Trematode Infection Treatment & Management

Author: Subhash Chandra Parija, MBBS, MD, PhD, FRCPath; Chief Editor: Burke A Cunha, MD more...

Updated: Sep 1, 2011

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Medical Care
Surgical Care
Consultations
Diet
Activity
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Medical Care

Causes of mortality include recurrent pyogenic cholangitis in persons with schistosomiasis; hemiplegia, cephalgia, and paresis in those with cerebral paragonimiasis; cholangiocarcinoma in those with clonorchiasis; and intercurrent bacterial infections in those with fascioliasis and/or intestinal fluke infections.

Praziquantel remains the drug of choice for all trematode infections except fascioliasis, for which bithionol is the drug of choice. Praziquantel is recommended when bithionol is not available.

Bithionol is the drug of choice for Fasciola infections. The drug of choice in the treatment of fascioliasis is triclabendazole, a member of the benzimidazole family of anthelmintics. The drug works by preventing the polymerization of the molecule tubulin into the cytoskeletal structures and microtubules. However, resistance of F hepatica to triclabendazole has already been recorded in Australia and Ireland. Artemether has been shown to be effective in a rat model of fascioliasis.

Emetine, dehydroemetine, chloroquine, albendazole, and mebendazole were once used in many trematode infections; however, this practice is now discontinued because these drugs are associated with toxicity and their efficacy is in doubt.

When trematode infections are complicated by intercurrent bacterial infections, institute antibiotic therapy.

Surgical Care

Surgical management may be needed for complications of trematode infection, which include bladder carcinoma in patients with urinary schistosomiasis, fibrosis and thickening of the intestinal wall in those with intestinal schistosomiasis, ascending cholangitis in those with fascioliasis, and cholangiocarcinoma in those with clonorchiasis.

Schistosomicidal drugs, steroids, and surgery are the currently available treatments for neuroschistosomiasis.^[23]

Consultations

The following consultations may be necessary:

Intestinal and liver trematode infections - Infectious diseases specialist
Urinary schistosomiasis - Infectious diseases specialist, gastroenterologist, and urologist
Pulmonary paragonimiasis - Chest disease specialist
Ectopic fluke infections (eg, abdominal and cerebral paragonimiasis; ectopic schistosomiasis in intestine, lung, brain, or spinal cord; ectopic clonorchiasis) - Consultations with appropriate specialists as required per particular manifestations

Diet

To prevent paragonimiasis and clonorchiasis, avoid eating raw or undercooked fish.

To prevent infection with intestinal flukes and fascioliasis, properly clean and thoroughly wash raw vegetables, watercress, and other water-grown vegetables before eating.

Cook water-grown vegetables thoroughly before eating.

Activity

The patient should be given adequate bed rest supplemented with an adequate protein-rich diet.

Proceed to Medication

Contributor Information and Disclosures

Author

Subhash Chandra Parija, MBBS, MD, PhD, FRCPath Director-Professor of Microbiology, Head of Department of Microbiology, Jawaharlal Institute, Postgraduate Medical Education and Research, India

Subhash Chandra Parija, MBBS, MD, PhD, FRCPath is a member of the following medical societies: Indian Academy of Tropical Parasitology, Indian Association of Biomedical Scientists, Indian Association of Medical Microbiologists, Indian Association of Pathologists and Microbiologists, Indian Medical Association, Indian Society for Parasitology, National Academy of Medical Sciences, India, and Royal College of Pathologists

Disclosure: Jawaharlal Institute of Postgraduate Medical education & Research , Pondicherry , India Salary Employment

Coauthor(s)

Thomas J Marrie, MD Dean of Faculty of Medicine, Dalhousie University Faculty of Medicine, Canada

Thomas J Marrie, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Society for Microbiology, Canadian Infectious Disease Society, and Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.

Shekhar Koirala MBBS, Vice Chancellor, Department of Medicine, BP Koirala Institute of Health, Dharan, Nepal

Disclosure: Nothing to disclose.

