Canine parasites exist internally and externally. Many are species-specific and exist only on the dog. Intestinal parasitism exists in all ages of dogs with the greatest frequency in puppies. Types and incidence of parasitism vary with geographic regions. Additionally, age and immune status are significant factors influencing gastrointestinal (GI) parasites. In most cases, microscopic analysis can diagnose parasitic infestation.

Intestinal Parasites


This is a one-celled protozoan that are intracellular parasites of the lining of the small intestine that occur with some frequency. Infection occurs upon ingestion of contaminated feces or food. When ingested, the parasite colonizes the lining of the small intestine and reproduction begins. As reproduction progresses, new Coccidia are shed through the feces to the environment. Shedding of the protozoan can be asymptomatic or associated with signs of diarrhea and bloody stools.

If a healthy adult dog contracts Coccidia, their immune system can usually fight off the parasites without treatment. As a result, most infections are not apparent and resolve on their own by self-immunization. Adult dogs usually display significant immunity.


Puppies are most commonly affected. Sometimes Coccidia can cause diarrhea and lethargy. When a puppy contracts Coccidia, the puppy will usually have watery stool. There is a possibility that due to the stress on the colon, there may be some blood in the puppy’s stool. If your puppy’s stool becomes watery or loose, please take him/her to the vet.  


Treatment for Coccidia consists of antimicrobials that are bacteriostatic. These drugs stop the growth of Coccidia and then the host’s immune system responds to rid the intestine of the parasite. The veterinarian will do a fecal exam.  Sometimes Coccidia can be hard to find on a fecal. If this is the case, your vet may choose to treat your puppy for it anyway. Do not worry, treatment is easy and painless. To treat coccidia, your vet will prescribe Albon or Toltrazuril oral treatment.  


A protozoan intestinal parasite that infects many mammals, including humans. The reaction to infection varies depending on the individual and age. Due to an immature immune system, young puppies are commonly the most affected. Signs usually occur 1-2 weeks after infection. At times, the infection can go unnoticed or may be self-limiting after a short course of diarrhea. Many cases that show signs are mild with minimal depression. However, in severe cases, giardia can produce severe diarrhea and fluid loss.  


Giardia is a parasite that is passed in the feces and is consumed directly by the next host. Unfortunately, Giardia is very hardy and can remain in the environment for many months waiting for a suitable host. Contaminated water is a frequent source of Giardia. Diagnosing Giardia through a fecal can be difficult so, luckily, there is now a snap test for diagnosis.  

Most vets will test Giardia with a snap test although it is not always your vet’s first idea. As a result, you may want to ask for a Giardia test if your puppy has runny stool and possible exposure to standing rainwater or food that has been left outside.

Giardia responds well to treatment. Metronidazole, an oral antibiotic, is the drug of choice given daily for 5 days. However, at this time, there are some other drugs that are being used when metronidazole does not work.  


Tapeworms are one of the few parasites that can be seen with the naked eye. These worms are caused by the ingestion of fleas. ALL IT TAKES IS ONE FLEA. Eggs are shed to the environment from the GI of the dog in small segments that look like small pieces of rice. These segments can often be seen in fresh feces or attached to the adjacent tissues or hair on or near the dog’s anus. Tapeworms can look rather nasty when seen in the puppy/dog’s stool. The segments move for the first few minutes after they leave the dog’s body. The tapeworm looks like tiny little worms moving in the feces. In looks, they are often compared to human pinworms.  


These simple parasites are easily treatable. The vet will give the dog the correct dosage of praziquantel. It is a one-time treatment. However, if the dog ingests another flea, the tapeworms will come back. Do not try to treat your puppy/dog’s tapeworms with an over the counter de-wormer. They do not work and you will be wasting your money. The common tapeworms of dogs pose no threat to humans. The best prevention of Tapeworms is of good flea control.


These are a common parasite that are usually found in puppies. Studies show that at one time between the ages of four and twelve weeks that 85% of puppies are infected with roundworms. Consequently, it is really important for breeders to make sure that they start deworming their puppies at 2 weeks of age with a well known, reputable dewormer. Toxocara Canis (TC) and Toxocara Leonina (TL) are the two roundworms of the dog, with the former being far more prominent.

Diagnosis of roundworms is done through a standard microscopic fecal exam. Signs of roundworms can be serious in puppies producing abdominal pain, bloating, dull coat, and diarrhea. However, the first and most common sign is loose stool. Treatment of roundworms in puppies consists of oral medication. Monthly heartworm prevention contains a monthly dose of dewormer and is the perfect prevention from the age of 12 weeks to 12+ years. Pyrantel pamoate is one of the more common, effective, and inexpensive wormers that works against roundworms.


