Fasciolopsiasis: is it a controllable food-borne disease?

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In the present chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

Occurrence of Cryptosporidium oocysts in commercial oysters in southern Thailand

The enteric parasite Cryptosporidium is spread through the fecal-oral pathway, most commonly by the consumption of contaminated water but also through food. Because eating raw or barely cooked shellfish might put consumers at risk for cryptosporidiosis, identifying the parasite in oysters is important for public health. A total of 240 oysters, collected from two shellfish aquaculture sites in Thailand's Gulf coast, Nakhon Si Thammarat and Surat Thani, were tested for the presence of Cryptosporidium. Escherichia coli, enterococci, and thermotolerant coliform total levels were measured to assess seawater quality in the shellfish production regions. Oocysts of Cryptosporidium spp. were detected in 13.8% of the samples processed by immunofluorescence analyses. The detection of Cryptosporidium spp. oocysts in oysters obtained from Surat Thani (17.5%) was higher than in those obtained from Nakhon Si Thammarat (9.2%). The difference in detection of positive samples obtained from Nakhon Si Thammarat and those obtained from Surat Thani may be attributed to the effects of physical, ecological, and anthropogenic conditions, resulting in an increased level of marine water contamination by Cryptosporidium spp. oocysts. These findings demonstrate that native commercial oysters obtained from Thailand's southern Gulf coast contained Cryptosporidium spp. oocysts which might serve as a source of human infection. Consequently, these findings pose a serious public health concern and suggest that more quality control measures need to be implemented by the oyster aquaculture business to ensure the safety of seafood.

Heavy Load of Intestinal Fluke in a Four-Year-Old Child with Severe Acute Malnutrition: A Case Report

Fasciolopsiasis, a food-borne intestinal parasitosis, occurs focally, and remains a significant public health problem in endemic areas. However, due to the wide spectrum of clinical presentation and unclear diagnosis or even misdiagnosis, it often goes unreported. The correlation between trematode infection and malnutrition is also often debated. We report a case of heavy infection of Fasciolopsis buski in a 4-year-old girl with severe acute malnutrition (SAM). The patient presented with a passage of many adult worms per stool following the consumption of some herbal concoction. A wet mount of the stool revealed ova of Fasciolopsis buski. She was treated successfully with praziquantel and food supplements. It raises the possibility of unidentified cases in this region and necessitates more extensive studies in the targeted population. This will also help raise awareness of fasciolopsiasis among clinicians, especially in vulnerable populations such as malnourished children.

Case Report: Surgical Intervention for Fasciolopsis buski Infection: A Literature Review

Fasciolopsis buski, also called the giant intestinal fluke, is the largest intestinal fluke of the zoonotic trematode parasites and found mainly in Southeast Asian countries, including China. Fasciolopsis buski infection was formerly a common health problem in many countries, but it is now rare. Typically, it can be cured by oral drugs, but some infected patients need surgical intervention because of the severity of their condition or because of an unclear diagnosis or even misdiagnosis. Here, we report a case of a 15-year-old girl from Guizhou Province, China, presenting with recurrent upper-middle abdominal pain that was misdiagnosed as a choledochal cyst. Through laparotomy combined with postoperative histopathological examination, the source of the pain was proven to be mechanical biliary obstruction caused by F. buski infection. In the past, mechanical obstruction, especially biliary obstruction, caused by F. buski infection leading to surgery was not uncommon, but it is very rare in modern society. Moreover, delayed treatment and misdiagnosis of parasitic infection can lead to severe consequences. Therefore, we reviewed the previous literature on F. buski infection treated by surgical operation and summarized the characteristics and therapeutic strategies of these cases to raise clinicians' awareness of this rare infection.

