Where do dogs get parasites from?

Dogs can get parasites from a variety of sources. Parasites are organisms that live on or in a host organism and get their food from or at the expense of the host. There are many different types of parasites that can infect dogs, including protozoa, worms, ticks, fleas, and mites. Some parasites can cause minor issues like skin irritation, while others can cause more serious illness and even death if left untreated.

How do dogs get infected with parasites?

There are a few main ways dogs can become infected with parasites:

  • From their environment – Eggs or larvae of parasites can be picked up from soil, grass, feces, or other places in the environment. For example, hookworm larvae can live in soil and infect dogs when they walk barefoot.
  • From their mother – Puppies can sometimes get roundworms or other parasites before birth or from nursing on an infected mother.
  • From other animals – Some parasites can be transmitted between animals directly or through vectors like fleas or ticks. For example, tapeworms are spread when a dog ingests a flea carrying tapeworm eggs.
  • From contaminated food or water – Eating or drinking things with parasite eggs, cysts, or larvae can lead to infection. For example, giardia is spread through ingesting contaminated water or feces.
  • From bites – Mosquitoes, fleas, and ticks can transmit parasites like heartworm through their bites.

The main routes of transmission depend on the specific type of parasite. Overall, any exposure to sources of parasites in the environment, other animals, or vectors like ticks and fleas can potentially lead to infections.

What are some common parasites in dogs?

There are many types of parasites that can infect dogs, but some of the most common include:


Roundworms are intestinal worms that look like long spaghetti strands. There are several species that infect dogs, including toxocara, toxascaris, and others. Puppies are often born infected with roundworms from their mother. Infections happen when dogs ingest roundworm eggs from contaminated soil, feces, or rodents.


Hookworms are intestinal worms that attach to the intestinal wall and feed on blood. Dogs get infected when larval hookworms penetrate the skin, often through the paws. This can happen when walking through contaminated soil. Hookworms cause blood loss, diarrhea, and weight loss.


Whipworms live in the large intestine and cause irritation, watery diarrhea, weight loss, and anemia. Dogs get whipworms by ingesting eggs from contaminated soil or feces.


Tapeworms are long, segmented flatworms that live in the small intestine. They can reach several feet in length. Parts of the tapeworm break off and pass in the feces. This lets the tapeworm spread its eggs. Dogs get tapeworms when they ingest fleas infected with tapeworm larvae.


Heartworms are spread by mosquito bites. The larvae migrate to the heart and lungs, causing respiratory disease, heart failure, and damage to organs. Heartworms are very serious and potentially fatal.


Giardia are single-celled protozoan parasites that infect the small intestine, causing foul-smelling diarrhea. Dogs ingest the cysts through contaminated food or water sources.


Coccidia are protozoans that infect the intestinal tract lining. Puppies and dogs with weak immunity are most vulnerable. Dogs ingest coccidia from contaminated soil, food, water, or feces.


Fleas are external parasites that live on the skin and feed on blood. They also transmit other parasites like tapeworms. Dogs get fleas from close contact with other infected animals.


Ticks are external parasites that embed in the skin and feed on blood. They can transmit diseases like Lyme disease, ehrlichiosis, anaplasmosis, and more to dogs. Ticks live in wooded, brushy areas waiting to latch onto a passing host.


Mites are tiny external parasites that can infest the skin, ears, and other body areas of dogs. Different mites cause mange, ear infections, and skin irritation. Mites spread through contact with infected animals, bedding, or grooming tools.

What are the most common parasite transmission routes?

Some of the most common ways parasites are transmitted to dogs include:

  • Fecal-oral transmission – When dogs ingest feces, soil, food, or water contaminated with parasite eggs or cysts. Roundworms, hookworms giardia, coccidia spread this way.
  • Vector-borne transmission – When parasites use vectors like ticks, fleas or mosquitoes to spread between hosts through biting. Heartworms, Lyme disease, and ehrlichiosis spread this way.
  • Skin penetration – When parasite larvae penetrate the skin and enter the body. Hookworms spread through skin penetration.
  • Ingestion of intermediate hosts – When dogs eat intermediate hosts like rodents or fleas carrying a parasite’s larval stage. Tapeworms spread this way.
  • Placental and milk transmission – When puppies get parasites before birth or from nursing on an infected mother dog.

Preventing fecal-oral contamination and exposure to vectors like fleas and ticks are the main ways to cut down parasite transmission risks in dogs.

Which dogs are at highest risk for parasites?

Some dogs have a higher risk of acquiring parasites than others. High risk groups include:

  • Puppies – Lack of immunity makes puppies very vulnerable to parasites like roundworms, hookworms, coccidia, and giardia.
  • Unweaned puppies – Can get roundworms, hookworms, or other parasites from their mother before birth or while nursing.
  • Strays or shelter dogs – Dogs who lived as strays or in shelters are more likely exposed to parasites from the environment, contaminated feces, or other animals.
  • Outdoor dogs – Spending time outdoors exposes dogs to parasite sources like feces, soil, ticks, fleas, mosquitoes, infected prey animals, etc.
  • Working, hunting dogs – Working dogs who track through vegetation have high exposure to ticks, soil, feces, and wildlife that may carry parasites.
  • Dogs in warm, humid climates – Parasites thrive in warm weather. Dogs in tropical or subtropical regions are at increased risk.
  • Unvaccinated dogs – Dogs not on a consistent preventative medication or vaccination schedule are more vulnerable to parasites.
  • Immunocompromised dogs – Dogs with weak immunity from illness or medication have a harder time fending off parasites.

