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The importance of routine parasite control in our pets

By Ian Wright, BVMS, MSc, MRCVS
Head of ESCCAP UK & Ireland, European Scientific Counsel Companion Animal Parasites


Routine preventative parasite treatments are used by millions of cat and dog owners across the UK to help keep their pets and owners safe from parasitic disease. This widespread use has led to questions of whether it is necessary to use preventative treatments in cats and dogs. This is an important question to ask as we don’t want to over treat out pets with any drug that they do not need. In the case of parasite prevention in pets however, these routine treatments are vital to help keep both pet and owner alike safe from a range of parasites lurking inside and outside the body.

Fleas found on UK pets are almost all cat fleas and they can infest a wide range of pets including, cats, dogs, ferrets and rabbits. They live very differently from parasitic mites and lice which spend almost their whole lives on the body of their host. Most of the flea’s life stages live off the pet with adult fleas on pets only representing 5% of the total flea population in your house. The rest are eggs, larvae and pupae in carpets, bedding, furniture and cars. Larvae hatching from eggs which have fallen off the pet live on flea faeces (“flea dirt”) which also falls off the coat. The larvae develop into pupae from which newly formed adult fleas emerge, triggered by the heat and movement of a passing host. People cannot act as hosts for cat fleas but can get bitten with itchy bite reactions then developing. Pets can also react to flea bites, with flea allergic dermatitis being the most common form of skin allergy in cats and dogs. Flea bites can transmit disease to both pets and owners such as feline infectious anaemia and Rikettsia felis. The cause of cat scratch disease, Bartonella henselae can also be transmitted to people through flea faeces accidentally rubbed into the skin. This can lead to chronic illness and can be fatal in the immune suppressed. Preventing flea infestations in the home is therefore vital to keep pets and humans safe from these diseases.

Control of existing flea infestations is a lengthy process as the pupae are nearly impossible to kill. Treating the house, bedding and cars with sprays containing insecticides and growth regulators, as well as daily vacuuming helps to speed up getting rid of an infestation. The most important step, however, is to treat all the pets in the house that might act as hosts with a product that will kill fleas before they lay eggs. If treatment lapses, fleas can start laying eggs again and infestation re-establish, so it is important to treat all cats and dogs routinely often enough with an effective product to prevent infestation. Fleas are often considered to be a seasonal problem, but mild winters and centrally heating allow fleas to survive all year round and thrive in our homes.

Tick prevention

UK ticks have enjoyed a lot of recent media attention with an outbreak of babesiosis in Essex dogs and increasing numbers of Lyme disease. Through attaching and feeding, ticks in the UK are capable of transmitting a range of tick-borne pathogens to cats and dogs including Babesiosis, anaplasmosis and Lyme. Unlike fleas, ticks currently living in the UK do not infest homes but are encountered in grassland, bracken, parks and pasture shared by ruminants and deer. A mild, wet climate, increased forest and green space in combination with an increase in outdoor activity are bringing pets and people into increased proximity to ticks. They are most active from spring until Autumn but can be encountered at any time of year. Increasing our national green spaces and enjoying the great outdoors with our pets are hugely beneficial things and with two simple precautions the risk of tick exposure can be massively reduced.

  • The bulk of tick-borne disease transmission takes at least 24 hours after ticks bite. Dogs and people who have been walking in pasture, tall grass or undergrowth should be checked for ticks at least every 24 hours and any found carefully removed with a tick hook, using a “twist and pull” action. Alternatively, fine tipped tweezers can be used with a “straight pull” action. Government health agencies in the US and UK point out that staying on well maintained paths will provide the best protection but this can be difficult to achieve with dogs enjoying off lead exercise. Squeezing, burning or applying paraffin to ticks will stress them, leading them to empty their salivary glands and regurgitate stomach contents. This increases the likelihood of disease transmission and should be avoided. Cats with outdoor access should also be checked for ticks but this is not always easy!
  • A product that rapidly kills ticks or repels them should be considered for dogs and cats whose lifestyle put them at increased risk of tick exposure. No preventative product is 100% effective however, so it is still important to regularly check pets for ticks.

Worm prevention

Parasitic worms are very common in cats and dogs and can cause serious illness. Some can also cause disease in people, making regular treatment of cats and dogs for worms important both for pet and human health. Three different types of worm are commonly found in cats and dogs; Roundworm, lungworm and tapeworm.


Toxocara roundworms are common intestinal parasites of cats and dogs, particularly puppies and kittens. Almost all puppies and kittens are infected by their mums at birth (puppies) or shortly afterwards via the milk (puppies and kittens). At 6 months of age, many of these worms are naturally eliminated but infection is topped up though the cat or dog’s life through ingesting Toxocara eggs passed in the faeces or eating small animals that have already eaten the eggs such as birds or rodents. Some worms hide from the body’s immune system in organs and tissues and then reactivate throughout the cat and dog’s life, so even indoor pets may be infected.

