Taenia asiatica: Historical overview of taeniasis and cysticercosis with molecular characterization

Imported taeniasis in the context of colon hydrotherapy

We report a case of imported taeniasis, under the modality of "visiting friends and relatives", in the context of colon hydrotherapy. This technique allows the detection of proglottids, diagnosed in this case as Taenia saginata based on the gravid proglottid that presented more than 13 uterine branches and showed active motility. Moreover, the patient did not consume pork for religious reasons. The treatment with paromomicin sulfate was effective. In this case, a trip to Ethiopia, together with the ingestion of raw beef, was the cause of parasitization. It is highly advisable to obtain detailed information from the patient on their background, especially their travel and dietary histories.

A rare case of human taeniasis caused by Taenia saginata with species undetermined cysticercosis

Taeniasis and cysticercosis, which are caused by Taenia saginata, Taenia solium and Taenia asiatica, are zoonotic parasitic infections with a significant disease burden worldwide. There is consensus amongst experts that T. saginata is a common tapeworm that causes taeniasis in humans as opposed to cysticercosis. This case study of a middle-aged Tibetan man conducted in 2021 challenges the prevailing notion that T. saginata exclusively causes taeniasis and not cysticercosis by documenting symptoms and laboratory studies related to both taeniasis and multiple cysticercosis. The patient's medical record with the symptoms of taeniasis and cysticercosis was reviewed, and the tapeworm's proglottids and cyst were identified from the patient by morphological evaluation, DNA amplification and sequencing. The patient frequently experienced severe headaches and vomiting. Both routine blood screenings and testing for antibodies against the most common parasites were normal. After anthelmintic treatment, an adult tapeworm was found in feces, and medical imaging examinations suggested multiple focal nodules in the brain and muscles of the patient. The morphological and molecular diagnosis of the proglottids revealed the Cestoda was T. saginata. Despite the challenges presented by the cyst's morphology, the molecular analysis suggested that it was most likely T. saginata. This case study suggests that T. saginata infection in humans has the potential to cause human cysticercosis. However, such a conclusion needs to be vetted by accurate genome-wide analysis in patients with T. saginata taeniasis associated with cysts. Such studies shall provide new insights into the pathogenicity of T. saginata.

Experimental animal models and their use in understanding cysticercosis: A systematic review

BACKGROUND

Cysticercosis and Neurocysticercosis (NCC) can be studied using several animal species in experimental models which contributes to the understanding of the human form of the disease. Experimental infections of Taenia spp. are vital in explaining the modes of transmission of the parasite and helps the understanding of transmission of the parasite in humans and thus may be useful in designing therapeutic and immune-prophylactic studies to combat the disease. Thus, this systematic review aims to explore the existing experimental animal models to the understanding of cysticercosis in both humans and animals and elucidate the risk factors of cysticercosis and identify the Taenia spp. used in these models.

METHODOLOGY

We systematically identified all publications from the Web of Science, Google Scholar, and Pubmed regarding experimental animal models using Taenia spp. that cause cysticercosis in both humans and animals. 58 studies were identified for eligibility. Of these, only 48 studies met the inclusion criteria from which data extraction was done and presented descriptively.

RESULTS

Pigs, cattle, gerbils, mice, rats, voles, monkeys, cats, dogs, and goats were used in which T. solium, T. saginata, T. saginata asiatica, T. crassiceps and T. asiatica were studied. The routes used to induce disease were; oral, intravenous, subcutaneous, intramuscular, intraperitoneal, intraarterial, intracranial, intraduodenal, and surgical routes using eggs, oncospheres, and proglottids. Besides, the establishment of infection using eggs and oncospheres was affected by the route used to induce infection in the experimental animals. The cysticerci recovery rate in all the experimental studies was low and the number of animals used in these experiments varied from 1 to 84. Although not analysed statistically, sex, age, and breed of animals influenced the cysticerci recovery rate. Additionally, the cysticerci recovery rate and antibody-antigen levels were shown to increase with an increase in the dose of oncospheres and eggs inoculated in the animals. Contrasting results were reported in which the cysticerci recovery rate decreased with an increase in the dose of eggs inoculated.

