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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
Next, one of two things happens. Occasionally, the definitive host consumes an infected tadpole. If so, mesocercariae are liberated during digestion and subsequently penetrate the intestinal epithelium, migrating to the lungs. After more than a month, a larval trematode, now called a diplostomulum metacercaria, moves up the trachea. After reaching the throat, it is swallowed, which returns it to the intestine. Back in the intestine, following sexual maturation in several weeks, the life cycle is completed.
Opisthorchis viverrini
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
T. Boonmars, R. Aukkanimart, P. Sriraj, S. Boonjaraspinyo, P. Luamuanwai, J. Songsri, P. Sripan
The O. viverrini life cycle is shown in Figure 74.7. First and second intermediate hosts are Bithynia snails and cyprinoid fish, respectively. Worms mature in mammals—humans and dogs or cats—when these mammals consume raw or undercooked fish contaminated with metacercariae. After ingestion by fish, juvenile worms escape from the metacercarial cyst under the influence of gastric and duodenal juices. They then migrate, via the duodenum, into the biliary tract where they mature to become adults. Eggs laid by adult worms in the biliary tract make their way into the gut and pass to the outside in feces. Eggs reaching freshwater habitats may be eaten by Bithynia snails in which asexual multiplication takes place leading to the production of many cercariae. Cercariae released from a snail survive for about 48 hours and must swim to find a fish host. After contact with a fish, a cercaria discards its tail and commences development to the metacercaria stage. Sixteen species of cyprinoid fish are reportedly second intermediate hosts for O. viverrini in Thailand, Cambodia, and Lao PDR, as shown in Table 74.6. Given possible morphological confusion with metacercariae of other trematode species, molecular confirmation of the identity of these will be useful in the future.
Opisthorchis viverrini
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
Normally, O. viverrini metacercaria from infected freshwater cyprinoid fish is needed for animal infection. Typically, fish is blended into a small size and digested with the pepsin-HCl solution at 37°C for 1 h. The digested solution is filtered through a sieve and then washed with normal saline multiple times until the sediment is easy to observe under stereomicroscope, and then 50 O. viverrini metcercariae are gastric-intubated (Figure 47.4).
Construction of a multiepitope vaccine candidate against Fasciola hepatica: an in silico design using various immunogenic excretory/secretory antigens
Published in Expert Review of Vaccines, 2022
Mesut Akıl, Mehmet Aykur, Muhammet Karakavuk, Hüseyin Can, Mert Döşkaya
The disease is transmitted to humans or animals by eating contaminated aquatic plants and/or drinking water with metacercaria. The metacercaria which is activated by digestive enzymes within the small intestines penetrates the duodenum. Thereafter, the juvenile parasite passes into the peritoneal cavity, reaches the liver parenchyma by passing through the Glisson capsule and settles in the bile ducts. During the migration of juvenile and adult parasite, excretory/secretory (E/S) products with immunomodulatory features are released [3,4]. Up to date, various E/S products modulating the host immune system such as Kunitz-type molecule, cysteine proteases, glutathione S-transferases, helminth defense molecule, fatty acid binding protein (FaBP), and TGF-like molecule (FhTLM) have been identified [5]. These enzymes are important for parasite’s defense mechanism and metabolic activities. In addition, these molecules have been used as vaccine candidate against fasciolosis [4,6–8].
Fish-borne trematode infections in wild fishes in Bangladesh
Published in Pathogens and Global Health, 2020
Sharmin S. Labony, M. Abdul Alim, Muhammad Mehedi Hasan, Md. Shahadat Hossain, Ausraful Islam, Mohammad Zahangir Alam, Naotoshi Tsuji
Infections by fish-borne trematodes (FBTs) affect human and animal health worldwide, particularly in Asian countries [1]. FBTs are an emerging and rapidly growing concern in developing and developed countries due to the expanding international trade in fishes and fish products, as well as human demographic diversity, especially mass refugee movement and global settlement, including in Bangladesh [2,3]. Recently, a total of 59 species of FBTs of public health importance have been identified. These trematodes have been divided into two groups: liver flukes (Opisthorchidae: 12 species) and intestinal flukes (Heterophyidae: 36 species, Echonostomatidae: 10 species and Nanophyetidae: 1 species) [4]. FBTs have a complex lifecycle, with a series of developmental changes in freshwater snails in which they produce cercariae, the freely swimming larval stage of trematodes. These cercariae emerge from snails into water and encyst in freshwater fishes, notably cyprinoid fishes, in which they develop into metacercariae (MC), the infective stage of trematodes for mammals and birds [5]. FBT infections are more common in wild fishes, which have a great public health concern [4]. Humans become infected through the consumption of raw or improperly cooked fishes containing viable MC [4,6].
Highlights of human ectopic fascioliasis: a systematic review
Published in Infectious Diseases, 2019
Ali Taghipour, Leila Zaki, Ali Rostami, Masoud Foroutan, Fatemeh Ghaffarifar, Atefeh Fathi, Amir Abdoli
Fascioliasis has two main stages in pathogenicity: acute and chronic stages. The acute stage (invasive phase) begins a few days after the ingestion of metacercariae, caused by the migration of the juvenile fluke. The clinical manifestations of this stage are abdominal pain, hepatomegaly, fever, vomiting, diarrhea, jaundice, urticaria and eosinophilia. The chronic stage (obstructive phase) occurs within 2–4 months, which caused by the adult fluke and induce intermittent biliary obstruction and inflammation [18,31]. Nevertheless, the diagnosis of ectopic fascioliasis (EF) is very problematic due to ectopic migration to other organs of the body, which may influence a clinician to misdiagnose the condition. The symptoms of EF are very different based on the ectopic place [32]. Therefore, accurate and timely diagnosis of EF can help the treatment procedures. Hence, we conducted a systematic review of the cases of EF in order to present the demographic situation, clinical manifestations, diagnostic methods, treatment and outcomes of patients with EF.