Parasitology Helminths Lecture 2 Flashcards
Phylum Platyhelminthes has three classes:
Trematoda (flukes), Eucestoda (true tapeworms), and Cotyloda (pseudotapeworms)
Nematoda are…
roundworms
Nematomorpha are…
horse-hair worms
Ancathocephala are…
“thorny-headed worms” or “spiny-headed worms”
Class Trematoda is subdivided into two subclasses:
Monogenea (monogenetic trematodes) and Digenea (digenetic trematodes)
Monogenetic trematodes…
do not occur in domestic animals! They are found in aquatic environments.
Digenetic trematodes…
have more than one intermediate hosts which is usually a snail.
The anterior feeding sucker of digenetic flukes is called…
the oral sucker
The ventral attachment sucker is the…
acetabulum “vinegar cup”
Flukes dispose of waste via
“fluke puke”; the excrete the waste out of their oral cavities.
Digenetic flukes have both…
male and female sex organs (hermaphroditic)
How many developmental stages are in a fluke? (list them in order)
Operculated egg–meracidium–sporocyst–redia–cercaria–metacercaria–adult fluke (7)
At which stage does the digenetic fluke enter its first intermediate host?
miracidium
The meracidium emerges from the…
operculum
Which two stages of life development occur entirely within the snail?
sporocyst and rediae
The three paths that the cercariae can take after escaping the snail include:
- they may penetrate or be ingested by the second intermediate hose2. they may encyst upon vegetation3. they may penetrate the definitive host directly
What is the scientific name of the “lancet fluke” of ruminants?
Dicrocoelium dendriticum (underline since its a scientific name)
Using two different intermediate hosts, describe the life cycle of the lancet fluke.
Snail (first intermediate host) consumes the fluke egg and coughs out cercariae (fluke undergoes the sporocyst stage within snail). The “slime ball” is then eating by an ant; the metacercariae emerge and affect the ant so that it latches onto a grassblade with its mandibles when environmental temperatures fall (usually night). The ant/grassblade/metcercaria is then consumed by the sheep in early morning hours, and the juvenile fluke enters the bile duct and grows into an adult.
What pathogenetic effects do Dicrocoelium dendriticum cause?
Primarily, they block the bile duct, but they also consume solid tissue within the body.
List 6 morphological traits of digenetic flukes.
- Dorsoventrally flat2. Smooth or spiny tegument3. Organs of attachment (oral for feeding and ventral for attachment)4. Digestive system5. Excretory system/nervous system6. Complex reproductive system
How are Dicrocoelium dentriticum diagnosed?
Operculated eggs on fecal floatation procedures
List four ways to control Dicrocoelium dentriticum.
- Treat infected animals2. Use poultry to control the population of land snails3. Disrupt ant nests in pastures.4. Selective grazing of animals; do not turn out sheep in the early morning hours to graze.
What is the scientific name for the “lizard poisoning fluke”?
Platynosomum fastosum
Where does the lizard poisoning fluke live in its host, and what is its host?
It occurs in the liver and bile ducts of cats in southeastern states.
What is the difference morphologically between the lizard poisoning fluke and the lancet fluke?
The lizard poisoning fluke has testes that are horizontal rather than in a tandem configuration.
What are the intermediate hosts of the Platynosomum fastosum?
1st intermediate host: land snail2nd intermediate host: lizard
Pathogenicity of the lizard poisoning fluke include:
inappetence due to hepatic disfunction. The bile ducts may be dilated and the duct epithelium desquamated.
How is the lizard poisoning fluke diagnosed?
fecal floatation
What is the genus of the land snail and the ant?
Cionella (land snail) and Formica (ant)
The miracidium leave the operculated via the…
operculum
