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Learn about the parasites we assess

Fleas

Fleas are small, dark brown insects that live on your pet and feed on their blood. They are the most common external parasite. Fleas multiply quickly; a single flea can lay up to 50 eggs per day. The problem is that the adult fleas on your pet are only about 5% of the total problem. The other 95% are eggs, larvae (tiny worms), and pupae (cocoons) living in your carpets, bedding, and furniture. This matters because flea bites cause intense itching, skin infections, and can transmit tapeworm. For pets with Flea Allergy Dermatitis (FAD), just one bite can cause severe misery and distress.

Fleas are most active in warm, summer months, but can be active all year particularly where central heating is used all year round.

Preventative tips and behaviour

  • Check for 'flea dirt': Use a flea comb and place the debris onto a damp white tissue. If red or brown spots appear, this is digested blood (flea dirt).
  • If treating, treat all pets: If you have multiple dogs or cats, you must treat every single one at the same time.
  • Wash bedding: Wash your pet's bedding regularly at a high temperature (60°C or more) to kill eggs and larvae.
  • Vacuum regularly: Vacuuming carpets, upholstery, and cracks in the floor helps remove eggs and pupae. Empty the vacuum cleaner outside.

Remember: Fleas can thrive indoors in centrally heated homes all year long.

Fleas can live for a long time inside their pupae (cocoons) in your carpet. They wait for the right conditions (warmth and vibrations) to hatch.

Fleas can bite humans, often around the ankles, but they cannot live on human hosts.

Ticks

Ticks are parasites that grab onto your pet to drink blood. They do not jump or fly; they wait on plants for your pet to brush past. Ticks are dangerous because they carry diseases. In the UK, the biggest concern is Lyme disease. Lyme disease can cause severe joint pain, fever, and serious long-term health issues in dogs. Ticks must be removed fast. Preventing the bite is the best way to keep your pet safe.

Preventative tips and behaviour

  • Check thoroughly every day: Feel all over your pet after they have been outside. Pay attention to ears, paws, and the neck.
  • Use the right tools: Only remove a tick using a special tick removal tool.
  • Be gentle: Do not crush the tick's body or try to smother it with creams. This can make the tick inject fluid into your pet.
  • Act fast: Ticks often spread disease only after 24 hours of feeding. Remove them quickly!
  • Reduce garden risk: Keep your grass cut short and limit dense shrubbery where ticks like to hide.
  • Know the hotspots: Be very careful when your pet walks through long grass or deep woods.

Ticks can be active almost all year in the UK as long as the temperature is above freezing.

Remember that ticks can also bite people. If you are bitten, remove it carefully with a tool. If you feel unwell after a human tick bite, please contact your doctor (GP).

Roundworm

Roundworms are long, white, spaghetti-like parasites that live inside your pet's intestines. Unlike tapeworms, they do not break off into rice-like segments; instead, whole worms or microscopic eggs are passed in your pet's poo. You might occasionally see adult roundworms in your pet's vomit or stool, particularly in young puppies and kittens.

Pets can contract roundworms easily through several routes, including from their mothers before birth or via milk, by accidentally swallowing microscopic eggs in contaminated soil or water, or by hunting small animals.

How your pet gets roundworm

  • Mother to Offspring (Puppies & Kittens): Roundworm larvae can pass from a mother to her puppies in the womb before they are born, or to both puppies and kittens through her milk while nursing. As a result, almost all newborn pets are born with or acquire roundworms early in life.
  • Contaminated Environment: Infected pets shed millions of microscopic eggs in their poo. These eggs can survive in soil, sandboxes, and parks for years. Pets pick them up on their paws or fur during walks and swallow them while grooming.
  • Hunting & Prey: Cats and dogs that catch small rodents (like mice, rats, or birds) or eat infected earthworms can ingest roundworm larvae hidden in the prey's tissues.

Preventative tips and behaviour

  • Regular Routine Deworming & Screening: Maintain a consistent, vet-recommended schedule combining regular faecal testing with appropriate deworming, especially for puppies, kittens, and nursing mothers, who require more frequent monitoring and care.
  • Discourage Hunting & Scavenging: Monitor outdoor activities to limit hunting of rodents or birds, and dispose of any prey your cat brings home safely and hygienically.
  • Safe Feeding Habits: Avoid feeding raw meat that has not been properly frozen or processed, as raw diets can harbour active parasite larvae.
  • Clean Up Swiftly: Pick up dog waste immediately on walks and scoop cat litter trays daily to prevent roundworm eggs from maturing and contaminating the soil or home environment.
  • Good Home Hygiene: Always wash your hands thoroughly with soap and water after cleaning up pet waste, gardening, or handling your pets, and cover outdoor children's sandboxes when not in use.
  • Keep an Eye Out: Watch for signs of roundworm infection, such as a dull coat, pot-bellied appearance in young pets, weight loss, or visible spaghetti-like worms in vomit or stool.

