Worms are internal parasites that live mainly in a dog's intestines, and the honest general truth is that many worm infections produce no outward signs at all — which is exactly why routine prevention and stool checks exist. When signs do appear, they tend to be gradual and nonspecific: a dog who is eating well but not holding weight, a coat that has lost its gloss, digestion that is intermittently off without an obvious dietary cause. Puppies, who can acquire some worms very early in life and have small reserves, show effects sooner and more clearly than healthy adults.
The visible evidence in stool and around the tail
Sometimes you get direct proof. Long, pale, spaghetti-like worms may appear in stool or, in heavier burdens, in vomit, particularly in puppies. Another common finding is small, flat, white or cream segments resembling grains of rice, seen in fresh stool, dried around the rear, or stuck to bedding where he sleeps; these come from a type of worm linked to swallowing fleas during grooming. More often, though, there is nothing to see: several common intestinal worms and their eggs are effectively invisible without a laboratory stool examination, so a clean-looking stool does not clear a dog, and that is worth remembering before you rely on inspection alone.
Body changes that can accompany a worm burden
A puppy with a significant burden often develops a characteristic look: thin over the ribs and spine yet with a rounded, pot-bellied abdomen, growing more slowly than littermates. In dogs of any age, look for weight loss or failure to gain despite a normal or even increased appetite, a dry and dull coat, intermittent soft stool or diarrhea, occasional vomiting, and reduced energy or stamina on walks. Scooting along the ground and licking or chewing under the tail are often blamed on worms; they can accompany them, but glands, irritation, and skin problems cause the same behavior, so scooting alone does not prove worms are present.
Signs that suggest the burden is affecting him seriously
A heavy burden, especially in a puppy or a small, old, or already unwell dog, can move beyond subtle signs. Marked weight loss, persistent diarrhea, blood or mucus in the stool, pale gums, weakness, a swollen painful abdomen, or a puppy who is failing to thrive all warrant a prompt veterinary visit rather than a wait-and-see approach. Some parasites of dogs also have implications beyond the intestines, and a few can affect people in the household, particularly young children — one more reason a suspected burden belongs in a veterinarian's hands, where a stool test can identify what is actually there and what it needs.
Prevention, testing, and why dates matter
Because signs are unreliable, parasite control runs on schedule rather than symptoms: regular preventive treatment as your veterinarian advises for your dog's age, lifestyle, and region, prompt removal of stool from the yard, flea control to cut off the rice-segment worm's route in, and periodic stool testing — routinely for puppies and at least periodically for adults, and whenever unexplained digestive or weight signs appear. Bring a fresh stool sample to the appointment when worms are suspected; it is the single most useful thing you can contribute. Never borrow another dog's treatment or guess at a product for a puppy by size; the right choice depends on which parasite, his age, and his weight, and that is a veterinary decision.
Keeping his parasite history in one place
Whether a dog is genuinely protected depends on a chain of dates: when he was last treated, with what, when his last stool test was done and what it showed, and when the next step is due. Those details scatter easily across receipts and memory. Recording prevention dates, stool results, and any episodes of visible worms in KinsLe's Pet Passport — his portable health packet — keeps that chain intact, so any veterinarian can see at once whether he is covered, overdue, or due for a test.