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The Parasite's Way of Life
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Some parasites relying on fecal–oral transmission have evolved adaptations in addition to resistant propagules that to some degree stack the deck in their favor by enhancing the likelihood of transmission. Cestodes, for instance, have indirect life cycles, and for many tapeworms, the adult host passes eggs in its feces that are subsequently consumed by the intermediate host. In some tapeworms using small aquatic crustaceans called ostracods as hosts, the tapeworm eggs appear similar to the aquatic algae on which the ostracod feeds, tricking the intermediate host into consuming them. Other tapeworms use copepods as intermediate hosts, and their eggs either sink or float, depending on whether or not the specific copepod in question is benthic or pelagic.
Surveillance and Control Programs for Cestode Diseases
Published in Max J. Miller, E. J. Love, Parasitic Diseases: Treatment and Control, 2020
Thirty cestode diseases of medical or veterinary importance have been identified. To attempt a comprehensive review of surveillance and control programs for all cestode diseases would be necessarily superficial, given the limitations of this chapter. Instead, this paper will review the current status of the two major forms of hydatid disease and the beef and pork tapeworms. I will try to place the public health impact of these infections into some perspective in relation to the achievements and prospects for success in controlling them.
An Overview of Helminthiasis
Published in Venkatesan Jayaprakash, Daniele Castagnolo, Yusuf Özkay, Medicinal Chemistry of Neglected and Tropical Diseases, 2019
Leyla Yurttaș, Betül Kaya Çavușoğlu, Derya Osmaniye, Ulviye Acar Çevik
Cestodes are a complex group of organisms, usually recognised as tapeworms, having a flat, ribbon-like white to yellowish body consisting of an anterior attachment organ (scolex) and a body (strobila) consisting of a chain of segments called proglottids. Proglottids are essentially packages of eggs which are regularly shed into the environment to infect other organisms. The width and length of tapeworms are different with some worms being several meters long (i.e., Diphyllobothrium latum is 2–15 m long, Taenids are 1–4 m long), while others can be very small (i.e., Hymenolepsis nana is 1.5–4 cm long, H. diminuta is 1–6 cm long) (Kotra and Dixit 2007).
The role of UDP-glycosyltransferases in xenobioticresistance
Published in Drug Metabolism Reviews, 2022
Diana Dimunová, Petra Matoušková, Radka Podlipná, Iva Boušová, Lenka Skálová
Helminths, parasitic worms such as cestodes, nematodes, and trematodes are a huge global health burden in humans, infecting hundreds of millions of people. In addition, helminth infections represent a common and often serious problem in veterinary medicine. Despite the widespread availability of anthelmintic therapy, the morbidity, and economic losses caused by helminths remain of great concern. Due to massive and inappropriate use of anthelmintics along with the limited types of this antiparasitic available for use, drug-resistant strains have developed in many helminths, thus anthelmintics have become less and less effective (Idris et al. 2019; Partridge et al. 2020). Due to the vastly increasing number of cases of helminth multi-resistance to all of the main classes of anthelmintics that have been reported, e.g. by Babjak et al. (2021), the mechanisms of drug-resistance in helminths have been intensively studied. Among these mechanisms, altered drug uptake as well as changes in drug metabolism have also attracted attention (Cvilink, Lamka, et al. 2009; Matouskova et al. 2016; Fairweather et al. 2020). Unfortunately, research has been focused mainly on cytochrome P450 enzymes and efflux transporters, while helminth UGTs have been neglected for a long time. At present, however, the importance of these UGTs is becoming clearer, specifically in nematodes.
Identifying novel candidates and configurations for human helminth vaccines
Published in Expert Review of Vaccines, 2021
Efforts to generate vaccines against helminths date back 50 years to the development of a dog hookworm vaccine using irradiated infective larvae of Ancylostoma caninum [9,10]. While not a commercial success (as the vaccine did not entirely prevent transmission), this demonstrated that vaccine-induced immunity was possible, and paved the way for a similar irradiated larval vaccine (Huskvac) for lungworm (Dictyocaulus viviparus) in cattle [11]. A separate initiative, also in the veterinary arena, led to the development of a vaccine based on purified intestinal antigens of Haemonchus contortus (the ‘Barber’s Pole’ worm), now marketed as Barbervax [12,13]. Finally, successful recombinant vaccines have been pioneered against cestode tapeworms of livestock [14], now marketed in a number of tropical countries as CysVax (for Taenia solium in pigs) and Hidatil (for Echinococcus granulosus in ruminants).
First steps in the formulation of praziquantel nanosuspensions for pharmaceutical applications
Published in Pharmaceutical Development and Technology, 2020
Noelia A. Martínez, Fátima Fernández-Álvarez, Ángel V. Delgado, María Luisa Badillo-García, Julio Raba, Soledad E. Cerutti, José L. Arias
Helminths are parasitic worms characterized by a bilateral symmetry and by an elongated, flat, or round morphology. Depending on the specie, the size of these invertebrates varies from millimeters to meters. In the group, nematodes include soil-transmitted helminthes or the so-called intestinal worms commonly responsible for helminthiasis, and filarial worms that are described to cause lymphatic filariasis and onchocerciasis. With respect to platyhelminths, trematodes or flukes (i.e. schistosomes) and cestodes or tapeworms are frequently defined to be responsible for parasitic infections in humans and animals (Hotez et al. 2008; Hotez and Aksoy 2017). Helminth infestation causes morbidity and mortality, affecting cognitive processes, compromising the nutritional status, inducing tissue reactions and causing intestinal obstruction or rectal prolapse. Preschool children and school-aged children, including adolescents, are commonly infected by intestinal worms and schistosomes, experiencing stunted growth and cognitive and memory impairments (resulting in cognitive and educational deficits) (Crompton and Nesheim 2002; Hotez and Aksoy 2017).