These are also common parasites of dogs regardless of age. They are most common in warm humid climates, but exist all over North America. In dogs, hookworm transmission is through contact with contaminated feces. In the dog, hookworms can be unapparent to severe. Once the hookworm matures in the body of the host, the worm attaches to the lining of the intestinal tract and sucks blood. Consistent deworming is important for puppies, starting at two weeks of age to ensure that severe infestation does not occur. 


If left untreated, hookworm infestations can cause marked anemia, intermittent bloody diarrhea, dull dry hair coat, weight loss and even death in small/young puppies. Severe infestations could require the need of IV medicines and blood transfusions. Regular deworming is important for all puppies, starting when the pups reach two weeks of age. Additionally, a fecal exam is necessary to check for parasites between 6-8 weeks of age or if the pup’s stool becomes irregular.


Diagnosis is through a simple fecal exam. Normal treatment consists of multiple de-wormings 1-3 weeks apart. Monthly heartworm prevention will reduce the risk of hookworm infection in puppies/dogs.

These parasites are zoonotic and transferrable to humans. Chance skin penetration of infective larvae penetrates the barefoot or other soft areas of skin such as the eye or mouth. Usually, a self-limiting local skin irritation is the result. However, it can be worse, so if something does not look right on your skin, go to the doctor.  


These parasites are common, but less prevalent. Whipworms are more common in warm humid climates and are less prevalent in the western, dry areas of North America. The egg is capable of surviving in the environment for months. Whipworms infestations are acquired by the ingestion contaminated feces. Upon ingestion, the egg matures and the adult infection occurs in 2-3 months. Once mature, the worm burrows into the lining of the large bowel and cecum. Clinical signs are that of colitis: straining, mucous diarrhea with occasional blood, and an urge to defecate small volumes frequently.


Treatment for whipworms requires several treatments with fenbendazole or febantel for 3-5 days and repeated in 3 weeks. Severe cases of whipworms are rare but can require surgical intervention. Prevention of whipworms includes careful removal of feces and bleaching regularly.

External Parasites


Flea infestation can make your dog quite ill and is the leading cause of skin problems in dogs. Fleas bite and suck the dog’s blood causing itching and mild to severe skin irritation. Small or weak animals can become anemic and have a decreased oxygen level in the blood. Fleas are also the cause of tapeworms.

Evidence of Fleas

The two most common places to find fleas are on the dog’s belly and rump (near base of tail). Adult fleas are small, brown, hard-bodied, and wingless, a little larger than the head of a pin. The adult fleas you see only account for 1% of the population. The rest are mostly unseen eggs and larvae.

Even if you do not see an actual flea, if “flea dirt” is visible, then there are fleas present. Flea dirt appears, black but when smeared on white paper or mixed with water, it is reddish brown. Although called “flea dirt,” these small, black-looking granules are actually flea poop. Flea eggs look like tiny, white grains of sand. They can drop off into any area frequented by the animal, infesting the dog’s bedding and the owner’s home. Heavy infestation can require multiple treatments for your pet and your home.


Treating your dog with a monthly flea and tick preventative is the best solution. Do not use any of the over the counter flea preventatives. These medicines are unproven, unregulated, and do not work well. In addition, they are not always safe. It is better to go with flea prevention provided by your veterinarian. For fleas, prevention is better and easier than treatment.


Ticks attach themselves to their host, burrow their head into the skin and suck blood. These parasites can carry diseases, such as Lyme disease and Rocky Mountain Spotted Fever. When found, ticks require immediate removal. Make sure to extract the head, otherwise, an abscess may form.

One method is to get the tick's head to relax or die by dabbing the tick with alcohol. Wait a couple of minutes, then use tweezers or your fingernails to grasp the tick near its mouth and twist to dislodge the tick. You will usually see what looks like a piece of dried skin near where the mouth of the tick should be. This means you got the head. You need to kill the tick by squashing it or drowning it. Warm compresses, antibiotic washes, or creams may help with possible infection.


“Ringworm,” is not a worm.  In actuality, it is an infectious fungus which grows within the skin. Signs are weak, broken hairs, and irritated, scaly, inflamed skin.  The name originates from the look of the rash that the fungus causes. This is typically in the shape of a circle or ring. Treatment can include special shampoos, clipping of the affected area, creams, and a drug given by mouth. Since it is zoonotic, ringworm can transfer to humans from their furry companions.  

