Endoparasitolgy

• Symbiosis

  Two organisms living together
• Types of symbiosis

  • Commensalism: one benefits, the other unharmed
  • Mutualism: both benefit
  • Parasitism: one benefits, the other is harmed
• Life cycle of a parasite

  The process of parasite maturation through various hosts and developmental stages
• Types of parasite life cycles

  • Direct: does not require a vector
  • Indirect: requires one or more vectors
• Tapeworms

  • Flatworms that lack a body cavity
  • Two subclasses: Eucestoda (True Tapeworms) and Cotyloda (Pseudotapeworms)
  • All tapeworms require an intermediate host to develop larval stage of life cycle
  • Eggs are contained in segments called proglottids
  • Contain a Scolex, the mouth part and Proglottids, the reproductive part
  • Both male and female reproductive organs occur in each proglottid
  • All tapeworm species that we will learn are found in the small intestine
• Dipylidium caninum


  Most common tapeworm, also known as "cucumber seed tapeworm", found in small intestine of dogs, cats, and occasionally in man
• Dipylidium caninum

  • Size: 10-70 cm
  • Color: White to Yellowish
  • Proglottids may be found in feces or moving outside the anus, can look like grains of rice or dried sesame seeds
• Dipylidium caninum life cycle

  1. Flea (or occasionally the dog louse) acts as intermediate host when the larvae ingests the dipylidium egg

  2. Egg will mature in the flea (or louse) to infective larval stage

  3. Infection occurs when the dog or cat eats the mature flea (or louse)

  4. Frequently ingested when grooming
• Prepatent period of Dipylidium caninum

  14 to 21 days
• Diagnostic test for Dipylidium caninum

  Identification of proglottids or fecal flotation
• Taenia pisiformis

  Intermediate host is the rabbit and hare
• Taenia pisiformis

  • Size: up to 200cm long
  • Color: white to yellow
  • Proglottids seen on anus and feces
• Taenia pisiformis life cycle

  1. Eggs develop in the abdominal cavity of rabbits and hares

  2. Rabbit eats grass contaminated with feces containing Taenia eggs

  3. Infection is by eating viscera or whole rabbit
• Diagnostic test for Taenia pisiformis

  Identification of proglottids
• Echinococcus granulosus


  Tapeworms associated with hydatid cysts, important due to zoonotic potential
• Echinococcus granulosus


  • Size: Very small, 2-5cm
  • Larvae create hydatid cyst in sheep, cattle, man etc.
  • Hydatid cysts are fluid filled cysts surrounded by connective tissue
  • Cysts contain numerous larvae (brood capsules) and can be as large as a mans head
• Diagnostic test for Echinococcus granulosus

  Fecal flotation
• Clinical signs of tapeworms

  • Abdominal discomfort
  • Intermittent diarrhea and or constipation
  • Vomiting
  • Flatulence
  • Enteritis may lead to poor absorption of food and an unthrifty animal
  • Dragging of rear end and biting or chasing tail may indicate irritation from proglottids migrating around anal area
  • Check the fullness of anal sacs
• Control and treatment of tapeworms

  • Keeping environment clean and free of feces
  • Removing intermediate hosts such as fleas
  • Not letting pets eat undercooked meat
  • Periodic checks by a veterinarian
  • Praziquantel (Droncit)
• Tapeworms are zoonotic, common source is contact with infected dog in an area where sheep are kept
• Tapeworms are reportable, must be reported to the State Vet and other authorities
• Nematodes

  Ascarids Roundworms
• Toxacara Canis

  Roundworm found in the small intestine of dogs
• Toxacara Canis


  • Found more frequently in puppies and kittens due to parasites life-cycle
  • Males 3.5-5 cm, Females 10-15 cm
  • Cylindrical, tapered at both ends
  • White to cream in color
  • Eggs are very resistant and can be present for several years
  • Eggs are large, oval and dark in color with a thick rough shell
• Toxacara Canis life cycle

  1. Egg

  2. Larvae develops within the egg

  3. Infective stage larva

  4. Egg will hatch in small intestine, infective larvae will penetrate the mucosa, migrate through the liver, pass through the heart, and go to the lungs

  5. Larvae develop further in lungs and are coughed up and swallowed

  6. Larvae develop to mature worms in small intestine
• In older puppies w toxacara and adult dogs, migration of infective stage stops in tissues of the body
• Toxacara Canis life cycle in the bitch

  Larva migrate again during pregnancy and are passed to the fetus (Transmammary or Transplacentally)
• Adult stage of Toxacara Canis is reached in 23-40 days in pups
• Clinical signs of Toxacara Canis

  • Pneumonia, coughing and dyspnea usually seen during first 2 weeks while larva are migrating
  • Irritation to the stomach and small intestines leads to vomiting and diarrhea
  • Less severe infections can lead to general unthriftiness, pot belly, poor hair coats, emaciation, anemia, diarrhea, or constipation and restlessness
• Diagnostic test for Toxacara Canis

  Fecal flotation
• Control measures for Toxacara Canis

  • Clean environment - Concrete kennel is the best control, Turn soil during hot weather, Flame Thrower
  • Puppies must be cleaned up after worming by owner or bitch can reinfect herself and the puppies
  • Schedule fecal analyses and good worming protocols
• Toxacara Canis is a zoonotic parasite - a human health hazard
• Visceral Larval Migrans


  Young children may ingest ova from soil, Larva migrate through organs, Can cause CNS problems, pneumonia, muscle ache, vision problems
• Toxacara cati

  Roundworm found in cats
• Prenatal infection (transplacental) does not occur in Toxacara cati
• Neonatal infection via transmammary is an important route of infection with kittens in Toxacara cati
• Probability of tracheal migration remains high throughout cat's life in Toxacara cati
• Human health hazard is significant with Toxacara cati
• Diagnostic test for Toxacara cati

  Fecal flotation
• Toxascaris leonina

  Roundworm found in the intestines of dogs and cats