The Risk Is Real — But Context Matters Enormously
Approximately 60 per cent of known human infectious diseases originated in animals, and around 75 per cent of recently emerging infectious diseases have animal origins. Those statistics sound alarming. But when it comes to the everyday pets sharing your sofa, the picture is considerably more reassuring — provided basic hygiene is observed.
Zoonotic diseases — illnesses that can transmit between animals and humans — do exist in domestic pets. What is often missing from the conversation is a clear-eyed look at how common transmission actually is, who is genuinely at risk, and what practical steps significantly reduce that risk.
The Most Common Zoonoses Associated with Pets
Bacterial Infections
Campylobacter and Salmonella are the bacterial zoonoses most frequently linked to pets in Europe and North America. Both can be present in the digestive tracts of healthy dogs, cats, reptiles, and poultry without causing visible illness in the animal. Transmission to humans occurs primarily through contact with faeces and then touching the mouth — often without the person realising it happened.
Cat scratch disease, caused by Bartonella henselae, is transmitted through scratches or bites from infected cats, particularly kittens. In immunocompetent adults, it typically resolves without treatment, though it can cause significant illness in people with weakened immune systems.
Parasitic Infections
Toxoplasma gondii is perhaps the most widely known pet-associated parasite, largely due to concerns about pregnant women and cats. Cats shed Toxoplasma oocysts in their faeces for only a short window after initial infection. Transmission to humans requires contact with contaminated faeces — and notably, the highest risk of Toxoplasma infection in humans comes not from pet cats but from eating undercooked meat.
Roundworms (Toxocara species) present in dogs and cats can cause toxocariasis in humans, particularly children who play in soil contaminated with infected faeces. Symptoms range from mild to serious, including potential effects on vision in rare cases. Regular deworming of pets is the primary prevention.
Ringworm, despite its name, is a fungal infection rather than a parasite. It transmits readily through direct skin contact with an infected animal and is among the more common zoonoses acquired from pets. It is unpleasant but straightforward to treat.
Viral Infections
Rabies remains the most lethal viral zoonosis globally, but in countries with robust vaccination programmes — including the UK, where terrestrial rabies has been eliminated — the risk from domestic pets is negligible. For travellers or those in endemic regions, it demands serious consideration.
Dog and cat bites can also transmit Capnocytophaga canimorsus, a bacterium that causes severe illness almost exclusively in people who are immunocompromised or have had their spleen removed. For healthy individuals, the risk is extremely low.
Who Is Actually at Risk
The healthy adult sharing a home with a well-cared-for, vaccinated, regularly dewormed pet faces a genuinely low risk of acquiring a zoonotic disease. The groups who require more caution are:
- Pregnant women, particularly regarding Toxoplasma and Listeria risks
- Children under five, who are more likely to have hand-to-mouth contact with contaminated surfaces
- People who are immunocompromised, including those on chemotherapy, organ transplant recipients, and individuals with HIV
- The elderly, whose immune responses may be reduced
For these groups, the risks are not zero, and conversations with both a physician and a veterinarian are genuinely worthwhile. However, in most cases, risk management rather than pet removal is the appropriate response.
What Actually Reduces Risk
The evidence consistently points to a small number of behaviours that account for the vast majority of preventable transmission:
- Wash hands thoroughly after handling pets, cleaning litter trays, or picking up faeces outdoors
- Keep pets up to date with vaccinations and parasite control — this protects you as well as them
- Do not allow pets to lick open wounds or mucous membranes
- Clean and disinfect any bites or scratches promptly
- Pregnant women should ideally have another household member manage the litter tray; if this is not possible, wearing gloves and washing hands afterwards significantly reduces risk
- Avoid contact with stray animals, whose vaccination and health status are unknown
- Keep children's sandpits covered when not in use to prevent cats using them as a latrine
Keeping the Risk in Perspective
The evidence base does not support avoiding pet ownership on grounds of zoonotic risk for the general population. Studies examining disease burden consistently find that most pet-associated infections are preventable through routine hygiene and standard veterinary care.
If you or a family member falls into a higher-risk category, speak with your GP and your veterinarian together. In most situations, sensible adjustments to how you interact with your pet — rather than giving them up — are all that is needed. The benefits of pet ownership for human wellbeing are well-documented; making an informed, proportionate assessment of the risks allows most people to enjoy those benefits safely.