CONCLUSION

This review describes the various animal experiments using Taenia species that cause cysticercosis highlighting the animals used, age and their breed, the routes of infection used to induce disease and the sample size used, and the cysticerci recovery rate in these animal models.

Insights to helminth infections in food and companion animals in Bangladesh: Occurrence and risk profiling

Introduction

A better understanding of the epidemiology of helminths in animal hosts is important in order to ensure animal welfare, public health and food safety. The aim of this study was to explore parasitism in common animals in Bangladesh. Perception and understanding of animal owners regarding parasitic diseases management were also assessed.

Materials and methods

A total of 550 fecal samples were examined from common animals (cattle, goat, pig, chicken, dog, and cat) across three different areas of Bangladesh (Dhaka, Sylhet, and Chattogram) from January 2020 to March 2021. Associated risk factors were assessed through questionnaire surveys among 50 animal owners. Parasitological assessment was done using the combined sedimentation-flotation method, and factors associated with infection were modeled using mixed-effects logistic regression.

Results

Helminths including Toxocara sp., Spirometra sp., Capillaria sp., Trichuris sp., opisthorchiid, Ascaris suum, Fasciola sp., Paramphistomum sp., strongyles, hookworms, roundworms, taeniid, and acanthocephalans were detected in the examined animals, and overall prevalence was 59.3% (95% CI = 54.1–62.8). Parasites were found in 61.3% (245/400) of food animals and 54.0% (81/150) of companion animals. Animal owners have a good understanding of parasite infections; however, that knowledge was not being translated into practice. Logistic regression analysis showed that frequency of deworming, animal husbandry practice, contact with untreated animals, and treatment-seeking behaviors were significantly associated with parasitic infection.

Conclusion

Several types of zoonotic parasites are widely prevalent in animals of Bangladesh and pose a potential risk to human health. This study highlights the need to diagnose animal parasitic infection and intensified case management to avoid spillovers to animals and humans.

Intestinal Perforation Due to Adult Tapeworm of Taenia: A Case Report and Review of the Literature

Taeniasis is an intestinal helminth infection due to adult tapeworms belonging to the genus Taenia. Taeniasis remains a major burden in low-income countries in Asia. We present a case of intestinal perforation caused by adult tapeworm of Taenia in a 50-year-old Nepali male. The patients presented to the hospital with severe abdominal pain and intermittent vomiting. Following clinical presentations and imaging features, gastrointestinal perforation was suspected. Surgical removal of adult tapeworm of Taenia, suspected to be T. saginata or T. asiatica, was carried out during exploratory laparotomy, which was followed by an uneventful postoperative period. In addition to case presentation, we systematically review published case reports on taeniasis-related intestinal perforation. A learning point from this case is clinician should maintain a clinical suspicion of taeniasis as a possible cause of intestinal perforation in endemic areas.

Advances in the treatment, diagnosis, control and scientific understanding of taeniid cestode parasite infections over the past 50 years

In the past 50 years, enormous progress has been made in the diagnosis, treatment and control of taeniid cestode infections/diseases and in the scientific understanding thereof. Most interest in this group of parasites stems from the serious diseases that they cause in humans. It is through this lens that we summarize here the most important breakthroughs that have made a difference to the treatment of human diseases caused by these parasites, reduction in transmission of the taeniid species associated with human disease, or understanding of the parasites' biology likely to impact diagnosis or treatment in the foreseeable future. Key topics discussed are the introduction of anti-cestode drugs, including benzimidazoles and praziquantel, and the development of new imaging modalities that have transformed the diagnosis and post-treatment monitoring of human echinococcoses and neurocysticercosis. The availability of new anti-cestode drugs for use in dogs and a detailed understanding of the transmission dynamics of Echinococcus granulosus sensu lato have underpinned successful programs that have eliminated cystic echinococcosis in some areas of the world and greatly reduced the incidence of infection in others. Despite these successes, cystic and alveolar echinococcosis and neurocysticercosis continue to be prevalent in many parts of the world, requiring new or renewed efforts to prevent the associated taeniid infections. Major advances made in the development of practical vaccines against E. granulosus and Taenia solium will hopefully assist in this endeavour, as might the understanding of the parasites' biology that have come from an elucidation of the nuclear genomes of each of the most important taeniid species causing human diseases.

