A Guide to Dog Parasites

Parasites are a common cause of disease and health problems in dogs. Whilst some provide a mere mild irritation, others can be seriously harmful to dogs. Parasites are organisms that live on (external) or inside (internal) a host.

They survive by getting their food from, or at the expense of their host. Unfortunately for dog owners, some parasites can move from dogs to people and cause similar symptoms. Educating owners to the different types of parasites and how to treat them is beneficial for both them and their pets.

The most commonly known parasites, or at least the ones most commonly known to dog owners, are fleas, ticks and lice. These, along with mites, are all external parasites and most can be treated simply with regular grooming, removal and treatment solutions from your vet or local supermarket.

Modern medicines make treatment, control and prevention of these nasty critters much easier than in the past. It is likely that at some points in their lives, dogs will experience one of these, if not all.


Fleas are small, around the size of a sesame seed. They move rapidly, jumping distances 150x their own body length and breed at an alarming rate. A female flea will lay around 50 eggs a day. These eggs can fall from a dog’s body onto floor, carpets, sofas and when hatched can soon infest a house.

Eggs can lay dormant for an astonishingly long time and could hatch after the first outbreak has been treated. For this reason, prevention is much easier than elimination. Fleas suck blood from a dog, Their bite causes skin irritation, making a dog itchy and scratch.

Some dogs can be allergic to flea saliva and react severely to their bites and even people are not off bounds to fleas. They will bite people too.


Ticks are usually found during warmer months in long grass, woody areas and often under leaves where they find rodents to attach themselves to as well as our beloved dogs. 

Dogs Ticks do not bite, get their fill and leave. They remain attached, continually drawing blood and growing in size.

While ticks themselves only cause mild irritation, they carry diseases that pose a serious threat to dogs and humans.

These pesky ticks will happily jump to a human host as they will a canine one.

These diseases include lymes disease and rocky mountain spotted fever which have serious long-lasting health issues.


Dog lice, although not as common as dog fleas, are also external parasites. There are two types – those that chew on the skin and those suck blood.

Both irritate causing itchiness, scratching and restlessness. Lice are species-specific. They do not move from one species to another. Owners do not get lice from their dogs, nor dogs from their owners.

Simply put, dog lice require dog blood to survive and human lice require only human blood. Pet lice cannot survive on human blood.


Mites are probably the less commonly known of the external parasites. There are four main species of mites that affect our dogs in different ways.

Ear mites, which are typically referred to as an internal parasite, burrow deep into the ear. They cause infection and in the worst cases can cause a dog to go deaf. The external mites are;


Sarcoptes scabiei – a burrowing mite that causes sarcoptic mange also known as canine scabies. These mites burrow into the skin and lay their eggs. They can create a variety of skin problems but the most common is hair loss and severe itchiness.


These mites can also be transferred to human, although their effect on us is not so serious. People will experience mild, temporary itchiness.


The Cheyletiella mite which is also referred to as “walking dandruff” due to the fairly large Cheyletiella parasites being seen scurrying along a dog’s skin or coat. This gives the illusion that the dandruff is moving.


They live on the surface of the skin and feed off of dead and dying skin flakes. They do not usually cause as much irritation as burrowing mites, or fleas but they can and do bite humans.


Demodex canis is a parasite that lives on the hair follicles of dogs. This mite causes the most common form of mange, Red Mange.


All dogs have a few of these mites on their skin and if the immune system is functioning properly. It is when the immune system is comprised that that this mite thrives and spread rapidly causing hair loss, skin scaling and redness.

It can sometimes produce oily smelly substance making a dog smell somewhat pungent. They do not pose a threat to a healthy dog, or human. Puppies often contract them from their mothers in the first few days but with a healthy immune system fend them off.

Internal Parasites

There are a number of intestinal worms that can infect dogs These are: roundworm, hookworm, whipworm, tapeworm and heartworms. Other internal parasites include toxoplasma, giardia and coccidia. 

Dogs generally pick them up by inadvertently digesting parasite eggs or spores in contaminated food, water, soil of faeces. Although deadly if left untreated, or not identified in time, many of these internal parasites can be easily suppressed with medicines.

It is preventing a second bout from occurring that tends to be the tricky bit. Identifying where the contaminated area is to prevent more accidental digestion is not always easy. Once in the environment, some parasite eggs can remain infective and present a health risk for your pet for years.

Humans can contract internal parasites from dogs. It can be passed via their saliva without an owners knowledge or from their infected dog poop.

Once in the intestine they will grow rapidly and can cause major problems, like blockages. if they form a ball within the body. There are medicines to flush out the worms but in extreme cases surgery is needed to remove them.

If you suspect that your pet of having some internal complications, seek veterinary advice asap. If you have any question on this article or would like to leave comments I would love to hear them and will respond promptly. 

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