Helminths Flashcards
(27 cards)
Helminths
Helminths = Worms
Most helminths are NOT parasitic - they are free living in the environment
A minority of helminths are parasitic, a minority are relevant to vet med and pub health
Large expenditure on vet med is spent on anthelmintic drugs
What are the two categories of parasitic helminths?
Nematodes (roundworms)
Platyhelminths (flatworms)
What is a model helminth?
Cenorhabdytis elegans - NOT a parasite, was the first complex organism to have its genome sequenced
Has 302 neurons - used extensively in studies of neural networks
How many sexes do parasitic nematodes have?
They have two separate sexes (di-ecious)
Are male or female parasitic nematodes generally larger?
The females are often bigger
What does one parasitic nematode (roundworms) egg give rise to?
One egg gives rise to one adult
What is the general structure of parasitic nematodes?
Organized body structure, with cavities
Nematodes (roundworms) of Grazing Animals:
Often have only one host (definitive host)
Infective larvae are spread via grass/plant material that is contaminated by eggs in host feces
Eggs mature, releasing larvae which become infective
More hosts = more eggs = more larvae = more infection
Generally, infection only significant above a certain level
Reducing the host number does work!
Platyhelminths (flatworms) are split into which two categories”
Trematodes (flukes)
Cestodes (tapeworms)
Nematode vs Flatworm
Nematode - organs in coelum, protective cuticle
Flatworm - organs in parenchyma, metabolically active tegument
How many hosts do Platyhelminths (flatworms) require to complete their life cycle?
Two or more
What is the Platyhelminths body structure like?
They have more primitive body structures than the nematodes (roundworms), organs directly embedded in a solid parenchyma
What is the outer surface of the Platyhelminths like?
The tegument is metabolically active, unlike the nematode cuticle
Are flatworms (Platyhelminths) hemaphrodites?
Often, but not always
What type of sexual reproduction does Platyhelminths have?
There is asexual as well as sexual reproduction, one egg produces many adults
Definitive host:
Helminth (worm) reproductive stages in this host
Intermediate host:
Immature helminth stages here
Paratenic host:
Optional extra host (not required for lifecycle completion)
Direct lifecycle:
One host only required
Indirect lifecycle:
More than one host species required
Other facts of helminths (worms):
Dampen the immune responses of their host
What are some current problems with helminths?
We have a very limited # of drugs available
Drug resistance
Few new drugs in development
Who do parasitic helminths infect?
All grazing animals - control is mostly based on keeping #s below production/disease/welfare levels
Parasitic helminths are common in:
Dogs, cats, wildlife and exotic pets
