Signs of Parasites in Dogs and Cats
Parasites are one of those problems that can build up quietly. A pet can be carrying fleas, worms, or mites for a while before anything looks obviously wrong, and by the time symptoms are visible, the infestation is often more established than it would have been if caught early. Knowing what to actually look for — not just "scratching a lot" — makes a real difference in catching these early.
Here's a breakdown of the most common parasites in dogs and cats, the specific signs each one causes, and when it's time to call your vet.
External Parasites
Fleas
The most common external parasite by far, and one that can affect indoor-only pets too — fleas hitch rides in on shoes, clothing, or other animals.
Signs to watch for: frequent scratching or biting at the skin, small dark specks in the fur that turn reddish-brown when placed on a wet paper towel (flea dirt, which is digested blood), visible small fast-moving insects especially near the base of the tail, hair loss or scabbing from repeated scratching, and in cats especially, small crusty bumps along the back known as miliary dermatitis.
Why it matters beyond the itching: fleas can transmit tapeworms and, in large numbers, cause anemia — especially dangerous in kittens and puppies.
Ticks
More common in pets with outdoor access, especially in wooded or grassy areas, but can also be brought inside on clothing or other pets.
Signs to watch for: a visible tick attached to the skin (often found around the ears, neck, or between toes during a physical check), a small bump or scab where a tick was recently attached, and in more advanced cases, symptoms of tick-borne illness like lethargy, joint swelling, or fever appearing days to weeks after a bite.
Prevention tip: a thorough hands-on check after time outdoors in tick-prone areas is one of the simplest, most effective habits — ticks generally need time attached to transmit disease, so early removal matters.
Ear Mites
Highly contagious between pets in the same household, and more common in cats than dogs, though both can be affected.
Signs to watch for: intense ear scratching or head shaking, a dark, coffee-ground-like discharge inside the ear, a strong odor from the ears, and visible redness or irritation inside the ear canal.
Internal Parasites (Intestinal Worms)
Roundworms
One of the most common intestinal parasites, especially in puppies and kittens, who are often infected before or shortly after birth from their mother.
Signs to watch for: a visibly bloated or "pot-bellied" appearance (especially noticeable in young animals), poor growth or weight gain despite a normal appetite, vomiting (sometimes with visible worms, which look like spaghetti strands), and diarrhea.
Tapeworms
Usually acquired from ingesting fleas during grooming, or from eating infected prey in cats with outdoor access.
Signs to watch for: small, rice-like segments visible around the anus or in bedding (these are actual tapeworm segments, and are often the first sign owners notice), scooting or excessive licking at the anal area, and sometimes mild weight loss despite normal eating.
Hookworms
These parasites feed on blood in the intestinal lining, making them particularly dangerous for young or small animals.
Signs to watch for: dark, tarry stool (a sign of digested blood), pale gums from anemia, weakness, and poor growth in puppies and kittens.
Whipworms
More common in dogs than cats, and can be trickier to detect since eggs aren't always shed consistently in every stool sample.
Signs to watch for: chronic, intermittent diarrhea (sometimes with blood or mucus), weight loss, and general poor condition despite normal appetite.
Heartworm (Dogs Especially, Cats Too)
Transmitted exclusively through mosquito bites, heartworm is one of the more serious parasites on this list because by the time symptoms appear, real damage may already be underway. It's far more common — and more severe — in dogs, but cats can be affected too, sometimes with fewer treatment options available.
Signs to watch for: a persistent mild cough, fatigue after moderate activity, reduced appetite and weight loss, and in advanced cases, difficulty breathing or a swollen belly from fluid buildup.
Why prevention matters more than treatment here: heartworm is far easier and safer to prevent with a monthly preventative than to treat once established — by the time visible symptoms show up, the infection has often been present for months.
Giardia
A microscopic intestinal parasite often picked up from contaminated water sources, and common enough that many pets encounter it at some point, especially those with regular outdoor or dog-park access.
Signs to watch for: soft, greasy-looking diarrhea, sometimes with a notably strong odor, occasional vomiting, and weight loss with chronic cases.
General Signs That Apply Across Multiple Parasite Types
- Changes in coat condition — dull, dry, or thinning fur can be a sign of an underlying parasite burden affecting nutrient absorption
- Excessive scooting or licking — often tied to anal irritation from tapeworm segments or general discomfort
- Unexplained weight loss despite normal or increased appetite — a classic sign that something is consuming nutrients before your pet can absorb them
- Visible worms or segments in stool, vomit, or bedding — always worth a vet visit even if your pet otherwise seems fine
- Lethargy or general low energy without an obvious cause
Prevention Is Far Easier Than Treatment
Most parasites on this list are preventable with routine care:
- Monthly flea, tick, and heartworm preventatives — prescribed by your vet and matched to your pet's specific risk factors
- Regular fecal exams at annual or biannual checkups, which can catch parasites before symptoms even appear
- Prompt deworming for puppies and kittens, since they're born with or quickly exposed to certain intestinal parasites
- Clean, dry bedding and regular grooming to catch fleas or ticks early
When to Call the Vet
Any visible worms, worm segments, or fleas warrant a call to your vet, even if your pet seems otherwise fine — parasites are far easier to treat early. Contact your vet promptly if you notice diarrhea lasting more than a day or two, blood in stool, pale gums, a persistent cough, or any of the general signs above lasting more than a couple of days.
About Pawmingos
At Pawmingos, we're building something for dog and cat people — by dog and cat people. We started with mini brick building sets shaped like your favorite dog breeds (yes, you can build a tiny Husky. Yes, it's as good as it sounds). But this blog is here for something broader: a real community space where pet owners can find honest, useful guidance about caring for the companions they love.
Because whether you're snapping bricks together or making memories with your furry companion, what drives you is the same thing — you love your pet.
That belief also shapes how we do business. With every purchase, a portion of our profits is donated to registered animal shelters and legitimate pet rescue organizations around the world, helping provide care, food, and second chances to animals still waiting for a loving home.
We'll keep creating products that bring joy, publishing content that treats you like the smart, caring owner you are, and supporting organizations that make a real difference for pets in need.
→ Visit us at pawmingos.com
👉 Explore the Pawmingos Collection — build a companion, and help a real one find home.
Frequently Asked Questions
Can indoor-only pets get parasites?
Yes — fleas and some intestinal parasites can enter a home on shoes, clothing, or other pets, and mosquitoes (which transmit heartworm) can get indoors too. Indoor pets are at lower risk overall, but not risk-free.
How often should I deworm my pet?
Puppies and kittens typically need a deworming schedule starting at a few weeks old, with follow-ups through their first several months. Adult pets are usually dewormed as needed based on fecal exam results at routine vet visits, rather than on a fixed schedule.
Is heartworm treatable once my pet has it?
In dogs, treatment exists but is intensive, costly, and carries real risks — which is exactly why monthly prevention is so strongly recommended. In cats, treatment options are more limited, making prevention even more important.
Can I see intestinal worms without a microscope?
Sometimes — tapeworm segments (small rice-like pieces) and roundworms (spaghetti-like strands in vomit or stool) can be visible to the naked eye. Other parasites, like whipworms and giardia, typically require a vet's fecal exam to detect.
Are parasites contagious between pets in the same household?
Many are, especially fleas, ear mites, and some intestinal parasites. If one pet in the household is diagnosed, it's worth discussing with your vet whether the others should be checked or treated too.
Sources: American Veterinary Medical Association (AVMA), American Heartworm Society, Companion Animal Parasite Council (CAPC), ASPCA.