Dr. Schmidt - Parasite Lecture

Parasites

By Calico E. Schmidt, DVM

External and Internal Parasites of Animals

Science - “Learning a new language”

Veterinary parasite words to consider

• Symbiosis: is any relationship where 2 or more species live closely together 

  • Three types of Symbiosis:

    • Mutualism (+/+)

    • Commensalism (+/0)

    • Parasitism (+/-)

• External Parasites: Live or bite on the outside of body 

  • Common: Tick, Flea, Louse, Mites, Mosquitoes, and Flies 

• Internal Parasites: Live inside the body 

  • Nematodes:

    • Roundworms 

    • Pinworms

    • Hookworms 

    • Strongyles

    • Lungworms 

    • And others 

  • Flatworms 

    • Trematodes 

      • Flukes 

    • Cestodes

      • Tapeworms 

  • Protozoa (one celled organisms)

    • Giardia 

    • Toxoplasma

  • Heartworms 

    • Adult worms that live in large blood vessels around heart and lungs 

• Examples of Internal Parasites 

  • Roundworms 

    • Adult worms - intestines 

  • Hookworms 

    • Adult worms - intestines 

  • Tapeworms 

    • Adult worms - intestines 

• Why do we care about parasites?

  • Causes illness and disease for our veterinary patients

• What do veterinarians need to know?

1. Where do they live in the body?

2. What problems do they cause?

3. Which types of animal can become infected?

4. How do they get infected?

5. How do we find them? (Diagnosis)

6. How do we get rid of them? (Treatment)

7. Can people get them? (“zoonotic”)

• Ex. Heartworms (Dirofilaria immitis)

  • Where do they live? 

    • Large blood vessels around heart 

    • Large blood vessels around lungs 

  • What problems do they cause?

    • Coughing 

    • Problems with normal blood circulation 

    • Death 

• The Heartworm Story - 6-7 months

  • Mosquito bites dog with heartworm, takes blood meal 

    • In blood meal is a little baby heartworm (microfilaria) 

    • Heartworms will live in the mosquito equivalent of kidneys, and the microfilaria grow 

      • Turn into 3rd stage larvae eventually (L3’s) 

        • Then they migrate to the mouth parts in the mosquito

          • Mosquito will bite dog, and the larvae will spill out of mouth of mosquito, and larvae will migrate into microscopic wound from the mosquito “sucker”

            • The heartworm larvae will burrow under the skin and will wiggle around and grow and eventually want to migrate into blood vessels (for some reason) 

              • Will make their way to the heart, and they will live there as adults, will mate, and grow more, cycle repeats

• More about Heartworms 

  • Hosts: Dogs (also cats, ferrets, others) 

  • How do animals get heartworm?

    • Bite of an infected mosquito 

    • For diagnosing Heartworm: blood test

  • How do we get rid of them?

    • Young Heartworms (larvae)

      • Heartworm preventative medication 

    • Adult Heartworm: medication containing arsenic

• Example Parasites: Roundworms (Ascarids)

  • Where do they live?

    • Intestines 

  • What problems do they cause?

    • Interfere with normal digestion 

      • Weight loss 

      • Rounded “pot belly”

        • In puppies with lots of roundworms 

    • Diarrhea 

    • Vomiting

• More about Roundworms 

  • Hosts: Dogs, cats, pigs, horses 

  • How do animals get roundworms 

    • Accidentally eating eggs of worms (via feces or otherwise) or predation (eating animal with roundworms)

    • Dogs- from “dam”/mom before born 

  • How do we find them?

    • Eggs in microscope exam of fecal sample

    • “Fecal float” test

  • How do we get rid of them?

    • Deworming medication

  • Can people get them?

    • Yes

Lab Activities 

• Perform fecal float test-to look for parasite eggs 

  • Video and instructions 

• Microscope examination of samples 

  • Fecal floats and Demonstration Slides 

• Observe parasite examples and cases