L38: Tapeworm and Fluke Infections of the GI Tract Flashcards
3 basic structures of adult tapeworms (cestodes)
- Scolex (rounded head of worm with hooks/suckers)
- Neck (area from which new body segments are generated)
- Body (strobila) with segments (proglottids)
Humans as hosts in cestodes
Can either be definitive host (adult tapeworms residing in small intestine like beef/pork/fish tapeworms) or intermediate host (larval stages present in various tissues (dog/pig tapeworm)
Transmission of Taenia saginata (beef tapeworm)
Ingestion of undercooked beef containing encysted larvae (cysticerci) – humans generally infected with single giant worm
Symptomology of Taenia saginata (beef tapeworm)
Generally asymptomatic except for mild abdominal pain and feeling of fullness
Diagnosis of Taenia saginata (beef tapeworm)
Identification of proglottids or eggs passed by infected individual
Control and prevention of Taenia saginata (beef tapeworm)
Prevent cattle from becoming infected by eliminating their contact with human feces and cook meat thoroughly
Transmission of Taenia solium (pork tapeworm)
Ingestion of undercooked pork containing cysts leads to intestinal disease and ingestion of embryonated eggs results in extraintestinal disease – less common than beef tapeworm
Intestinal disease of Taenia solium (pork tapeworm)
Similar to beef tapeworm disease
Extraintestinal infection of Taenia solium (pork tapeworm)
Ingested eggs hatch in intestine and release infectious larvae which enter cirulation and travel to various body sites where they encyst, creating a lesion that induces inflammation (pathology determined by location/size)
Neurocysteicercosis of Taenia solium (pork tapeworm)
Severe complication that leads to seizure and neurological defects – VERY big problem because it can infect brain (or eye)
Diagnosis of Taenia solium (pork tapeworm)
Proglottids or eggs in stool for intestinal infection, CT scan/MRI or serology for extraintestinal infection
Prevention and control of Taenia solium (pork tapeworm)
Keep pigs away from human feces and cook pork thoroughly
Life cycle of Diphyllobothrium latum (fish tapeworm)
When eggs get into the water, they release a coracidium that gets ingested by a crustacean –> fish ingests crustacean and gets infected
Transmission of Diphyllobothrium latum (fish tapeworm)
Ingestion of raw or undercooked fish with infectious larvae – infected fish can be found in freshwater lakes in MN, MI, FL, and CA
Symptomology of Diphyllobothrium latum (fish tapeworm)
Transient nausea, abdominal pain, diarrhea, etc. – infection with multiple worms can cause intestinal obstruction – 2% of patients develop macrocytic anemia
Diagnosis of Diphyllobothrium latum (fish tapeworm)
Eggs in stool
Control and prevention of Diphyllobothrium latum (fish tapeworm)
Cook fish adequately and limit exposure of fish to human feces
Transmission of Echinococcus granulosus (dog tapeworm)
Humans are accidental/intermittent host between dogs and sheeps/goats when they come into contact with infected dog feces (ingestion of eggs) – happens where livestock are raised in association with dogs
Life cycle of Echinococcus granulosus (dog tapeworm)
Ingested eggs hatch in the intestine, releasing larvae which travel via bloodstream to multiple body sites where they secrete a hyaline membrane and a cyst forms
Symptomology of Echinococcus granulosus (dog tapeworm)
Depends on location of the cysts, but ruptured cysts release large amounts of antigen and can induce anaphylactic response (hyatid cyst disease – large bag of cysts)
Trematode (fluke) basics
Humans are definitive host, freshwater snails are intermediate hosts – larval forms released from snails encyst on fish, shellfish, or vegetation and are acquired by ingestion
Fasciolopsis buski basics
Intestinal fluke with leaf-shaped appearance that comes from water chestnuts
Transmission of Fasciolopsis buski
Ingestion of freshwater aquatic plants with encysted cercariae attached – pigs, dogs, and rabbits can be reservoirs
Life cycle of Fasciolopsis buski
Cercariae excyst in the small intestine, attach to columnar epithelium and mature to egg-laying adults
2 types of infection by Fasciolopsis buski
- Light infection (single worm) – focal inflammation, intermittent diarrhea
- Heavy infection (multiple worms) – continuous diarrhea, intestinal hemorrhage, ulceration, abscess formation
Diagnosis of Fasciolopsis buski
Presence of eggs in stool
Prevention of Fasciolopsis buski
Control snail populations, improve sanitation, restrict harvesting of aquatic plants from contaminated areas
2 types of liver flukes
Fasciola hepatica and Clonorchis sinesis
Life cycle of Fasciola hepatica
Lives in bile duct –> gets out through feces into water –> gets into snails –> comes out of snails (comes from aquatic plants originally)
Life cycle of Clonorchis sinesis
Larval forms exist in fish and are ingested
Fasciola hepatica (transmission and disease)
Found in SE US, acquired through ingestion of aquatic plants, migrates through liver and causes liver tenderness, hepatomegaly, fever, and eosinophilia – sometimes causes biliary obstruction (jaundice)
Fasciola hepatica (diagnosis and control)
Diagnosed by eggs in feces, controlled by controlling snail populations, improving sanitation, restricting harvesting of aquatic plants from contaminated areas
Clonorchis sinesis (Opisthorchis sinesis)
Endemic in Asia (25% of Chinese immigrants), acquired by ingestion of under-prepared freshwater fish with encysted cercariae, can be asymptomatic (light) or cause biliary obstruction, jaundice, hepatitis, hepatomegaly, and gallstones (heavy) – 10-15x more likely to develop bile duct cancer if heavy infection
