How dog illnesses spread, and how to protect your dog

This guide is general information, not veterinary advice. If you're worried about your dog, speak to your vet.

Most of the serious infections UK dogs catch travel in a handful of everyday ways: other dogs, poo, water, parasites and wildlife. Knowing the routes makes prevention much simpler. This page brings together advice from UK vet charities, with links to our full guides.

Warning signs at a glance

If you spot any of these, ring your vet. Each full guide lists the emergency signs.

Parvovirus: severe, foul-smelling, often bloody diarrhoea, vomiting and extreme tiredness (PDSA). Puppies go downhill very quickly (Blue Cross). Parvovirus guide
Kennel cough: a forceful, hacking cough. See the vet quickly if your dog is off their food, lethargic or breathing heavily (Royal Veterinary College). Kennel cough guide
Lungworm: coughing, breathing problems, unexplained bleeding or bruising, and seizures (PDSA; Blue Cross). Lungworm guide
Leptospirosis: jaundice (yellow gums and eyes), vomiting, diarrhoea, lethargy and drinking more. A dog can die within two days of showing symptoms (PDSA). Leptospirosis guide

Dog-to-dog contact

Kennel cough spreads by direct contact, through the air and on surfaces, and is most common where lots of dogs gather, such as kennels, shows and day care (PDSA).
Distemper spreads in an infected dog's saliva when they cough or sneeze, and through urine (Blue Cross).
Parvovirus spreads by direct contact with an infected dog (Dogs Trust).

What helps: keep vaccinations up to date (PDSA), and keep a coughing or poorly dog away from other dogs (PDSA). Puppies should only meet fully vaccinated dogs until their own course is complete (PDSA).

Poo and contaminated ground

Parvovirus is shed in poo and can survive in the environment for months to years, in gardens, parks and fields (PDSA).
Roundworm eggs in poo contaminate soil and can stay a threat for years. Dogs often swallow them while grooming dirt from their fur (Blue Cross).
Giardia, a gut parasite that causes watery diarrhoea, spreads in poo and can survive in the environment for months (PDSA).
Dogs with lungworm pass larvae in their poo, which then infect slugs and snails (Blue Cross).

What helps: always pick up after your dog, especially in your own garden, where worm eggs can build up (Blue Cross). Worm your dog regularly. Blue Cross says adult dogs need worming at least four times a year, or more often if there are young children at home, but always ask your vet (Blue Cross).

Puddles, ponds and standing water

Leptospirosis bacteria live in water or soil for months. The risk is highest around slow-moving or stagnant water such as ponds, canals, drains and floodwater (PDSA).
Giardia can be caught from infected water (PDSA).
Dogs can swallow lungworm-infected slugs and snails while drinking outside (PDSA).

What helps: a yearly leptospirosis vaccine (PDSA), keeping puppies away from stagnant water until they're protected (Dogs Trust), and changing the water in outdoor bowls regularly (Blue Cross).

Shared bowls, toys, leads and bedding

Parvovirus can be carried on bowls, leads, collars, toys, bedding, shoes, clothes and hands (PDSA; Blue Cross).
Kennel cough can pass on food and water bowls, toys and other shared objects (Blue Cross; Royal Veterinary College).
Ringworm, a fungal skin infection, can live on bedding, towels and grooming equipment for up to two years (PDSA).

What helps: wash your hands after handling a dog that might be unwell (Dogs Trust). If your dog has been ill, ask your vet how to clean their things and how long to keep them apart from other dogs (PDSA; PDSA).

Slugs, snails and frogs

Dogs catch lungworm by eating infected slugs, snails or frogs, often by accident when eating grass, drinking outside, or picking them up on toys or their fur (PDSA; Blue Cross).

What helps: ask your vet for a prescription wormer that covers lungworm. Standard pet shop wormers don't (Blue Cross; PDSA). Full details are in our lungworm guide.

Ticks and fleas

Ticks live in woodland, moorland, long grass and areas with lots of wildlife, and are most active in warmer months. They can pass on diseases such as Lyme disease (PDSA). The NHS says ticks are found all over the UK, sometimes in urban parks and gardens (NHS).
Fleas cause itchy skin, spread disease, can bite humans, and can cause anaemia in young, old or ill pets (PDSA). Dogs most often catch tapeworm by swallowing fleas while grooming (PDSA).

