Zoonotic Diseases: What Pet Owners Should Know About Infections That Jump Species
Key Takeaways
- Zoonotic diseases can pass between pets and people through bites, scratches, contact with feces, saliva, or contaminated surfaces.
- Common zoonoses in US households include ringworm, salmonella, toxoplasma, and campylobacter.
- Immunocompromised individuals, children under five, pregnant people, and older adults face higher risk.
- Routine veterinary care, parasite prevention, and good hand hygiene are the core prevention strategies.
- Keeping pets current on vaccinations significantly reduces zoonotic risk for both animals and people.
Zoonotic Disease (Zoonosis)
A zoonotic disease — often called a zoonosis — is any illness caused by a pathogen (such as a bacterium, virus, parasite, or fungus) that can be transmitted between animals and humans. These infections can travel in either direction: from a pet to a person, or from a person to a pet. Common household pets, including dogs, cats, reptiles, and birds, can all be involved in zoonotic transmission under certain conditions.
The CDC estimates that more than 6 out of every 10 known infectious diseases in humans are zoonotic in origin, highlighting the deep interconnection between human and animal health — an approach now formally studied under the "One Health" framework.
How Zoonotic Transmission Actually Works
Understanding how pathogens move between species helps pet owners focus on the right preventive habits. Transmission generally occurs through one of several routes:
- Direct contact: Touching an infected animal's saliva, urine, feces, blood, or skin. Cat scratches and dog bites are classic examples.
- Indirect contact: Handling contaminated objects — food bowls, bedding, aquarium water, or litter boxes — without washing hands afterward.
- Vector-borne transmission: Fleas, ticks, and mosquitoes that feed on infected animals can then bite humans, carrying pathogens like Bartonella henselae (cat scratch disease) or Rickettsia species. Our guide to parasite prevention explains how these vectors work in more detail.
- Foodborne routes: Handling raw pet food or contaminated animal products without proper hygiene can expose people to salmonella and other bacteria.
The severity of illness varies widely — some zoonoses cause mild, self-limiting symptoms, while others can be serious, particularly in vulnerable populations.
Zoonotic Risk Is Real but Manageable
The existence of zoonotic diseases does not mean pet ownership is inherently dangerous. For healthy adults practicing basic hygiene, the everyday risk from a well-cared-for pet is low. Most zoonotic infections in the US are mild and self-limiting. Awareness and simple preventive habits — not fear — should guide how households interact with their animals.
Common Zoonotic Diseases in US Households
Several zoonotic diseases are encountered with enough regularity in US households that every pet owner should be familiar with them:
Ringworm
Despite its name, ringworm is a fungal infection — not a worm — that dogs and cats commonly carry and transmit to people through skin contact. It causes circular, scaly patches on skin and is typically treatable but requires veterinary and medical attention simultaneously.
Salmonellosis
Reptiles, poultry, and even some dogs and cats can shed Salmonella bacteria. Infection in humans typically causes gastrointestinal illness. The risk is higher when handling reptiles or feeding pets raw diets without careful hygiene protocols.
Toxoplasmosis
Cats are the definitive host for Toxoplasma gondii. Infection in healthy adults is often mild or asymptomatic, but it poses serious risks during pregnancy and for immunocompromised individuals. The parasite is shed in cat feces; thorough handwashing after litter box cleaning and avoiding contact with stray cats significantly reduces exposure.
Campylobacteriosis
Young puppies and kittens frequently carry Campylobacter bacteria, which cause diarrheal illness in people. This is one reason veterinarians recommend hand hygiene after handling young animals, particularly those with loose stools.
Cat Scratch Disease
Caused by Bartonella henselae, this bacterial infection is transmitted through cat scratches or bites, or via flea feces entering a scratch wound. Most healthy people recover without complications, but it can be more serious in immunocompromised individuals.
6 in 10
Known human infectious diseases with animal origins
According to the CDC, approximately 60% of known infectious diseases affecting humans are zoonotic — originating in or shared with animals.
3 in 4
New or emerging diseases linked to animals
The CDC also notes that about 75% of new or emerging infectious diseases affecting people come from animals, underscoring the ongoing public health relevance of human-animal contact.
~70 million
Pet cats in the US
The American Pet Products Association estimates tens of millions of US households include at least one cat, making feline-related zoonoses — such as toxoplasmosis and cat scratch disease — a broad public health consideration.
Who Is Most at Risk — and Why It Matters
While any person can contract a zoonotic illness, certain groups face a meaningfully higher risk of serious outcomes:
- Children under five: Developing immune systems and less consistent handwashing habits increase exposure.
- Pregnant individuals: Toxoplasmosis, in particular, can cause severe complications for a developing fetus.
- Adults over 65: Age-related immune changes can make infections harder to resolve.
- Immunocompromised individuals: People living with HIV, undergoing chemotherapy, or taking immunosuppressive medications have limited ability to fight off pathogens that a healthy immune system would typically manage without incident.
If any member of your household falls into these categories, it is worth discussing your specific pet situation with both a physician and a veterinarian. The goal is not to create unnecessary alarm but to implement targeted precautions — such as having a different household member handle litter box duties during pregnancy.
Prevention Starts With Routine Pet Care
The most effective way to reduce zoonotic risk is not to avoid pets — it is to practice responsible ownership consistently. Key habits include:
Keep Vaccinations Current
Rabies vaccination is legally required for dogs and cats across most of the US and is one of the most critical zoonotic disease protections available. Other vaccines also reduce the likelihood that your pet becomes a reservoir for transmissible illness. Review your pet's schedule with your veterinarian using guidance like our pet vaccination schedule overview.
Maintain Parasite Prevention
Parasites are a major bridge for zoonotic transmission. Regular flea, tick, and heartworm prevention products — recommended by your veterinarian — dramatically lower this risk. Roundworms and hookworms, which are common internal parasites in dogs and cats, can also infect humans, particularly children who play in soil contaminated with pet feces.
Practice Consistent Hand Hygiene
Washing hands with soap and water after handling pets, cleaning up waste, feeding animals, or touching pet equipment is one of the simplest and most effective zoonotic safeguards available. Hand sanitizer can supplement but should not fully replace soap-and-water washing in high-risk situations.
Handle Waste Safely
Clean litter boxes daily — Toxoplasma oocysts typically become infectious only after one to five days in the environment, so prompt removal reduces risk. Pick up dog waste promptly and dispose of it properly. Avoid allowing children to play in areas where pets routinely defecate.
Make Hand Hygiene a Household Routine
Place a hand soap dispenser at every sink where pet-related tasks happen — near the laundry room if you wash pet bedding, near the back door if pets come and go outdoors. Building handwashing into the physical environment makes it easier for everyone, including children, to do it consistently without reminders.
This article is for general educational purposes only and is not a substitute for medical or veterinary advice. If you or a family member may have been exposed to a zoonotic pathogen, consult a qualified healthcare provider. For guidance specific to your pet's health, speak with a licensed veterinarian.