Echinococcus granulosus (Dog Tapeworm)
Hosts:
- Intermediate: Grazing animals, pigs
- Definitive: Dogs
Disease:
- Intermediate hosts: Cystic echinococcosis (Hydatid disease)
Morphology - Adult:
- Size: 2-7mm long
- Segments: 3 proglottids
- Scolex: 4 suckers, rostellum with 2 rows of hooks
- Body:
Strobila with 3 segments
Morphology - Hydatid Cyst:
- Spherical or semi-spherical
- Size varies with age, can grow several centimeters in diameter
Structure:
Wall: Composed of two layers:
- Outer layer: Acellular laminated layer (produced by host tissue)
- Inner layer: Nucleated germinal layer (produced by parasite
- Location: Lungs, liver
Life Cycle:
- Eggs ingested by definitive host (dog) -> Adult in intestine
- Eggs released in feces -> Contaminate environment
- Eggs ingested by intermediate host -> Hatching -> Hydatid cyst develops
- Protoscolex develops in cyst -> Ingested by dog -> Adult -> Release eggs
Hymenolepsis nana (Dwarf Tapeworm)
Other Names: Taenia nana
Hosts:
- Definitive: Humans (esp. children)
- Intermediate: Arthropods (insects)
Symptoms:
- Nausea, weakness, loss of appetite, diarrhea, abdominal pain
Morphology:
- Size: Up to 40mm long, 1mm wide
- Scolex: 4 suckers, rostellum with circle hooks
- Neck: Long and slender
- Genital pores: Unilateral
Life Cycle:
- Eggs (embryonated) shed in feces
- Ingested by human (directly) or insect
- In insect: Cysticercoid develops from egg
- Oocosphere hatches in human intestine -> Cysticercoid develops
Scolex attaches to intestine -> Adult -> Release eggs in feces