What is a zoonosis, and which ones should pet owners know about?

A disease that can pass between animals and humans — and while the risk from well-cared-for pets is low, a small number are worth knowing about because the precautions are simple and the consequences occasionally serious.

The ones most relevant to pet owners:

Toxoplasmosis. A parasite shed in cat faeces. Usually harmless, and significant in pregnancy and for immunocompromised people because of the risk to a developing baby. The practical points are underappreciated: cats shed the parasite for only a short period after first infection; the oocysts require a day or more to become infectious, so daily litter tray cleaning largely removes the risk; and undercooked meat and unwashed vegetables are more common sources of human infection than cats. Pregnant women should avoid handling litter or wear gloves and wash hands — not rehome the cat.

Toxocariasis. Roundworm from dogs and cats, particularly puppies and kittens. Rare in humans and occasionally serious, affecting eyes or organs. Regular worming and picking up faeces are the controls, and this is the principal reason dog fouling matters beyond unpleasantness.

Ringworm — a fungal skin infection, not a worm, common in kittens and readily transmitted by contact.

Campylobacter and salmonella, from faeces and from raw meat diets, which is a genuine consideration for households with young children or immunocompromised members.

Leptospirosis, from rodent urine and contaminated water, which dogs are vaccinated against.

Psittacosis, from birds.

Reptiles and amphibians carry salmonella very commonly, which is why they are not recommended for households with children under five.

Fleas can transmit tapeworm, and ticks transmit Lyme disease — the tick is the risk to humans rather than the pet itself.

Bites and scratches, which cause infection far more often than exotic disease. Cat bites in particular carry a high infection rate and puncture deeply — medical advice should be sought promptly.

The sensible precautions, which cover almost all of it: wash hands after handling animals, faeces or raw food; worm and treat for parasites on schedule; pick up faeces promptly; cover sandpits; keep vaccinations current; and take bites seriously.

General information, not medical advice.