Platyhelminthes

VMP 920Infection & Immunity II

Veterinary Parasitology

Nematoda Triploblastic Bilateral Cuticle (secreted) Longitudinal Muscles

only Psuedocoelomate Dioecious Complete Digestive Tract Cylindrical body

Triploblastic Bilateral Syncytial Tegument Longitudinal & Circular

Muscle Layers Acoelomate (=>

Parenchyma) Hermaphroditic =

Monoecious (Except Blood Flukes are

Dioecious) Incomplete Digestive

Tract (Absent in Cestodes) Dorso-ventrally Flattened

Platyhelminthes

Platyhelminthes Groups

Class Turbellaria = Planarians Class Trematoda = Flukes

Subclass Aspidogastrea Subclass Digenea

Class Monogenea = Mongeneans

Class Cestoda = Tapeworms

PlanariansFree-living Flatworms

Dugesia sp., Marine Flatworms, Bipalium sp.

Aspidogastrean Trematodes

Ecto-Parasites of Molluscs, Fish, & Reptiles

Aspidogaster sp., Cotylogaster sp.

MonogeneansFlukes: Ecto-Parasites of Fish

Group of Veterinary Importance Gyrodactylus sp., Polystomum sp.,

Benedinia sp.

Digenean TrematodesFlukes: Endo-Parasites of Vertebrates

Group of Veterinary ImportanceFasciola sp., Paragonimus sp., etc.

CestodesTapeworms: Endo-Parasites of Vertebrates

Group of Veterinary Importance Taenia sp., Anoplocephala sp., etc.

Digenean Trematodes

1. Flatworms 2. Complex Life Cycles

a. digenea ==> (di = two), (genea = beginnings)

b. Sexual Reproduction => Adult worms in definitive host

c. Asexual Reproduction => Larval worms in snail host

Digenean TrematodesMorphology

1. General Flatworm Characteristics 2. Suckers and/or holdfast organs3. Incomplete gut4. Reproductive organs

(testes, ovary, vitellaria)

Digenean TrematodesComplex Life Cycle

1. Definitive Hosta. Adult Worms (Sexual Reproduction)

2. Environmenta. Ovum (Distribution)b. Miracidium (Distribution)

3. Molluscan 1st Intermediate Host a. Sporocysts and/or Rediae (Asexual

Reproduction)4. Environment

a. Cercaria (Distribution)5. 2nd Intermediate Host or Environment

a. Metacercaria (Transmission)

Adult Worm & Ova

Ovum

Miracidium

Snail & Redia

Cercaria & Metacercaria

Digenean Groups

Large Animals

Liver Flukes & Bile Duct Flukes

Fasciola (ruminants)Fascioloides (ruminants)Dicrocoelium (ruminants)

Intestinal FlukesLecithodendrid Fluke

(bat/horse)

Small AnimalsBile & Pancreatic Duct

FlukesPlatynosomum (cats)Eurytrema (cats)

Lung FlukesParagonimus (dogs, cats)

Intestinal FlukesNanophyetus (dogs, cats)

Blood FlukesHeterobilharzia (dogs)

In general, flukes are grouped by location in definitive host.