Trematode Infection Follow-up

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

Updated: Sep 1, 2011

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Further Inpatient Care
Further Outpatient Care
Transfer
Deterrence/Prevention
Complications
Prognosis
Patient Education
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Further Inpatient Care

Anemia may be treated with iron supplements and vitamins, which may be administered orally to facilitate iron absorption.

Further Outpatient Care

Further outpatient care includes health education. Thorough cooking of fish and aquatic vegetables, fruits, and plants is necessary to prevent ingestion of infective forms of the parasite.

Transfer

Transfer if access to specialized health care services is lacking.

Deterrence/Prevention

Note the following practices for deterrence and prevention of trematode infection:

Elimination of molluscan hosts to control infection with schistosomes and intestinal, liver, and lung flukes
Proper sanitary disposal of human and pig excreta to avoid water contamination
Chemotherapy of infected persons
Avoidance of consumption of contaminated water, water plants, fruits, fish, crab, and raw liver
Thorough cleaning and washing of raw vegetables and aquatic fruits to prevent infection with intestinal flukes
Thorough cooking of water-grown vegetables before eating
Cooking of crab and crayfish before eating to prevent infection with lung flukes

Complications

Schistosomiasis complications can include the following:

Cor pulmonale
Portal hypertension
Urinary bladder carcinoma
Neurological complications: Cerebral and cerebellar tumour–like neuroschistosomiasis can present with increased intracranial pressure, headache, nausea and vomiting, and seizures. Myelopathy (acute transverse myelitis and subacute myeloradiculopathy) is the most common neurological complication of S mansoni infection. Schistosomal myelopathy tends to occur early after infection and is more likely to be symptomatic than cerebral schistosomiasis. The conus medullaris and cauda equina are the most common sites of involvement. Severe schistosomal myelopathy can provoke a complete flaccid paraplegia with areflexia, sphincter dysfunction, and sensory disturbances.^[23]

Lung fluke complications can include the following:

Lung abscess
Pleural effusion
Ectopic lesions in the brain

Liver fluke complications can include the following:

Intercurrent bacterial infections
Less commonly, pancreatitis in fascioliasis^[24]
Anemia
Recurrent pyogenic cholangitis and cholangiocarcinoma in clonorchiasis

Intestinal fluke complications can include asthenia with ascites in fasciolopsiasis.

Prognosis

Prognosis is excellent in patients with mild-to-moderate trematode infection, with early disease, and/or without severe complications.

Patients with heavier worm infection are less likely to improve, and the outcome in such infections may be serious and fatal.

Patient Education

Avoid high-risk food habits. Inform patients about the danger of eating raw or undercooked vegetables and fish and the importance of cleaning, washing, and adequately cooking vegetables and fish or raw liver.

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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