38 - Tapeworm and Fluke Infections of the GI Tract Flashcards
A seven-year-old child was taken to the doctor for abdominal pain, gas, bloating and intermittent diarrhea. The symptoms started about two days after returning from summer camp. Stool specimens were collected in formalin and polyvinyl alcohol (PVA) and sent to a commercial lab for ova-and-parasite (O&P) examination. Figures A-F show what was observed on a trichrome-stained smear made from the PVA-preserved stool. The images were captured at 1000x magnification. What is your diagnosis? Based on what criteria?
Giardia
Key: abdominal pain, gas, bloating and intermittent diarrhea
What are cestodes?
Tapeworms
There are three basic structures of adult tapeworms. What are they?
- Scolex
- “Neck”
- Body (strobila)
What is the scolex of an adult tapeworm?
The rounded head of the worm, usually armed with hooks and/or suckers
What is the “neck” of the adult tapeworm?
The area from which new body segments are generated
What is the body (strobila) of the adult tape worm?
A long SEGMENTED structure - individual segments are called proglottids
What does it mean to say that humans are the “definitive host” of tape worms?
Some adult tapeworms reside in the GI tract of the host… Typically the small intestine
Which tapeworms are an example of having humans as the definitive host?
- Taenia saginata (beef tapeworm)
- Taenia solium (pig tapeworm)
- Diphyllobothrium latum (fish tapeworm)
What does it mean to say that humans are the “intermediate host” of tape worms?
Some adult tape worms are present in different larval stages in various tissues in the body
Which tapewomrs are an example of having humans as an intermediate host?
- Echinococcus granulosus (dog tapeworm)
- Taenia solium (pig tapeworm)
How is the beef tapeworm transmitted?
Ingestion of undercooked beef containing encysted larvae
How many adult worms are humans generally infected with?
A single worm
How large do beef tapeworms (saginata) get?
10-30 feet long
They can live up to 25 years
What are the symptoms of beef tapeworm (saginata)?
Generally asymptomatic
- Mild abdominal pain
- Feeling of “fullness”
How do you diagnose beef tapeworm (saginata)?
Identification of proglottids or eggs that are found in the stool of an infected individual
How do you prevent beef tapeworm (saginata)?
- Prevent cattle from becoming infected
- Eliminate contact with infected cattle
- Prevent human infection by cooking meat thoroughly
What do we commonly call Taenia solium?
Pork tapeworm
Which is more common pork or beef tapeworm?
Beef tapeworm (saginata) is more common
Pork tape worm (solium) is less common
These are the trends in the US AND worldwide
How do you transmit Taenia solium (pork tapeworm)?
Ingestion of undercooked pork containing cycsts that result in intestinal disease
Ingestion of embryonated eggs will result in extra-intestinal disease (cysticercosis)
What is the intestinal disease of pork tapeworm similar to?
Beef tapeworm
What is an extra-intestinal disease caused by the Taenia solium (pork tapeworm) called?
Cysticercosis
What is the disease process of Cysticercosis?
Ingested eggs hatch in intestine and release infectious larvae which enter the circulation and travel to various body sites where they encyst.
What does this induce?
Cysticercus creates a space filling lesion and induces localized inflammation.
Where can you see this happening?
Striated muscle, heart, brain, eyes
Which form will you see the most severe complications with?
Neurocysticercosis
What complications would you see?
Seizure and neurological defects
How many cases do we see each year in the US of Neurocysticercosis?
2000
How do you diagnose pork tapeworm (solium)?
Intestinal infection with proglottids or eggs in the stool
How would you diagnose a pork tapeworm (solium) in an extra-intestinal infection?
- CT
- MRI
- Serology
Need to have an idea and go looking for it
How do you prevent and control pork tapeworm (solium)?
- Keep pigs away from human feces
- Cook pork thoroughly
What is the common name for Diphyllobothrium latum?
Fish tapeworm
How do you diagnose fish tapeworm (Diphyllobothrium latum)?
Eggs in stool
You don’t need to know the characteristics of these eggs
How do you control and prevent fish tapeworm (Diphyllobothrium latum)?
- Limit exposure of fish to human feces
- Cook fish thoroughly
What do we commonly call Echinococcus granulosus?
