Parasites in Dogs: The Most Commonly Overlooked Health Concern

Parasites in Dogs
John Walton
Written by John Walton

Our fur babies come in different sizes, colors, personalities, but they all have their means to touch our hearts. Man’s best friend, a cuddly couch buddy, a fearless guard dog, they can be what you want them to be and do it with all their might and all their hearts. These qualities allow them to explore their home, their territory, which makes them healthy and active at the same time.

However, the process of going outdoors and mingling with other dogs or exploring a different area exposes them into different factors that may affect their health. Parasites in dogs are considered as one of the easiest health-related concern that dogs can get because these are everywhere.

Even if you are the most hygiene freak when it comes to your dog’s cleanliness and safety, which does not give you and your dog the absolute protection that you think it does.

The Parasite Paradise: Your Lawn

There are a lot of parasites that affect dogs, and the best place to find them is surprisingly near – your lawn. In a neighborhood that has a decent canine population, it will not be such an uncommon feat that your lawn is the life of the party for some parasites. Unfortunately, some parasites have already inflicted a significant amount of health problem to your dog before you know it. This is one of the most common areas where it is highly likely that your dog will get a particular parasite.

Dog at parasite paradise your lawn

As we move forward, we will identify the general classifications of parasites and how to prevent them as much as possible. Prevention is better than cure, but for situations that cannot be prevented, it is very important to have at least basic knowledge on how to deal with parasites in dogs.

Digestive System Parasites

It is well known that one of the most common parasite groups for pets is the digestive system parasites.

Coccidia of odgs diagram

Because mastication and digestion are two of the normal physiologic processes for dogs, the digestive system becomes the primary portal of entry for parasites that thrive in the digestive structures such as the stomach, intestinal wall, and surrounding vasculature.

  • Coccidias are one-celled organisms, or protozoans, that thrive in the intestinal walls of both cats and dogs. This protozoan is more prevalent in younger dogs and puppies, particularly those that are less than six months old. It can also attack older dogs that are immunocompromised or has a weak immune system. Coccidias are not present in the intestinal tract when a puppy is born.
    Due to the frequent exposure to the mother dog’s fecal matter, which can contain viable cysts, it can be ingested by the puppy and develop inside its body thereafter. The most common symptom for a puppy that suffers from coccidiosis is diarrhea that varies in severity. They can also vomit, lose appetite, and become dehydrated due to the significant fluid loss.
  • Blood flukes are the culprit for water dermatitis, or canine schistosomiasis. It is a parasite that is more common in mud flats and swamplands in the United States. The life cycle of this parasite involves a snail and dogs. Once the fluke enters the dog’s body through the blood vessels, it goes to the heart and lungs. It also travels into the liver and intestines.
    They proliferate inside the dog’s body and the eggs are passed along with the feces. These parasites can cause serious health problems, such as cirrhosis and systemic effects such as loss of appetite and extreme malnutrition.
  • Another protozoan, Giardia prefers to thrive in the small intestine of cats and dogs. This is one of the not very well known parasites because it is a large family and there are types that affect specific animals that are yet to be properly analyzed. Most giardiasis infections can go unnoticed because they have no relatively obvious symptoms.
    One of the more common signs is diarrhea, which is also one of the most common signs of digestive tract parasites. Giardia, like most parasites in this category, robs the dog from nutrition and can often lead to a severely emaciated appearance.
  • Hookworms are considered as the most common intestinal parasites for dogs. In fact, there are types of hookworms that affect both dogs and humans. These parasites have sharp teeth and they «hook» along the intestinal lining to feed on the host’s blood. There are several means on how dogs can have hookworms, via skin, ingestion, and even lactation for young puppies.
    Because hookworms thrive on blood, which is the main vehicle for nutritional transportation to make sure that the nutrients reach the cells that require nourishment, untreated hookworm infestation can lead to some serious health concerns and even death.
  • Roundworms, or medically known as ascarids, is another common intestinal parasites for our fur babies. All members of the roundworm family are distributed all over the United States, and because these parasites can pass more than a million eggs through the feces each day, you read that right, a million eggs on a daily basis, and not during their entire lifetime. This is why they are one of the easiest to contract in the group of digestive parasites because they are almost always present wherever you go.
  • Physaloptera is found all over the world and can affect dogs, as well as other pets like doves, hedgehogs, monkeys, and doves. These parasites look like roundworms, only a little bit shorter. The similar appearance gives the confusion sometimes that it is indeed a roundworm.
    What sets physaloptera apart from other digestive tract parasites is that it prefers to thrive in the stomach, attaching itself along the stomach lining of dogs. Due to the nature of their preferred location, it can cause gastric bleeding which is evident once the infected dog is passing black and tarry fecal matter.
  • Spirocerca is one of the unique digestive tract parasites because they want to live in the upper gastrointestinal tract, within the esophagus and stomach. Spirocerca infestation can inflame or damage large veins and capillaries around the region, and can ultimately lead to esophageal cancer in dogs. The scarring that it leaves due to the inflammation becomes nodules that will eventually interfere with the normal swallowing and digestive process.
  • Tapeworms are well known for pet owners because this can affect both humans and dogs as well. These flat, segmented worms proliferate quite fast, and can cause a serious parasitic infestation in households, kennels, and the entire community. Due to its unique process of reproduction, it is easily accessible to unaware pets that tend to eat or become exposed to feces where segments can be available.
  • Strongyloides, or threadworms are thin, thread-like worms that also affect dogs and humans. These smaller worms can go on with their lives inside a dog’s body, and those with the stronger immune system and nourishment can become carriers of threadworms without manifesting symptoms. However, once a puppy or younger adults get this parasite, it can lead to an extremely life-threatening situation that is almost always fatal.
  • The Tricuris family, or whipworms are a group of worms that tend to thrive along the lining of the large intestine and cecum. This is one of the unique aspects of this parasite because most parasites prefer to be in the earlier portions of the gastrointestinal tract like the esophagus, stomach, and the small intestine. Whipworms can be contracted once a dog ingests contaminated water that contains eggs. The life cycle progresses once they enter the body and ultimately find their way into the large intestine.

