Fleas & Other Parasites


Parasites are the cause of many diseases in puppies and dogs. To keep your dog healthy, learn how to recognise the symptoms of parasites, as well as how to prevent and treat parasite infestations.

Click on a parasite below to learn more

  • Fleas
  • Ear mites
  • Sarcoptic Mange
  • Roundworm

What is a parasite?

A parasite is a plant or animal that lives on or inside another living organism (called a host). A parasite is dependent on its host and obtains a benefit, such as survival, at the host's expense.

Are there different kinds of parasites?

There are two basic types:

  • Internal parasites (endoparasites) such as roundworms live inside the body of a host dog.

  • External parasites (ectoparasites) such as fleas, ticks, ear mites and sarcoptic mange mites live on the body of their host dog.

How dangerous are parasites to my dog?

It depends on three things: the type of parasite, the degree of infection or infestation, and your pet's individual reaction. A mild flea infestation may be of no great consequence to some dogs, while others may show hair loss, itching and discomfort. Severe flea infestations can lead to significant skin disease, anaemia or even death, especially in young puppies. Infestations by ear mites can cause inflammation of the outer ear (i.e. 'otitis') that can be further complicated by secondary fungal and bacterial infections characterised by an unpleasant odour and a crusty brown discharge. Sarcoptic Mange Mites can cause severe itchiness, hair loss and discomfort. These mites can also infect humans who come into contact with affected dogs.


There's no other way to put it - fleas are blood-sucking ectoparasites (live on the skin surface of their 'host').

What is a flea?

Fleas are blood-sucking ectoparasites. There are 2,200 flea species known in the world today. Only a few of these commonly infest dogs and cats. Fleas are not the same as ticks.

The most common flea that affects both dogs and cats is the cat flea, or Ctenocephalides felis. It's dark brown or black body is about one to three millimetres long. They can also feed on people, but we're not their first choice of meal.

Why do dogs get fleas?

Fleas love warm, humid environments. And they are determined, nimble creatures capable of Olympian feats. When they're hungry and looking for a home, they can jump 10,000 times in a row up to 60 centimetres high. Plus their flat bodies allow them to move quickly through a dog's fur.

You'll usually find fleas on a dog's abdomen, the base of the tail and the head. However, a heavy infestation can thrive anywhere on the body.

What are common signs that my dog has fleas?

  • You may be able to see fleas on your dog, especially if there is a large burden
  • Fleas are small, and just because you don't find one on your dog, it doesn't mean that they're not there or that your dog is not being bitten by them!
  • Fleas suck your dog's blood and can cause terrible skin irritation that will make your dog scratch, lick and bite themself. This may result in rashes, scaly skin, hot spots and hair loss
  • Droppings, digested blood known as flea dirt, in your dog's coat

The 4 life cycle stages of a flea

  • Adult fleas (5% of lifecycle):

    • are the ones you see jumping around your dog's coat
    • bite then feed on the blood of their host
    • make up 5% of the flea lifecycle
    • male and female adult fleas mate and lay eggs
  • Flea eggs (50% of lifecycle):

    • are not sticky and once laid quickly fall off the dog into the surrounding environment
    • can't be readily seen with the naked eye
    • make up 50% of the flea lifecycle
    • take between 1-10 days to hatch into larvae
  • Flea larvae (35% of lifecycle):

    • hatch from the flea eggs
    • are a small worm-like life form that move away from the light
    • bury themselves in dark places eg deep in carpet pile
    • last 5-11 days while they undergo 2 moults to become a pupa (cocoon)
  • Flea pupae (10% of lifecycle):

    • in a sticky impenetrable cocoon that becomes covered in debris
    • usually lasts 5-14 days, but may lay dormant for up to 6 months

What do fleas do to dogs?

Adult fleas have specially adapted mouth parts for piercing the skin and sucking blood. More than just annoying and irritating to your dog, they can also cause significant skin disease. Flea blood feeding is also associated with the transmission of several infectious diseases to both pets and people in New Zealand.

What is flea allergy dermatitis (FAD)?

It's an itchy skin disease animals develop from an allergic reaction to the saliva of fleas feeding on their blood. An affected dog will be very itchy – often from scratching, biting, licking and chewing. Their skin is usually reddened and there may be lesions and hair loss.

