Parasitic Tapeworms

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Flashcards on parasitic tapeworms, covering morphology, epidemiology, life cycle, disease, diagnosis, treatment, and prevention.

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89 Terms

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Diphyllobothrium latum

Fish tapeworm, also known as the human broad tapeworm.

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Diphyllobothrium latum Morphology

Very large tapeworm, longest found in humans (up to 20m), scolex with two grooves called bothria, wider proglottides with rosette-shaped uterus.

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Diphyllobothrium latum Proglottids

3000-4000 proglottids, creamy white in color.

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Diphyllobothrium latum Scolex

Spoon-shaped scolex with two long sucking grooves.

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Diphyllobothrium latum Gravid Proglottide

Centrally located rosette-shaped uterine structure.

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Diphyllobothrium latum Eggs

Only tapeworm that produces operculated eggs, unembryonated, oval or ellipsoidal, has terminal knob (abopercular knob), contains coracidium, size range: 55-75 μm by 40-55 μm.

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Diphyllobothrium latum Epidemiology

Common in Northern Hemisphere (Europe, Former Soviet Union, Baltic countries, North America, Asia), some cases reported in Uganda and Chile; endemic distribution in Alaska, Great Lakes region, and Scandinavia.

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Diphyllobothrium latum Transmission

Fish infected with Diphyllobothrium larvae are transported and consumed globally.

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Diphyllobothrium latum Life Cycle

Infection acquired by eating raw or undercooked fish, complex life cycle requiring two intermediate hosts and water environment.

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Diphyllobothrium latum Disease

Diphyllobothriosis; mostly asymptomatic, symptoms include digestive disturbances (vomiting, diarrhea, abdominal pains), intestinal obstruction, gall bladder disease, weight loss, weakness, and anemia due to vitamin B12 deficiency.

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Diphyllobothrium latum Diagnosis

Identification of operculated eggs or segments in stool sample with microscope; proglottides and scolex are seldom found.

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Diphyllobothrium latum Treatment

Praziquantel and niclosamide are effective medications; surgical removal if larval stage occurs in human body.

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Diphyllobothrium latum Prevention

Avoid eating raw or undercooked fish; freezing (-10°C for 15 min) or cooking fish kills the parasite; health education in endemic regions, proper disposal of human wastes, and treatment of infected people.

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Taenia saginata

Beef tapeworm.

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Taenia saginata Morphology

Up to 10 m long, about 800 proglottides, pear-shaped scolex with 4 suckers without rostellum or hooks, gravid proglottide is longer than wider with branched uterus.

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Taenia saginata Scolex

Equipped with 4 suckers.

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Taenia saginata Gravid Proglottide

Lateral branches of uterus (15-30 per side).

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Taenia saginata Egg

Three pairs of hooklets, radial striations on yellow-brown embryophore, size range: 28-40 μm by 18-30 μm; indistinguishable from T. solium.

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Taenia saginata Larval Stage

Bladder cysticercus (cysticercus bovis).

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Taenia saginata Epidemiology

Occurs worldwide wherever contaminated raw beef is eaten, particularly in Eastern Europe, Russia, eastern Africa, and Latin America; common in areas of low sanitation where cattle infection is frequent; cattle are intermediate hosts, and humans are definitive hosts.

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Taenia saginata Source of Infection

Raw and undercooked beef containing cysticerci (cysticercus bovis).

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Taenia saginata Detection

Eggs can be detected in the stool 2 to 3 months after the tapeworm infection is established.

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Taenia saginata Disease

Taeniosis, teaniarhynchosis, beef tapeworm infection; usually asymptomatic, symptoms include loss of appetite, weight loss, digestive problems, abdominal pain, upset stomach, inflammation of small intestine, diarrhea, and appendicitis.

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Taenia saginata Symptoms

More symptoms than T. solium due to larger size; most visible symptom is the active passing of proglottids through the anus and in the feces; in rare cases, tapeworm segments become lodged in the appendix, bile, or pancreatic ducts.

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Taenia saginata Diagnosis

Examination of stool samples based on the detection of gravid proglottides and eggs. Differentiation between T. saginata and T. solium is important (based on the number of lateral uterine branches).

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Taenia saginata Treatment

Praziquantel or niclosamide.

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Taenia saginata Prevention

Cook meat to safe temperatures, beef meat inspection, and treatment of infected persons.

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Taenia solium

Pork tapeworm.

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Taenia solium Morphology

Usually 4m in length (up to 8m), scolex with 4 suckers, rostellum, and double crown of hooks (about 30) - "armed", gravid proglottides are longer than wider but contains less lateral uterine branches.

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Taenia solium Scolex

Equipped with 4 suckers, rostellum and double crown of hooks.

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Taenia solium Gravid Proglottide

Lateral Branches (7-15 per side).

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Taenia solium Egg

Eggs are indistinguishable from T. saginata.

