rediae. Knowledge of medically important snails and their parasitic diseases, and prevention were given to Takua Pa people by poster, pamphlets and broadcasting through community radio.

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.

[Gastrodiscoidosis is a dangerous zoonosis].

The paper gives data on the helminthiasis--gastrodiscoidosis, a zoonotic disease caused by the trematode Gastrodiscoides hominis (Lewis et McConnall, 1876) parasitizing in the animal and human intestine in the endemic foci of both Russia and foreign countries. It also presents information on the morphology of the helminth, the biological cycle of development of the parasite and its habitat and spread, as well as its induced abnormalities and on the method of diagnosing of the disease.

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.