Sarcoptic Mange

Caused by the parasite Sarcoptes scabies, this condition is commonly referenced as canine scabies or red mange. To infect the host, these microscopic mites invade the skin of healthy dogs or puppies and create a variety of skin problems, the most common of which is hair loss and severe itching. While they will infect other animals and even humans, they prefer to live their short lives on dogs. Fortunately, there are successful treatments and the control of the associated skin condition is possible.

Who Can Get Sarcoptic Mange?

Sarcoptic mange can infect all ages and breeds of dogs. While it prefers to live on dogs, this particular mite will also infect cats, humans, and foxes. Cats, foxes, and humans all have their own particular species of mite within the Sarcoptes family. Each species of mite prefers one specific kind of host (e.g. dog), but may also infect others. Since all of these species of mites have a similar life cycle and respond to the same treatment.  

Life Cycle of the Mite

The mites usually spend their entire life on a dog. The female mite burrows into the skin and lays eggs several times as she continues burrowing. These tunnels can reach the length of several centimeters. After she deposits the eggs, the female mite dies. In 3-8 days, the eggs hatch into larvae which have 6 legs. The larvae mature into nymphs which have 8 legs. The nymph then molts into an adult while it is still in the burrow. The adults’ mate, and the process continues. The entire life cycle requires 2-3 weeks.

The mites prefer to live on the dog, but will live for several days off of the host in the environment. In cool moist environments, they can live for up to 22 days. At normal room temperature in a home, they will live from 2 to 6 days. Due to of the mite’s ability to survive off the host, dogs can become infected without ever coming into direct contact with an infected dog. However, an infected dog will have had to have been in the same area within the week.


The symptoms are varied but usually include hair loss and severe itching on the elbows, ears, armpits, hocks, chest, and ventral abdomen (belly). These mites prefer to live on areas of the skin that have less hair. As the infection worsens it can spread over the entire body. Small red pustules often develop along with yellow crust on the skin. As a result of the severe itching and resultant scratching from the dog, the skin soon becomes traumatized and a variety of sores and infections can develop as a result.

The itching seems to be much worse in warm conditions such as indoors or near a stove or heat vent. Skin darkening and enlarged lymph nodes may result if the infection goes untreated or is mistakenly treated as an allergy. Sarcoptic mange infection and may carry a misdiagnosis of severe atopy (inhalant allergy).


Often, trying to get a diagnosis for scabies can be frustrating. The standard method is to perform a skin scraping and then identify the organism under the microscope. Unfortunately, on average, only twenty percent of the infected dogs will show Sarcoptes mites on any given scraping. Therefore, a negative scraping does not rule out Sarcoptic mange. Therefore, many vets will treat a dog for Sarcoptic mange on the visual exam alone. 


There are several products on the market that are extremely effective, safe, and convenient in treating Sarcoptic mange. The most widely used is the liquid cattle wormer Ivermectin (Ivomec). In most practices, it is the first choice for treatment. Most dogs get one oral dose and then another oral dose two weeks later. The success and safety rating is excellent.

Prior to using this treatment, Collies, Shetland sheepdogs, and other herding breeds should be tested for ivermectin sensitivity. In dogs that are sensitive to Ivermectin, some veterinarians have been having success using milbemycin oxime (Interceptor) at an off-label dose of once a week for three weeks. Both Ivermectin and Interceptor should only be used under direct veterinary supervision and care.

Revolution is a common topical treatment. It provides prevention against heartworms, fleas, ticks, and sarcoptic mange with a once-a-month dosage. Environmental treatment with a residual insecticide (e.g.; permethrin) is also suggested.

“Alternative Treatments”



Since your dog does not have to come into direct contact with an infected dog to contract scabies, it is difficult to completely protect him/her. Places, where large numbers of dogs congregate, are obviously more likely to harbor the mange mite. Since foxes and the environment in which foxes may spend a large amount of time can transmit the mite to dogs, keep dogs away from foxes and these areas.

This type of infestation is not common when dogs are well groomed; on a good diet; have mature immune systems; have healthy skin/coat; and do not spend much time with other unknown dogs. Since the topical heartworm prevention, Revolution, treats this mange, it would be the best type of heartworm preventative to use if you like to take your dog to canine play-dates, dog parks, or local parks on a regular basis.

