General concepts of worms of medical importance Flashcards
Worms that are unsegmented and possess a mouth, esophagus, and anus. The sexes are separate in general
Nematodes (Roundworms)
Reproduction of nematodes
Oviparous, larviparous
How nematodes usually infect
- Ingestion of eggs
- Penetration of larvae through surfaces
- Arthropod vector
- Ingestion of encysted larvae
Worms that have false segmentation and absent gut. Possess scolex, neck, and proglottids. Hermaphroditic
Cestodes (Tapeworms)
Reproduction of cestodes
Oviparous, sometimes multiplication within larval forms
How cestodes usually infect
Generally by ingestion of encysted larvae
Worms that are unsegmented and typically have a blind sac for gut. Leaf-like or cylindrical shaped and generally hermaphroditic
Trematodes (Flukes)
Reproduction of trematodes
Oviparous, sometimes multiplication within larval forms
How trematodes usually infect
Mainly by larval stages entering the intestinal tract, sometimes through the skin
Typical life cycle of nematodes
- Eggs
- Four larval stages (L1 - L4) separated by molting
- Adult
The usual infective stage of many nematodes
Rhabditiform (L3) larvae
Typical life cycle of cestodes
- Eggs from the gravid proglottids (Hexacanth embryo)
- Intermediate host infection
- Metacestode
- Definitive host infection
- Adult
Typical life cycle of trematodes
- Eggs
- Miracardium (Free-swimming)
- Sporocyst (Asexual reproduction in snails)
- Cercaria
- Metacercaria
- Adult
The usual infective stage of many trematodes except for Schistosoma sp.
Metacercaria
