Parasitology Unit 8 Chapter 46 Cestodes, Trematodes, and Acanthocephalans Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Phylum Platyhelminthes Trematodes and cestodes Flatworms that lack a body cavity Cestodes Eucestoda True tapeworms Cotyloda Pseudotapeworms Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 2

Phylum Acanthocephala Thorny-headed worms Not commonly encountered in companion animals Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 3

Life Cycle Always indirect and involves one or two intermediate hosts Intermediate hosts Arthropods, fish, or mammals Domestic animals can be definitive hosts and/or intermediate hosts for tapeworms Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 4

Eucestodes True tapeworms are multicellular but lack a body cavity Organs embedded loosely in cellular tissue Body is long and dorsoventrally flattened and consists of three regions Head – scolex Attachment organ with 2 to 4 muscular suckers (acetabula) May have a snout (rostellum) that has hooks Neck – short and undifferentiated tissue Body – strobila Composed of segments (proglottids) Those close to the neck are immature followed by sexually mature proglottids Gravid proglottids break off and pass out of the body Each proglottid has reproductive organs Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 5

Eucestodes (cont.) Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 6

Eucestodes (cont.) Eggs Each egg contains a fully developed embryo Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 7

Eucestodes (cont.) Pseudotapeworms Similar in structure to true tapeworms except reproductive tissues are centrally located Organ of attachment A slit like pair of organs known as bothria located on the lateral aspect of the scolex Eggs are operculated and usually released from the uterus and passed in the feces Eggs contain an embryo referred to as a coracidium Released when the eggs makes contact with water Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 8

Life Cycle of Dipylidium caninum Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 9

Dipylidium caninum (cont.) Most common tapeworm found in the small intestine of dogs and cats Dogs and cats infected by ingesting fleas Prepatent period 14 to 21 days Gravid proglottids found in feces and on the pet’s hair coat and bedding Ricelike Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 10

Canine Taeniid Tapeworms Taenia pisiformis, Taenia hydatigena, and Taenia ovis are canine taeniids (tapeworms) T. pisiformis Dogs become infected by ingesting rabbits and hares T. hydatigena and T. ovis Dogs become infected by ingesting ruminants Feline tapeworms Taenia taeniaeformis or Hydatigera taeniaeformis Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 11

Canine Taeniid Tapeworms (cont.) Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 12

Life Cycle T. pisiformis Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 13

Multiceps spp. Multiceps multiceps and Multiceps serialis Are tapeworms of the small intestines canids? Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 14

Echinococcus spp. Echinococcus granulosus Dogs Echinococcus multilocularis Cats Tapeworms associated with unilocular and multilocular hydatid disease Zoonotic potential Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 15

Echinococcus spp. (cont.) Tiny tapeworms Three proglottids One immature, one mature, and one gravid Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 16

Eucestodes of Large Animals Horses and ruminants can have tapeworms Found on fecal flotations Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 17

Tapeworms in Humans Bladderworms (Cysticercus tenuicollis) or larval stages can infect humans T. saginata – beef tapeworm in humans Beef measles T. solium – pork tapeworm in humans Pork measles Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 18

Eucestodes of Small Mammals Vampirolepis nana and Hymenolepis diminuta Parasites of the small intestine of rodents and occasionally dogs and cats Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 19

Pseudotapeworms Spirometra sp. Zipper tapeworms Often found in the small intestine of dogs and cats in Florida and along the Gulf Coast Attaches to the jejunum Mature proglottids separate along the long axis for a short distance Unzip Diphyllobothrium sp. Broad fish tapeworms 2 to 12 m long Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 20

Pseudotapeworms (cont.) Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 21

Trematodes Unsegmented and leaflike Organs embedded in loose tissue Two muscular attachment organs One anterior sucker at the mouth One ventral sucker located on the ventral surface of the worm near the middle of the body Digenetic trematodes Only trematode parasite of domestic animals Outer wall or cuticle Simple digestive tract Both male and female reproductive organs in same individual Nervous and excretory system are present Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 22

Life Cycle of Digenetic Trematodes Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 23

Trematodes of Dogs and Cats Platynosomum fastosum Lizard poisoning fluke of cats Nanophyetus salmincola Salmon poisoning fluke of dogs NW region of North America Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 24

Trematodes of Dogs and Cats (cont.) Alaria sp. Intestinal fluke of dogs and cats Northern half of North America Heterobilharzia americanum Canine schistosome – blood fluke Enzootic in the Mississippi Delta and coastal swampland in Louisiana Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 25

Trematodes of Dogs and Cats (cont.) Paragonimus kellicotti Lung fluke of dogs Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 26

Trematodes of Ruminants Fasciola hepatica Liver fluke of cattle, sheep, and other ruminants Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 27

Trematodes Dicrocoelium dendriticum Lancet fluke of sheep, goats, and oxen Reside in the fine branches of the bile ducts Rumen flukes Paramphistomum and Cotylophoron Reside in rumen and reticulum of cattle, sheep, goats, and other ruminants Schistosoma sp. Blood flukes of humans Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 28

Acanthocephalans Thorny-headed worms Uncommon parasites in veterinary medicine Do not have a true gut Absorb nutrients through their body wall Recovered at necropsy Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 29

Summary Phylum Platyhelminthes includes flatworms Subclass Eucestodes – true tapeworms Subclass Cotyloda – pseudotapeworms Tapeworms have an indirect life cycle D. caninum – most common tapeworm in dogs and cats The intermediate host of D. caninum is the flea Trematodes are flatworms that require 1 or 2 intermediate hosts and one is usually a mollusk Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved. 30