Demodectic Mange

This mange, also known as follicular mange, Demodex, or puppy mange, is a skin disease, generally of young dogs, caused by the mite, Demodex Canis. Demodectic mites of various species live on the bodies of virtually every adult dog and most human beings, without causing any harm or irritation. These small (0.25 mm) ‘alligator-like’ mites live inside of the hair follicles (i.e., the pore within the skin through which the hair shaft comes through,) hence the name follicular mange.) Demodex is the most common type of mange in puppies.

Most dogs naturally carry this mite because they are transferred from dam to pup soon after birth. The Demodex mite is commonly present in the hair follicles on puppy skin and usually does not cause symptoms. A weakened immune system is suspected to be the reason these “harmless” mites “activate” and cause scaly hair loss. However, the complete reason is unknown.

Cause of Outbreak

Whether or not Demodex causes an outbreak on a dog depends on the animal’s ability to keep the mite under control. Demodectic mange is not a disease of poor living conditions It is generally a disease of young dogs that have inadequate or poorly developed immune systems or older dogs that are suffering from a depressed immune system.  However, commonly, physiological stress is a significant factor in an “outbreak” of Demodex.

 The mites produce a substance that lowers the dog’s resistance to them and makes use of an opportunity to multiply.  A mature immune system is able to keep this “substance” at bay. In turn, this disease occurs primarily in puppies who are 2-8 months of age. In most cases, as a dog matures, the immune system also matures and will naturally fight the Demodex. It is best to treat any outbreaks with medication. Demodectic mange is not dangerous or transferrable (as far as the hair loss). 


Individuals that are sensitive to the mange mites may develop a few (less than 5) isolated lesions or bald spots (localized mange). Alternatively, they may have generalized mange, in which case, there are more than 5 lesions or bald spots involving the entire body or region of the body. Most lesions/bald spots in either form develop after two months of age.

The lesions and signs of Demodectic mange usually involve hair loss, crusty, red skin and at times, dandruff. The mites prefer to live in the hair follicles, so in most cases, hair loss is the first noted sign. Usually, hair loss begins around the muzzle, eyes, and other areas on the head. Localized mange is when there are only a few circular crusty areas seen on the dog’s skin. Most frequently, this hair loss is around the muzzle and ears. Most of these lesions will self-heal as the puppies become older and develop their own immunity.

Generalized Demodectic Mange

Generalizes mange is when there are areas of hair loss over the entire coat, including the head, neck, abdomen, legs, and feet. In addition, the skin along the head, side, and back will be crusty and oftentimes inflamed. The skin could possibly crack and ooze a clear fluid. In most cases, the dog’s hair will be nonexistent or very thin. Unfortunately, some animals can become quite ill and develop a fever, lose their appetite, and become lethargic. Patients with generalized Demodectic mange need immediate vigorous treatment.


Demodectic mange mites are not visible to the naked eye. A veterinarian will collect skin scraping of the affected animal when Demodectic mange is suspected. The vet will then look at the scraping under the microscope to confirm the presence of the mite. Remember that these mites are present in every dog, so by themselves, they do not constitute a diagnosis of mange. For the pup/dog to actually get a diagnosis of a demodectic mange infection, the mite and skin lesions, in tandem, are required.

Basic Treatment

Lotions, dips, shampoos, or Ivermectin are common Demodex treatments. Fortunately, 90% of Demodectic mange cases are localized and can often be treated topically and without oral medications.

A treatment that has been successful for years has been a 1% rotenone ointment (Goodwinol ointment), or more recently, a 5% benzoyl peroxide gel applied daily. Bathing periodically with a benzoyl peroxide shampoo and feeding a high-quality diet and a multivitamin with a fatty acid may also help some dogs. Most of these localized lesions will heal on their own and do not require overly aggressive treatment.

Generalized Treatment

Generalized Demodex requires a more aggressive treatment. Thirty to fifty percent of dogs that develop generalized Demodex recover without treatment. However, treatment is always recommended.

Oral Ivermectin is the most common treatment for Demodex. Daily dosage necessary until hair growth returns. In addition, your veterinarian will test to diagnosed the dog as free of the mite.  

Commonly, dogs that have generalized demodicosis often have underlying skin infections. As a result, for the first several weeks of treatment, antibiotics are commonly given. Additionally, it is recommended that immune boosting supplements are provided to infected dogs. Since Demodex flourishes on dogs with a suppressed immune system, it is wise to check for underlying causes of immune system disease, particularly if the animal is older when they develop the condition.

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