Specialty Editor Board

Larry I Lutwick, MD Professor of Medicine, State University of New York Downstate Medical School; Director, Infectious Diseases, Veterans Affairs New York Harbor Health Care System, Brooklyn Campus

Larry I Lutwick, MD is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Ronald A Greenfield, MD Professor, Department of Internal Medicine, University of Oklahoma College of Medicine

Ronald A Greenfield, MD is a member of the following medical societies: American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Central Society for Clinical Research, Infectious Diseases Society of America, Medical Mycology Society of the Americas, Phi Beta Kappa, Southern Society for Clinical Investigation, and Southwestern Association of Clinical Microbiology

Disclosure: Pfizer Honoraria Speaking and teaching; Gilead Honoraria Speaking and teaching; Ortho McNeil Honoraria Speaking and teaching; Abbott Honoraria Speaking and teaching; Astellas Honoraria Speaking and teaching; Cubist Honoraria Speaking and teaching; Forest Pharmaceuticals Speaking and teaching

Eleftherios Mylonakis, MD Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital

Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

References

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Trematode infection. Adult worms in humans reside in the veins in various locations: Schistosoma mansoni in the superior mesenteric veins, Schistosoma japonicum in the inferior mesenteric veins, and Schistosoma haematobium in the vesical veins (these locations are not absolute). The females (size 7-20 mm; males slightly smaller) deposit eggs in the small venules of the portal and perivesical systems. The eggs are moved progressively toward the lumen of the intestine (S mansoni and S japonicum) and of the bladder and ureters (S haematobium), and they are eliminated with feces or urine, respectively. Under optimal conditions, the eggs hatch and release miracidia, which swim and penetrate specific snail intermediate hosts. The stages in the snail include 2 generations of sporocysts and the production of cercariae. Upon release from the snail, the infective cercariae swim, penetrate the skin of the human host, and migrate through several tissues and stages to their residence in the veins. Human contact with water is thus necessary for infection by schistosomes. Various animals serve as reservoirs for S japonicum and Schistosoma mekongi. Image courtesy of the US Centers for Disease Control and Prevention.

Trematode infection. Clonorchis sinensis egg. These are small operculated eggs. Size is 27-35 μm X 11-20 μm. The operculum, at the smaller end of the egg, is convex and rests on a visible "shoulder." At the opposite (larger, abopercular) end, a small knob or hooklike protrusion is often visible (as here). The miracidium is visible inside the egg. Image courtesy of the US Centers for Disease Control and Prevention.

Trematode infection. Fasciola hepatica eggs. Wet mounts with iodine. The eggs are ellipsoidal. They have a small, barely distinct operculum (upper end of the eggs in panel A). The operculum can be opened (egg in panel B), for example, when slight pressure is applied to the coverslip. The eggs have a thin shell that is slightly thicker at the abopercular end. They are passed unembryonated. Size range is 120-150 μm X 63-90 μm. Image courtesy of the US Centers for Disease Control and Prevention.

Trematode infection. Adult fluke of Fasciolopsis buski. Adult flukes size range is 20-75 mm by 8-20 mm. Image courtesy of the US Centers for Disease Control and Prevention.

Trematode infection. Eggs are excreted unembryonated in the sputum, or, alternately, they are swallowed and passed with stool (1). In the external environment, the eggs become embryonated (2), and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues (3). Miracidia go through several developmental stages inside the snail (4): sporocysts (4a), rediae (4b), with the latter giving rise to many cercariae (4c), which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, in which they encyst and become metacercariae. This is the infective stage for the mammalian host (5). Human infection with Paragonimus westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite (6). The metacercariae excyst in the duodenum (7), penetrate through the intestinal wall into the peritoneal cavity, and then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (8) (7.5-12 mm X 4-6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this occurs, completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65-90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. Image courtesy of the US Centers for Disease Control and Prevention.

