Parasites in Veterinary Practice: Ectoparasites vs Endoparasites ✨

arasites are something we talk about all the time in veterinary practice, but they can feel really overwhelming when you first start learning them.

There are fleas, mites, lice, worms, protozoa, lungworm, tapeworms — and suddenly it feels like a lot to remember.

A simple way to start is by splitting them into two main groups:

Ectoparasites and endoparasites.

Once you understand where they live and what type of parasite they are, the rest starts to make much more sense.

✨ What are ectoparasites?

Ectoparasites are parasites that live on the outside of the body.

They are usually found on the skin, coat, ears or in the surrounding hair.

Common ectoparasites include:

• Fleas
• Lice
• Mites

These parasites can cause itching, irritation, hair loss, skin inflammation and secondary infections. Some can also spread between animals, so they are important from both a patient care and infection control point of view.

✨ Fleas

Fleas are one of the most common ectoparasites seen in practice.

Examples include:

• Ctenocephalides canis
• Ctenocephalides felis

Fleas can cause:

• Pruritus
• Hair loss
• Flea allergic dermatitis
• Skin irritation
• Anaemia in severe infestations
• Tapeworm transmission

A key point to remember is that fleas are not just found on the patient. Eggs, larvae and pupae can be present in the environment too, which is why environmental treatment is often needed alongside treating the animal.

✨ Lice

Lice are also ectoparasites and tend to be more host-specific.

Examples include:

• Felicola subrostratus
• Trichodectes canis
• Linognathus setosus

Lice may cause:

• Itching
• Dry coat
• Scaling
• Hair loss
• Skin irritation

They are often seen in animals who are young, elderly, unwell, neglected or unable to groom properly.

✨ Mites

Mites are another important ectoparasite group.

Examples include:

• Otodectes cynotis
• Sarcoptes scabiei
• Cheyletiella
• Demodex

Mites can affect different areas depending on the species.

For example:

Otodectes cynotis is commonly associated with ear irritation and dark ear discharge.

Sarcoptes scabiei can cause intense itching and is contagious.

Cheyletiella is sometimes known as “walking dandruff” due to the appearance of moving scale.

Demodex mites can be found in hair follicles and may cause issues when there is overgrowth or an underlying problem.

✨ What are endoparasites?

Endoparasites are parasites that live inside the body.

They may affect the gastrointestinal tract, lungs, heart, blood or other tissues depending on the parasite.

Common endoparasite groups include:

• Nematodes
• Cestodes
• Protozoa

These parasites may cause signs such as vomiting, diarrhoea, weight loss, coughing, poor coat condition, anaemia or general poor health.

Some are also zoonotic, meaning they can pose a risk to humans.

✨ Nematodes

Nematodes are roundworms.

Examples include:

• Toxocara
• Ancylostoma
• Trichuris vulpis
• Dirofilaria immitis
• Lungworms

Nematodes can affect different areas of the body.

Some live in the intestines, while others may affect the lungs or cardiovascular system.

They may cause signs such as:

• Diarrhoea
• Vomiting
• Pot-bellied appearance in young animals
• Weight loss
• Coughing
• Poor growth
• Anaemia in some cases

Regular parasite prevention and faecal testing can help reduce risk, depending on the patient and practice protocol.

✨ Cestodes

Cestodes are tapeworms.

Examples include:

• Dipylidium caninum
• Taenia
• Echinococcus

Tapeworms live in the intestines and are often linked to intermediate hosts.

A common example is Dipylidium caninum, which is associated with fleas.

This is why flea control is important when managing some tapeworm infections.

Tapeworms may cause:

• Visible segments around the anus or in faeces
• Scooting
• Mild gastrointestinal signs
• Weight loss in heavy burdens

Some cestodes, such as Echinococcus, are important because of their zoonotic risk.

✨ Protozoa

✨ Why parasite identification matters

Parasite identification helps guide treatment, prevention and infection control.

It can help answer questions like:

• Is this an ectoparasite or endoparasite?
• Is it contagious?
• Is there zoonotic risk?
• Does the environment need treating?
• Are other animals in the household at risk?
• Is routine parasite prevention enough, or is specific treatment needed?

This is why it is helpful for nurses to feel confident recognising the main parasite groups.

✨ The nurse's role in parasite cases

Veterinary nurses are often involved in parasite prevention, client education and sample handling.

This might include:

• Discussing parasite prevention with clients
• Checking treatment history
• Collecting faecal samples
• Preparing skin or coat samples
• Performing basic parasite identification
• Supporting infection control
• Cleaning kennels and equipment appropriately
• Advising clients under practice guidance

Parasite control is not just about treating the patient in front of us. It is also about reducing reinfection, protecting other animals and managing environmental contamination.

✨ Key takeaways

• Ectoparasites live on the outside of the body
• Endoparasites live inside the body
• Fleas, lice and mites are common ectoparasites
• Nematodes are roundworms
• Cestodes are tapeworms
• Protozoa are single-celled organisms
• Some parasites are zoonotic
• Nurses play an important role in prevention, education and infection control

✨ Want to learn about parasites in a simpler way? ✨

If you’re studying parasites and want everything broken down into clear, student-friendly sections, my Parasites Guide (+ poster) goes through the key topics in a simple, visual way.

It’s designed to help student veterinary nurses understand the basics without feeling overwhelmed — perfect for revision, placement support or building confidence with parasitology topics.

You can find the guide here:
https://thatvetnurselife.co.uk/products/parasite-study-28pp-guide-student-veterinary-nurse-pocket-a6-booklet?_pos=3&_psq=parasite&_psid=3c356a7a0&_ss=e

 

Thank you, Jade x