While all dogs are at some risk, young, unvaccinated outdoor dogs in warm climates are the most prone to parasitic infections.

What are the symptoms of parasitic infections in dogs?

Symptoms of parasitic infections can vary widely depending on the type of parasite involved and the severity of the infestation. Some common signs to watch for include:

  • Diarrhea or loose stools, potentially with mucus or blood
  • Vomiting
  • Weight loss or lethargy from malnutrition
  • Loss of appetite
  • Anemia from blood loss
  • Coughing or difficulty breathing (with heartworm disease)
  • Skin irritation, hair loss, or lesions
  • Itching around the anus or tail

In some cases, dogs may show no signs at all or very subtle symptoms. Puppies with roundworms may have distended bellies. Regular deworming is important even without obvious symptoms to prevent intestinal damage and malnutrition.

How are parasitic infections diagnosed in dogs?

There are several diagnostic tests vets can use to identify parasites, including:

  • Fecal exam – Microscopic examination of a stool sample to check for parasite eggs, larvae, or cysts. The type of parasite can be identified by the appearance.
  • Fecal flotation – Uses a solution to make parasite eggs float to the top for easier viewing under the microscope.
  • Fecal smear – A thin layer of feces is smeared onto a slide and stained to detect parasite cysts and eggs.
  • Fecal sedimentation – Centrifuging a fecal sample to concentrate parasite eggs for identification.
  • ELISA or PCR blood tests – For parasites like heartworms, blood tests can detect antibodies or DNA.
  • Skin scraping – Takes a small skin sample to check for mite infestation under the microscope.

In some cases, imaging like x-rays or ultrasound may also be used to detect parasites like heartworms. Knowing the travel and medical history of a dog can provide helpful clues about possible parasite exposure as well.

How are parasitic infections treated in dogs?

Treatment of parasites involves using dewormers and medications that are safe and effective against the specific type of parasite detected. Common medications for parasite infections include:

  • Fenbendazole – Broad spectrum dewormer for roundworms, hookworms, whipworms, and more.
  • Pyrantel pamoate – Treats hookworms, roundworms, and ascarids.
  • Praziquantel – For tapeworm infections.
  • Metronidazole – Antiprotozoal drug for treating giardia.
  • Milbemycin – Prevents heartworm disease and controls hookworms, roundworms, and whipworms.
  • Ivermectin – Prevents heartworm disease and treats mange mites.
  • Selamectin – Controls fleas, some types of ticks, ear mites, and intestinal parasites.
  • Amitraz – Used to kill demodectic mange mites.

The specific medication, dose, and duration is tailored to the patient and type of parasitic infection they have. Some medications treat the active infection, while others like heartworm preventatives help prevent reinfection. Environmental treatments like flea/tick prevention may also be part of the parasite control plan.

Are there any risks or side effects to deworming drugs?

Most deworming medications are considered very safe with minimal risks. However, there are a few potential side effects owners should be aware of:

  • Gastrointestinal upset like vomiting or diarrhea shortly after giving medication.
  • Allergic reactions in pets sensitive to ingredients in the dewormers.
  • Interaction with other medications – should follow veterinarian advice on medication interactions.
  • Overdose toxicity if given at too high a dose.
  • Weakness or lethargy for 1-2 days as parasites dying off can cause inflammation.

Using the proper dosage of dewormer for your dog’s weight is important to minimize side effects. Veterinarians consider the risks very low when used appropriately, and the benefits far outweigh potential risks.

How can parasitic infections be prevented in dogs?

There are several key things owners can do to reduce the risk of parasitic infections, including:

  • Use monthly heartworm and intestinal parasite prevention medication prescribed by your vet.
  • Treat the dog and environment for fleas. Vacuum regularly and use flea control products.
  • Check for and remove ticks after time spent outdoors. Ask your vet about tick prevention.
  • Have a fecal test done 1-2 times per year and deworm as needed.
  • Clean up feces promptly from your yard and when walking your dog.
  • Prevent your dog from eating feces or dead animals.
  • Avoid areas with lots of wild animal feces if possible.
  • Bathe and groom dogs regularly to prevent mites and parasite eggs on the coat.
  • Disinfect food and water bowls regularly.

Vaccinations, proper nutrition, and maintaining overall good health are also important for your dog’s immune defenses against parasites. Following your vet’s recommendations for prevention, testing, and deworming is key for parasite protection.


Dogs can pick up parasites from many sources in their environment, food, water, other animals, and vectors like fleas and ticks. Common parasites include intestinal worms, heartworms, protozoa like giardia, and external parasites like mites. Certain groups like young dogs and outdoor dogs are at higher risk. Symptoms depend on the parasite, but may include diarrhea, coughing, skin irritation, and lethargy. Diagnostic tests on feces, blood, or skin can identify the type of parasite infection. A variety of oral and topical deworming medications are available, tailored to the parasite identified. monthly prevention and good sanitation practices are the best way for owners to reduce parasitic infections in their canine companions.

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