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Taenia solium Larval Stage

Second larval stage - bladder cysticercus (cysticercus cellulose).

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Taenia solium Epidemiology

Infections found worldwide, more prevalent in underdeveloped communities with poor sanitation where raw or undercooked pork is eaten, higher rates in Latin America, Eastern Europe, sub-Saharan Africa, India, and Asia; pigs are intermediate hosts, and humans are definitive hosts.

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Taenia solium Source of infection

Raw and undercooked pork containing cysticerci (cysticercus cellulosae) - oral route of infection.

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Taenia solium Strobilar Forms

Develop during 2 to 3 months, and eggs can be detected in the stool 2 to 3 months after the tapeworm infection is established.

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Taenia solium Disease

Taeniosis (pork tapeworm infection) AND cysticercosis. Intestinal taeniosis is similar to T. saginata; cysticercosis may occur when T. solium eggs are ingested accidentally and can be a very serious disease.

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Taenia solium Cysticercosis

Parasitic tissue infection caused by larval cysts of the pork tapeworm; larval cysts infect brain, muscle, eye, or other tissues and are a major cause of adult onset seizures and increased intracranial pressure.

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Taenia solium Cysticercosis Transmission

  1. EGZOINFECTION: eating food contaminated with T. solium eggs; 2. EGZOAUTONIFECTION - people with poor hygiene will shed tapeworm eggs and accidentally ingest them; 3. ENDOAUTONIFECTION - eggs may get into small intestine during antiperistalsis.
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Taenia solium Diagnosis

Examination of stool samples and based on the detection of gravid proglottides and eggs. Differential species diagnosis between T. saginata and T. solium is important (based on the number of lateral uterine branches).

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Taenia solium Cysticercosis Diagnosis

Requires some additional methods like X-ray examination, biopsy, computerized tomography (CT scans) and MRI; immunological test may also be helpful.

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Taenia solium Treatment

Praziquantel or niclosamide; in case of cysticercosis: albendazole and surgical removement of cysticercus larvae may be needed.

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Taenia solium Prevention

Cook meat to safe temperatures, pork meat inspection and treatment of infected persons.

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Echinococcus granulosus

Hydatid worm.

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Echinococcus granulosus Human Role

Human is intermediate host.

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Echinococcus granulosus Morphology

Very small: 2-6 mm in length; scolex equipped with four suckers and rostellum with a double crown of hooks; immature, mature and gravid proglottides.

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Echinococcus granulosus Eggs

Infective eggs (30-40μm) contain oncospheres surrounded by their envelopes and are similar to Taenia eggs.

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Echinococcus granulosus Larval Stage

Second larval stage is the bladder uniocular hydatid cyst that is filled with fluid and may reach up to 20 cm!!! in diameter and hold as much as 15 liters of fluid. External laminated acellular cuticula and inner germinal layer.

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Echinococcus granulosus Composition

Inside the capsules the protoscolices develop (millions of them) that may sink to the bottom of the bladder forming so-called hydatid sand.

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Echinococcus granulosus Epidemiology

Cosmopolitan tapeworm found in Africa, Europe, Asia, Central and South America, and in North America; intermediate hosts may be herbivorous mammals (especially sheep) and man; definitive hosts are carnivores, particularly dogs.

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Echinococcus granulosus Transmission

Main source of human infection: infected dogs and food or water contaminated with their eggs. Transmission: ONLY by INGESTION of the infective EGGS (oral route).

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Echinococcus granulosus Route

Oncospheres hatch in the human intestine and migrate to organs, like liver or lungs where they develop.

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Echinococcus granulosus Disease

Cystic echinococcosis (CE), hydatid disease, hydatidosis; often remains asymptomatic until cysts grow large enough to cause discomfort, pain, nausea and vomiting.

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Echinococcus granulosus Symptoms

Symptoms are related with the organs that are affected; cyst rupture may cause mild to severe anaphylactic reactions.

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Echinococcus granulosus Diagnosis

Imaging techniques, such as CT scans, ultrasonography, and MRIs are used to show the presence of E. granulosus cysts (if they are calcified); serologic tests (immunological methods) may be used to confirm the diagnosis

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Echinococcus granulosus Radiological exam

Radiological and ultrasonografic examination may be also confirmed by direct microscopic identification of the hydatid sand.

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Echinococcus granulosus Treatment

Surgery remains the most effective treatment, chemotherapy, cyst puncture, and PAIR (percutaneous aspiration, injection of chemicals and reaspiration).

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Echinococcus granulosus Prevention

Health education, maintenance of high personal hygiene, and avoidance of food or water that may have been contaminated by fecal matter from dogs. In endemic regions, household dogs should be regularly de-wormed.

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Echinococcus multilocularis

Causes alveolar echinococcosis.

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Echinococcus multilocularis Morphology

Adult tapeworm consists of 4 proglottids and is smaller that E. granulosus (1.2-1.3 mm in length); cysts contain NO daughter cysts and brood capsules.

