External Parasites

Parasites on your Dog Parasites are living organisms that live either inside or outside of your dog. Some parasites can cause illness in your dog by consuming nutrients or blood from your dog, other parasites can transmit diseases. Some of the parasites can also infect people, so keeping your dog parasite free is an important part of your dog’s total health and well being.

External parasites live on the skin or in the ears of your dog. Some of the parasites are large enough to be seen by the naked eye while some can only be seen with the help of a microscope. Internal parasites are either in the intestinal tract or can be in the blood vessels or heart of your dog. These parasites cannot be seen, so special testing is required to detect them.


Fleas are the most common parasite of dogs. They are very small, about twice the size of the head of pin and are brown in color.  On puppies, fleas like to congregate on the back of the neck, while in adult dogs, they prefer the area on the back by the base of the tail. You can see the fleas by parting the hair and see them scurry back into the fur. Other evidence of fleas are the black specs of flea dirt left on your dog. This is actually the digested blood of your pet excreted by the flea (flea poop). To verify if this is flea dirt compared to regular dirt, place a small amount of the debris on a white paper towel and add water. If the towel turns red when the dirt dissolves, then you know it is flea dirt.

Fleas cause intense itching on your dog, and dogs can develop a hypersensitivity to the flea bite resulting in a flea bite allergy which can be further complicated by skin infections in the broken skin. In young puppies, a massive flea infestation can cause anemia from the loss of blood.  Fleas are also a source for tapeworm infestation in your pet. Fleas prefer to feed on your dog because of their higher body temperature, but will bite people if a pet is not around. This often happens when returning from a vacation.

There are several great products available for flea control and will be covered in a separate post.


Lice are smaller than fleas and are whitish in color. Their eggs, or nits, can be seen attached to the pets hair shafts. In dogs, lice are much less common than fleas. I do see lice on guinea pigs. The chewing lice can cause a skin irritation and sucking lice can cause anemia from blood loss. Insecticidal shampoos and products used for fleas will kill lice. You will also have to treat the bedding and carpets where your pet has been to kill the lice in the environment. Fortunately, lice are generally species specific so lice that infect dogs do not like people and human head lice generally do not like dogs.


Ticks are not an insect, but an arachnid which is a relative of spiders.


There are many different kinds of ticks ranging in size from a small dot to a pea. The female tick must feed on blood to feed the eggs. Ticks also carry many diseases such as Lyme disease and Ehrlichia, both of which can cause serious disease in your dog. Ticks can also attach to humans and is a source of Lyme disease to people.

Frequent checking of your pet, especially in the ears and between the toes, can identify ticks. If you know you are going camping or live in a wooded area where ticks are prevalent, the tick products such as Advantix or Vectra 3D can help with tick control.

In the event your pet has been infested with ticks, your veterinarian may want to put your pet on antibiotics and test your pet periodically for the tick borne diseases.


Mites are also arachnids with eight legs, but are very much smaller than fleas or ticks. Most mites can only be seen with magnification or with a microscope.

Ear mites are by their name, found in the ears of dogs, cats and rabbits.  They cause intense itching and set the ear up for other infections.

DemoDemodexdex mites and Scabies mites are found on the skin of the dog and are the cause for “mange”. Demodex mites are a normal parasite for the dog that live inside the hair follicle. In some dogs, the immune system is out of balance and these mites multiply to larger than normal numbers, bursting the hair follicle resulting in hair loss and skin infections. They do not infect humans and cannot be “cured” , but can be controlled with today’s medications.

Sarcoptic mites are contagious to dogs and can occasionally infect people. (I can confirm from personal experience) . These mites burrow into the skin, laying eggs as they go. It reminds me of a Twilight Zone episode. The mite causes an intense itching from the allergic response to the body parts.  In dogs, the preferred location of these scabies mites are along the ear margins and elbows of the dog. The demodex mites sometimes show up first around the eyes and give a “moth eaten” appearance to the hair loss on the body. In severe infestations they can cover the entire body. The broken skin and intense itching will then set up for skin infections. Your veterinarian will perform a skin scraping of the affected areas and view the slide with a microscope. Once the mite is identified, then the treatment for the specific type of mite can be started. Over the counter medications for mange can make your pet worse and are not effective.

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