Pet Parasites – Treatment and Prevention

Parasites can pose a risk to both animal and human health. In last week’s article we discussed what parasites are and how they can affect our pets. Here, we look into treating parasites in dogs and cats, and how to prevent parasites becoming a problem in the first place!

How do we treat animals for parasites?

pet parasites

Which parasitic treatment to use should be discussed with your vet

Treatment for parasites is often the same, regardless of the type of parasite, mainly depending on whether the parasite lives inside (endoparasite) or on the outside (ectoparasite) of the affected pet.

Some medication is designed to spread within the skin and also into the blood to kill both internal and external parasites. Others only kill specific parasites inside the guts, and shampoos only kill certain parasites on the skin. Which one to use should be discussed with your vet and should aim to target the parasite in question, as well as take into account any other diseases at that time, your animal’s situation or their risk, such as his/her living environment (e.g. livestock farms), raw meat feeding, exercising/walking area (lots of dogs and cats) and any in-contact humans (such as HIV patients).

Medications often only affect/kill adult parasites, so may need to be repeated to deal with remaining larvae or hatching eggs as they mature (e.g. at 2-4 week intervals). How often and when or how to treat is very variable, sometimes relating to actual disease, but also being used to prevent disease and stop parasites infecting ‘at risk’ animals. This should always be discussed with your vet and should incorporate factors as outlined above, including the animal’s age, known habits such as hunting, scavenging or whether an animal is only housed indoors or in kennels. There is no single regime that is appropriate or applicable to all companion animals and pets.

Are parasites a problem for pet owners?

Since contact between humans and companion animals has become very close, many parasites can also affect or infect pet owners, coming directly from the animal, but also often from the (contaminated) environment, such as soil, or eating affected/contaminated meat which is eaten raw or poorly prepared/cooked. Other animals such as foxes can also be significant sources. Eggs in the environment are initially not a hazard, but after a few weeks become infectious and can survive for months and possibly for years, acting as a potential source for people. Parasitic eggs are often very resistant and not killed by many common household disinfectants.

It is very important to worm your dog or cat regularly. Humans, including young children, can be severely affected by roundworm larvae..

It is very important to worm your dog or cat regularly. Humans, including young children, can be severely affected by roundworm larvae.

Again, the exact source of any infection is often unclear and the number of infections generally seems very low, in part due to regular preventative treatment of animals by caring, responsible owners. Since 2000, between 1 and 8 newly diagnosed cases of human Toxocarosis have been reported annually, with infections occurring in all age groups. So called zoonotic infection is generally thought rare in this country, but its effects can be very severe in some cases, as the parasitic larvae damage specific tissues, such as the eyes and brain in some people.

Migration of roundworm larvae through human tissues, most often in young children between 2-4 years old, is called “visceral larva migrans” while migration to the eyes is called “ocular larva migrans.” These describe the major tissue affected, but the migration and effects are variable and can be without any external symptoms.

Transmitted disease symptoms or signs can include: weakness, blindness, miscarriage/abortion, fitting, anaemia, itchy skin ‘blistering’ or rash, vomiting, diarrhoea. These signs though can be produced by many very different diseases or infections, checking with a doctor being strongly advised if you are affected by these.

General methods for parasite prevention


  • Always pick up your dog’s or cat’s faeces using a disposable glove or dedicated bags and place in the correct waste bin.
  • When cleaning litter trays, always wear gloves and place the litter with the faeces/urine in a disposable bag into the correct waste bin.
  • Clean the litter tray with clean hot water and then disinfect as required using dedicated cleaners/brushes, all away from food preparation surfaces and kitchen sinks.
  • Minimise soil/outdoor contamination for others by training dogs to go to the toilet in certain areas.
  • Prevent cats using vegetable patches or compost as toilet areas by using ‘barriers’ such as meshes or pebble stones and cover children’s play areas and sand pits.
  • Where possible, minimise dogs eating anything other than their known pet food, especially soil, snails, rodents, rotting food/wind fall. Cats are much harder as they are usually free roaming and also more often out hunting rodents and birds.
  • Always wash your hands after touching animals, food bowls and handling litter trays or faecal bags.
  • Wear gloves when gardening and wash hands thoroughly once finished.
  • Puppies and kittens with children in families – supervised thorough hand washing due to higher risk of heavy infections (in the puppy/kitten) and children learning about hygiene, as well as putting ‘hands in mouths’ more often!
  • Inspect animals for ticks daily and remove any ticks found.
  • Flea treatment should always target both the animal and also the house to prevent a build-up of eggs that hatch out, even over the winter as the central heating is on.
WARNING: highly concentrated synthetic pyrethroids or amidines in some flea treatments (especially those made for dogs only) are harmful to cats. Always read the label and/or check with your vet before using any flea treatment.