Intestinal Parasites in Dogs and Cats: The Most Common Types

What Are Intestinal Parasites in Pets?

Intestinal parasites in pets are organisms that live inside your pet’s gastrointestinal tract, stealing nutrients and sometimes causing inflammation or tissue damage.

The most common types of intestinal parasites in dogs and cats include:

• Roundworms (Toxocara spp.): Long, spaghetti-like worms common in puppies and kittens.
• Hookworms (Ancylostoma spp.): Tiny but dangerous parasites that feed on blood, leading to anemia.
• Whipworms (Trichuris vulpis): Found mainly in dogs, these cause chronic diarrhea and weight loss.
• Tapeworms (Dipylidium caninum): Segmented worms spread by fleas that are often visible in stool.
• Protozoan parasites like Giardia and Coccidia: Microscopic organisms that cause diarrhea and dehydration.

Even indoor pets can become infected. Parasite eggs can be tracked inside on shoes, fleas or other animals.  

What Causes Intestinal Parasites in Dogs and Cats?

Pets can contract intestinal worms in several ways:

• Contact with contaminated soil or feces (most common)
• Eating infected prey, such as rodents or insects
• Flea ingestion, a leading cause of tapeworm infection
• From mother to offspring, as some parasites cross the placenta or are transmitted through milk
• Exposure at boarding, grooming, or dog parks

Because many eggs and larvae can survive in the environment for months, pet parasite prevention requires both hygiene and consistent control measures. 

A recent prevalence study shows that many pet owners underestimate parasite exposure risk, particularly in urban settings. Climate and geography also play a role—pets in warmer, humid regions face higher year-round parasite pressure, while those in colder areas encounter more seasonal risks when temperatures rise.

What Are Intestinal Parasite Symptoms in Pets?

Signs vary by parasite type and infection level, but these are the most common intestinal parasite symptoms in pets:

• Diarrhea (sometimes with blood or mucus)
• Vomiting or loss of appetite
• Weight loss despite normal eating
• Bloated abdomen, especially in puppies or kittens
• Dull coat 
• Lethargy
• Visible worms or rice-like segments in stool or around the tail

Some infections are asymptomatic in early stages, which is another reason routine fecal exams are such an important part of pet parasite prevention. Studies confirm that intestinal parasites remain prevalent even among apparently healthy pets.

How Are Intestinal Parasites in Pets Diagnosed and Treated?

Veterinarians diagnose intestinal parasites in pets using a fecal flotation test, which detects eggs or larvae under a microscope.

Treatment depends on the specific parasite:

• Broad-spectrum dewormers (e.g., pyrantel, fenbendazole, praziquantel) eliminate most common worms.
• Targeted antiparasitic medications may be used for Giardia or Coccidia.
• Follow-up fecal testing ensures the infection is fully cleared.

At Mixlab, we work with veterinarians to compound parasite medications into easier-to-administer forms, such as chicken-flavored chewables or tuna-flavored liquids, making compliance simpler and stress-free for both you and your pet.

Can Intestinal Parasites in Dogs and Cats Spread to People?

Yes, some intestinal parasites in dogs and cats are zoonotic, meaning they can spread from pets to humans. 

For example:

• Roundworm and hookworm larvae can migrate through human tissue, potentially causing organ or eye damage.
• Giardia can occasionally spread through contaminated water or surfaces.

Practicing good hygiene, like hand-washing after cleaning litter boxes or handling soil, and staying on a pet parasite prevention program greatly reduces the risk.

How to Prevent Parasites in Pets

Pet parasite prevention is far easier (and less stressful) than treatment.

• Keep your pet on a year-round parasite preventative prescribed by your veterinarian.
• Pick up waste promptly and keep litter boxes clean.
• Wash bedding and food bowls regularly.
• Prevent fleas since they can transmit tapeworms.
• Schedule annual fecal exams to catch infections early.

Consistency is key. Even missing one or two months of preventatives can create an opportunity for reinfection.

If you have multiple pets, ask your veterinarian about synchronizing pet parasite prevention schedules. Treating all animals at once can help break the parasite lifecycle and prevent reinfection.