Fleas and Ticks

Fleas and ticks are well known to be bugging our fur babies since ancient times. They are considered as the perfect transmitters of diseases, and even other parasites. They multiply at an overwhelming rate, which can pose a challenge once their numbers become out of control.

In as little as one full month, about twenty to thirty female fleas can produce over a million eggs, and even if some of these can be manually killed or treated with medicated solutions, imagine those who will manage to survive.

Fleas and Ticks

There are several types of fleas that have preferred hosts other than dogs; some prefer to thrive on horses, chickens, and other livestock.

However, they will still feed on canine blood, making the process a little bit complicated when it comes to extermination.

Other Ectoparasites

There are other less common ectoparasites, or parasites that thrive in the skin or other superficial parts of the dog’s body that you as a pet parent should be aware of.

  • The walking dandruff, caused by Cheyletiella mites are one of the mildest parasitic conditions in this list because they do not pose life-threatening adverse effects. Cheyletiellia mites got this name because they lodge under the scales and make the flakes appear as if they move.
  • Chiggers are one of the most common skin parasites that are found throughout the central United States. Scientifically known as Trombicula mites, chiggers are also known as harvest mites. Chiggers can infect dogs, cats, and even humans. Due to their availability, because they are basically everywhere, chiggers are one of the most difficult to prevent parasites in our list.
    However, the good news is that they are quite easy to treat. Chiggers are more prevalent during the spring and autumn season, and are commonly found in soils that have a chalky texture. You can easily identify chiggers because they appear as a reddish-orange mite that is about the size of a pinhead.
  • Cuterebra is a large fly that looks like a small bee. Cuterebra sounds cute, but these parasites can lay eggs that are seemingly harmless on stones, plants, or soil. The problem starts once a dog brushes itself against the contaminated stones or plants and the eggs stick to the coat. The eggs will hatch and form larvae and will enter the dog’s body through any of its orifices such as the nose.
    The larva that entered the body will mature under the dog’s skin and will present a swelling or nodule-like appearance. There can be drainage that will come out from that nodule’s breathing hole.
  • Canine scabies, commonly known as sarcoptic mange in dogs, canine scabies is caused by the Sarcoptes scabies. These tiny, microscopic mites invade the skin of adult dogs or even puppies and can lead to a variety of skin problems. The most common skin problem that Sarcoptes scabies can give includes severe itching and hair loss. Sarcoptic mange can affect other animals and even humans, but they seem to prefer dogs as their hosts.

Other Endoparasites

There are several endoparasites outside the common category of digestive parasites that affect dogs. These endoparasites pose varying levels of health concerns that can affect dogs, regardless of size or breed, by invading other parts of the dog’s body.

Baylisascaris procyonis diagram

Some of the endoparasites in this list are not very common, but knowing them gives you better knowledge on how to know if you are dealing with the uncommon varieties of parasites in dogs.

