E3- Helminths Flashcards
What is the causative agent of enterobiasis “pinworm disease”?
Enterobius vermicularis
What is the lifecycle of Enterobius vermicularis?
- Eggs are deposited on perianal region and are then ingested
- Adults mature and gravid females migrate at night to the perianal region to deposit eggs
- Deposited eggs becomes infectious in 4-6 hours
How does a Enterobius vermicularis infection present clinically?
Pruritis ani
How is Enterobius vermicularis dx?
-Tape method to detect the presence of eggs on perianal skin
What is the most effective way to minimize the spread of Enterobius vermicularis?
Handwashing
Which 2 types of nematodes are transmitted via contaminated soil ingestion?
- Ascaris lumbricoides
- Trichuris trichiura
What nematode is known as the “large intestinal roundworm”?
Ascaris lumbricoides
What nematode is known as the “whipworm”?
Trichuris trichiura
What is the lifecycle of Ascaris lumbricoides?
- Infective eggs are ingested
- Larvae travel through the bloodstream to the lungs
- Larvae travel to the mouth where they are swallowed
- Adult worms produce eggs that take weeks to become infectious
What syndrome is a Ascaris lumbricoides infection associated with?
Pulmonary-Loeffler’s syndrome
How is Ascaris lumbricoides dx?
Eggs in stool
What is seen on the morphology of Trichuris trichiura?
- Whiptail
- Egg capsules
What is the lifecycle of Trichuris trichiura?
- Infective (embryonated) eggs are ingested
- Larvae are released and mature into adults
- Adults release eggs
How does a Trichuris trichiura infection present clinically?
- Frequent painful passage of stool
- Rectal prolapse can occur
- Children may suffer growth retardation and anemia
How is Trichuris trichiura dx?
Presence of eggs in stool
Which worms are considered hookworms?
- Necator americanus
- Ancylostoma duodenale
What is the pathophysiology of Necator americanus and
Ancylostoma duodenale?
Feed on blood from intestinal mucosa
How are Necator americanus and
Ancylostoma duodenale transmitted?
Infective stage larvae (filariform) penetrate skin
How do Necator americanus and
Ancylostoma duodenale infections present clinically?
- Blood-filled, pruritic lesions at the site of larval penetration “ground itch”
- Anemia
How are Necator americanus and
Ancylostoma duodenale dx?
Presence of eggs in stool sample
What worm is known as “threadworms”?
Strongyloides stercoralis
What are the two multiplication cycles of Strongyloides stercoralis?
In host (parasitic) or in soil (free living)
How is Strongyloides stercoralis transmitted?
Infective larvae in soil penetrate the skin
How does Strongyloides stercoralis present clinically?
- Diarrhea, pain constipation, malabsorptioon
- Autoinfection can occur leading to chronic infection
A Strongyloides stercoralis infection can be life threatening in pts with what?
A defect in cell mediated immunity
How is Strongyloides stercoralis dx?
-Presence of larvae in stool sample
What is the morphology of trematodes (flukes)?
- Flattened, leaflike body
- Presence of suckers
- Hermaphroditic
What type of worms have 2 intermediate hosts and 1 definitive host?
Trematodes (flukes)
What type of worm is commonly found in pork?
Taenia solium
What type of worm is commonly found in beef?
Taenia saginata
What type of worm are Taenia solium and Taenia saginata?
Tapeworms
What structure is unique to tapeworms (Taenia solium and Taenia saginata)?
Scolex (head structure)
Are eggs released in the proglottids of Taenia solium and Taenia saginata infectious or non-infectious?
Immediately infectious
What are the larvae of Taenia solium and Taenia saginata called?
Cysticeri
What is the lifecycle of Taenia solium and Taenia saginata?
- Infective eggs ingested by cattle or pigs
- Cysticerci (larvae) develop in muscle
- Poorly cooked meat ingested by a human releases the cysticercus
- Proglottids (segments) released in the feces contain infectious eggs
What can develop in Taenia solium infections if infective eggs are ingested?
Cysticercosis
-Typically asymptomatic, but serious sequlae can occur depending on infected site
How are Taenia solium and Taenia saginata dx? (3)
- Presence of eggs or proglottids in stool sample
- Lesions demonstrated by CT scans
- Definitive = histology
What type of worm can become very long and contain thousands of proglottids?
Diphyllobothrium latum
What is the difference between the proglottids in Taenia solium/Taenia saginata and Diphyllobothrium latum?
Diphyllobothrium latum eggs are released singly, not in proglottids
Where is Diphyllobothrium latum geographically predominant?
The great lakes region and Alaska
What is the lifecycle of Diphyllobothrium latum?
- Infective larvae found in muscles of fish
- Poorly cooked fish ingested by a human release the larvae
- Adult worm develops and releases eggs in the feces
- Eggs hatch in fresh water and are ingested by crustaceans
- Crustaceans ingested by a small fish
What does the Diphyllobothrium latum worm compete for in humans?
What other infection did we talk about that can cause this?
Vitamin B12
Giardia lamblia
How is Diphyllobothrium latum dx? (3)
- Presence of eggs in stool
- ID of adult worm
- Anemia
