Platyhelminthes VMP 920 Infection & 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

Planarians Free-living Flatworms Dugesia sp., Marine Flatworms, Bipalium sp.

Aspidogastrean Trematodes Ecto-Parasites of Molluscs, Fish, & Reptiles Aspidogaster sp., Cotylogaster sp.

Monogeneans Flukes: Ecto-Parasites of Fish Group of Veterinary Importance Gyrodactylus sp., Polystomum sp., Benedinia sp.

Digenean Trematodes Flukes: Endo-Parasites of Vertebrates Group of Veterinary Importance Fasciola sp., Paragonimus sp., etc.

Cestodes Tapeworms: 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 Trematodes Morphology 1. General Flatworm Characteristics 2. Suckers and/or holdfast organs 3. Incomplete gut 4. Reproductive organs (testes, ovary, vitellaria)

Digenean Trematodes Complex Life Cycle 1. Definitive Host a. Adult Worms (Sexual Reproduction) 2. Environment a. 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 Flukes Lecithodendrid Fluke (bat/horse) Small Animals Bile & Pancreatic Duct Flukes Platynosomum (cats) Eurytrema (cats) Lung Flukes Paragonimus (dogs, cats) Intestinal Flukes Nanophyetus (dogs, cats) Blood Flukes Heterobilharzia (dogs) In general, flukes are grouped by location in definitive host.