Parasites causing diarrhea in Minneapolis dogs

Hookworm disease is zoonotic, meaning it can be spread from dogs to humans.

Dog owners should know about two common intestinal parasites, hookworm and Giardia, that are prevalent in Southwest Minneapolis. Although both are treatable, these parasites can cause significant illness in pets.


Hookworm disease is a terrible disease for both dogs and humans. It is zoonotic, meaning it can be spread from dogs to humans.

Early in the disease, dogs may have no symptoms, but during this time they can be spreading thousands of hookworm eggs daily in their stool and contaminating the environment. Later in the disease, patients will develop diarrhea and weight loss. Hookworms are voracious bloodsuckers. They attach to the intestinal lining and release an anti-coagulant to stimulate bleeding. Hookworm disease can cause anemia, and puppies that are exposed to hookworm as neonates can become so anemic that they can die.

Humans that are exposed to dog hookworm typically develop a skin rash. The migrating larvae leave red, itchy tracks under the surface of the skin.

The primary way hookworm is transmitted is through the stool. Dogs with adult hookworms in their gastrointestinal tract will pass hookworm eggs in the stool.  These eggs are not immediately infective. It takes 2–9 days for the eggs to hatch into infective larvae. Contaminated stool left in the environment can mix with the soil and turn it into a source of contamination. These larvae live for many months in the soil, even in winter. Minnesota has its own cold weather hookworm that can survive freezing temperatures.

It takes a community effort to help control the spread of hookworm. You can do your part to control this disease by following these tips:

  • Pick up your dog’s stool and throw it away as soon as it is produced.
  • Keep your dog on a monthly parasite preventative, even in the winter. The monthly heartworm preventative you give your dog likely protects against hookworm, but it would be prudent to double check with your vet.
  • Keep your dog on a leash to stop him from eating soil that may be contaminated with hookworm larvae.
  • Wear gloves when gardening and shoes when walking outside. It doesn’t take long for microscopic hookworm larvae to penetrate the skin and cause disease.
  • Wash all fresh fruits and vegetables. Hookworm can also enter people through accidental ingestion of contaminated soil.
  • Have your veterinarian screen your dog’s stool on a regular basis for parasite eggs, even if he is not showing diarrhea or illness. Early in the disease, dogs are usually asymptomatic and during that time (sometimes months), they can be spreading disease and contaminating their environment. The Companion Animal Parasite Council recommends that all adult dogs have a routine fecal exam for parasites twice a year.


Giardia are single-celled parasitic organisms that infect many types of animals around the world. Humans can become infected as well, but it is rare for canine Giardia to transmit to people.

Organisms are passed into the environment through feces and once outside the body, they turn into hardy, tiny cysts that can survive for months. Once they are ingested by a new host (for example from contaminated water, or a dog licking her feet after walking in the grass) the shell dissolves and every cyst releases two infectious organisms. Once free from the cyst, Giardia “swim” around inside the host’s intestines until they find a good spot to attach and feed. Once there, they can move around in different parts of the intestines looking for different nutrients.

It takes about five days to two weeks for the Giardia to be passed out into the stool of an infected pet and diarrhea can precede the shedding. Infection is more prevalent in places with high dog density, such as dog parks, kennels and daycare facilities. Symptoms of infection can include diarrhea (sometimes bloody), vomiting and loss of appetite.

Testing has become more reliable and efficient with the development of a newer test called an Elisa SNAP test. This test takes minutes and can be done while you are at the clinic for the appointment. Because of the inconsistent shedding habits of the organism, repeat testing is sometimes necessary to detect it.

As with prevention of all parasites, cleaning your yard of stools daily helps greatly in reducing contamination and re-infection. Freezing temperatures and direct sunlight kill the cysts, and so do diluted bleach solutions and other chemicals.