Trematode infection. Paragonimus westermani egg. The average egg size is 85 μm by 53 μm (range, 68-118 μm X 39-67 μm). They are yellow-brown, ovoidal or elongate, have a thick shell, and are often asymmetrical with one end slightly flattened. At the large end, the operculum is clearly visible. The opposite (abopercular) end is thickened. The eggs of P westermani are excreted unembryonated. Image courtesy of the US Centers for Disease Control and Prevention.

Table 1. Comparative Features of Major Human Schistosoma Species

	S haematobium	S mansoni	S japonicum
Adult
Body surface of male	Finely tuberculate	Grossly tuberculate	Nontuberculate (smooth)
Testes	4-6, in a cluster	6-9, in a cluster	7, in a linear series
Position of ovary	Posterior to middle of body	Anterior to middle of body	Posterior to middle of body
Number of eggs in uterus	20-30	1-4	50-300
Egg
Size and shape	110-170 μm long 40-70 μm wide Terminal spine	114-175 μm long 45-68 μm wide Lateral spine	70-100 μm long 50-65 μm wide Central spine
Cercaria
Cephalic glands	2 pairs, oxyphilic	2 pairs, basophilic	4 pairs, oxyphilic

Table 2. Vectors and Geographical Areas Associated With Certain Trematode Types

Vector	Geographical Area	Type of Trematode
Biomphalaria glabrata	Brazil	S mansoni
Bulinus globosa	Nigeria	S haematobium
Bulinus truncate	Iran	S haematobium
Oncomelania hupensis nosophora	Japan	S japonicum
Thiara granifera	China	P westermani; M yokogawai
Semisulcospira libertine	China	P westermani; M yokogawai
Polypylis hemisphaerula	China	F buski
Parafossarulus manchouricus	China	C sinensis
Bithynia leachi	Germany	O felineus
Pirenella conica	Egypt	H heterophyes
Lymnaea truncatula	England	F hepatica

Table 3. List of Definitive and Intermediate Hosts and Sources of Infection of Major Trematodes

Trematode	Definitive Host	Intermediate Host 1^st 2^nd	Source of Infection
S haematobium	Humans	Freshwater snails (genus Bulinus)	Absent	Contact with water contaminated by cercariae
S mansoni	Humans, occasionally baboons and rodents	Freshwater snails (genus Biomphalaria)	Absent	Penetration of skin by cercariae
S japonicum	Humans, dogs, pigs, cattle, mice, mustelids, and monkeys	Amphibian snails (Oncomelania species)	Absent	Penetration of skin by cercariae
S mekongi	Humans and dogs	Aquatic snails (Tricula aperta)	Absent	Penetration of skin by cercariae
F hepatica	Sheep, goats, cattle, and other herbivorous animals	Amphibian snails (family Lymnaeidae)	Aquatic vegetations and watercress	Ingestion of aquatic plants and watercress infected with metacercariae
C sinensis	Humans, dogs, pigs, cats, rats, and several species of wild animals	Freshwater snails (family Bulinidae)	Freshwater fish (family Cyprinidae)	Eating raw or partially cooked freshwater fish or dried, salted, or pickled fish infected with encysted metacercariae
O felineus	Humans and other fish-eating mammals	Aquatic snails	Freshwater fish	Eating fish infected with metacercariae
P westermani	Humans, wolves, foxes, tigers, leopards, lions, cats, dogs, and monkeys	Freshwater snails (family Pleuroceridae and Thiaridae)	Freshwater crab or crayfish	Ingestion of freshwater crabs or crayfish infected with metacercariae
F buski	Pigs and humans	Planorbid snails of the genera Segmentina, Hippeutis, and Polypylis	Freshwater plants such as water caltrops, water chestnut, water bamboo, water hyacinth, and lotus	Ingestion of freshwater aquatic plants that harbor metacercariae

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