Endoparasites

• 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 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"
• Dipylidium caninum

  • Found in small intestine of dogs, cats, and occasionally in man
  • 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

  5. Prepatent Period: 14 to 21 days
• Taenia pisiformis

  Intermediate host: rabbits and hares
• Taenia pisiformis

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

  1. Intermediate host is the rabbit and hare

  2. Eggs develop in the abdominal cavity

  3. Rabbit eats grass contaminated with feces containing Taenia eggs

  4. Infection is by eating viscera or whole rabbit
• Echinococcus granulosus

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

  • Size: Very small, 2-5cm
  • Man, domestic animals and numerous wild animals act as intermediate hosts
  • 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
• Clinical signs of tapeworms

  • In general, not very harmful
  • May see vague signs consisting of intestinal upset
  • Heavy infections will show signs of: 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, too
• Control and treatment of tapeworms

  1. Keeping environment clean and free of feces

  2. Removing intermediate hosts such as fleas

  3. Not letting pets eat undercooked meat

  4. Periodic checks by a veterinarian

  5. 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
• Toxocara canis

  Roundworms found in the small intestine of dogs
• Toxocara canis

  • Seen more frequently in puppies and kittens due to parasites life-cycle
  • Size: Males 3.5-5 cm, Females 10-15 cm
  • Shape: cylindrical, tapered at both ends
  • Color: white to cream
  • Eggs are very resistant and can be present for several years, large, oval and dark in color with a thick rough shell
• Toxocara canis life cycle

  1. Developmental period to infective-stage average about 4 weeks

  2. 5 stages of development: Egg, Larvae develops within the egg, Infective stage larva, Larvae develop further in lungs and are coughed up and swallowed, Larvae develop to mature worms in small intestine

  3. In older pups and adult migration of infective stage stops in tissues of the body

  4. In the bitch, larva migrate again during pregnancy and are passed to the fetus (Transmammary or Transplacentally)

  5. Adult stage is reached in 23-40 days in pups
• Clinical signs of Toxocara 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
• Control of Toxocara canis

  1. Clean environment: Concrete kennel is the best control, Turn soil during hot weather, Flame Thrower

  2. Puppies must be cleaned up after worming by owner or bitch can reinfect herself and the poppies

  3. Schedule fecal analyses and good worming protocols
• Toxocara canis is zoonotic, human health hazard is Visceral Larval Migrans where young children may ingest ova from soil and larva migrate through organs, can cause CNS problems, pneumonia, muscle ache, vision problems
• Toxocara cati

  Roundworms found in cats
• Toxocara cati

  • Prenatal infection (transplacental) does not occur
  • Neonatal infection via transmammary is an important route of infection with kittens
  • Probability of tracheal migration remains high throughout cat's life
  • Human health hazard is significant
• Toxascaris leonina

  Roundworms found in the intestines of dogs and cats
• Toxascaris leonina

  • Size, Shape, and color is the same as Toxocara spp.
  • Eggs are lighter in color, more egg shaped and have a thick smooth shell
• Toxascaris leonina life cycle

  1. Developmental period to infective stage can be as short as 3 days but normally takes one week

  2. Development is 5 stages but the 3rd stage infective larvae will hatch from the egg and penetrate the intestinal mucosa to develop for about 2.5 months and then return to the lumen of the intestine as adult worms

  3. Adult worms may be present by 6 weeks and eggs in feces by 8 weeks
• Clinical signs of Toxascaris leonina

  • Same as less severe infections of Toxoxara spp.
  • Rarely are there deaths
  • There is some discrepancy as to whether Toxascaris spp. are related to parturition
• Control of Toxocara and Toxascaris spp.

  1. Clean environment

  2. Mice, other small rodents and chickens can harbor the infective larval stage of Toxocara and Toxascaris spp.

  3. Prevention and Treatment: Pyrantel (Nemex or Strongid), Milbemycin oxime (interceptor), Fenbendazole (Panacur), Febantel (Rintal)
• Strongyloides stercoralis


  Common name "Thread worm", may be free living or parasitic
• Strongyloides stercoralis

  • Patent in 5-7 days
  • Skin> blood> lungs> intestine
  • Severe cases may cause diarrhea
  • Most cases asymptomatic
• Hookworms

  Ancylostoma Caninum is zoonotic
• Ancylostoma Caninum

  • Found in the stomach and small intestine of dogs
  • Size: males 6-12mm, females 6-20mm
  • Shape: Short , thick parasites
  • Color: Gray to reddish brown
  • Commonly found in areas of warm, humid climates
• Ancylostoma Caninum life cycle

  1. Developmental period is 2-8 days

  2. Undeveloped eggs pass into the environment

  3. Eggs hatch and release 1st stage larva

  4. Larvae then develop to second stage

  5. Larvae then develop to 3rd infective stage

  6. 3 routes of infection: Through the skin penetration, Through oral ingestion, Fetus may be infected transplacentally or transmammary
• Clinical signs of Ancylostoma Caninum


  • Dependent of the route of infection
  • Peracute disease seen in prenatal infections, Acute disease usually seen in nursing and recently weaned pups, Chronic disease can always be diagnosed through fecals
• Summary of clinical signs of Ancylostoma Caninum

  • Anemia, lethargy, emaciation, stunted growth, dry harsh hair coat, fluid feces, reddened skin lesions, ulceration of skin
  • Skin problems are usually associated from scratching due to the larval migrans
• Control of Ancylostoma Caninum

  1. Keep kennel area and bedding dry and clean

  2. Perform fecals on pups 2-4- weeks

  3. Clients should be encouraged to have veterinarian treat sick animals that may need a transfusion or with other anthelmintics
• Uncinaria


  Similar to Ancylostoma but much smaller
• Whipworms

  Trichuris vulpis