Introduction to Helminths Flashcards
(60 cards)
What kind of organisms are helminths?
Worms
Are most helminths parasitic?
No, they are free-living in the environment and only a minority are parasitic.
A very significant proportion of expenditure on veterinary medicine is spent on what?
Anthelminthic drugs
Parasite control programs for helminth diseases are based on what?
- Drugs
- Management measures such as keeping stocking densities down and understanding life cycles
What are the categories of parasitic helminths?
- Nematodes (roundworms)
- Platyhelminthes (flatworms)
What was the first complex organism to have its genome sequenced?
Cenorhabitis elegans
Is C. elegans a parasitic helminth?
No
What are the uses for Cenorhabditis elegans as a model helminth?
- Used in a wide variety of broad biological studies, including studies on developing new anthelminthic drugs
- Has 302 neurons and therefore used extensively in studies of neural networks
How many hosts do parasitic nematodes have?
One host (definitive)
Name 4 key facts about parasictic nematodes
1) They have separate sexes (di-ecious)
2) Females are often bigger
3) One egg = One adult
4) Organized body structure with cavities.
How are infective larvae of parasitic nematodes are spread?
Via grass and plant material, which is contaminated by eggs in host species
More animal feces = more contamination.
True or false: Infection by parasitic nematodes generally is only significant about a certain level.
True
Control of parasitic nematodes works best by reducing _________ numbers.
Host; you have to break the cycle of infection.
What are the 2 groups of flatworms?
- Trematodes (flukes)
- Cestodes (tapeworms)
What are the major differences between nematodes and platyhelminthes?
- Nematodes: organs in the coelom, protective cuticle
- Platyhelminthes: organs in parenchyma, metabolically active tegument
How many hosts do flatworms have?
At least 2 or more are needed to complete their life cycle.
Flatworms body structure is more ________ than nematodes.
Primitive
Which classification of helminths are often hermaphrodites?
Flatworms
Describe the reproduction of flatworms.
Can be asexual or sexual, so one egg produces many adults.
Taenia solium is what kind of helminth?
Flatworm
What is the scientific name for the liver fluke?
Fasciola hepatica, which is a flatworm.
They live in the bile ducts of ruminant and other mammalian hosts
Anemia is a common sign of infection.
What is the Life Cycle of Fasciola hepatica?
1) Adult liver flukes produce fertilizd eggs that leave the host via the common bile duct (CBD)iand intestinal tract feces.
2) If eggs fall into water, a ciliated miracidium develops over weeks or months depending on water temperature.
3) On hatching, they seek** lymnaeid snails** to develop 1 generation of sporocysts and 2 generations of rediae. No snail within 24 hrs = it dies.
4) It reproduces in the snail to become cercaria, tadpole-like larva and migrate above water level.
5) Cercaria mature, lose tadpole tail, become **metacercaria and climb up plants. **
6) **Metacercaria are infective to sheep and other grazing animals. **
In Life Cycle Terminology, define a helminth definitive host.
Helminth reproductive stages in the host.
In Life Cycle Terminology, define a helminth intermediate host.
Immature helminth stages occur here.