A parasite is an organism that gains its nutrients from another host.

An endoparasite is an organism that lives inside the host e.g., worms.

An ectoparasite is an organism that lives outside of the host e.g., fleas and ticks.


  • The cat flea (Ctenocephalides felis) affects dogs, cats, rabbits and ferrets (Figure 1).
  • Because fleas have a two-stage lifecycle both the animal and the environment need to be treated.
  • Puppies and kittens can be treated from 8 weeks of age.
  • Many products treat fleas or a combination of fleas and worms.
  • Spot on treatments are great for owner compliance.
  • Sprays are usually used for the environment as well as mechanical treatment such as vacuuming.


  • Biting louse (Trichodectes canis) (Figure 2) and sucking louse (Linognathus setosus) both affect dogs and the sucking louse (Felicola subrostratus) affects cats.
  • Usually found on animals that are kept in unhygienic conditions, but less of an issue than fleas.
  • Some topical treatments are available as well as owners washing bedding regularly.


  • Usually affect rabbits in warm conditions, but can affect other species too.
  • Flies lay eggs and larvae/maggots hatch out.
  • They can cause a lot of skin damage and sometimes secondary infection.
  • To try and prevent this from happening in rabbits a topical treatment can be applied to their rear which lasts approximately 10 weeks.


  • Commonly found in grassy areas, heathland or woodland as well as where sheep and deer graze.
  • Ticks should be removed a soon as they are found using a specialist tick hook (Figure 3).
  • If an animal is infested with ticks then they are susceptible to contracting Lyme’s disease and Babesiosis.
  • Many products are available for tick prevention, some are combined with flea control.
  • However, no product will stop ticks from physically attaching (Figure 4).

Figure 1. Ctenocephalides felis.


Figure 2. Trichodectes canis.


Figure 3. Tick removal using a hook.


Figure 4. Well fed tick.


  • Mange is a skin disease caused by mites.
  • Sarcoptic mange (canine scabies) is the most common form and it is very contagious (Figure 5).

Figure 5. Sarcoptic mange.

  • Dogs tend to pick the mite up from the environment including wildlife such as foxes.
  • Humans can also develop sarcoptic mange but the life cycle cannot be completed on us so it is usually short lived.
  • The other type of mange is Demodectic mange which is less common and passed from a mother to her puppies.
  • Some breeds of dog are more susceptible to it than others.
  • There are other mites such as harvest mites, ear mites and Cheyletiella (known as walking dandruff).
  • Treatments vary from spot on treatments to shampoos.


  • The most common worms in dogs and cats are Roundworm (e.g. Toxocara canis), Tapeworm (e.g. Dipylidium caninum) (Figure 6), Heartworm (e.g. Diroflaria immitis) (Figure 7), Hookworm, (e.g. Ancylostoma caninum) (Figure 8) Whipworm, (e.g. Trichuris vulpis), and Lungworm (e.g. Angiostro­ngylus vasorum).

Figure 6. Tapeworm in the digestive tract.

Figure 7. Heartworm Dirofilaria immitis.

Figure 8. Hookworm.

  • Worming protocols for kittens and puppies can start as young as 2 weeks of age.
  • They should then be wormed with an age-appropriate wormer (anthelmintic) every 2 weeks until they are 12 weeks of age.
  • At 12 weeks of age until 6 months of age they are wormed monthly.
  • After that, worm every 3 months (but always follow manufacturer’s instruct­ions).
  • Wormers can come in a variety of formulations: granules, liquids, syringeable paste, tablets and chewable tablets.
  • Pregnant bitches should be wormed at 42 days gestation, ideally with a fenbendazole wormer.
  • This is to try and decrease the number of roundworms that can be passed on to the puppies.

Additional information

Notes on contributors


Jayne qualified from Hartpury College (University of the West of England) with BSc (Hons) in Veterinary Nursing Science in 2006. Having previously started in practice in 1996 as a kennel assistant. She has worked in all types of veterinary practice including busy out of hours hospitals and equine practice.
She lectured at a college for 6.5 years and more recently moved to the role of Sales Manager for Invicta Animal Health which she thoroughly enjoys. It allows her to share her passion of surgical nursing with vet teams across the country, improving standards of practice with an evidence-based approach.

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