Echinococcus spp.
Peter M. Lydyard, Michael F. Cole, John Holton, William L. Irving, Nino Porakishvili, Pradhib Venkatesan, Katherine N. Ward in Case Studies in Infectious Disease, 2010
Echinococcus species are tapeworms, also known as cestodes. Adults are only 3–8.5 mm in length. Two species are responsible for the majority of human infections. Echinococcus granulosus arises from dogs and other canids and has been described worldwide. It causes cystic echinococcosis. Echinococcus multilocularis arises from arctic or red foxes and is restricted to the Northern Hemisphere. It causes alveolar echinococcosis. Infection with the latter seems to be spreading as red fox populations have been growing. Adult tapeworms live in the intestines of the dog or wild canid hosts. They attach to the mucosa with suckers and hooks. There are different parts to the structure of the tapeworm, and these are shown in Figure 2. The adult tapeworms lay eggs, which pass out in the feces and contaminate the soil. These may be swallowed by an intermediate host such as sheep for E. granulosus and small mammals for E. multilocularis.
The Ecology of Parasitism
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2023
A general pattern of parasite overdispersion as described by the binomial distribution seems certain, but what are the underlying factors driving this distributional pattern? Encounter and compatibility filters and particular parasite- and host-related factors all play a role in generating aggregated distributions. Some parasites for instance produce progeny that remain grouped together within a particular host, such that if that host is encountered and ingested, the next host would in one event acquire a large number of parasites. Imagine a dog consuming the viscera of a sheep containing a hydatid cyst of the cestode Echinococcus granulosus. Hydatid cysts are distinctive for producing many protoscolices by asexual reproduction. In this way, that dog would come to harbor an enormous number of E. granulosus adults, whereas another dog that did not happen to encounter and ingest parts of the sheep contaminated with a hydatid cyst would have none. Some hosts may be prone to infection by virtue of where they live, by being especially mobile, or engaging in behaviors that put them at special risk of acquiring heavy infections.
Gastrointestinal Infections
Miriam Orcutt, Clare Shortall, Sarah Walpole, Aula Abbara, Sylvia Garry, Rita Issa, Alimuddin Zumla, Ibrahim Abubakar in Handbook of Refugee Health, 2021
Echinococcus granulosus causes cystic echinococcus and E. multilocularis causes alveolar echinococcus. Cysts can occur anywhere, but the liver (around two-thirds) and lung (around one-quarter) are the most common sites. Cystic echinococcus can be asymptomatic, particularly in early disease, and can have a long latent period. Infection occurs by ingestion of parasite eggs after excretion by tapeworm-infected animals, for example, dogs (definitive host). It is present in the Middle East, South America, Eastern Mediterranean and sub-Saharan Africa, particularly among rural/farming communities. Diagnosis is based on serology and typical imaging appearances on ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI). The WHO classification grades cystic echinococcus from grade 1 to grade 5 based on size and type, for example active, degenerating and inactive. There is a risk of anaphylaxis or secondary echinococcosis if cysts rupture or spill. Treatment depends on staging and can include surgery (if complicated or size >10 cm with risk of rupture), with adjunctive drug therapy with albendazole (15 mg/kg orally twice daily; usual adult dose is 400 mg twice daily; liver function should be monitored.) Puncture Aspiration Injection Re-aspiration (PAIR) is an option for some cysts. For cystic echinococcus stages 4 and 5 (degenerated cysts and solid) or inoperable, monitoring with ultrasound every 6 months is recommended.
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
Echinococcosis is a chronic zoonotic infection causing a significant public health problem that affects many people around the world. World health organization (WHO) has considered echinococcosis as a major neglected disease [1-3]. This disease is classified into cystic echinococcosis (CE) and alveolar echinococcosis (AE), which are caused by the larvae stages of the tapeworms Echinococcus granulosus sensu lato and Echinococcus multilocularis, respectively [4]. Humans as the accidental intermediate host can be infected with the larval stage of the Echinococcus granulosus known as hydatid cyst. Canines are the definitive hosts for both species. CE is mainly perpetuated in a dog-livestock cycle, whereas AE is maintained in foxes and rodents [5]. The fluid-filled hydatid cysts mostly develop in the liver and lungs [6]. AE generally affects people in the northern hemisphere while CE has a higher prevalence across the world, especially in western China, Central Asia, the Middle East, Africa, South America, and Mediterranean countries [7,8].
Hydatid cyst involvement of both pulmonary arteries in a 14-year-old girl
Published in Paediatrics and International Child Health, 2018
Mecnun Çetin, Kamuran Karaman, Mesut Özgökçe, Hadi Geylan, Bedrettin Yildizeli
Oral albendazole (15 mg/kg/day) was commenced and continued after surgery for 6 months. The patient underwent pulmonary endarterectomy as described previously [4]. The operation was undertaken under deep hypothermia (20°C) associated with complete circulatory arrest. Surrounding tissues were initially protected from spreading of the hydatid cysts with wet sponges soaked with hypertonic saline solution, and the main right pulmonary artery was incised. A loose thrombus and hydatid vesicles were removed from the endothelium. A true endarterectomy was accomplished for both right and left pulmonary arteries, and the entire pulmonary tree was irrigated with normal saline solution. Following this, the right atrium was opened and the calcified hydatid cyst in the right ventricle was removed. When the operation was completed, warming circulation was restarted. Post-operative recovery was uneventful, and the patient was discharged on the 6th post-operative day. Figure 4 demonstrates the multiple hydatid cystic structures which were removed. Histological examination confirmed the diagnosis of hydatid cyst caused by Echinococcus granulosus. The cardiorespiratory symptoms were significantly improved after the operation. The systolic pulmonary artery pressure measured by echocardiography decreased to 43 mm Hg.
Echinococcosis in a non-endemic country – 20-years’ surgical experience from a Norwegian tertiary referral Centre
Published in Scandinavian Journal of Gastroenterology, 2022
Sheraz Yaqub, Mogens Jensenius, Ole Einar Heieren, Anders Drolsum, Frank O. Pettersen, Knut Jørgen Labori
Echinococcosis in humans occurs as a result of infection by the larval stages of taeniid cestodes of the genus Echinococcus. Echinococcus granulosus sensu lato causes cystic echinococcosis (CE), a chronic cyst-forming disease [1,2]. E. multilocularis causes alveolar echinococcosis (AE), in which the larval mass resembles a malignancy in appearance and behaviour, and proliferates indefinitely by exogenous budding and invades the surrounding tissues. CE occurs worldwide in sheep-raising areas including Africa, the Mediterranean region of Europe, the Middle East, Asia, South America, Australia, and New Zealand [1]. Conversely, AE is primarily endemic in northern latitudes where wild foxes and coyotes act as principal hosts. The incidence of echinococcosis is very low in the Scandinavian countries and is almost exclusively seen as imported cases [3,4].
Related Knowledge Centers
- Cestoda
- Cyst
- Echinococcosis
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- Eucestoda
- Rostellum
- Pathogen Transmission
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