Infectious diseases from fleas

It's not just your dog at risk here. Fleas can carry infectious diseases that are transmitted to humans such as:

  • Rickettsia spp. - causes flea-borne spotted fever
  • Bartonella henselae – causes cat scratch fever
  • Yersinia pestis – causes Plague, an identified agent of bioterrorism.

How can I treat or prevent fleas?

Products such as Revolution® can be used to treat, control and prevent flea infestations, as well as control flea allergy dermatitis.

Flea preventatives should be used year round. Your vet will be able to help you choose the right one for your dog.

Ear mites

These troublesome pests are unpleasant for pet and owner alike.

Pets Most Often Affected

All dogs, from puppies to seniors

What You Should Know

Ear mites are highly contagious and pass easily from pet to pet. Otodectes cynotis, the ear mite of dogs, accounts for 5–10 percent of otitis externa cases in dogs. Otitis externa, an inflammation of the external ear, results in frequent head shaking and pawing, an unpleasant odor, and discharge.

Ear mites are easily transmitted among animals and are spread by direct contact. These oval mites are fairly large, and look like coffee grounds in the dog's ear. These troublesome pests do not burrow in the ear; rather, they live on the ear canal's inner surface.


  • Ear infection
  • Intense scratching or head shaking
  • Red-brown or waxy ear discharge
  • Itching skin around ears, head, neck
  • Thick crust around outer ear
  • Possible crust and scales on neck, rump, and tail

What You Can Do to Help

Your veterinarian can recommend preventive treatment such as Revolution (selamectin).

Monthly use of Revolution treats and controls ear mite (O. cynotis) infestations in dogs, and in puppies as young as 6 weeks. Ask your veterinarian about Revolution.

Sarcoptic mange

Hair loss and skin infections can result when scabies mites affect your pet.

Pets Most Often Affected

All dogs, from puppies to seniors

What You Should Know

Mange is a broad term that describes skin disease. Scabies, a form of mange, is caused by microscopic mites that lay eggs under a dog's skin. Scabies mites are round and are so tiny that they are barely visible to the naked eye.

These types of mites tend to prefer areas on a dog with no hair or very little hair. Mange often results in severe skin inflammation, which can trigger intense itching and eventual hair loss. Scratching may cause a secondary skin infection. Sarcoptic mange is easily transmitted to other dogs and can be transmitted to humans.


  • Intense itching, scratching and biting, especially around face, chest, legs, elbows, ears, or hocks (ankles)
  • Small red bumps
  • Hair loss
  • Crusty scabs

What You Can Do to Help

Your veterinarian can recommend preventive treatment such as Revolution (selamectin).

Monthly use of Revolution treats and controls scabies (S. scabiei) infestations in dogs, and in puppies as young as 6 weeks.

Ask your veterinarian about Revolution.


Roundworms are one of the most common of the parasitic worms found inside a dog.

What is Roundworm?

Roundworm, another common intestinal parasite in dogs, lives within the small intestine and migrates through the liver and lungs causing organ damage which can be severe if there are large numbers.

What you should know

Roundworm can cause fatal infections in puppies. A puppy may become infected with roundworm when it suckles its mother or by consuming roundworm eggs shed by another dog.

People can become infected by consuming roundworm eggs. This is more likely to happen to children who encounter a contaminated outdoor area, and get the sticky roundworm eggs on their clothes or toys, then their hands and, eventually, in their mouth.


  • Vomiting
  • Diarrhoea
  • A pot-bellied appearance
  • Abdominal discomfort

What you can do to help

Revolution is an aid in the treatment and control of roundworms (Toxocara canis and Toxascaris leonina).

Revolution should be applied once as a single treatment.

Following the initial treatment, we recommend monthly use of Revolution to aid in controlling roundworm infections.

Additional roundworm treatment should be administered to puppies less than 12 weeks of age.

Related Links

Treatment & Prevention Plan

Did you know?

Only 5% of fleas live on your pet, the rest live in the environment. Revolution is unique because it can be effective against flea eggs and larvae in the environment as well as adult fleas on your dog, stopping the flea life cycle.

Life stages of flea infestation

It's not just your dog at risk here, fleas can carry infectious diseases that are transmitted to humans too!