Fascioliasis and fasciolopsiasis: Current knowledge and future trends

Food-borne zoonotic trematodiases are classified as neglected diseases by the World Health Organization. Among them, fascioliasis is caused worldwide by Fasciola hepatica and F. gigantica, and represent a huge problem in livestock production and human health in endemic areas. Fasciolopsis buski, restricted to specific regions of Asia, causes fasciolopsiasis. The incidence of these trematodiases is underestimated due to under-reporting and to the lack of sensitive and widely accepted tool for their diagnosis. This, together with a rising trend in reporting of drug resistance and the need for an effective vaccine against these parasites, pose a challenge in the effective control of these diseases. Here, the latest reports on fascioliasis outbreaks between 2000 and 2020 and the most recent advances in their epidemiology, diagnosis, treatment and control are revised. Finally, future needs in the field of fascioliasis and fasciolopsiasis are presented, which could be addressed based on current knowledge and by means of new emerging technologies.

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver, and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods, and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In this chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

An Autochthonous Human Case of Fasciolopsiasis in Nepal

Fasciolopsiasis is rarely known as the parasitic disease in Nepal. Herein, we report a case of fasciolopsiasis in a 22-year-old man who was admitted in the hospital with abdominal pain, distension and loss of appetite for a month. He had previously diagnosed with acute viral hepatitis but, his abdominal pain was not resolving despite improvement in his liver function and general condition. During endoscopy an adult digenean worm was seen in the first part of the duodenum. After isolation, the worm was identified morphologically as Fasciolopsis buski. Microscogic examination of the patient’s stool revealed eggs with a morphology consistent with F. buski. Eggs were yellow-brown, ellipsoidal, unembmbryonated, operculated, filled with yolk cells, with thin shell and ranging 118–130 μm in length and 60–69 μm in width. The abdominal pain of the patient was resolved after treatment with praziquantel. By the present study, it was confirmed for the first time that fasciolopsiasis is indigenously transmitted in Nepal. Accordingly, the epidemiological studies in humans and reservoir host animals should be performed intensively in near future.

Bovine fascioliasis risk factors and space-time clusters in Mymensingh, Bangladesh

A hospital-based case-control study was undertaken to identify risk factors for - and space-time clusters of - bovine fascioliasis in Mymensingh, Bangladesh. Fascioliasis cases diagnosed using fecal sample test between January 2006 and December 2015 (n=593) at the Bangladesh Agricultural University Veterinary Teaching Hospital (BAUVTH) and three controls per case (n=1563) were selected. Data on date of report, location, age, breed, sex and body weight were extracted from the hospital records. A mixed multivariable logistic regression model with location as a random effect was built to identify risk factors for fascioliasis. The scan statistic (Bernoulli model) was used to identify space-time clusters. Compared to cattle ≤1year of age, the odds of fascioliasis were 5.2- (95% confidence interval [CI]: 3.6-7.4), 6.1- (95% CI: 4.2-8.7) and 10.7-times (95% CI: 6.9-16.6) greater in cattle aged >1-3, >3-8 and >8years, respectively. The odds of fascioliasis were 1.4- (95% CI: 1.03-1.99) and 1.5-times (95% CI: 1.13-2.11) greater in post-monsoon and monsoon seasons, respectively, compared to winter. Five significant (P<0.05) clusters (7-13 locations each) were identified, lasting from six months to 5years. Six locations - Bhangnamari, Deuhakhola, Gauripur, Ishwarganj, Nandail and Rasulpur - appeared to be at more risk for fascioliasis: these locations were part of at least 3 significant clusters. Anthelmintic treatment should focus on high risk age groups (>1year, especially those >8years). Importantly, we have demonstrated high-risk periods (monsoon and post-monsoon) and disease hotspots of bovine fascioliasis. Focusing disease control efforts in time and space offers an opportunity to more effectively control bovine fascioliasis in Bangladesh and in other similar geo-climatic zones throughout the world.