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Echinococcus multilocularis Epidemiology

Found across the globe and is especially prevalent in the northern latitudes of Europe, Asia and North America; man is only accidental intermediate host.

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Echinococcus multilocularis Life cycle

Definitive hosts are foxes, dogs, cats, coyotes and wolves; intermediate host are small rodents; larval growth (in the liver) remains indefinitely in the proliferative stage.

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Echinococcus multilocularis Disease

Alveolar (multilocular) echinococcosis (AE); human cases are rare; parasitic tumors in the liver and may spread to other organs.

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Echinococcus multilocularis Morbidity

Larval forms of E. multilocularis do not fully mature into cysts but cause vesicles that invade and destroy surrounding tissues; it cause discomfort or pain, weight loss, and malaise. AE can cause liver failure and death because of the spread into nearby tissues.

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Echinococcus multilocularis Diagnosis

Imaging techniques such as CT scans are used to visually confirm the parasitic vesicles and cyst-like structures; serologic tests can confirm the parasitic infection.

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Echinococcus multilocularis Treatment

Radical surgery, long-term chemotherapy or both; if left untreated, infection with AE can be fatal.

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Echinococcus multilocularis Prevention

Avoiding contact with wild animals and their fecal matter; limiting interactions between dogs and rodent populations.

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Hymenolepis (Vampiriolepis) nana

Dwarf tapeworm.

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Hymenolepis nana Morphology

Smallest tapeworm (10-60mm in length and 1 mm wide) infecting human intestine; possesses scolex equipped with 4 suckers, rostellum and single ring of hooks (20-30); eggs are oval or spherical with hexacant oncosphere surrounded by its envelope and equipped with 4-8 polar filaments.

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Hymenolepis nana Epidemiology

Worldwide; common in hot countries, most often found in children in countries in which sanitation and hygiene are inadequate; most frequently encountered tapeworm in some areas, including United States.

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Hymenolepis nana Transmission

No intermediate host required in life cycle; monoxenous; main source of infection: human carriers and utensils contaminated with H. nana eggs. Transmission is most frequently direct – from hand to mouth (oral route).

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Hymenolepis nana Disease

Hymenolepiosis; usually asymptomatic; may lead to mild intestinal distress with diarrhea, vomiting, nausea, weakness, loss of appetite and abdominal pains and cramps.

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Hymenolepis nana in Children

Young children may develop a headache, itchy bottom or have difficulty with sleeping; may be misdiagnosed for pinworm infection.

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Hymenolepis nana Diagnosis

Direct microscopic detection of characteristic eggs in feces of infected person; concentration methods may be also helpful; examination of stool should be performed with extreme care.

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Hymenolepis nana Treatment

Praziquantel; medication causes the dwarf tapeworm to dissolve within the intestine; sometimes more than one treatment is necessary.

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Hymenolepis nana Prevention

Environmental sanitation and proper personal hygiene, particularly in children institution; treatment of infected persons. Control of beetles and fleas where grains and cereals are stored.

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Hymenolepis diminuta

Rat tapeworm.

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Hymenolepis diminuta Morphology

Much larger than H. nana - 20-60 cm long, - 800-1000 proglottids; scolex is rhomboidal and has 4 suckers and rostellum without hooks.

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Hymenolepis diminuta Disease

Hymenolepiosis diminuta; infection is usually asymptomatic; most characteristic symptom is diarrhea.

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Hymenolepis diminuta Diagnosis

Direct microscopic detection of characteristic eggs in feces of infected person.

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Hymenolepis diminuta Treatment

Praziquantel and niclosamide.

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Hymenolepis diminuta Prevention

Environmental sanitation and proper personal hygiene, particularly in children.

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Dipilidium caninum

Dog tapeworm, also infects cats and humans.

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Dipilidium caninum Morphology

15-70 cm long; scolex with 4 suckers and 30-150 hooks (in 3-4 raws); proglottids are pumpkin seed- shaped, often resemble rice grains when dried.

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Dipilidium caninum Epidimiology

Common everywhere, more common in cats and dogs. More common in children then adults when hygiene standards are bad. Gravid proglottids contain eggs and are passed in feces singly or in groups of two or three and are active.

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Dipilidium caninum Diseae

Dypylidiosis; most infections are asymptomatic; mild gastrointestinal disturbances may occur like abdominal pain and diarrhea. The passage of proglottids is most striking for children and animals. Motile proglottids may be mistaken for maggots or fly larvae.

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Dipilidium caninum Diagnosis

Direct microscopic detection of characteristic packets of eggs or gravid proglittids in feces of infected person.

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Dipilidium caninum Treatment

Praziquantel and niclosamide.

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Dipilidium caninum Prevention

Environmental sanitation and proper personal hygiene, children show most frequent contacts with dogs and cats.