Canine Internal Parasites

In the warmer months and longer days more people are getting outdoors and taking their dogs along with them going on hikes, going to parks and going on vacation with the family. But without having your dog on a year round preventive, the outdoors can become a gauntlet full of harmful hazards for both your dog and your family.


  • Zoonotic – transmissible to humans
  • Most common canine intestinal parasite
  • The adult roundworm lives freely in the intestine where they feed off of partially digested intestinal contents.
  • Dogs become infected by ingesting the microscopic eggs by either sniffing or licking infected feces.
  • Puppies can be become infected through the mother. Roundworm larvae can cross the placenta into unborn puppies. Roundworm larvae can also enter into the mammary glands and be transmitted through the mother’s milk.
  • Puppies will normally appear pot-bellied; will have some abdominal discomfort; depressed appetite; vomiting; diarrhea and/or poor growth. Some adult dogs may not show any signs of infection.
  • Roundworms can lay up 100,000 eggs per day. They can survive in the soil for up to 10 years.

Roundworm infection is the 6th most common reportable disease
in the US with 10,000+ cases reported to CDC.

  • People become infected by ingesting eggs usually via soil contaminant.
  • Once in the human body the larvae can migrate through various organs, with the most common organ being the eye.
  • There were over 700 cases of roundworm related blindness reported to the CDC each year.

Using a once monthly preventive year round is highly recommended to keep your dog and family safe.

  • Zoonotic – transmissible to humans
  • Second most common canine intestinal parasite
  • The adult hookworm “grazes” along the lining of the small intestine and feeds off of the tissue and blood.
  • Dogs become infected by swallowing (often by grooming/chewing the feet) the microscopic larvae or by the larvae migrating through the skin (particularly the feet).
  • While they are feeding on tissue and blood they inject an anti-coagulant. This anti-coagulant can cause major blood loss in dogs. Other signs included: presence of digested blood in the stool, poor haircoat and weight loss.
  • Hookworms can lay up to 20,000 eggs per day. They can survive for months in the soil. Hookworms do not mature in humans. The larval stage migrates through the different layers of the skin. This migration causes a disease called cutaneous larval migrans or “ground itch”.
  • People become infected by having skin contact with moist, larvae infected soil.

Using a once monthly preventive year round is highly recommended to keep your dog and family safe.

  • Some species are zoonotic
  • Most common internal parasite that can be seen by the human eye.
  • Adult tapeworms attach to the wall of the small intestine where they feed on nutrients being passed through the gut. They anchor themselves by using hook-like mouthparts.
  • Tapeworms are flattened intestinal worms (that can become several inches long) that are made up of many small segments (1/4-1/2 inches long). As the adult matures the segments start to break off and pass through the feces.
  • Tapeworm segments may be seen moving around the dog’s anus or maybe seen in freshly passed feces.
  • Unlike other intestinal parasites, dogs CAN NOT become infected by ingesting the segment. The tapeworm must pass through an intermediate host, a flea, before they can infect a dog.
  • Dogs become infected by ingesting an infected flea, usually through grooming or chewing/biting at the skin.
  • Humans can become infected by accidentally swallowing an infected flea. Adult worms do not develop in humans. Instead the larvae produce large cysts inside the body, most commonly on the liver, lungs and/or brain.
  • More Information

Flea control is critical in the management and prevention of tapeworm infection in both pets and people.
Using a once monthly flea/tick preventive year round is highly recommended to keep your dog and family safe.

  • Only infects canines.
  • They live in the cecum and colon of dogs where they cause severe irritation to the lining.
  • Whipworms are the most pathogenic (disease causing) intestinal parasites found in dogs, resulting in watery/bloody diarrhea, weight loss and general debilitation.
  • Dogs become infected when microscopic eggs are swallowed and return to the lower intestinal tract.
  • Whipworm eggs are very resistant to drying and heat, so they are capable of living in the environment for many years.
  • Whipworms are not infectious to people.

Using a once monthly preventive year round is highly recommended to keep your dog and family safe.

  • Heartworm infection or disease is a serious and potentially fatal to dogs.
  • They are a blood-borne parasite. They are found in the heart and the adjacent blood vessels most commonly the pulmonary arteries.
  • They can live for 5 years.
  • In dogs, the female can produce millions of offspring. These immature heartworms live in the small vessels of the bloodstream. The immature heartworms cannot complete their life cycle in the dog.
  • Dogs become infected by being bitten by an infected mosquito. There are as many as 30 species of mosquitoes that can transmit heartworms. Once transmitted the immature heartworm travels to the heart and completes its life cycle.
  • Having a long haired dog DOES NOT prevent them from getting bitten or infected.
  • Signs of heartworms for dog include:
    • soft/dry cough
    • shortness of breath
    • weakness
    • nervousness
    • listlessness
    • loss of stamina
    • fainting after exercising
    • congestive heart failure
    • weight loss
    • and/or anemia
  • Adult heartworms cause: clogging of the heart and major vessels which results in reduced blood flow to other organs (particularly the lungs, liver and/or kidneys) causing them to malfunction.
  • Dogs can be tested using a simple blood test.
  • Treatment for canine heartworm disease is very costly and extremely hard on the dog.

Prevention YEAR ROUND is key!

We here at the Animal Hospital of Waynesville strive to keep you, your dog and your family healthy.

By using a monthly heartworm preventive and a flea/tick preventive year round you are reducing the chances of you, your dog or your family coming into contact with potentially harmful internal parasites.