A survey for potentially zoonotic gastrointestinal parasites of dogs and pigs in Cambodia

There is little information available on parasites of zoonotic significance in Cambodia. In 2011, in an effort to obtain data on potentially zoonotic gastrointestinal parasites in domestic animals, 50 dogs and 30 pigs residing in 38 households located in Ang Svay Check village, Takeo province, Cambodia were examined for parasites from faecal samples. The samples were processed using the formalin-ethyl acetate concentration technique (FECT). Hookworms were the most common zoonotic parasite found in dogs (80.0%) followed by Echinostomes (18.0%). While, in pigs, Fasciolopsis buski was the most common zoonotic parasite (30.0%) followed by Ascaris suum (13.3%). This study provides baseline data on gastrointestinal parasites in dogs and pigs from Cambodia and underscores the importance of domestic animals as reservoir hosts for human parasites for Cambodian veterinary and public health agencies. Follow-up studies are required to further taxonomically characterize these dog and pig parasites and to determine their role in human parasites in this community.

The prevalence and diversity of intestinal parasitic infections in humans and domestic animals in a rural Cambodian village

In Cambodia, intestinal parasitic infections are prevalent in humans and particularly in children. Yet, information on potentially zoonotic parasites in animal reservoir hosts is lacking. In May 2012, faecal samples from 218 humans, 94 dogs and 76 pigs were collected from 67 households in Dong village, Preah Vihear province, Cambodia. Faecal samples were examined microscopically using sodium nitrate and zinc sulphate flotation methods, the Baermann method, Koga Agar plate culture, formalin-ether concentration technique and Kato Katz technique. PCR was used to confirm hookworm, Ascaris spp., Giardia spp. and Blastocystis spp. Major gastrointestinal parasitic infections found in humans included hookworms (63.3%), Entamoeba spp. (27.1%) and Strongyloides stercoralis (24.3%). In dogs, hookworm (80.8%), Spirometra spp. (21.3%) and Strongyloides spp. (14.9%) were most commonly detected and in pigs Isospora suis (75.0%), Oesophagostomum spp. (73.7%) and Entamoeba spp. (31.6%) were found. Eleven parasite species were detected in dogs (eight helminths and three protozoa), seven of which have zoonotic potential, including hookworm, Strongyloides spp., Trichuris spp., Toxocara canis, Echinostoma spp., Giardia duodenalis and Entamoeba spp. Five of the parasite species detected in pigs also have zoonotic potential, including Ascaris spp., Trichuris spp., Capillaria spp., Balantidium coli and Entamoeba spp. Further molecular epidemiological studies will aid characterisation of parasite species and genotypes and allow further insight into the potential for zoonotic cross transmission of parasites in this community.

Hygienic aspects of livestock manure management and biogas systems operated by small-scale pig farmers in Vietnam

Biogas digesters are widely promoted and increasingly used to treat and generate gas from pig slurry worldwide. The objective of this study was to describe manure management practices with focus on biogas digestion among small scale pig farmers in Hue (50 farmers) and Hanoi (96 farmers) and to assess fecal contamination levels in biogas effluent. Results showed that 84% of the farmers in Hanoi and 42% in Hue used both pig slurry and human excreta for biogas production. Biogas digestion only reduced E. coli concentrations by 1 to 2 log units to 3.70 ± 0.84 Escherichia coli (log10) cfu/ml on average in effluent as compared with raw slurry. Biogas effluent was commonly used to fertilize vegetables or discharged directly into the garden or aquatic recipients. Reduced problems with bad smells and flies were reported as main reasons for establishing a biogas digester. Further studies are needed to assess human and animal health hazards associated with the discharge and use of biogas effluent from small-scale biogas systems.

Effects of cadmium exposure on embryogenesis of Stagnicola elodes (Mollusca, Gastropoda): potential consequences for parasite transmission