Infected pets are rarely ill although large worm burdens can cause diarrhoea or coughs. The eggs passed in the faeces however, can infect people if they are accidentally ingested after maturing in sand or soil. The eggs are sticky and can contaminate fruit, vegetables, gardening equipment and outdoor toys. The most well known health problem it can cause in people, is when larval worms migrate to the eye (ocular larval migrans). While many people exposed to the parasite have no ill effects, the migration of worm larvae through the body is linked to a variety of health problems including headaches, lethargy, abdominal pain, learning difficulties and asthma. Although the consequences of infection (toxocarosis) can be serious, a few simple precautions, “the 5 pillars of toxcoarosis control”, will massively reduce the risk of exposure.

  1. Regular treatment of cats and dogs for worms– Treatment for worms should start at 2 weeks of age for puppies and 3 weeks of age for kittens. Treatment should be repeated every 2 weeks until 2 weeks after weaning, and then every month until 6 months old. The mum should also be treated at the same time. Adult cats and dogs should be treated at least every 3 months to reduce egg shedding. Some pets such as those living with young children or immune suppressed adults, those that hunt or are on raw diets should be treated monthly. This will almost entirely eliminate egg shedding. This is important, as once shed, eggs can last for years in the environment and survive composting.
  2. Picking up and responsibly disposing of dog faeces – This reduces environmental egg contamination and is an important part of responsible dog ownership.
  3. Thorough washing of fruit and vegetables – Cats are particularly good at contaminating home grown fruit and veg by defecating on them. By burying their faeces, cats also inadvertently create perfect conditions for the egg’s survival and development, hidden away from light and dry conditions. It also creates an unpleasant surprise for people playing in a sandpit or digging in the garden! Fruit and veg can be made completely safe for human consumption by thorough washing or cooking.
  4. Good hand hygiene– Washing of hands before eating, after playing with pets and after outdoor activity reduces the risk of many parasites being transferred from hand to mouth.
  5. Covering sandpits – To prevent cats using them as giant litter trays!

Cats and dogs may also carry other intestinal worms such as hookworms and whipworms which can cause weight loss, anaemia and diarrhoea in cats and dogs. By following the 5 pillars, of which regular worm treatment is a key, pets and owners can be kept safe.


There has been a lot of press attention on the television and newspapers over the past few years talking about the risk of infection with the lungworm Angiostrongylus vasorum in dogs. Foxes are the natural host for the parasite and appear to tolerate infection very well. Domestic dogs can also be infected and carry the parasite without being ill but coughs and breathing difficulties commonly occur. The worry for pet owners highlighted in the media is that a small percentage of infected dogs will develop blood clotting complications, neurological signs, or die suddenly.

Dogs become infected mostly through eating slugs, snails and frogs. Some dogs are fascinated by slugs and snails and will eat them deliberately. Others will be eaten accidentally when dogs consume grass or faeces in the garden, bread left out for birds or in water bowls where slugs and snails frequently drown. The parasite is present across the whole country but is very patchy in its distribution, being more common in some places than others. Whether dogs require protection against lungworm depends on where they live and the lifestyle of the pet. Some dog owners live in areas where infection levels are very high and, in these cases, a monthly treatment licensed for lungworm prevention is essential to keep dogs safe. By having a discussion with your vet, you will be able to establish if there have been cases of dogs being infected locally and whether your dog’s lifestyle is putting them at significant risk.


The most common tapeworms seen in cats and dogs are very large (often several meters long!) with white segments seen in the faeces. Taenia tapeworms are the largest with slow moving segments passed in faeces. Dogs are infected through eating raw meat or offal and cats through hunting small mammals. The health of pets is rarely affected by infection but segments crawling around in bedding and furniture can be an unpleasant sight and large numbers can cause weight loss and anal irritation. Cows or sheep eating dog tapeworm eggs from segments in grass or feed contaminated with faeces can develop cysts leading to meat and offal condemnation. This can lead to heavy financial losses for farmers. A small tapeworm of dogs called Echinococcus granulosus is also transmitted the same way and can lead to large hydatid cysts forming in the human body if we accidentally ingest this tapeworm’s eggs. This tapeworm is present in many parts of Wales and the Western Isles of Scotland and is likely to be present in other parts of the UK. Dogs and cats shedding segments should be treated monthly with a product effective against tapeworm, as should dogs on a raw diet or with access to fallen livestock.

The flea tapeworm Dipylidium caninum is another common large tapeworm of cats and dogs that can grow to 50cm in length. It sheds tapeworm segments in the faeces which are the size of a grain of rice and can be fast moving. They are infected through grooming fleas off their coat. People can also rarely be infected if we accidentally ingest bits of flea under our fingernails, in food or from pet saliva if we get a lovely post grooming kiss. Good flea control will reduce the risk of both pets and people being infected.

The human animal bond is a strong and hugely beneficial one and by the use of routine parasite preventative products and simple practical steps, pets and their owners can be kept safe from parasitic disease.