China
Africa
Explore chapters and articles related to this topic
Prospects for Vaccination Against Larval Cestode Infections
Published in Max J. Miller, E. J. Love, Parasitic Diseases: Treatment and Control, 2020
Rickard3 and Rickard and Williams4 have reviewed research on vaccination against larval cestodes. Most studies have been carried out on the sheep parasite T. ovis (adult worm in dogs), the bovine parasite T. saginata (adult worm in humans), or the experimental models T. taeniaeformis in mice and T. pisiformis in rabbits. Antigens from the oncosphere stage of these parasites can be used to vaccinate animals against either laboratory or natural infection with these parasites, and vaccination of pregnant animals confers protection to their offspring via colostral antibody. A program of dam and calf vaccination has been shown to substantially reduce the incidence of T. saginata infection on a farm where pasture contamination with eggs was high. While vaccination with oncospheral antigens is highly effective at preventing establishment of infection, it has no apparent effect on the survival of metacestode (cysticercus) stages of these parasites. Recent experiments with T. taeniaeformis in mice5 and T. pisiformis in rabbits6 showed that while vaccination with metacestode antigens did not significantly reduce establishment of a challenge infection with eggs, it did result in markedly reduced survival of the metacestodes to maturity. It should be possible, therefore, to produce a “cocktail” vaccine combining both oncospheral and metacestode antigens to enable complete control of infection.
Echinococcus and Echinococcosis
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Wenbao Zhang, Jun Li, Dominique A. Vuitton, Patrick Giraudoux, Donald P. McManus, Hao Wen
The life cycle of Echinococcus tapeworms requires two mammalian hosts (Figure 62.1), a definitive host and an intermediate host. Carnivores (canids and felids) serve as definitive hosts for adult stage of tapeworms and their herbivore prey (ungulates, rodents and lagomorphs) as intermediate hosts for the metacestode larvae of the worms. For E. multilocularis and E. granulosus, humans can be as accidental hosts, because they are usually a “dead end” for the lifecycle.
Taenia
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
The genus Taenia encompasses a large group of parasitic tapeworms that undergo three distinct stages of development (i.e., adult worm, eggs, and larva/metacestode) during their life cycles and require two mammalian hosts for transmission. The ribbon-like adult worm (so called tapeworm) resides in the intestines of carnivores or omnivores, causing intestinal taeniasis, whereas the cyst-like larva (metacestode) occurs in the internal organs of herbivores or omnivores, causing cysticercosis or neurocysticercosis (representing different forms of taeniasis).
Helminthiases in North Korea: a neglected public health challenge
Published in Pathogens and Global Health, 2019
From the four studies, 40% of subjects were refugees (defectors) living outside North Korea. The total positive rate for helminthiasis among residents living in North Korea was significantly higher than that among North Korean refugees (47.2% vs. 23.4%, chi-square p-value < 0.001). Refugees living in Seoul, South Korea, had the lowest rate (13.5%) while the residents of North Korea rated the highest (57.6%) [29,32]. Although North Korean residents had a generally higher prevalence of helminthiasis than North Korean refugees did, except for Taenia solium metacestode, the differences in prevalence estimates were statistically different only in cases of C. sinensis and sparganum (chi-square p-values of < 0.001 and 0.002, respectively). No North Korean refugees were found to be infected with sparganum, whereas 8% of North Korean residents were ELISA-positive. No Paragonimus case was detected either in North Korean residents or refugees.
Liver transplantation for hepatic alveolar echinococcosis: literature review and three new cases
Published in Infectious Diseases, 2018
Mohsen Aliakbarian, Fariba Tohidinezhad, Saeid Eslami, Kambiz Akhavan-Rezayat
Echinococcosis or hydatid disease is a helminthic infection caused by the progressive proliferation of the metacestode of one of four members of the Echinococcus genus, namely vogelii, oligarthus, granulosus and multilocularis. The last two species are of medical importance which develops cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively. CE is the most common type (1–200 per 100,000 inhabitants) and is presented as smooth, clearly demarcated cystic hepatic lesion in about 60% of patients. In contrast, AE is a rare infection (0.03–1.2 per 100,000 inhabitants) which is characterized by poor prognosis (>90% mortality within 10–15 years of diagnosis in untreated patients). In about 98% of cases, AE develops destructive tumour-like hepatic lesions and is characterized by unlimited budding to adjacent or distant organs. This tapeworm colonizes in the small intestine of a definitive host (dog, fox and other canines). Once an intermediate host (rodents, humans, etc.) ingests the eggs which are dispersed through the faeces of a definitive host, the larvae are liberated in the duodenum and gradually form multilocularis cysts. As globalization has been intensified since 1990s, the disease is widely distributed across all continents and is endemic throughout the northern hemisphere. Contact with free roaming dogs and their associated offal in sheep rearing areas has been previously found to be a significant risk factor for hydatid disease [1].
Diagnosis of echinococcosis by detecting circulating cell-free DNA and miRNA
Published in Expert Review of Molecular Diagnostics, 2023
Mahboubeh Hadipour, Majid Fasihi Harandi, Hossein Mirhendi, Hossein Yousofi Darani
Jingkai JI and colleagues applied ultra-high-throughput sequencing technology for detecting cell-free Echinococcus spp. DNA in the plasma of echinococcosis patients and they detected cfDNA in all samples. They reported a comprehensive characterization of cell-free DNAs including release source, concentration, and fragment length pattern in the plasma of echinococcosis patients. The results showed that most reads were from the nuclear genome rather than the mitochondrial genome with a uniform distribution on the nuclear genome. Due to the different growing process of the metacestode of E. multilocularis, the mixture of necrotic parasite tissue and actively proliferating tissues and a lack of clear edge to human tissue, the cyst of AE can release much more cfDNA to blood circulation than the what CE cyst do. This issue can be confirmed by previous studies which reported that the sensitivity of PCR-based methods in detecting AE samples was higher than that of CE samples [80–82]. The concentration of cell-free Echinococcus spp. DNA may be affected by many factors such as the location and size of the cyst, disease stage, and parasite species. It has been shown that the fragment length of cell-free Echinococcus spp. DNA has a different pattern from human cell-free DNA. Human cfDNA had an obvious peak at around 166 bp while cell-free DNA fragments of the CE samples had a broad length range and more irregular distribution pattern without a noticeable peak. cfDNA fragments of AE displayed a more regular distribution pattern and a noticeable peak of about 135 bp. The size of cfDNA fragments is related to their release mechanisms such as necrosis, active release, and apoptosis, although the well-defined release mechanism of cfDNA is still vague [83].