Parasitic Infections of the Gastrointestinal Track and Liver

Parasites have coevolved with humans. Several of them colonize the human body and establish a symbiotic relationship. Other parasites cause severe and lethal diseases. Prevalence of parasitic infections is decreased in highly industrialized countries, largely due to enforced hygienic practices. In contrast, parasites cause significant morbidity and mortality in parts of the world with barriers to effective public hygiene. Some parasites have emerged as potent pathogens in specific patient populations, such as immune suppressed individuals, regardless of sanitation. This article reviews common parasites encountered in clinical practice and, in the setting of host-parasite symbiosis, discusses their immune regulatory role.

Occurrence of a Hybrid Between Taenia saginata and Taenia asiatica Tapeworms in Cambodia

Human infection with Taenia asiatica or a hybrid between Taenia saginata and T. asiatica has not been reported in Cambodia. We detected for the first time a hybrid form between T. saginata and T. asiatica in Preah Vihear Province, Cambodia. An adult tapeworm specimen, i.e., 75 cm long strobila without scolex, was expelled from a 27-year-old man after praziquantel medication and purging. It was morphologically indistinguishable between T. saginata and T. asiatica. Several proglottids were molecularly analyzed to confirm the tapeworm species. The mitochondrial gene encoding cytochrome c oxidase subunit 1 (cox1) and nuclear genes encoding elongation factor-1α (ef1) and ezrin-radixin-moesin (ERM)-like protein (elp) were sequenced, and a single-allele analysis was performed to confirm the haploid genotype. The results revealed that our sample showed a discrepancy between the mitochondrial and 2 nuclear genes. It possessed homozygous sequences typical of T. saginata at cox1 and ef1 loci. However, it was heterozygous at the elp locus, with 1 allele in T. asiatica (elpA) and 1 in T. saginata (elpC), which indicates that it is a hybrid between T. saginata and T. asiatica. The present results confirmed the presence of a hybrid between T. saginata and T. asiatica in Cambodia and strongly suggest the existence of also ‘pure’ T. asiatica in Cambodia.

Taenia solium taeniasis/cysticercosis: From parasite biology and immunology to diagnosis and control

Infection with the pork tapeworm (Taenia solium) is responsible for a substantial global burden of disease, not only restricted to its impact on human health, but also resulting in a considerable economic burden to smallholder pig farmers due to pig cysticercosis infection. The life-cycle, parasitology and immunology of T. solium are complex, involving pigs (the intermediate host, harbouring the larval metacestode stage), humans (the definitive host, harbouring the adult tapeworm, in addition to acting as accidental intermediate hosts) and the environment (the source of infection with eggs/proglottids). We review the parasitology, immunology, and epidemiology of the infection associated with each of the T. solium life-cycle stages, including the pre-adult/adult tapeworm responsible for human taeniasis; post-oncosphere and cysticercus associated with porcine and human cysticercosis, and the biological characteristics of eggs in the environment. We discuss the burden associated, in endemic settings, with neurocysticercosis (NCC) in humans, and the broader cross-sectoral economic impact associated both with NCC and porcine cysticercosis, the latter impacting food-value chains. Existing tools for diagnostics and control interventions that target different stages of the T. solium transmission cycle are reviewed and their limitations discussed. Currently, no national T. solium control programmes have been established in endemic areas, with further work required to identify optimal strategies according to epidemiological setting. There is increasing evidence suggesting that cross-sectoral interventions which target the parasite in both the human and pig host provide the most effective approaches for achieving control and ultimately elimination. We discuss future avenues for research on T. solium to support the attainment of the goals proposed in the revised World Health Organisation neglected tropical diseases roadmap for 2021-2030 adopted at the 73rd World Health Assembly in November 2020.

