You love your cat. That fluffy purring companion is family. But lurking in the back of every responsible owner's mind is a quiet question: what diseases do cats carry to humans? The internet is full of scary headlines, especially if you're pregnant or immunocompromised. Let's cut through the noise. The risk of getting seriously ill from your cat is low if you understand the pathways. This isn't about fear; it's about smart, practical knowledge. We'll cover the main zoonotic diseases—the ones that jump from animals to people—how they actually spread, who's most at risk, and the simple steps that make cohabitation safe. Spoiler: good hygiene and regular vet care for your cat solve 95% of the problem.

Diseases You Can Share with Your Cat

Zoonotic diseases from cats aren't a long list of horrors. They fall into a few clear categories: parasitic, bacterial, and fungal. The transmission almost always follows a specific route—a scratch, a bite, contact with feces, or, in rare cases, fleas. Indoor-only cats who are regularly dewormed and vaccinated present a dramatically lower risk than outdoor cats who hunt.

I've seen owners get overly anxious about remote possibilities while ignoring the common, easy-to-fix issues. For example, worrying about rabies in a fully vaccinated indoor cat in a rabies-free region, but then not washing their hands after gardening (a major toxoplasmosis risk) or letting their cat lick an open wound.

The Big Three: A Deep Dive on Toxoplasmosis, Cat Scratch Disease, and Roundworm

Let's get specific. Understanding the "how" is the first step to effective prevention.

1. Toxoplasmosis: The Pregnancy Scare (Often Overblown)

Toxoplasma gondii is a parasite. Cats are the definitive host, meaning it reproduces sexually in their intestines. An infected cat sheds millions of microscopic oocysts (eggs) in its feces for about 1-3 weeks after first infection. Here's the critical detail everyone gets wrong: these oocysts are not immediately infectious. They need 1 to 5 days in the environment to "sporulate." This is your prevention window.

How you really get it:

• #1 Source: Eating undercooked, contaminated meat (pork, lamb, venison).
• #2 Source: Gardening or handling soil/sand contaminated with old cat feces.
• #3 Source: Handling cat litter that has sat for >24 hours, then touching your mouth.

My vet friend has a saying: "We tell pregnant clients to wear gloves gardening before we tell them to rehome the cat." If you're pregnant, have someone else change the litter daily. If you must do it, wear gloves and wash your hands. That's it. Testing your cat is of limited value—a negative test just means it isn't shedding now, and a positive test likely means it's already had its one-time shedding period and is now immune, not shedding.

2. Cat Scratch Disease (CSD): More Than a Simple Scratch

This is probably the most common direct bacterial infection from cats. About 40% of cats carry Bartonella henselae at some point, usually with no symptoms. Kittens are more likely to be bacteremic (have it in their blood) and are therefore higher risk. Fleas are the vector between cats. No fleas, drastically lower risk of CSD in your household.

The scratch or bite introduces the bacteria. 3-14 days later, you might see a small bump or blister at the site. Then, lymph nodes in that area (armpit for a hand scratch, neck for a face scratch) swell up, become tender, and can even fill with pus. Fever and fatigue are common.

The expert nuance: Most cases resolve on their own in 2-4 months. The medical consensus on antibiotics is shifting. Many doctors now reserve them for severe cases or immunocompromised patients, as the evidence for their benefit in mild cases is weak. The key is monitoring and not panicking over a simple scratch.

3. Roundworm: A Sandbox Hazard

Toxocara cati eggs are passed in cat feces. They can survive in soil, sand, or litter for years. A child playing in a sandbox that outdoor cats use as a toilet is the classic scenario. The child gets eggs on their hands, then into their mouth.

In humans, the larvae hatch and migrate, but they can't complete their life cycle. This migration can cause inflammation. If they end up in the liver, lungs, or brain, it's called Visceral Larva Migrans (VLM). If they migrate to the eye, it's Ocular Larva Migrans (OLM), which can mimic retinoblastoma (eye cancer) and is a leading cause of infectious blindness in children.

Prevention is straightforward: Deworm your cat regularly as per your vet's advice. Cover sandboxes. Teach kids to wash hands after playing outside. The Companion Animal Parasite Council (CAPC) recommends year-round broad-spectrum parasite control.

Managing Risks for Vulnerable People: Pregnancy, HIV, and Chemotherapy

If you or a family member is immunocompromised (due to HIV/AIDS, chemotherapy, organ transplant) or pregnant, the calculus changes, but the answer is rarely "get rid of the cat." The emotional benefit of a pet is significant. The strategy becomes one of meticulous management.

For pregnant women: The focus is toxoplasmosis. Assign litter duty. No gardening without gloves. Cook meat thoroughly. Wash fruits/vegetables. Get your cat tested? Discuss with your vet and OB-GYN. A study published in the BMJ concluded that contact with cats was not a significant risk factor for toxoplasmosis seroconversion in pregnant women, pointing to foodborne sources as dominant.

For immunocompromised individuals: The list expands. CSD, Cryptosporidiosis (another parasite), and even routine bacteria from a bite can become serious. Avoid rough play that leads to scratches/bites. Keep cats indoors to reduce their exposure. Immediately wash any wound. Consider adopting an adult, indoor-only, healthy cat rather than a kitten, as kittens are more likely to be shedding various organisms.

I knew a family where the father was undergoing chemo. They kept the cat. Their rules: he didn't clean the litter, he avoided contact with cat saliva (no face-licking), and they were hyper-vigilant about flea control. It worked fine. The problem is irrational fear, not the cat.

Your Actionable Prevention Checklist

Knowledge is useless without action. Here’s your to-do list.

• Veterinary Care is Non-Negotiable: Annual check-ups. Keep up with deworming (even for indoor cats) and vaccinations (like rabies, as required). Discuss flea and tick control with your vet—it prevents CSD at the source.
• Litter Box Protocol: Scoop daily. This removes toxoplasma oocysts before they sporulate. Wash hands thoroughly with soap afterwards. Pregnant/immunocompromised: use gloves or avoid the task.
• Bite/Scratch First Aid: Immediately wash the wound with soap and running water. Apply an antiseptic. Monitor for signs of infection (redness, swelling, pus).
• Control Hunting: Indoor cats are safest. If your cat goes out, a bell on the collar may reduce successful hunting, lowering exposure to prey that can carry worms and other diseases.
• Hand Hygiene: Wash hands after handling cats, their food, or their litter. Before eating. After gardening. Make it a habit.
• Discourage Risky Behaviors: Don't let your cat lick your mouth or open wounds. Avoid rough play that triggers biting/scratching. Trim nails regularly.
• Food Safety: If you feed raw, accept the higher hygiene burden. Cook meat for your cat if you're concerned. Store and handle all pet food separately from human food.

That's it. It's not about living in a bubble. It's about simple, consistent habits that break the chain of transmission.

The bottom line is simple. The diseases cats can carry to humans are manageable. Panic and misinformation are your real enemies. By understanding the real transmission routes—feces, scratches/bites, fleas—you can implement targeted, effective prevention. Keep your cat healthy, practice good hygiene, and enjoy the countless benefits of your feline friend without undue worry. The risk is low, and you have all the tools to make it negligible.