So called worms can be divided roughly into three groups:

1. Trematodes

   Flukes. Most common veterinary fluke pathogen is the Liver Fluke or Fasciola hepatica which affects cattle. Won't concern us here. Trematodes have only one body segment, unlike the cestodes which have several linked segments.

2. Cestodes

   Tapeworms

3. Nematodes

   Round worms

1. Cestode anatomy

   Each segment (proglottid) is sexually complete

2. The cestode live cycle

   1. Always alternates between "predator", such as a dog or human and "prey" such as a sheep or cattle

   2. The worm alternates between the "Cestode" in the predator and "Metacestode" in the prey

   3. Cestode, the adult, is usually non-pathogenic tapeworm in the intestine of the predator

   4. Metacestode, cyst or cysticercus is usually a pathogenic (hydatid) cyst, of various size, in body tissues of the prey.

3. Echinococcus multilocularis

   1. Dog/herbivore cycle

   2. Hydatid cysts in herbivores eg horses, man

   3. Eating the hydatid cyst completes the cycle

4. Taenia spp of carnivores

   Several tapeworms of carnivores (dog and cat) using a variety of herbivorous mammals as intermediate hosts which complete the cycle when eaten

5. Taenia saginata - human/beef tapeworm

   1. Cows eat human feces

   2. Human eats metacestode cysts in beef

   3. Human gets tape worms

   4. Cook beef!

6. Taenia solium - human/pig

   1. Dangerous to eat raw pork

   2. Adult in human can cause dangerous auto infection

   3. Human becomes infected with metacestodes

   4. Cook pork!

7. Monezia sp

   1. Example of a tapeworm of herbivores

   2. Horse or cow are "predators"

   3. Orbatid mites in soil are "prey"

   4. Herbivores eat the mites as they graze

8. Dipylidium caninum

   1. Most common dog or cat tapeworm in an urban/indoor environment

   2. Flea is intermediate host

   3. Eaten during self grooming

   4. "Rice grains"seen around anus

   5. Control fleas!

Larvae are the infectious stage!

1. Ascarids (Round worms)

   1. Life cycle

      1. Oocysts shed in feces

      2. Persist in soil

      3. Eating soil completes cycle

      4. Paratenic hosts, such as the human, get sick, but can't complete cycle

   2. Toxocara canis

      1. Ascarid of dogs

   3. Toxocara felis

      1. Ascarid of cats

   4. Pathogenesis

      1. Infection of young animals

      2. Unthrifty young

   5. Visceral or ocular larval migrans in children

      1. If a child ingests oocysts they migrate through the body and form cysts

      2. Don't let kids eat the sand in the sand box!

      3. Use pooper scoopers

2. Hookworms

   1. Strongyle type worms

   2. Ancylostoma caninum life cycle

      Hookworms are a potentially life threatening disease in puppies

      1. Fecal - oral route

      2. Transcutaneous

      3. Transmammary

   3. Peracute neonatal hemorrhage

   4. Encysted larvae and persistent shedding

   5. Cutaneous larval migrans in children

3. Whipworms

   1. Trichuris vulpis

   2. Diarrhea

   3. Multiple

4. Trichinosis

   Trichinosis is an important food borne illness. Pigs ingest the parasite and the worms encyst in the pork. If this meat is eaten by humans, and has not been cooked to the necessary temperature of 77C, humans will become infected with the worm which will migrate through the human body.

   1. Trichinella spiralis

   2. Cysts in pork

   3. Infect humans

   4. Don't eat pink pork (77C)

1. Dirofilaria immitis

2. Life Cycle

   1. Adult in right heart ventricle

   2. Releases microfilaria into blood

   3. Heart worm test looks for microfilaria

   4. Mosquitoe sucks blood

   5. Worm matures in mosquitoe to L3 stage

   6. L3 infects another dog via the mosquitoe

   7. Lodges in heart to become adult worm

3. Pathogenesis

   1. Untreated

      1. Pulmonary disease

      2. Blockage of the vena cava and liver failure

   2. Treated

      1. Worms in heart killed

      2. Anaphylactic shock

      3. Pulmonary embolism

4. Treatment

   1. Preventative kills L3

   2. Treatment kills adults and microfilaria

   3. Different drugs may be required to kill each of the three stages

   4. An older preventative, Diethyl carbamazine (filaribits) can cause a fatal reaction if given to a heartworm positive dog

   5. Ivermectin (heartguard) is the more common preventative now

1. What is the difference between a trematode, nematode and a cestode?

2. Briefly describe the life cycle of the typical cestode

3. Name two species that get hydatid cysts

4. There are many species of tapeworm of what genus in carnivores?

5. How to cows get infested with the human tapeworm?

6. If you are a human (and you are) why is Taenia solium bad for you?

7. For which tape worm does a horse play the role of "predator" in the life cycle?

8. How do you control tapeworm infection in urban dogs and cats?

9. Rice grains around the anus of a dog or cat mean what?

10. Generally the infective stage of a nematode is what stages?

11. What is the common name for ascarids?

12. In addition to the host, what completes the ascarid life cycle?

13. Ascarids commonly infect what sort of animals?

14. Ascarids carry what public health concern?

15. What are the latin names for the roundworms of dogs and cats?

16. What are the three routes of trasnsmission of hookworms?

17. What is the latin name for the dog hookworm?

18. What clinical syndrome do hookworms cause in young puppies?

19. Why, inspite of treatment, might a dog continue to shed hookworm oocysts?

20. What public health concern goes along with hookworms?

21. What is the latin name for the dog whip worm?

22. What syndrome do whip worms cause in dogs?

23. Why should you cook pork to 77C?

24. What is the latin name for the canine heartworm?

25. Describe the canine heartworm life cycle

26. What disease happens in the untreated dog infested with heartworms?

27. What may happen in the treated dog?

28. What are the three stages of the heartworm that we kill when treating heartworm disease? Which stage do we kill with preventative?

29. Why are dogs tested for heartworm before being placed on heartworm preventative?