Internal Parasites

Internal parasites are especially a problem with puppies and kittens although adults may also be infected. Internal parasites may make your pet sick with diarrhea (ranging from loose stool to bloody diarrhea), poor hair coat, anemia, failure to thrive, pneumonia and, in extreme cases, death. Additionally, some of the internal parasites carried by your pet can be transmitted to humans. For many internal parasites, diagnosis can only be made through microscopic analysis of a stool sample. For these reasons, it is important to bring a stool sample when your pet has his examinations.

Common internal parasites of dogs and cats are:

  • Roundworms or ascarids are found in both dogs and cats. Roundworms are acquired by ingesting contaminated soil or feces or by eating infected rodents, birds, and insects. Many puppies and kittens are born with roundworms as they are infected while still in the uterus. Puppies and kittens may also be infected while nursing. Roundworms are especially a concern as they can be transmitted to people and cause a serious illness known as visceral larval migrans (migration of larvae through the internal organs) and blindness.
  • Hookworms are a serious parasite of cats and dogs. Pets acquire them by ingesting infective larvae or by the actual penetration of larvae through their skin or feet. They can also be transmitted from the mother during pregnancy or through nursing. Hookworms attach to the intestinal lining and feed off the blood of their host. They can cause a fatal anemia (low red blood cell count). Hookworms can also be transmitted to humans and cause a skin disorder known as cutaneous larval migrans (creeping eruption), or migration of larvae in the skin.
  • Tapeworms live in the intestines of both dogs and cats. The most common routes of infection are by eating small rodents or rabbits or by ingesting fleas carrying the tapeworm in its larval stage. Tapeworms are passed in the stool in segments, and may appear as ¼ to ½ inch white ribbon or small yellow grains of rice. If you see your pet constantly licking his anal area, it’s a good idea to inspect the area and his stool for bits of tapeworm.
  • Whipworms are small, thin worms that live in the large intestine and cecum of dogs and can cause bloody diarrhea. They are extremely rare in North American cats. Dogs acquire them by ingesting eggs from contaminated soil/feces.
  • Coccidia are single celled organisms that infect the intestines of dogs and cats. Your pet becomes infected by ingesting contaminated dirt/feces or intermediate hosts such as mice. This parasite is especially common in young and stressed animals. 
  • Giardia is a protozoal (one-celled) organism that parasitizes the small intestine of dogs and cats. Humans can contract giardia, though they normally contract if from other humans, not animals. Pets/people are infected by ingesting the cyst form of this organism from contaminated food and water.