  • Baylisascaris procyonis is considered as one of the rarer endoparasites in dogs. This is because they are more prevalent in raccoons. However, this family of roundworms can create intestinal obstructions, especially for younger dogs that will be infected with the parasite.
    It can also be fatal to humans and dogs because it can lead to the condition called cerebrospinal nematodiasis, which causes a disturbance in the central nervous system. Aside from the brain, it also has the ability to invade the gastrointestinal tract, the liver, and even the eyes.
  • Babesia canis previously called Piroplasma canis, is a protozoan that infects dogs as well as other carnivores such as wolves and foxes. This parasite is more common in the southern United States, although there are isolated instances of infestations in medium to large-scale kennels.
  • Capillaria plica and its feline counterpart, Capillaria felis cati, are considered as rare parasites that affect dogs and cats, respectively. Generally found in the eastern part of the United States, this is a generally harmless parasite unless it is amplified by another underlying infection or infestation. The eggs of Capillaria can be confused with whipworms and lungworms, this is why the treatment protocol can become a mistake due to the confusion.
  • Demodectic mange, which is also known as follicular mange, red mange, or puppy mange, is a skin disease that generally affects the young dog population. Caused by a mite a called Demodex canis, it is one of the most abundant parasites out there because they live on almost every adult dog or human. These parasites are generally harmless, but if they proliferate above the normal limits, they can cause irritation or extreme flaking.
  • Heartworms, or also called as Dirofilaria immitis, shares the same classification as roundworms. Actually, they too look like roundworms, but that is basically the similarity that there is to it. Heartworms thrive at, as their name implies, the right side of the dog’s heart, as well as the large blood vessels that connect the heart to both lungs.
  • The giant kidney worm, Dioctophyma renale, is a parasite that is most commonly found in minks. However, there are rare occasions that they are found in dogs. In fact, there are rare and isolated reports of D. renale infecting humans. Found all around the United States, this is not much of a problem due to its rarity.
    However, once it infects a dog, the worm can infect the kidneys and inhibit proper urination and pose significant accumulation of microorganism growth, which eventually leads to other more critical infections. Giant kidney worms can infect a dog by eating an infected fish, frog, or even contaminated water with the young worms and cysts.
  • Trypanosoma cruzi is a protozoan parasite that causes the disease called American trypanosomiasis, which is more known as the Chagas disease in humans. T. cruzi is transmitted from one host to the other with insects more known as the kissing bugs. Generally more common in South and Central America where it is a significant cause of disease in humans, T. cruzi can affect the dog population as well.
    There is an estimated 16-18 million infected people in South and Central America. This protozoan is considered rare in mainland United States. Dogs, cats, and even exotic pets such as rats act as a vital instrument in the life cycle of these protozoans, because they act as reservoirs in the growth and development of these single-celled parasites.


In diagnosing the kind of parasite that affects your dog, it will require an appointment with your veterinarian. Because the majority of the parasites share something, be it by appearance or by a classic symptom, pet parents that end up self-medicating their pets are exposed to a risk of giving their fur babies the wrong kind of treatment. For example, anti-helminthic drugs sound the same, but they are scientifically formulated to target a specific type of worm.

Vet examines the dog's hair and looking for parasites

It would be best to have your dog checked once you have observed changes in appetite, skin color, discharge, or any unusual nodule or swelling that were not there before. In addition, it is very important to document the appearance of the discharge because your veterinarian will need those types of information to narrow down the possible diagnosis. If you can bring a sample of urine, stool, or discharge during your visit, kindly do so because the vet will also check them under the microscope.


In general, treatment protocols for parasites in dogs are divided into two segments – medical management and supportive management. Medical management involves the administration of the medication needed by the dog based on the impression and final diagnosis of the veterinarian. This can be topical for skin-related parasites, oral medications for endoparasites and protozoans, or a combination of both preparations.

It is very important to follow the administration schedule that will be given by the veterinarian to make sure that the dog receives the most effective dose of the medication that was prescribed. Always follow the advised number of days that the dog needs to take the medication even if you are seeing signs of improvement.

Treatment of dog parasites

Remember: It is very common that dogs with parasite infestation to miss some doses because their pet parents believe that once the dogs experience improvement in symptoms and overall well-being, they no longer need the medication. Completed medications reduce the risks of medication resistance, and ensure that the dog will be treated properly. If you think you will be able to save money by skipping dosages, you might end up spending more once it happens again.

Ectoparasites will have a specific protocol when it comes to topical and bath. Your veterinarian will explain the frequency of application and bath to make sure that the remaining defense system of the skin will not be stripped off completely, exposing the dog to other skin problems. Some parasites will require the dog to be shaved down, so necessary precautions will be needed and followed on point.


Cleanliness is your greatest weapon in preventing parasites in dogs. Most of the parasites that we were able to discuss involve ingestion or exposure to contaminated locations, food, or animals. It is best to keep your surroundings clean. There are parasites that can be prevented through routine medication schedules such as heartworms, while there are other parasites that can only be contracted if you happen to reach a contaminated area.

Keep your surroundings clean

In cases that the parasite is too available to be missed, such as tapeworms and fleas, proper hygiene and regular visits to the veterinarian will not prevent them, but will prevent these conditions from worsening. Also, if you own more than one dog, always make sure they are healthy and eats a balanced meal each and every time.

A healthy body increases the resistance of not being infected that is why nutrition is your foundation for prevention.


Parasites are everywhere, but you do not have to be extremely worried that your dog might get them. It is very important to know what causes the infestations, and how to prevent them.

Having the knowledge of knowing these parasites, no matter how common or rare they are, saves you from the trouble and unnecessary stress because you have no idea what is going on. As a pet parent, we are responsible for the health of our fur babies, as responsible we are to our own health.

About the author
John Walton
John Walton

John Walton lives in Somerville, MA, with his two dogs, two sons, and very understanding mate. He is a Certified Pet Dog Trainer, a member of the International Association of Animal Behavior Consultants, a mentor trainer for the Animal Behavior College, an AKC Certified CGC Evaluator, and the Training Director for the New England Dog Training Club.