Frequently Asked Questions From Pet Parents

#1. How Often Should I Test for Intestinal Parasites in Dogs and Cats?

Most veterinarians recommend testing for intestinal parasites in dogs and cats at least annually when healthy, but every six months for high-risk pets, such as young animals, outdoor cats, multi-pet households or dogs that frequent dog parks. Since many infections are asymptomatic, testing is the only way to catch them early.

#2. My Indoor Cats Never Go Outside. Do They Still Need Deworming?

Yes, indoor cats can still get intestinal parasites because:

• Fleas carrying tapeworm larvae may hitch a ride into the house (on humans or other pets).
• Parasite eggs from outdoor pets can be tracked inside on shoes or clothing.
• Some parasites transmit from mother to kitten before birth or via nursing.

Even with minimal outdoor exposure, maintaining a pet parasite prevention plan is best practice.

#3. What if My Pet Fails a Deworming Treatment or Gets Reinfected?

Repeat or persistent infections can happen due to:

• Re-exposure in the environment (For example, untreated other pets or an infested yard)
• Sub-optimal absorption or dosing issues
• Resistant parasite populations (rare)

If your pet fails treatment:

• Ask your veterinarian about environment-control measures.
• Confirm dosing and drug suitability with a compounding pharmacy like Mixlab.
• Consider follow-up fecal testing and possibly switching to a different, appropriate medication.

#4. What’s the Difference Between Intestinal Parasites and Heartworms?

Heartworms are transmitted through mosquito bites and live in the heart and lungs, not the intestines. They require different medications and prevention strategies. 

#5. How Do Pet Parasite Preventatives Work?

Pet parasite preventatives are carefully formulated medications that interrupt a parasite’s life cycle before it can cause harm. 

While the exact mechanism depends on the active ingredient, most fall into two main categories:

1. Neurotoxic Action: Many preventatives disrupt a parasite’s nervous system, causing paralysis and death. These compounds, such as macrocyclic lactones (ivermectin, milbemycin, selamectin) or isoxazolines (fluralaner, sarolaner), are highly selective, targeting parasite receptors without affecting mammals when used as directed.
2. Reproductive or Metabolic Disruption: Other medications prevent parasites from growing, molting or reproducing. Flea growth regulators, for instance, block chitin synthesis (the tough outer “shell”) or interfere with hormone signaling, stopping eggs and larvae from developing into adults.

Preventatives also differ by delivery method:

• Topical treatments work primarily on contact. Once applied, the medication spreads through the oils on your pet’s skin and coat, killing or repelling parasites when they attempt to bite. Some formulations are also absorbed through the skin into the bloodstream, providing systemic protection that kills parasites when they feed. This dual action—contact and systemic—helps ensure broad, continuous coverage against external and internal parasites alike.
• Oral preventatives circulate in your pet’s bloodstream, killing intestinal parasites in dogs and cats only once they feed—effectively stopping them from surviving long enough to transmit disease.
• Injectable preventatives (like certain long-acting heartworm formulations) provide sustained protection for months at a time.

When used consistently, these products act as a protective barrier, stopping infestations before they start and reducing environmental contamination from eggs or larvae.

The most effective pet parasite prevention plans combine:

• Routine medication use (year-round, not seasonal)
• Environmental control (washing bedding, cleaning litter boxes, yard care)
• Regular veterinary testing to confirm ongoing protection

Together, these steps provide long-term, layered defense against internal and external parasites alike.

Effective Protection Against Intestinal Parasites in Dogs and Cats

Intestinal parasites in dogs and cats are common, but with the right care and prevention plan, your pet can stay healthy and worm-free year-round.

If your veterinarian prescribes a dewormer or preventative, ask if it can be filled through Mixlab. If you already have a prescription, simply submit it online here.

We make it easy with:

• Custom flavors and dosage forms for better compliance
• Fast, free delivery nationwide
• Compounded and commercial options for every pet’s needs

Protect your pet from the inside out and enjoy peace of mind knowing Mixlab makes care simple. Get in touch with us if you have any questions!