Experiments on the toxicity of cadmium (Cd(2+)) to the embryonic development of Stagnicola elodes (Mollusca, Gastropoda), obligatory first intermediate host of numerous trematodes of pathogenic importance, were carried out as part of a study on the effects of metal pollution on host-parasite relationships. Freshly laid snail eggs were exposed to Cd concentrations of 0, 0.02, 0.2, and 2.0 mg Cd(2+)/L, and survival and embryogenesis were examined for 30 days. Mean survival time (+/- SD) of the control group was 23.1 (+/- 5.3) days compared with 10.1 (+/- 3.2) at 0.02 mg Cd(2+)/L, 3.9 (+/- 0.7) at 0.2 mg Cd(2+)/L, and 1.1 (+/- 0.08) at 2.0 mg Cd(2+)/L. Mortality patterns of all test groups differed significantly from each other, demonstrating that the percentage of surviving individuals at any given time was inversely related to Cd concentration. Concentration-dependent effects of Cd exposure on snail embryogenesis were noted. While embryos of the control group developed properly and started hatching on day 16, eggs exposed to 0.02 mg Cd(2+)/L exhibited a prolonged gastrula period and failed to hatch. Eggs in the 0.2 mg Cd(2+)/L group were blocked in the gastrula stage on day 5, whereas individuals exposed to 2.0 mg Cd(2+)/L died in the morula stage on the second day. Data showed that Cd severely affects S. elodes embryogenesis. By implication, Cd contamination at concentrations >or=0.02 mg Cd(2+)/L will thus decrease transmission success of various trematodes by decreasing intermediate host snail abundance.

Food-borne parasitic zoonoses in China: perspective for control

Food-borne parasitic zoonoses (FBPZs) cause death and serious diseases in humans and animals worldwide, and are of both public health significance and socioeconomic importance. The FBPZ problem is severe in mainland China, where approximately 150 million people are suffering from FBPZs and more people are at risk. Here, the current status of the FBPZ problem in mainland China is reviewed and strategies and measures for effective control of FBPZs are proposed. Major parasitic zoonoses transmitted through consumption of infected or contaminated meat, fish, plants and/or water will be discussed.

Human waterborne trematode and protozoan infections

Waterborne trematode and protozoan infections inflict considerable morbidity on healthy, i.e., immunocompetent people, and may cause life-threatening diseases among immunocompromised and immunosuppressed populations. These infections are common, easily transmissible, and maintain a worldwide distribution, although waterborne trematode infections remain predominantly confined to the developing countries. Waterborne transmission of trematodes is enhanced by cultural practices of eating raw or inadequately cooked food, socio-economical factors, and wide zoonotic and sylvatic reservoirs of these helminths. Waterborne protozoan infections remain common in both developed and developing countries (although better statistics exist for developed countries), and their transmission is facilitated via contacts with recreational and surface waters, or via consumption of contaminated drinking water. The transmissive stages of human protozoan parasites are small, shed in large numbers in feces of infected people or animals, resistant to environmental stressors while in the environment, and few are (e.g., Cryptosporidium oocysts) able to resist standard disinfection applied to drinking water.

Immunology and pathology of intestinal trematodes in their definitive hosts

This review examines the significant literature on the immunology and pathology of intestinal trematodes in their definitive hosts. We emphasize information on selected species in six families for which the literature on these topics is extensive. The families are Brachylaimidae, Diplostomidae, Echinostomatidae, Gymnophallidae, Heterophyidae, and Paramphistomidae. For most of these families, coverage is considered under the following headings: (i) background; (ii) pathology of the infection; (iii) immunology of the infection; (iv) immunodiagnosis; and (v) human infection. Some of these heading have been subdivided further, based on the literature available on a particular topic. Following this coverage, we include a final section on the important topical literature on selected trematodes in families other than the six mentioned above.

