Zoonotic Diseases: What Pet Owners Should Know About Illnesses That Can Cross Species

What Are Zoonotic Diseases?

A zoonotic disease (also called a zoonosis) is any infection that can pass naturally between animals and humans. The transmission can flow in both directions — from animals to people or from people to animals — though the animal-to-human direction is the more common household concern for pet owners.

Zoonotic pathogens include bacteria, viruses, fungi, and parasites. The CDC estimates that more than 6 out of every 10 known infectious diseases in people can be spread from animals, though that figure includes wildlife, livestock, and exotic animals — not just household pets. The day-to-day risk from a well-cared-for domestic pet is meaningfully lower, but not zero.

Transmission routes vary. Some pathogens spread through direct contact with an infected animal's skin, saliva, or fur. Others travel via feces (either direct contact or contaminated soil and water), bites and scratches, or contact with contaminated surfaces and food bowls.

Common Zoonotic Diseases from Household Pets

Most pet-associated zoonoses are preventable or treatable, but knowing what to watch for is the first step. The following infections are among those most commonly linked to dogs, cats, and small animals kept as household pets in the United States.

Bacterial Infections

• Salmonellosis: Salmonella bacteria can be shed in the feces of reptiles, birds, and sometimes dogs and cats, often without the animal appearing sick. Handling reptile habitats or pet food without washing hands afterward is a known transmission route.
• Campylobacteriosis: Puppies and kittens with diarrhea are common sources of Campylobacter infection in people. Symptoms in humans typically include diarrhea, cramping, and fever.
• Cat scratch disease: Caused by Bartonella henselae, this bacterial infection can be transmitted through a scratch or bite from an infected cat, particularly kittens. Most healthy adults recover without treatment, but it can be more serious in immunocompromised individuals.

Parasitic Infections

• Toxoplasmosis: Cats shed Toxoplasma gondii oocysts in their feces. Infection is primarily a concern for pregnant people and those with weakened immune systems. See our parasite prevention guide for more on managing parasite exposure.
• Roundworm and hookworm: Larvae from dog and cat intestinal parasites can penetrate human skin or be accidentally ingested from contaminated soil, causing conditions known as cutaneous larva migrans and visceral larva migrans.

Fungal Infections

• Ringworm (dermatophytosis): Despite the name, ringworm is a fungal infection transmitted by contact with infected pets or their bedding. It causes circular, scaly skin lesions and is especially common in children.

Who Is at Higher Risk?

While most healthy adults who practice good hygiene face a relatively low risk from household pets, certain groups require extra caution. These include:

• Children under 5 — their immune systems are still developing, and they are more likely to have close, unguarded contact with animals.
• Pregnant individuals — some zoonoses, particularly toxoplasmosis, carry specific risks for fetal development.
• Adults over 65 — age-related changes in immune function can increase susceptibility.
• Immunocompromised individuals — people undergoing chemotherapy, organ transplant recipients, or those living with HIV/AIDS may experience more severe disease from pathogens that cause only mild illness in others.

If your household includes someone in one of these groups, it is worth having a direct conversation with both your physician and your veterinarian about tailored precautions. Rehoming a pet is rarely the answer — practical risk-reduction strategies are usually sufficient.

Practical Hygiene Habits That Reduce Risk

The good news: most zoonotic transmission from household pets is preventable with consistent, low-effort habits. These measures are effective for the vast majority of pet owners.

• Wash hands thoroughly after handling pets, cleaning litter boxes or cages, or preparing pet food. Use soap and water for at least 20 seconds — not just hand sanitizer, which is less effective against some pathogens.
• Keep veterinary care current. Regular wellness exams, vaccinations, and parasite prevention reduce the likelihood that your pet is harboring transmissible organisms. This complements the guidance in our new pet health checklist.
• Manage litter boxes and waste promptly. Scoop cat litter daily, and have a non-pregnant household member handle this task if possible. Wear disposable gloves and wash hands after any waste cleanup.
• Avoid letting pets lick wounds or mucous membranes. A pet's mouth carries bacteria that are harmless to them but potentially problematic for humans, especially through open skin.
• Store and handle pet food safely. Raw pet food diets carry a documented higher risk of Salmonella contamination for both pets and their owners. Wash hands and surfaces after handling.
• Keep pets free of parasites. Fleas, ticks, and intestinal worms are vectors for several zoonotic pathogens. Consistent preventive treatment, recommended by your vet, is among the most protective steps you can take.

When to Talk to a Doctor or Veterinarian

Knowing when to seek professional guidance is as important as the day-to-day habits. Contact a veterinarian promptly if your pet develops diarrhea, skin lesions, unexplained weight loss, or any signs of illness — even if they seem mild. A sick pet may be shedding pathogens at higher levels, temporarily increasing household risk.

On the human side, consult a physician if you develop unexplained fever, skin rashes, gastrointestinal symptoms, or lymph node swelling — particularly after a bite, scratch, or close contact with an ill animal. Be sure to mention your pet exposure history, as this context is clinically relevant and often overlooked.

A healthy, well-monitored pet is one of the best defenses against zoonotic risk in your home. Consistent veterinary care, thoughtful hygiene, and staying informed are the pillars of safe pet ownership. For a broader view of how your pet's health intersects with household wellbeing, see our overview of nutrition and common health conditions in pets.

This article is for general informational and educational purposes only. It is not a substitute for advice from a licensed veterinarian or medical doctor. If you have concerns about your pet's health or your own, consult the appropriate qualified professional.