Toxocariasis is common in kittens and adult cats and is usually not life-threatening. Diagnosis and treatment are straightforward, but the infection can spread to people, and infective eggs are difficult to remove once they contaminate the environment. 

Toxocara cati is a parasitic roundworm (ascarid) that infects cats. Some infected cats show no signs, but the worm can cause serious illness in cats and sometimes disease in people. Because its eggs can survive in the environment for years, it is widely recommended that cats should be wormed routinely throughout their lives. 

Toxocara leonina is another roundworm that can infect cats, but it is less likely to cause disease than Toxocara cati and cannot infect people. 

What are the signs of Toxocara cati? 

Kittens with intestinal worms may develop a typical ‘potbelly’, especially in a heavy infestation. Some infected cats show few signs, but worms can still affect their health. Adult worms can reach 10cm and live in the small intestine, where they may interfere with digestion and growth. 

Severe infections in kittens or cats may cause: 

  • Variable or complete lack of appetite  
  • Vomiting (especially after feeding)  
  • Diarrhoea, alternating with constipation.  
  • Poor growth and thin body condition  

Cats may also pass large numbers of live worms in vomit. Adult cats often have milder signs, but severe infections can cause gastrointestinal irritation, including vomiting, diarrhoea, and weight loss. 

What causes Toxocara cati in cats? 

Toxocara cati can pass from queens to kittens through milk. Cats may also become infected by swallowing eggs from the environment or by eating an infected intermediate host, such as a rodent or bird. 

When to contact your veterinary team 

Contact your veterinary team if you think your cat may have worms, if they show any of the signs listed above, or if you would like advice on routine preventative care. 

How your vet diagnoses Toxocara cati 

Your vet may suspect Toxocara cati from your cat’s signs and worming history. They may confirm the diagnosis by examining a faecal sample under a microscope for worm eggs. Sometimes, worms are visible in vomit or faeces. 

As part of routine preventative healthcare, cats should receive regular worming treatment throughout the year, in accordance with their risk status. 

How is Toxocara cati treated and prevented? 

Several products can treat and prevent worm infections in cats, including spot-ons, tablets and liquids. If your cat is diagnosed with Toxocara cati, your vet will prescribe a suitable treatment. 

Ongoing care 

Routine faecal testing or treatment for roundworms should continue throughout a cat’s life, based on their risk of infection. 

Are people at risk from Toxocara cati? 

Toxocara canis, the dog roundworm, causes most human toxocariasis cases, but Toxocara cati can also infect people and may be an under-recognised cause of disease. 

People are usually infected by swallowing eggs from contaminated soil, sand, or food. Infection can also follow eating raw or undercooked meat from intermediate hosts, such as chickens or cattle. In people and animals, Toxocara species do not become adult worms; signs are caused by migrating larvae. Disease severity depends on: 

  • The extent of tissue damage 
  • The affected tissue 
  • The number of migrating larvae 
  • The person’s age. 
  • The person’s immune response 

Visceral larva migrans (VLM) 

Children, especially toddlers, are at higher risk of VLM because they are more likely to have close contact with areas that may contain Toxocara eggs, including sandpits, sandboxes, gardens, and playgrounds. 

Signs of VLM in children may include: 

  • Fever or an elevated temperature 
  • Feeling unwell, tired, or lethargic 
  • Abdominal pain 

The infection can affect the liver, lungs, heart, and central nervous system, causing signs linked to the organs involved. 

Ocular larva migrans (OLM) 

OLM can occur at any age but is more common in children aged 5 to 10 years. Its main sign is impaired vision, which can progress to complete sight loss. Other signs include seeing lights, squinting, and glaucoma caused by increased pressure inside the eye. 

To help prevent human infection, cover sandpits so cats cannot use them as litter trays, wash hands regularly, wash vegetables, and follow healthy food hygiene, including thorough cooking. 

Best wormers for cats 

Cat worming products include tablets, liquids, pastes, and spot-on treatments. Choose a product that treats both tapeworms and roundworms and is practical to give, such as a spot-on, liquid or paste if your cat will not take tablets. 

Prescription wormers 

  • Where possible, use a prescription worming treatment supplied by your vet. 
  • If your cat is healthy and has been seen recently, your veterinary practice may be able to dispense worming treatment without another appointment. They will need your cat’s current weight to provide the correct dose. 
  • If your cat has not been examined recently, book an appointment with a veterinary surgeon. 

Non-prescription wormers 

  • Many wormers are available without a prescription, but their quality and suitability vary, so it is important to choose carefully. 
  • Off-the-shelf products sold without advice or questions about your cat are often less reliable than NFA-VPS products. NFA-VPS products must be sold by a suitably qualified person, are kept in secure storage, and require information such as your cat’s weight before purchase. 

Other risks 

Cats that hunt have a higher risk of infection because prey animals, including rabbits and rodents, can carry several types of roundworms and tapeworms. 

Lungworm is an increasing concern in the UK, and cats can become infected by eating slugs or snails. If lungworm is common in your area, ask your vet about prevention and treatment options. Established infections need careful management because adult lungworms live in the heart, and a single dose of a non-prescription wormer will not prevent infection. 

Adult cats may encounter many different worms, and their worming schedule should reflect their lifestyle. Indoor cats with limited outdoor access and little contact with wildlife usually need worming every three months, provided flea control is also maintained. 
 
Cats that spend time outdoors, hunt regularly or scavenge in the garden are more likely to need monthly worming alongside routine flea treatment. 

How do I treat my cat for worms? 

With so many worming products available, choosing the right one can be difficult. Although many are sold in pet shops and supermarkets, they may not be the best option for your cat. Your veterinary team can advise on the worms found locally and recommend a safe, effective treatment. 

Worming products come as tablets, liquids, and spot-ons. The best choice depends on how easily you can medicate your cat, and which worms the product treats.