From his skin to his intestines to his heart, your dog can be host to a number of different parasites and pests.

Pest vs. Parasite What is the difference between the two? While the two terms are often used interchangeably, a parasite is certainly a pest, but not all pests are parasites. Fleas, ticks and mites are considered pests while common dog parasites include roundworms, tapeworms and heartworms.

Fleas and Ticks

The most common skin parasites, fleas and ticks, are bothersome to both dog and owner. Treatments include shampoos, dips, repellant sprays and collars. Adding brewer’s yeast and/or garlic to your dog’s diet may help to control fleas.

Fleas can cause itching, irritation and an allergy called flea allergy dermatitis (FAD) in sensitive dogs. Fleas can also transmit certain diseases and conditions. In puppies, an infestation of fleas can lead to anemia. Fleas can harbor an early stage of tapeworm known as called cystercoid. When your dog ingests fleas with cystercoids, tapeworms can develop in his small intestine.

Another common dog pest is the tick. The brown dog tick can usually be found between a dog’s toes and on his ears. In wooded areas, the deer tick is of greater concern because it transmits a spirochete called Borellia burgdorferi that causes Lyme disease.

The Mighty Mites

Some mites are microscopic and affect either the skin or the ears of a dog. If a dog’s skin is infected with mites, a skin condition called mange arises. A medicated shampoo and dip can help eliminate skin mites.

While more common in cats, Otodectes, or the ear mite, does infect dogs. It’s contagious to other animals and can cause severe inflammation of the ear canal. Head shaking and a coffee ground-like discharge in the ears are the most common symptoms. Eardrops are typically prescribed to treat an ear mite infestation. If the infestation is severe, your veterinarian may flush the ears to remove debris and increase the effectiveness of the medication.

Intestinal Parasites and Worms

The intestinal worms that affect dogs include tapeworms, roundworms, hookworms and whipworms. While some worms may appear in dog feces, some of these parasites, like hookworms and whipworms, aren’t so easily detected.

Fleas are the source of transmission for tapeworms. Routes of transmission for roundworms and hookworms include ingestion of an intermediate host (such as a rodent), transmission in the uterus or transmission through the milk in nursing bitches. Hookworms can burrow through the skin. Whipworms are transmitted through contaminated food or water.

Non-worm intestinal parasites (protozoans) affecting dogs include coccidia, giardia and ameba. Infection by protozoan parasites is common in puppies as they’re exposed to the cysts shed in their mother’s feces. The most common symptom in both adults and puppies is diarrhea.

Intestinal parasites and worms are diagnosed by means of a microscopic evaluation of the fecal matter for eggs or cysts. A dewormer is typically given upon diagnosis.


Dirofilaria immitis is the species of roundworm known as “heartworm.” One of the most common dog parasites, the heartworm is transmitted through a mosquito bite. The larvae enter the mosquito bite wound and migrate through the skin to the circulatory system and on to the heart and lungs where they complete their life cycle.

A mature heartworm can measure a foot or more in length. When a dog is infected with a large number of heartworms, severe damage to the lungs and heart tissue can occur. Left untreated, a heartworm infection can be fatal. Because the treatment itself can be dangerous to the dog, prevention is the best course of action.

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