Current situation of human Taenia asiatica taeniosis in Japan

This report describes 33 confirmed cases of "Taenia asiatica" taeniosis in Tokyo, Japan, and six adjacent prefectures between 2010 and 2019. Of the 33 cases, 28 were domestic infections. Thirty patients had histories of eating raw pork and/or beef liver. It was highly suspected that the sources of infection were foreigners from T. asiatica-endemic countries who had worked on pig farms in these prefectures. We postulated that the rate of domestic infection has decreased as a result of legal regulations that have banned the serving of raw and undercooked pig and cattle viscera in restaurants in Japan. Haplotype analyses of genetic markers revealed that "T. asiatica" in Japan are the descendants of hybrids of T. asiatica and Taenia saginata that originated from the Philippines and/or Taiwan. It is critical that close attention continues to be paid to domestic recurrences and imported cases of T. asiatica taeniosis, with the goal of communicating information on risk factors for this infection to consumers, pig farmers, restaurant owners, physicians, and visitors coming to Japan.

Prevalence of meat-transmitted Taenia and Trichinella parasites in the Far East countries

Taenia and Trichinella parasites are globally distributed foodborne zoonotic pathogens transmitted from animal to humans via consumption of raw or undercooked meats. This short review is intended to provide the parasites community a snapshot of the literature on the current and recent prevalence of taeniasis and trichinellosis in humans and animals in the Far East countries. Prevalence rates in these countries are highly diverse due to differences in development, culture, ethnic and religious background, animal forming practices, and eating habits. Taenia and Trichinella remain as important meat-transmitted pathogens in the Far East. A One Health approach is needed to eliminate or continuously reduce the foodborne zoonotic taeniasis and trichinellosis in the Far East.

Medical Parasitology Taxonomy Update, January 2018 to May 2020

The taxonomy of parasites of medical and public health importance is rapidly evolving. This minireview provides an update of taxonomic revisions and additions in the field of medical parasitology from January 2018 to May 2020. Several established human parasites have been reassigned to different genera over the past 2 years, while a number of novel parasites of humans have been identified. A comprehensive summary of these changes is provided here, and Taenia suihominis is proposed as a replacement name for Taenia asiaticus Eom et al., which is a homonym of Taenia asiatica von Linstow.

Occurrence of Taenia species in pigs in slaughterhouses in Phu Tho province, northern Vietnam

Pigs act as the intermediate hosts of the zoonotic tapeworms Taenia solium and Taenia asiatica, as well as of the non-zoonotic Taenia hydatigena. In Vietnam, human taeniasis and cysticercosis have been reported throughout the country; however, data on porcine cysticercosis are scarce. Our study aimed to estimate the prevalence of Taenia spp. in slaughtered pigs in two districts in Phu Tho, a mountainous province in northern Vietnam from where neurocysticercosis patients commonly originate. The carcasses of 399 pigs from 51 small-scale abattoirs were checked for cysticerci, while tongue, liver, masseter muscles, diaphragm and heart were sliced and examined. Retrieved cysticerci underwent polymerase chain reaction-restriction fragment length polymorphism and sequencing for species confirmation. Blood was also collected to detect antibodies by lentil lectin-purified glycoprotein enzyme-linked immunoelectrotransfer blot (LLGP-EITB) and recombinant T24H antigen (rT24H)-EITB and circulating antigens by B158/B60 Ag-ELISA. In two pigs, T. asiatica cysticerci were found, confirming the presence of the parasite in pigs in Vietnam at a low prevalence (0.5%; 95% exact confidence interval (CI): 0-1.19%). Cysticerci of T. solium were found in none of the pigs, although one serum sample was positive for antibodies in both LLGP-EITB and rT24H-EITB. Furthermore, a high prevalence of T. hydatigena cysticercosis was observed (18.0%; 95% Wilson score CI: 14.6-22.1%). In more than half of the T. hydatigena-positive pigs, circulating antigens were detected by Ag-ELISA, confirming that this test cannot be used to diagnose T. solium cysticercosis in this region. Finally, Spirometra erinaceieuropaei was found in one pig liver. It is the first record of this zoonotic cestode species in pigs in Vietnam. Overall, the findings confirmed the complex epidemiology of Taenia spp. in pigs in Vietnam.