Cestodes Quiz: Structure and Characteristics Test

Study Notes

Cestodes (Tapeworms)

Characterized by segmented, ribbon-like morphology
All are hermaphroditic
Lack nervous and digestive systems
Morphology consists of:
- Scolex: main organ of attachment to definitive host
- Neck: region of growth
- Segments or proglottids: become more mature distally, with most distal segments being gravid

Taenia Saginata (Beef Tapeworm)

Intermediate host: cattle
Definitive host: human
Life cycle:
- Eggs go into blood vessels within cattle's intestines and are transported to skeletal muscles, where they develop as larvae (cysticerci)
- Infection occurs through ingestion of improperly cooked or raw beef containing infective larva (cysticercus)
- Maturation occurs in small intestine, taking approximately 3 months
Can grow up to 10 meters in length
Adult tapeworms are irritated by alcohol, leading to passage of proglottids after consumption
Causes Taeniasis, leading to diarrhea, abdominal pain, loss of appetite, and weight loss
Laboratory diagnosis: examination of fecal specimens
Treatment: Praziquantel
Prevention and control: proper waste disposal, sanitation practices, and adequate cooking of beef; freezing of beef meat for 10 days can kill encysted larvae

Taenia Solium (Pork Tapeworm)

Humans are both intermediate and definitive hosts
Life cycle:
- Ingested worm eggs hatch in small intestine, burrow to intestinal wall, and disseminate to various organs
- Infection occurs through ingestion of improperly cooked or raw pork meat containing infective larva (cysticercus cellulosae)
Diagnostic methods:
- Stool examination
- Perianal swabs
- Examination of gravid proglottids flattened between two glass slides
- Injection of India ink through genital pore to count lateral branches of uterus
- CT scan, MRI for neurocysticercosis
- Ophthalmoscopy for ophthalmic cysticercosis
Causes Cysticercosis, a parasitic infection caused by larvae of tapeworm

Pathogenesis of Taenia Solium

Minor intestinal damage from adult tapeworms
Irritation at site of attachment
Entangled proglottids may cause intestinal obstruction
Cysticerci can develop in various tissues, including striated muscle, brain, subcutaneous tissues, eye, heart, lung, and peritoneum
Living cysticerci can cause inflammation or death, leading to inflammation and calcification

Diphyllobothrium Latum (Broad Fish Tapeworm)

1st intermediate host: copepods (Cyclops and Diaptomus)
2nd intermediate host: fish
Longest medically important tapeworm
Has two elongated sucking grooves for attachment
Has operculated eggs (unique among cestodes)
Causes Diphyllobothriasis, characterized by:
- Abdominal pain and diarrhea
- Hyperchromic, megaloblastic anemia (due to vitamin B12 deficiency)
- Thrombocytopenia and leukopenia
Treatment: Praziquantel
Criteria for cure: recovery of scolex

Hymenolepis Nana (Dwarf Tapeworm)

Smallest tapeworm
Most frequently found tapeworm in developed countries
Common in orphanages, day care centers, and mental institutions
Can complete its entire life cycle in a single host (no intermediate host required)
Ingestion of infected rice or flour beetles with cysticercoid larvae can cause infection
Eggs are directly infectious for humans and can pass in stool or reinfect small intestine (autoinfection)
Eggs have 8-10 polar filaments and six-hooked larva
Treatment: Praziquantel

Description

Learn about the morphology and features of cestodes, also known as tapeworms. Understand the importance of scolex, neck, and proglottids in their structure. Discover how they attach to definitive hosts and their unique characteristics.