Zaporozhyan state medical university departement of infectious diseases

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through its genital atrium or when its membrane disintegrates. Eggs are 

immediately infective when passed with the stool and cannot survive more than 10 

days in the external environment. 

Hymenolepis nana (dwarf tapeworm) 

 

Clinical Manifestations. H. nana infection, even with many intestinal 

worms, is usually asymptomatic. When infection is intense, anorexia, abdominal 

pain, and diarrhea develop. 

Some proglottids release eggs or disintegrate themselves already in the small 

intestine. Larval oncospheres (hexacanth embryo) might hatch prematurely and 

penetrate villi without leaving the body resulting in autoinfection. Hymenolepis 

nana does not necessarily need an intermediate host to complete its life cycle. 

Larvae can develop in spite of the high temperature of a human body. Adults live 

4–6 weeks, but internal autoinfection allows hymenolepiasis to persist for years. 

Hymenolepiasis is usually asymptomatic in adults. But prolonged infection 

or multiple tapeworms especially in children can cause more severe symptoms. 

The worms eat your food and cause inflammation of the intestinal mucosa. The 

inflamed tissue will have a reduced ability to absorb nutrients. People with little 

food to begin with and those who are weakened by other diseases suffer the most. 

Hymenolepiasis symptoms sometimes include: anal itching, diarrhea (can be 

bloody), headache, increased appetite or loss of appetite, insomnia, muscle spasms  

nausea, nervousness, seizures, stomach ache, vomiting, weakness, weight loss. 

Diagnosis. Infection is diagnosed by the finding of eggs in the stool. 

Treatment. Praziquantel (25 mg/kg once) is the treatment of choice, since it 

acts against both the adult worms and the cysticercoids in the intestinal villi. 

Nitazoxanide (500 mg bid for 3 days) may be used as an alternative. 

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Prevention.  Good personal hygiene and improved sanitation can eradicate 

the disease. Epidemics have been controlled by mass chemotherapy coupled with 

improved hygiene. 

 

HYMENOLEPIS DIMINUTA, a cestode of rodents, occasionally infects 

small children, who ingest the larvae in uncooked cereal foods contaminated by 

fleas and other insects in which larvae develop. Infection is usually asymptomatic 

and is diagnosed by the detection of eggs in the stool. Treatment with praziquantel 

results in cure in most cases. 

 

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TREMATODOSES 

 

Class flukes (Trematodoses) includes the agent of fascioliasis, fascipsidosis, 

clonorchiasis, paragonimiasis, schistosomiases, opisthorchiasis. 

These trematodes belong to the Opisthorchidae. Some species of the genus 

Opisthorchis cause infections in humans occasionally while other species do so 

quite frequently. Opisthorchis felineus has endemic foci in water reservoirs and 

river deltas. It is a common parasite in Siberia. Snails of the genus Bythinia are its 

first intermediate host. Normal final hosts include dogs, cats and pigs. The adult 

worm is found in the bile ducts. Recurrent cholangitis may occur. People become 

infected by eating an infected fish.  

Opisthorchis viverrini is common in humans in North Thailand. Bithynia 

snails are the first intermediate host. Various freshwater fish are intermediate hosts. 

The adult worm is found in the bile ducts where it is responsible for recurrent 

cholangitis, but the majority of infections are subclinical.  

Opisthorchis sinensis (previously called Clonorchis sinensis) is a very 

common parasite in Southeast Asia. The adult worms are found in the biliary tract 

or the Wirsung duct in the pancreas. The first intermediate hosts are snails 

(Bythinia, Assiminea, Melanoides, Parafossarulus). Subsequently fish become 

infected. Cats, dogs, pigs and fish-eating carnivores are the normal final hosts. 

People become infected by eating infected fish. The parasitosis is a problem not 

only because of the direct damage to the biliary tract and the risk of pancreatitis, 

but also due to the risk of bile duct carcinoma (cholangiocarcinoma) for those 

infected.  

Etiology. Organisms: are Platyhelminth trematodes. Adult is 10

‐25 mm long 

x 3

‐5 mm wide. Reservoir: cats and dogs. Intermediary hosts: fresh water snail and 

fish. Magnitude: –13.5 million infected worldwide. Up to 26 % of Asian 

immigrants in USA have  liver flukes. Acquisition: ingestion of fresh

‐water fish, 

raw,  pickled, smoked, or dried. 

Epidemiology.  The natural-focal zoonosis. Biohelmintiasis. The definitive 

hosts are human and animals (cats, dogs, pigs).  The intermediate hosts are fresh 

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water mollusk from the family Bithynia; fishes from the family. The factors of the 

transmission is fish with larvae (metacercariae). 

Life Cycle: Water is contamination. Eggs operculate an release miracidia. 

Miracidia is eaten by fresh

‐water snail and changes to sporocyst then to rediae. 

Rediae matures to cercaria and is released into the water and penetrates the skin of 

a fish transforming into a cyst that matures to metacercaria. Human eats fresh 

water fish.  Metacercaria excyst in duodenum and migrate inside the lumen into 

biliary duct, GB, and pancreatic duct. Then matures to adult and lays eggs after 4 

weeks.  

Metacercariae penetrates to bile ducts, gall bladder, intrahepatic bile ducts 

and ducts of the pancreas 

Early acute phase characterized toxic action of the products of the 

destruction of larvae, toxic-allergic reactions, lesion of the walls of bile ducts and 

ducts of pancreas. Late chronic phase characterized allergic action of helminthes, 

toxic and mechanic actions. 

 

Clinical Manifestations. Acute phase. Light infection are asymptomatic 

but may be repetitive and cause heavy parasite burden. Heavy infections cause 

symptoms for less than 1 month, including fever, diarrhea, epigastric pain, 

anorexia, tender hepatomegaly, and sometimes jaundice. Leukocytosis and 

eosinophilia are very common. Eggs appear in stool 1 month after infection. 

Chronic phase is due to the invasion of adult worms in the biliary tree, 

pancreatic duct, and/or GB. If < 100 flukes, usually asymptomatic. Moderate 

infestations (< 1000) cause anorexia, nausea, abdominal fullness and distress. 

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