1. Eukaryotic Pathogens: Helminthes
What types of eukaryotic organisms are pathogenic, and how do they differ from bacteria?
Helminthes (The Worms)
• Specializations of Animal Parasites
• Flatworms (Platyhelminthes)
• Flukes and tapeworms
• Roundworms (Aschelminthes/Nemtodes)
• Egg infective: pinworm, ascaris
• Larvae infective: hookworm, trichinella
Eukaryotic pathogens are mostly parasitic and are difficult to target selectively with drugs since their cells are
so similar to human cells.
4. Pathogenic Helminths (Worms)
• Pathogenic helminthes belong to:
• Flatworms (Phylum Platyhelminthes)
• Roundworms (Phylum Nematoda/Aschelminthes)
•As parasites, they have:
•Little or no digestive system
•A very simple nervous system
•Little or no means of locomotion
•A complex reproductive system, sometimes with multiple
hosts (definitive and intermediate)
6. Flatworm Characteristics
General Characteristics
• Flattened shape
• Incomplete gut
• Same individual makes both
sperm and eggs (monoecious)
Divided into two groups:
Flukes (Trematoda)
• Suckers on ventral surface
Tapeworms (Cestodes)
• Barbed scolex “head”
• Proglottid segments
8. Humans as Definitive Host: Lung Fluke (A Trematode)
Intermediate hosts: snail,
then crayfish or crab
Definitive host: human
Lung fluke: Paragonimus westermanii
Figure 12.26
9. Shistosomiasis or Blood Fluke
(Shistosoma)
Blood fluke
Flatworm (Platyhelminthes)
Intermediate host: snail
Definitive host: human
10. Beef/Pork Tapeworms (Cestode in Platyhelminthes)
Intermediate host: pig or cow
Definitive host: human
Figure 12.27
20. Making a Table to Study and Associate Characteristics
Species
Helminth
Group and
Subgroup
Disease
Name
Disease
description
Reproduction
Hosts
Sketch
21. Arthropods as Vectors
• Kingdom: Animalia
• Phylum: Arthropoda
(exoskeleton, jointed legs)
• Class: Insecta (6 legs)
• Lice, fleas,
mosquitoes
• Class: Arachnida (8 legs)
• Mites and ticks
• May transmit
diseases (vectors)
Figure 12.31, 32
