Cestodes Flashcards
Tapeworms General morphology
Scolex: Organ of attachment at the anterior end of the organism
Proglottids
1) Individual segment in a chain of segments
2) Each contains male and female reproductive organs
3) Classed as immature, mature, and gravid
4) Gravid is at the end of the strobila and contains the fully developed uterus full of eggs
Strobila: entire chain of proglottids
Rostellum: can be armed (with hooklets) or unarmed; this is the area around the attachment device on the scolex
The uterine structure is used as a main criteria for identification
Taenia saginata Distribution
1) Worldwide, particularly in Islamic countries
2) Wherever beef is eaten raw or insufficiently cooked
Taenia saginata Infectious Stage
Ingestion of raw or poorly cooked beef containing encysted larvae
Taenia saginata Adult
- May live up to 25 years and grow to approx 25 ft in length
- Scolex has 4 weak developed suckers and an unarmed rostellum
- Proglottid is longer than it is wide and has an eccentric uterine pore. It has 15-20 branches on each side
Taenia saginata egg
- Round to slightly oval
- 35-45 um in diameter
- Thick striated shell
- 6 hooked oncosphere
Taenia saginata Disease
1) Usually very few symptoms
2) Rarely causes obstruction.
3) Diarrhea, hunger pains, weight loss, and appendicitis
4) Most common complaint is proglottids crawling from the anus. This may be first clue that a patient has a tape worm
Taenia saginata Diagnostic Stage & Treatment
Diagnosis
- Recovery and examination of gravid proglottids or scolex
- Egg is indistinguishable from T. saginata and T. solium
Treatment
- Prazinquantel or niclosamide
Taenia solium (pork tapeworm) Distribution
1) Worldwide
2) Most common in countries where raw or insufficiently cooked pork is eaten: Mexico, South America, Balkan states, and Slavic countries
Taenia solium Adult
- Matures to adult form in 5-12 weeks.
- May live up to 25 yrs and grow to 6-10 ft in length.
- Usually only single worm present but individuals can have multiple worms
- Scolex has four suckers with an armed rostellum and two rows of hooks
- Proglottids have 7-13 lateral uterine branches on each side
- Less than 100 proglottids
- Gravid proglottids break off from main strobila and passed in stool
Taenia solium Disease
Two Infections:
- Adult = slight irritation at site of attachment, vague abdominal symptoms
- Cysticercosis - systematic infection, involve any organ
Serious complications: invasion of spinal cord, brain, and eye
Taenia solium Diagnostic Stage & Treatment
Diagnosis
- Adult worm recovery and examination of gravid proglottids
- Cysicercosis surgical removal of parasite and microscopic examination for presence of suckers and hooks on scolex
Treatment
- Adult worm: Praziquantel or niclosamide
- Cysticercosis: Surgical removal where possible
Hymenolepis nana Distribution
1) Worldwide
2) Occurs frequently in children in the tropics and subtropics
Hymenolepsis nana Infectious Stage
Ingestion of egg if primarily from human stool. Rodents may be involved
Hymenolepis nana Adult
1) Matures in several weeks and is approx 40 mm.
2) Scolex has four suckers, short rostellum with hooks
3) Rarely seen in stool
Hymenolepis nana egg
- Round to oval
- 30 - 50 um
- Colorless thin shell
- Six hooked oncosphere has two polar thickenings from which arise polar filaments
Hymenolepis nana Disease
1) Asymptomatic
2) Heavy infection may have abdominal pain, nausea, vomiting, weight loss, nervousness, headaches, and diarrhea
Hymenolepis nana Diagnostic Stage
Diagnosis
- Recovery and identification of eggs in feces
Treatment
- Praziquantel and niclosamide
Hymenolepis diminuta Distribution
1) Worldwide in normal rat host
2) Human cases are accidental and rare