Roundworms and hookworms in dogs and cats
Also called Intestinal parasites, deworming
Intestinal worms are common in puppies and kittens. They can cause diarrhoea, a pot belly, poor growth and, with hookworms, dangerous anaemia, and some can infect people.
Cause and spread
- Cause
- Roundworms (Toxocara canis, Toxocara cati, Toxascaris leonina) and hookworms (Ancylostoma and Uncinaria species).
- How it spreads
- By swallowing eggs or larvae from the environment or from other animals, from the mother before birth or in milk, and by eating infected prey.
- People
- Toxocara roundworms can infect people, especially children, so deworm pets and wash hands.
Signs to watch for
- Often none
- Dull coat, pot belly and poor growth in young animals
- Mucus-coated diarrhoea and weight loss
- Hookworms: anaemia, which can be fatal in puppies, and dark, tarry stools
- Cough as larvae migrate through the lungs
Many diseases look alike. Only a laboratory test can tell them apart, so please see a veterinarian for any sick animal.
How it is diagnosed
Diagnosis is by looking for eggs in a faecal sample (flotation); some antigen tests are available. A faecal egg count before treatment and again 14 days later shows whether the dewormer worked: a drop of less than 75% in hookworm eggs suggests drug resistance.
- Usually the first testFaecal FlotationFinds worm eggs in faeces.
- Supports the diagnosisFaecal Examination (Routine)A general look at the faeces.
- Supports the diagnosisComplete Blood Count (CBC)Shows anaemia from hookworms.
- Supports the diagnosisVomiting and Diarrhoea Panel (panel)Blood count with faecal tests for gut upset.
- Follow-up and monitoringFaecal Egg Count (McMaster)Counts eggs; repeated 14 days after treatment to check it worked.
Prevention and control
- Deworm puppies several times in the first 3 months, and treat all dogs and cats preventively, as advised by your veterinarian
- Pick up faeces promptly
- Some monthly heartworm preventives also control hookworms
Where this information comes from
- Roundworms in Small Animals · Merck Veterinary Manual
- Hookworms in Small Animals · Merck Veterinary Manual
General information for animal owners and veterinarians, last checked October 2026. It does not replace the advice of your veterinarian, who should decide which tests and treatment your animal needs.