When dogs eat poop, parasites can come along for the ride

My 9-year-old dog, Harper, recently underwent a battery of blood tests and a fecal exam for an upcoming surgery. Her results were normal for the most part, but the fecal exam turned up an unexpected parasite: Eimeria spp.

Dogs and cats are not normally hosts of this genus of coccidian parasites. It’s more commonly found in the intestinal tracts of birds such as geese and ducks, who may suffer diarrhea and even death if infected.

How did Harper end up hosting an avian parasite? Well, we live near a lake, and she is extremely fond of snacking on goose droppings when she can get away with it. Apparently, they are the canine version of pate de foie gras. Fortunately, this type of Eimeria isn’t infective to dogs or cats. For that reason, it’s known as a pseudoparasite, or false parasite. It passes through the intestines and doesn’t require treatment. Other animals that carry Eimeria that isn’t infective to pets include rabbits and deer.

This doesn’t mean that eating poop is safe for your dog. This habit, known as coprophagy, derives from the Greek words “copros,” meaning feces, and “phagein,” meaning “to eat.” Dogs like Harper who chow down on goose poop can be at risk for salmonella or Campylobacter bacteria, both of which can cause diarrhea in dogs. Rarely, they may suffer severe diarrhea, but most dogs with healthy immune systems aren’t affected.

If you know your dog has a goose-poop habit and he suffers a case of the runs, that may be the cause. Check with your veterinarian if the diarrhea continues for 48 hours or more. Infected bird droppings are also the source of a fungal infection called histoplasmosis. It’s common in the Midwest, in the Ohio and Mississippi river valleys, in the area surrounding the Great Lakes, and in parts of Canada. Young, large-breed dogs seem most likely to develop the disease, especially if they live in those areas and have prolonged exposure to Histoplasma-having organisms.

One study found that other dogs at greater risk of histoplasmosis are pointers, Weimaraners and Brittanys. That’s likely because these hunting breeds spend more time outdoors. Signs of histoplasmosis are vague: mild fever, depression, weight loss and loss of appetite. Some dogs develop labored breathing or a chronic cough. X-rays, urinalysis and blood tests can rule out other problems with the same signs. A definitive diagnosis requires microscopic examination of cells from lymph nodes or tissue samples. The disease is treated with antifungal agents. Treatment can take up to six months to be successful, and not all dogs survive.

Birds aren’t the only culprits when it comes to spreading disease. Dogs can acquire coccidiosis from eating the waste of infected dogs. Coccidian protozoa infective to dogs are Cystoisospora canis, Cystoisospora ohioensis, Cystoisospora neorivolta and Cystyisospora burrowski.

Cats can be infected by Cystoisospora felis and Cystoisospora rivolta. Pets infected with one of these parasites may not show signs. Adult animals may shed the oocysts in their feces but otherwise be symptom-free. Puppies and kittens are at highest risk, suffering diarrhea, weight loss and dehydration. Stress can make the disease worse. In severe cases, young animals may die.

The good news is that cats and dogs can’t transmit coccidiosis to each other. Even better, they can’t transfer it to humans.

Lastly, many dogs love snacking on cat poop. That can be the source of roundworms, tapeworms, toxoplasmosis and giardia. One way to prevent your dog from taking up this nasty habit is to scoop the litter box once or twice daily to remove temptation. If possible, place it in an area that’s accessible to the cat but not the dog.

Pet Connection is produced by a team of pet-care experts headed by veterinarian Dr. Marty Becker and Kim Campbell Thornton, author of many pet-care books. The two are affiliated with