8. Classifying Animal Parasites Flashcards
What is the state of human disease like in today’s world?
- Evolution of resistant strains: drugs used for faster growth of farm animals resulted in a massive overuse
- High density farms and virulent diseases in animals can go to humans
How has population size impacted disease in the modern world?
- Increased human density has led to poverty
- More urbanisation has led to national poverty and inequality: less public health spending has led to less resistance
What are the key differences between viruses/bacteria and eukaryotic protists?
- Viruses and bacteria have the ideal characteristics for effective parasites
- Simple organisms with short life cycles, leading to very rapid reproduction
- Rapid mutation and thus genetic change
- Eukaryotic protists
- Less simple organisms that have more complex but short life cycles (rapid reproduction)
- Alternation of sexual, asexual reproduction, thus high genetic variation)
What are the three most disease causing phyla of animal parasites?
Platyhelminates, nematodes and Arthropoda
Collectively known as protosoems
What is the common name for platyhelminathes?
Flatworms
What is the simple body structure of flatworms?
3 cell layers
- Ectoderm
- Mesoderm
- Endoderm
No coelom (acoelomate)
What are the two classes of flatworms?
Trematoda - flukes
Cestoidea - Tapeworms
What are acoelomates?
Acoelomates do not have enclosed body cavities
What is the structure of the fluke flatworm?
- The flatworm gut has a single exterior opening. The pharyngeal opening serves as both the mouth and the anus
- They have suckers, a branching gut, and complex reproductive organs
- Most are hermaphrodites
What is the typical life cycle of a trematode?
- Eggs are shed 8-12 weeks after infection
- Miracidium 10-12 days
- Mud snail
- Cercaria 5-7 weeks
- Metacercariae on grass
What is the structure of the tape worm?
- Scolex, or head with suckers and hooks
- Proglottids each with male and female reproductive organs
(Hermaphrodite) - No gut, food absorbed through body wall
What is the typical life cycle of a cestode?
- Eggs or gravid proglottids in faeces and passed into environment
- cattle (T. Saginata) and pigs (T. Solium) become infected by ingesting vegetation contaminated by eggs or gravid proglottids
- Oncospheres hatch, penetrate intestinal wall, and circulate to musculature
- Oncospheres develop into cysticerci - Humans infected by ingesting raw or undercooked infected meat
- Scolex attaches to intestine
- Adults grow in small intestine
What is the structure of the nematoda (round worms)?
- Moult their outer cuticle (ecdysozoan)
- Slender, round body, tapers at both ends
- 3 body layers
What is the cavity like in nematoda?
- Pseudocoelem, space between muscle and gut
- No membrane around the cavity
- Pseudocoelomates have a cavity lines with mesoderm on the outer side, but no mesoderm surrounds the internal organs
What are the types of roundworms?
Hookworms, pinworms, hairworms