Fascioliasis and other plant-borne trematode zoonoses

Fascioliasis and other food-borne trematodiases are included in the list of important helminthiases with a great impact on human development. Six plant-borne trematode species have been found to affect humans: Fasciola hepatica, Fasciola gigantica and Fasciolopsis buski (Fasciolidae), Gastrodiscoides hominis (Gastrodiscidae), Watsonius watsoni and Fischoederius elongatus (Paramphistomidae). Whereas F. hepatica and F. gigantica are hepatic, the other four species are intestinal parasites. The fasciolids and the gastrodiscid cause important zoonoses distributed throughout many countries, while W. watsoni and F. elongatus have been only accidentally detected in humans. Present climate and global changes appear to increasingly affect snail-borne helminthiases, which are strongly dependent on environmental factors. Fascioliasis is a good example of an emerging/re-emerging parasitic disease in many countries as a consequence of many phenomena related to environmental changes as well as man-made modifications. The ability of F. hepatica to spread is related to its capacity to colonise and adapt to new hosts and environments, even at the extreme inhospitality of very high altitude. Moreover, the spread of F. hepatica from its original European range to other continents is related to the geographic expansion of its original European lymnaeid intermediate host species Galba truncatula, the American species Pseudosuccinea columella, and its adaptation to other lymnaeid species authochthonous in the newly colonised areas. Although fasciolopsiasis and gastrodiscoidiasis can be controlled along with other food-borne parasitoses, fasciolopsiasis still remains a public health problem in many endemic areas despite sustained WHO control programmes. Fasciolopsiasis has become a re-emerging infection in recent years and gastrodiscoidiasis, initially supposed to be restricted to Asian countries, is now being reported in African countries.

Waterborne zoonotic helminthiases

This review deals with waterborne zoonotic helminths, many of which are opportunistic parasites spreading directly from animals to man or man to animals through water that is either ingested or that contains forms capable of skin penetration. Disease severity ranges from being rapidly fatal to low-grade chronic infections that may be asymptomatic for many years. The most significant zoonotic waterborne helminthic diseases are either snail-mediated, copepod-mediated or transmitted by faecal-contaminated water. Snail-mediated helminthiases described here are caused by digenetic trematodes that undergo complex life cycles involving various species of aquatic snails. These diseases include schistosomiasis, cercarial dermatitis, fascioliasis and fasciolopsiasis. The primary copepod-mediated helminthiases are sparganosis, gnathostomiasis and dracunculiasis, and the major faecal-contaminated water helminthiases are cysticercosis, hydatid disease and larva migrans. Generally, only parasites whose infective stages can be transmitted directly by water are discussed in this article. Although many do not require a water environment in which to complete their life cycle, their infective stages can certainly be distributed and acquired directly through water. Transmission via the external environment is necessary for many helminth parasites, with water and faecal contamination being important considerations. Human behaviour, particularly poor hygiene, is a major factor in the re-emergence, and spread of parasitic infections. Also important in assessing the risk of infection by water transmission are human habits and population density, the prevalence of infection in them and in alternate animal hosts, methods of treating sewage and drinking water, and climate. Disease prevention methods, including disease surveillance, education and improved drinking water treatment are described.

Food-borne intestinal trematodiases in humans

Food-borne trematodiases still remain a public health problem world-wide, despite changes in eating habits, alterations in social and agricultural practices, health education, industrialization, environmental alteration, and broad-spectrum anthelmintics. Food-borne trematodiases usually occur focally, are still persistently endemic in some parts of the world, and are most prevalent in remote rural places among school-age children, low-wage earners, and women of child-bearing age. Intestinal fluke diseases are aggravated by socio-economic factors such as poverty, malnutrition, an explosively growing free-food market, a lack of sufficient food inspection and sanitation, other helminthiases, and declining economic conditions. Control programs implemented for food-borne zoonoses and sustained in endemic areas are not fully successful for intestinal food-borne trematodiases because of centuries-old traditions of eating raw or insufficiently cooked food, widespread zoonotic reservoirs, promiscuous defecation, and the use of "night soil" (human excrement collected from latrines) as fertilizer. This review examines food-borne intestinal trematodiases associated with species in families of the Digenea: Brachylaimidae, Diplostomidae, Echinostomatidae, Fasciolidae, Gastrodiscidae, Gymnophallidae, Heterophyidae, Lecithodendriidae, Microphallidae, Nanophyetidae, Paramphistomatidae, Plagiorchiidae, and Strigeidae. Because most of the implicated species are in the Echinostomatidae and Heterophyidae, emphasis in the review is placed on species in these families.