Lecture 5 Parasite diversity 4 Trematodes

Question 1

Describe Phylum Platyhelminthes.

Answer 1

• macroparasites
  • 3 parasite classes
  • dorso-ventrally
  flattened bodies

Question 2

Describe class trematoda in Phylum Platyhelminthes.

Answer 2

-flukes
-endoparasites
–>every infect class of vertebrates
• members: 3 subclasses

Question 3

What is a subclass of of Class Trematoda in Phylum Platyhelminthes.

Answer 3

Digenea

Question 4

Describe subclass Digenea in class trematoda in Phylum Platyhelminthes (kind of life cycle, kind of reproduction, type of hosts, intermediate hosts?)

Answer 4

-complex life cycles
–>alternating sexual & asexual stages
–>intermediate & final/definitive hosts
final host
• variations on life cycle
—–>2 or more 2nd
intermediate hosts
—–>no 2nd intermediate

Question 5

Describe life cycle of subclass Digenea in class trematoda in Phylum Platyhelminthes. (include hosts, reproductive stages, transmission, final/intermediate hosts)

Answer 5

Definitive host: predatory fish/human have flukes that (sexual reproduce) -> egg

• > (hatch)-> miracidium -> (infection in first intermediate host; snail) -> miracidium (transformation)-> sporocyst-> (asexual reproduction)-> rediae-> (pooped)
• > free-swimming cercariae-> (attach to second intermediate host fish & encyst) -> Metacercariae -> eaten by final host human/predatory fish flukes (trophic transmission)

Question 6

Describe morphology of subclass Digenea in class trematoda in Phylum Platyhelminthes.

Answer 6

much variation -> key to spp id

suckers: oral and ventral (adhesion) in adults all ventral

reproductive organs: ovary, testes, vitellarium (monicious)

Question 7

Describe Haematoloechus spp of Trematode.

Answer 7

-frog lung fluke
• larval insect 2nd
intermediate host
• dozens in lungs!

Question 8

Describe Alaria spp. of Trematode

Answer 8

- mostly canid(canine) final
hosts
• sometimes paratenic (beside)
hosts involved
• no \_\_metacercariae_ but has mesocercaria
-->unusual stage

Question 9

Describe Ribeiroia ondatrae of Trematode.

Answer 9

• associated with most amphibian malformations

—>greatly increased reports

Question 10

Ribeiroia ondatrae and ambhibian malformation - Why might this reflect a parasite strategy?

Answer 10

cercarian burow in hind limbs to get itself transmitted so now the frog is slower. Malformed legs fared worst.

Question 11

Describe Euhaplorchis californiensis of Trematode.

Answer 11

marine trematode
-cysts form in fish brain
-swim on side in top of water
site choice for parasite: brain increase/decrease? serotonin activity acted weird

Question 12

Describe Dicrocoelium dendriticum of Trematode.

Answer 12

-many alterations - ant behaviour weird

Question 13

Describe Fasciola spp. of Trematode.

Answer 13

• very large adults in liver
• no 2nd intermediate host
—>common zoonotic (transmits/infect from animals to humans)

Question 14

Describe Halipegus eccentricus of Trematode.

Answer 14

potentially 4 hosts in life cycle!

Question 15

Why care about the trematodes?

Answer 15

• importance to amphibian

* aquatic fisheries importance • importance for human health (shistosomiasis)

Question 16

trematode Schistosoma spp.

Answer 16

-3 species infecting humans
• no 2nd intermediate host
—>no metacercariae
• paired adult worms reproduction

Question 17

what are the 3 main species infecting humans

Answer 17

3 main species infecting humans:

• > S. mansoni – large intestine portal veins
• -> S. haematobium – venous plexus veins
• ->S. japonicum – small intestine veins
  id. via shape/size

Question 18

What and name event when the pathology of

S. haematobium was discovered ?

Answer 18

Pathology:
• S. haematobium & S. mansoni
—>Napoleon’s army in Egypt

Question 19

what is major source of pathology

Answer 19

bladder and splien
pulmonary/portal veins - blood shunting 
somach is extended
-normal adult worm 
development _decreased_ host immune system cues
But....
As long as 30 years!
• _decrease_ of host immune system
-no antibiotics
---mechanism unknown

Question 20

So how can we control

schistosomiasis?

Answer 20

Challenges to consider:
• ease of transmission
–final & intermediate hosts persistence
– ________________
basic strategies: selective recombinant production -> vaccinate animals