Dogs and cats are curious by nature, investigating every corner of the yard, sniffing everything along their path, licking things of interest, and mixing with the neighborhood's other pets. Those natural tendencies mean they innocently expose themselves to all sorts of things, parasites included.
Parasites are common in pets—fleas, ticks, heartworm, and a range of intestinal worms can all do real damage to your pet's health. They live off their host, causing problems that range from mild skin irritation to severe gastrointestinal illness and, in some cases, death. What makes parasites in dogs and cats a broader concern is that several are zoonotic, meaning they can be passed to people—so parasite control protects your household as well as your pet. That's why it's a central part of preventive care for cats and dogs alike.
External Parasites in Pets
External parasites include fleas, ticks, lice, mites, and ear mites, and they're a good deal more than a nuisance.
Fleas cause intense itching, and many pets develop flea allergy dermatitis, where a single bite triggers a disproportionate reaction. Swallowing an infected flea while grooming is how pets pick up tapeworm, and fleas also carry Bartonella, the bacterium behind cat scratch disease in people. A heavy infestation can cause anemia, which is genuinely dangerous in kittens, puppies, and small or elderly animals.
Ticks transmit a range of diseases including Lyme disease, ehrlichiosis, anaplasmosis, and Rocky Mountain spotted fever. Which of these matter depends a great deal on where you live, so it's worth asking us what's prevalent locally.
Mites cause mange and are intensely itchy. Sarcoptic mange in particular is contagious to people, and ear mites spread readily between pets in the same household—so one affected animal usually means treating everyone.
Internal Parasites in Pets
Internal parasites include roundworms, tapeworms, hookworms, whipworms, and single-celled organisms such as giardia and coccidia. Most live in the intestinal tract, causing discomfort and diarrhea while taking nutrients your pet needs.
They matter most in the young. A significant worm burden in a puppy or kitten affects growth and development, and hookworms can cause anemia serious enough to be fatal in a very young animal. Pets with weakened immune systems are also vulnerable.
Heartworm is in a category of its own. Spread by mosquitoes, it lives in the heart and lungs and can prove fatal even in an otherwise healthy pet. Treatment in dogs is lengthy, expensive, and hard on the animal, and there is no approved treatment at all for cats—which makes year-round prevention the only real answer for both species.
Common signs of internal parasites in pets include:
- Diarrhea, sometimes with mucus
- Blood in the stool
- Vomiting, occasionally with visible worms
- Weight loss, or failure to gain weight in a young animal
- A pot-bellied appearance, particularly in puppies and kittens
- A dull, poor coat
- Abdominal discomfort
- Lethargy or pale gums
- Rice-like segments around the tail or in bedding, which indicate tapeworm
- Scooting or excessive licking under the tail
Many infected pets show no signs at all, though, which is why we recommend a fecal test at least once a year—more often for puppies, kittens, and pets who spend a lot of time outdoors. Heartworm requires a separate blood test, and dogs need one annually even on continuous prevention.
Parasites That Can Affect People
This is worth spelling out, because it's the part most owners don't realize. Roundworm and hookworm eggs pass out in feces and become infective in soil after a period of days, and they can survive there for a long time. People—children in particular—can be infected by contact with contaminated soil or sand, and hookworm larvae can penetrate skin directly through bare feet.
In people, roundworm larvae can migrate through tissue and, rarely, damage the eye or other organs. Children are most at risk simply because they play in the dirt and put their hands in their mouths. This is why picking up feces promptly, washing hands, keeping sandboxes covered, and keeping pets on routine parasite control genuinely protect your family as well as your pet.
Fleas, sarcoptic mange, ringworm, and some tick-borne diseases can also affect people, and cat scratch disease is transmitted by fleas via cats. None of this is cause for alarm—it's a straightforward argument for keeping prevention up to date.
Parasite Prevention in Pets
The good news is that parasites are largely preventable. Between basic hygiene and modern preventive medications, there's a great deal you can do.
Prevent parasites in your pets in the following ways:
- Keep your pet on year-round parasite prevention rather than seasonally—fleas survive indoors through winter, ticks are active whenever it's above freezing, and a lapse of a few weeks leaves a gap
- Wash your hands after handling your pet, cleaning the litter box, or picking up after them
- Groom your pet regularly, which also gives you a chance to spot fleas, ticks, and skin problems early
- Check your dog or cat over after time outdoors, paying attention to the ears, neck, armpits, groin, and between the toes
- Pick up feces daily, since most intestinal parasites are transmitted by eggs or larvae in stool
- Keep sandboxes covered when not in use, and discourage children from playing where pets toilet
- Bring a fresh stool sample to your pet's annual visit for testing, and more often if we've advised it
- Follow the deworming schedule we recommend, which starts in the first weeks of life for puppies and kittens
- Avoid raw meat diets, which carry a risk of parasites and bacterial contamination for your pet and your household
- Don't let your pet drink from puddles, streams, or standing water, which is a common source of giardia
A word on products, though. Please talk to us before buying parasite prevention over the counter. Effectiveness varies considerably, some older over-the-counter products are much less reliable than what we'd dispense, and a few carry real risks—flea and tick products made for dogs can be lethal to cats, and permethrin poisoning in a cat treated with a dog product is one of the more distressing emergencies we deal with. Never use a dog product on a cat, and if you have both in the household, check with us about keeping a freshly treated dog away from your cat.
What your pet needs depends on their species, weight, age, health, and where and how they live, and no single product covers everything. We'll help you work out a combination that makes sense.
Whether external or internal, parasites cause real discomfort and can seriously affect your pet's quality of life—and some of them affect yours too. So your pet can explore freely without picking up unwanted passengers, talk to us about the right preventive plan for them. Contact us if you'd like to discuss parasite prevention for your pet.