Microscopic roundworm eggs (Toxocara) passed in pet waste can infect humans if accidentally ingested via unwashed hands or contaminated soil. In rare cases, this can lead to Toxocariasis, causing health complications or vision issues, making strict hygiene and routine pet deworming vital for family health.

Tapeworm

Tapeworms are long, flat parasites that live inside your pet's small intestine. They are made up of small segments that break off as they mature. You might notice these segments, which look like tiny, white grains of rice, around your pet's rear end, near their tail, in their bedding, or in their poo.

Pets cannot contract tapeworms directly from another dog or cat. Instead, they must ingest an "intermediate host" that is carrying the parasite's larvae, most commonly an infected flea or a hunted animal.

How your pet gets tapeworm

  • Fleas (The most common cause): Flea larvae can ingest tapeworm eggs. When your dog or cat grooms themselves and swallows an infected adult flea, the tapeworm develops inside their gut. Because cats are naturally meticulous groomers, they are particularly prone to flea tapeworm.
  • Hunting & Scavenging: Cats and dogs that hunt small rodents (like mice and rats) or scavenge on raw meat, offal, or carcasses from sheep and farm animals can easily pick up tapeworm species.

Preventative tips and behaviour

  • Combined Flea & Worm Control: If your pet has fleas, always assume they are at risk for tapeworm.
  • Discourage Hunting & Scavenging: Prevent your dog from eating wild carcasses or raw offal on walks, and dispose of any prey your cat brings home safely and hygienically.
  • Safe Feeding Habits: If you feed your dog or cat a raw diet, ensure the meat is commercially processed and pre-frozen to destroy potential parasite larvae.
  • Clean Up Swiftly: Pick up dog waste immediately on walks and clean cat litter trays daily to stop tapeworm segments from spreading into the environment.
  • Good Home Hygiene: Always wash your hands thoroughly after picking up poo, cleaning litter trays, or handling your pets.
  • Keep an Eye Out: Check your pet's fur, rear end, and bedding regularly for rice-like segments.

While rare in cats, dogs that scavenge farm carcasses or raw offal can carry the Hydatid tapeworm (Echinococcus). Poor hygiene around an infected dog can allow eggs to pass to humans, where they can form serious, fluid-filled cysts.

Lungworm

Lungworm (Angiostrongylus vasorum) is a potentially life-threatening parasite that primarily affects dogs and foxes. Unlike intestinal worms, lungworms travel through a dog's bloodstream to live in the heart and major blood vessels supplying the lungs. While lungworm infection is exceptionally rare in cats, who are susceptible to a different, generally milder species, it poses a severe health hazard to dogs.

Lungworm is a dangerous parasite because it causes severe respiratory damage, heart failure, and life-threatening blood clotting disorders, which can lead to sudden, uncontrolled internal bleeding. Once considered restricted to specific regional hotspots in the South of England and Wales, lungworm has rapidly spread geographically across large parts of the UK.

How your dog gets lungworm

  • Slugs, Snails, and Frogs: Lungworm larvae are carried by slugs, snails, and frogs. Dogs become infected when they intentionally or accidentally swallow these garden pests.
  • Chewing Grass & Contaminated Foliage: Small slugs and snails often hide on blades of grass. When dogs chew on grass in the garden or on walks, they can easily ingest these tiny pests or their infectious slime trails without you ever noticing.
  • Contaminated Toys & Water Bowls: Slugs and snails leave microscopic larvae in their slime trails. If a slug crawls over a dog's outdoor toy, stick, or water bowl, your dog can ingest larvae while playing or drinking outside.
  • Foxes in the Environment: Foxes act as natural reservoirs for lungworm. As infected foxes travel through gardens and parks, they pass larvae in their poo, spreading the parasite into local green spaces where slugs and snails feed.

Preventative tips and behaviour

  • Routine Faecal Screening: Your vet can test your dog's faeces using specialised laboratory methods to screen for microscopic lungworm larvae, helping detect hidden infections early before clinical signs or tissue damage occur.
  • Targeted Preventative Care: Not all standard off-the-shelf wormers cover lungworm. Ensure your dog is on a specific, vet-recommended preventative plan tailored to your local risk and individual lifestyle.
  • Discourage Grass Eating & Pica: Keep an eye on your dog on walks and in damp gardens to prevent them from chewing grass, soil, or garden pests where hidden slugs and snails thrive.
  • Tidy Outdoor Toys & Bowls: Bring dog toys, chew bones, and water dishes inside overnight so slugs and snails cannot crawl over them and leave infectious slime trails behind.
  • Clean Up Swiftly: Pick up your dog's waste immediately on walks and in the garden to prevent larvae from re-entering the environment and infecting local wildlife or other pets.
  • Keep an Eye Out: Watch for warning signs such as a persistent cough, tiring easily during exercise, unexplained bruising, pale gums, or nosebleeds, and contact your vet immediately if noticed.