Nematode Infection

Nematode is just the scientific word for roundworm, a large family of parasitic worms with a round, tube-shaped body. It isn't one single parasite: the group covers several worms you might already know by name, from intestinal roundworms, hookworms and whipworms through to the more serious heartworm and lungworm, which travel beyond the gut into the lungs, heart or blood vessels. These worms are genuinely common. Recent estimates put roughly one in nine dogs and around one in six cats as carrying the common intestinal roundworm Toxocara at any given time, which is one reason routine deworming matters even in pets that seem perfectly well.

Pets typically pick up nematodes by swallowing eggs or larvae left in soil, grass or another animal's droppings, or by eating an infected prey animal or contaminated meat. Puppies have extra routes in: roundworm larvae can cross the placenta before birth, and hookworm larvae in particular can pass through a mother's milk, so even very young puppies can already be carrying a heavy worm burden before they've set a paw outside.

What an infection looks like depends heavily on which worm is involved and how many are present. Plenty of infected pets show nothing obvious at all, especially with light burdens, which is why routine deworming and faecal checks matter rather than waiting for symptoms. When signs do show up, they can include:

• Diarrhoea, sometimes with blood
• Vomiting
• Weight loss, or slow growth in a young puppy or kitten
• Pale gums from blood loss, particularly with hookworms
• Coughing or breathing trouble, which points more toward lungworm or heartworm than gut worms

Whipworms are notoriously hard to catch on a single stool sample, because the adult worms shed eggs only intermittently, so one clean test doesn't reliably rule them out.

A few nematodes, especially the common roundworm Toxocara, can also infect people. Children are most at risk because they're more likely to play in contaminated soil, and public playgrounds have been found to carry infective eggs at meaningful rates. Picking up after your pet promptly and washing hands after gardening or handling soil are simple ways to cut that risk.

Diagnosis is usually straightforward for a vet: a stool sample checked under the microscope, sometimes paired with an antigen test that can pick up infections a standard flotation misses, or a blood test for heartworm. Treatment relies on anthelmintic medication chosen for the specific worm involved, since no single dewormer covers every type equally well. It's also worth knowing that hookworm resistant to several common deworming drug classes has become a widespread problem in dogs in parts of the United States, so if treatment doesn't seem to clear an infection, a follow-up faecal check and a change of drug may be needed rather than simply repeating the same one. Because reinfection from the environment is so easy, most vets recommend an ongoing deworming schedule built around your pet's age, lifestyle and local risk rather than a one-off treatment. If you're ever unsure what your pet's routine should look like, a vet can help build a plan suited to where you live and how your pet spends time outdoors.