Parasites are a major concern for pets and their families. Dogs and cats can be affected by a wide range of internal parasites (helminths) that live in the intestines, lungs, or bloodstream. These parasites don’t just impact your pet’s health—they can also pose zoonotic risks to humans.
This guide covers the most common intestinal worms in dogs and cats, how they spread, signs to watch for, and treatment options.
What Are Helminths?
Helminths are parasitic worms that live inside a host. In pets, these include:
- Roundworms (Toxocara spp.)
- Tapeworms (Taenia, Dipylidium, Echinococcus)
- Hookworms (Ancylostoma spp.)
- Whipworms (Trichuris spp.)
- Heartworms (Dirofilaria immitis)
They can cause illness in dogs and cats, and some species can also infect people.
Roundworms in Dogs and Cats (Toxocara spp.)
- Species: T. canis (dogs), T. cati (cats), T. leonina (both)
- Transmission: Eating contaminated feces, infected prey (rodents, birds), or through mother’s milk
- Symptoms: Pot-bellied appearance, coughing, diarrhea, poor growth
- Zoonotic Risk: Can cause visceral larva migrans or ocular larva migrans in humans, especially children
- Treatment: Fenbendazole, with routine deworming starting at 6 weeks for puppies
Tapeworms in Pets
Taenia spp.
- Hosts: Dogs, cats, rodents, rabbits
- Spread by: Eating infected intermediate hosts
- Zoonotic concern: Rare, but Taenia solium and saginata can infect humans through undercooked meat
Dipylidium caninum
- Hosts: Dogs and cats
- Spread by: Ingesting infected fleas during grooming
- Signs: Often asymptomatic; may see tapeworm segments around anus or in stool
- Zoonotic risk: Children can be infected by accidentally swallowing a flea
Echinococcus multilocularis
- Hosts: Dogs, wild canids (rarely cats)
- Risk: Can cause life-threatening alveolar echinococcosis in humans and dogs acting as aberrant hosts
- Treatment: Long-term albendazole, sometimes surgery
Hookworms in Dogs and Cats
- Species: Ancylostoma caninum, A. braziliense, A. ceylanicum, Uncinaria stenocephala (dogs); A. tubaeforme (cats)
- Spread by: Ingesting larvae, skin penetration, nursing
- Signs: Anemia (especially puppies), dermatitis, diarrhea
- Zoonotic Risk: Humans can develop cutaneous larva migrans from contaminated soil
Whipworms (Trichuris vulpis)
- Host: Dogs (rare in cats)
- Spread by: Ingesting larvated eggs from soil
- Signs: Chronic diarrhea with mucus, but often subclinical
- Zoonotic risk: Very low
Heartworm Disease (Dirofilaria immitis)
- Hosts: Dogs (main), cats (less common)
- Spread by: Mosquito bites carrying larvae
- Signs: Coughing, exercise intolerance, heart failure, pulmonary hypertension
- Diagnosis: Antigen ELISA blood tests
- Zoonotic risk: Humans can rarely be infected, but adult worm disease is uncommon
Protecting Your Pet (and Family) From Parasites
- Regular fecal exams: At least 1–2 times per year
- Deworming schedule: Begin at 6 weeks for puppies/kittens, repeat per veterinary advice
- Year-round preventives: Monthly medications for heartworm, intestinal parasites, and fleas
- Prompt feces removal: Reduce environmental contamination and zoonotic risk
FAQs About Pet Parasites
Can humans get worms from dogs and cats?
Yes—roundworms, hookworms, and tapeworms can infect people, especially children
How do I know if my dog or cat has worms?
Look for diarrhea, weight loss, bloating, coughing, or visible worms in stool. Regular fecal testing is essential.
What’s the best parasite prevention?
Monthly preventives prescribed by your veterinarian are the safest and most effective.
Talk to your veterinarian about testing, deworming, and monthly parasite prevention to protect both your pet and your family.