What helps: check your dog for ticks after walks, especially the head, ears, armpits, groin and tummy, and remove any you find quickly and correctly (PDSA). The NHS suggests fine-tipped tweezers or a tick-removal tool, grasping the tick close to the skin and pulling slowly upwards without squeezing or crushing it (NHS). Use a regular, licensed flea and tick product. PDSA recommends a prescription product from your vet where possible (PDSA; PDSA).

Rats, foxes and other wildlife

Rats are the main source of leptospirosis-contaminated water and soil, and dogs can also catch it from the urine of other wildlife and farm animals (PDSA).
Dogs can pick up tapeworm by eating rats, mice or animal carcasses (PDSA).
Roundworm eggs are found in some dog, cat and fox poo (NHS).

What helps: keep up with regular worming (PDSA) and the yearly lepto vaccine, and let your vet know if your dog regularly kills rodents (PDSA).

Prevention basics

Vaccinate and keep up with boosters. See our vaccinations guide and puppy vaccination timeline (PDSA).
Treat for parasites. The BSAVA recommends treating pets for internal parasites such as worms and external ones such as fleas, ticks and mites, based on your dog's lifestyle and local risk. It says this also helps reduce the risk to human health (BSAVA).
Pick up poo and bin it quickly (Blue Cross; NHS).
Wash hands after handling dogs and before eating (Blue Cross).
Know the warning signs and call your vet early. See the list at the top of this page.

Illnesses dogs can pass to people

Most dog illnesses don't affect people. Parvovirus, for example, doesn't infect humans (Blue Cross), and lungworm isn't known to (Blue Cross). A few infections can pass between dogs and people, though they're rare:

Leptospirosis (Weil's disease): spread in the pee of infected animals, including rats and dogs. The NHS says it's rare in the UK and very rare to catch from pets (NHS). PDSA says it can pass from dogs to people, but is rare in people (PDSA). More in our leptospirosis guide.
Ringworm: a common fungal infection, not a worm. People can catch it through close contact with an infected person or animal, or from objects like bedding, combs or towels (NHS). In dogs it causes hair loss and red, crusty skin, often in circular patches (PDSA).
Roundworm (toxocariasis): caught when soil, sand or poo containing worm eggs gets into the mouth. It isn't caught from fresh poo, but usually from soil or sand that has held eggs for weeks or months. It's rare but can occasionally cause serious problems, including sight loss (NHS). Blue Cross says cases are more common in children (Blue Cross).
Giardia: humans can catch it, so wash your hands after picking up poo or meeting a dog with diarrhoea (PDSA).
Lyme disease: you can't catch it from your dog, but the same ticks that bite dogs can bite people and spread it (PDSA; NHS).

Hygiene tips for families

Wash hands regularly, especially before eating and after touching animals or soil (NHS; NHS).
Teach young children not to eat soil or sand, and don't let them play where there might be lots of animal poo (NHS).
Don't let dogs poo where children play, such as sandpits or playgrounds, and pick up and bin poo quickly (NHS).
Worm your dog regularly (NHS), and more often if you have young children, as your vet advises (Blue Cross).
Wear gloves when gardening, and wash vegetables before eating them (NHS).
Don't share towels or bedding with a person or pet who has ringworm, and take your dog to the vet if they have patches of missing fur (NHS).
Check children and pets for ticks after time outdoors (NHS).
Cover cuts with waterproof plasters and shower after being in water that might be contaminated (NHS).

If you're worried about your own health, speak to your GP, a pharmacist or NHS 111 (NHS; NHS).

Finding a vet in Liverpool

Your vet can tailor vaccines and parasite treatment to your dog's lifestyle. Browse our Liverpool vets directory to find a practice near you.

Out-of-hours emergencies in Liverpool: Medivet 24 Hour Alder, 410 Eaton Road, West Derby, L12 3HG, says it is open 24 hours a day, 365 days a year. Call 0151 220 4668 (Medivet, checked 18 Oct 2026). Vets Now Liverpool, based in the PDSA Pet Hospital on Woolfall Heath Avenue, Huyton, L36 3YD, opens from 6pm on weeknights, from noon on Saturdays, and all day on Sundays and bank holidays. Call 0151 271 5727 (Vets Now, checked 18 Oct 2026). Always ring before you set off, and ask your own vet which service covers their out-of-hours calls.

More in our dog health series

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There are no affiliate links on this page. Affiliate disclosure. This guide is general information, not veterinary advice. Always speak to your vet.