Dog tapeworm
Why do we say that humans are an accidental host for the dog tapeworm (Echinococcus granulosus)?
It is acquired through exposure to dog feces and the ingestion of eggs
When does disease occur from dog tapeworm (Echinococcus granulosus)?
Where livestock are raised in association with dogs
How many cases do we see each year in the US?
100-200, mostly in immigrants
What is the life cycle of dog tapeworm (Echinococcus granulosus)?
- Ingested eggs hatch in the intestine
- They release larvae
- The larvae travel via the bloodstream to multiple body sites
- In the tissue, larvae secrete a hyaline membrane
- Over time, this forms a fluid filled cyst (hydatid cyst)
What do the signs and symptoms of this disease depend on?
The location of the cysts
What happens when the cysts rupture?
They release large amounts of antigen and can induce an anaphylactic response
How do you diagnose dog tapeworm (Echinococcus granulosus)?
By the presence of cysts and a history that is consistent with exposure
What is another name for trematodes?
Flukes
What is the definitive host for flukes?
Humans
What are the intermediate hosts?
Snails
What is the life cycle of flukes?
- Larval forms are released from snails
- They form cysts on fish, shell fish or vegetation
- They are acquired by humans through ingestion
What type of fluke is Fasciotopsis buski?
An intestinal fluke that can be 1-3 inches long and 1/2 to 1 inch wide and is commonly associated with the consumption of water chestnuts
Where do we find Fasciotopsis buski?
Throughout china, southeast asia and india
What animal reservoirs do we see with Fasciotopsis buski?
Pigs, dogs and rabbits
How do humans acquire infection of Fasciotopsis buski?
By ingesting fresh water aquatic plants with encysted cercariae attached
What happens to the cercariae excyst in the small intestine?
It attaches to the columnar epithelium where it matures to egg-laying adults
What are egg-laying adults of Fasciotopsis buski called?
Hermaphroditic
What would constitute a light infection from Fasciotopsis buski?
A single worm
- Focal inflammation
- Intermittent diarrhea
What would constitute a heavy infection from Fasciotopsis buski?
Multiple worms
- Continuous diarrhea
- Intestinal hemorrhage
- Ulceration
- Abscess formation
How do you diagnose Fasciotopsis buski?
By the presence of egg in the stool
How do you prevent Fasciotopsis buski?
- Control snail population (hard to do)
- Improve sanitation
- Restrict harvesting of aquatic plants from contaminated areas
What are the two types of Liver Flukes?
- Fasciola hepatica
- Clonorchis (opisthorchis) sinensis
What type of hosts can F. hepatica have?
Parasites in sheep, cattle and humans
Where do we see infection of F. hepatica?
Worldwide, including southeast US
How do humans acquire a F. hepatica infection?
Through the ingestion of aquatic plants
How does an F. hepatica infection affect the liver?
Migration through the liver may induce…
- Liver tenderness
- Hepatomegaly
- Fever
- Eosinophilia
- Biliary obstruction and jaundice
How do you diagnose F. hepatica?
Eggs in feces
How do you control F. hepatica?
- Control snail population
- Imporved sanitation
- Restrict harvesting aquatic plants from contaminated areas
What is Clonorchis (opisthorchis) sinensis?
Another liver fluke which is endemic throughout Asia and is acquired by the ingestion of under prepared fresh water fish with attached encysted cercariae
How many Chinese immigrants are estimated to have Clonorchis (opisthorchis) sinensis?
25%
They have it colonized in the bile duct
What symptoms will you see with a light infection of Clonorchis (opisthorchis) sinensis?
No symptoms
What symptoms will you see with a heavy infection of Clonorchis (opisthorchis) sinensis?
- Biliary obstruction
- Jaundice
- Hepatitis
- Hepatomegaly
- Gallstones
What are heavily infected individuals more likely to develop?
** 10-15 times more likely to develop bile duct cancer **
An adult man passed a segmented worm and submitted it to his local state health department for identification. The worm was placed in 10% formalin and sent to CDC (Figure A). In addition to gross examination, a segment was removed from the distal end and compressed between two glass slides, producing the objects shown in Figure B. What is your diagnosis? Based on what criteria?
Diphyllobothrium
