A Guide to Canine Parasites

Dogs are not just pets, they are valuable members of our families. Just like all family members, we care deeply about their happiness and health. This is why it is crucial to keep them free of parasites. It is common for dogs to be infected by some sort of internal or external parasite at some point during their lives. If left unattended, the effect of these parasites on your canine companion can range from mildly irritating to life-threatening. With that said, let us take a look at the most common parasites that could effect your four-legged friend.


Coccidia are tiny single-celled parasites that infect your dog’s intestinal wall. Although they are more commonly found within puppies due to their underdeveloped immune system, they can also infect adult dogs, cats, and kittens. They cause a condition called Coccidiosis. One of the most prominent symptoms that dogs exhibit is watery, mucus-based diarrhea. If the condition is left untreated, bloody diarrhea and a diminishing ability to control bowel movement will develop. Pets are usually infected after digesting soil that is contaminated with coccidia-infested dog excrement or other substances.

Ear Mites

Ear mites are tiny mites that dwell on the surface of ear canal skin, barely detectable to the naked eye. An infestation of these mites will cause irritation and inflammation or more serious skin and ear infections if left untreated. An infestation usually produces a characteristic black or brown discharge, and in some cases, a dog’s ear canal may become obstructed by a coffee ground-like substance. Ear mites are most commonly passed from pet to pet, outside and indoors. Ear Mites are highly contagious and are most common within outdoor cats, who in turn infect their canine companions.


Fleas are a wingless external parasite that feed off blood. This parasite might trigger skin allergies. They can also transmit other parasites to your pet, such as tapeworms. The pet will often repeatedly scratch and chew themselves if fleas are present. The constant itching might cause red skin irritation and patches of fur loss. Fleas are visible to the human eye, so you might see tiny brown fleas darting through your dog’s coat. Fleas leave behind “flea dirt”. This dark, soil-like residue is actually flea feces, which will turn a red or rusty color when dampened with water.


Giardia are a single-celled parasite that lives within your dog’s intestine. It is more common in puppies than it is in older dogs. Water and substances that have been contaminated with feces are the main cause of Giardia in dogs. This tiny parasite can cause a Giardia infection, which is marked by diarrhea. Prolonged and untreated cases of this infection may cause weight loss, vomiting, poor health, and even death.


Heartworms are parasitic worms that live in the heart and pulmonary arteries of an infected dog. They are only transmitted from mosquitoes that carry infective heartworm larvae. Symptoms of a heartworm infestation may be very subtle or not show at all in the earlier stages of the disease. The longer it goes untreated, the more pronounced the symptoms become. A once active animal might tire easily, cough, and show shortness of breath.


Hookworms are parasitic worms that live within the digestive system of your dog. They hook themselves onto the lining of the intestines and feed off the animal’s blood. The parasite lays eggs that are transferred into the environment through your dog’s feces. Young hookworms, called larvae, live in the soil and can infect other animals simply by contact and penetration of the skin. Dogs can also contract hookworms when ingesting dirt that contains larvae. Hookworms cause internal blood loss, diarrhea, and notable weight loss.


Roundworms are the most common parasitic worm. They live and feed within your dog’s digestive system. There is a variety of ways roundworms can be contracted, making it difficult to contain spreading and infection. A pregnant dog may transmit roundworms to her unborn puppies, and a nursing dog can infect puppies through milk. Dogs can also get roundworms if they ingest feces containing eggs or other contaminated wild animals. Dogs may not show any signs or symptoms of an infection, although major infestations trigger diarrhea, weight loss, vomiting, a dull coat, and a potbellied appearance.


Tapeworms are long, flat parasitic worms that latch themselves onto your dog’s intestines, generally the small intestine, using hook-like suckers. The medical term for a tapeworm infestation is called Cestodiasis. Dogs commonly get infected by ingesting a tapeworm-infected flea. As a tapeworm grows, segments of its body will break off and pass through your dog’s intestines. These fragments might manifest as dried white or cream-colored “rice grains” embedded within your dog’s feces. Due to irritation caused by this condition, dogs will scoot while in a seated position and lick their rears frequently to relieve discomfort.

• Tapeworm Infection in Dogs

• Intestinal Parasites – Cyclophyllidean Tapeworms


Whipworms are a common intestinal parasite in dogs. Whipworms reside in the cecum, the area where the large and small intestine meet. Dogs contract whipworms through consumption of soil and feces contaminated with whipworm eggs. Dogs infected with just a few whipworms may not exhibit any symptoms, but severe cases can cause bloody diarrhea, serious disease, and death.

• Whipworm Overview

• Fast Facts – Whipworms


A tick is a common parasitic arthropod that latches itself onto animals’ skin and feeds off of their blood. Ticks are attracted to movement and warmth, which compels them to seek out mammals. Tall grass or plants in wooded areas are prime hunting grounds for ticks and likely places where dogs might pick them up. This is one reason many pet owners choose to contain their animals through the use of dog fences. On dogs, ticks usually like to latch themselves onto skin in crevices or areas with little to no hair – frequently around the ears, in between the toes, inside the inner legs, and within skin folds. It is vital to be remember that ticks can spread serious diseases such as Lyme disease and Rocky Mountain spotted fever.

• Tick Encounter Resource Guide

• NPIC – Ticks


Demodex are tiny parasitic mites that cause a skin disease known as mange or canine demodicosis. While certain kinds of mites are common residents of your dog’s hair and skin follicles, some are far more harmful. If the mite population proliferates, it can cause mild to severe skin infections. Usually, if a dog develops mange, it indicates that the immune system has been compromised by another medical condition. Demodex mites create patches of missing fur, generally originating around the muzzle and advancing towards the rear due to irritation and itching.

• DNR – Mange

• Pets and Parasites – Mange


Sarcoptic Mange, also called scabies, is caused by a highly contagious skin parasite called the Sarcoptes scabiei mite. This type of mite burrows into the skin, resulting in severe itching and irritation that causes scabbing and hair loss. These symptoms are most often seen on the ears, chest, abdomen, elbows, and hocks of infected dogs. It is a nonseasonal parasite, and it can be found in all ages and breeds of dogs.

• Sarcoptic Mange Information

• Mange in Dogs – Canine Scabies