Key takeaways
- Heartworm is spread by mosquitoes and can be fatal — prevention is far easier than treatment.
- Most vets recommend year-round flea, tick and heartworm prevention in many regions.
- Puppies are dewormed every 2 weeks from about 2 weeks of age until 8 weeks, then monthly.
- Some parasites (like roundworms) can infect people, especially children — prevention protects your family too.
Parasites are among the most common health problems in dogs. Luckily, modern preventives make them easy to control. Your vet will recommend products based on where you live, your dog's lifestyle and its health.
Never use cat products on dogs or dog products on cats, and always dose by weight. Some dog flea products (permethrin) are highly toxic to cats. Dogs with the MDR1 gene (common in some herding breeds) can react badly to certain drugs — ask your vet.
Fleas
Signs: scratching, biting at the lower back and tail base, hair loss, small black specks ("flea dirt") that turn red on a damp paper towel.
Why they matter: itching, flea allergy dermatitis, anemia in puppies and small dogs, and they transmit tapeworms.
Prevention: monthly or longer-acting oral chewables, spot-on treatments or collars. If you have fleas, you must treat all pets in the home and the environment — most of the flea population lives in carpets and bedding as eggs and larvae.
Ticks
Why they matter: ticks spread diseases like Lyme disease, ehrlichiosis, anaplasmosis and Rocky Mountain spotted fever. Some can also cause tick paralysis.
Prevention: oral or topical tick preventives or collars; avoiding tall grass; checking your dog after walks — especially between toes, around ears, under the collar and in the groin.
How to remove a tick
- Use fine-tipped tweezers or a tick removal tool.
- Grasp the tick as close to the skin as possible.
- Pull upward with steady, even pressure — don't twist or squeeze the body.
- Clean the area and your hands. Don't use heat, petroleum jelly or alcohol to "smother" ticks.
- Watch the area and your dog for lethargy, fever or lameness in the following weeks.
Heartworm
Heartworm is spread by mosquitoes. Worms live in the heart and lungs and can cause heart failure and death. It has been reported in all 50 U.S. states and many other countries.
Prevention: monthly chewables, topical products or an injection that lasts 6 or 12 months. The American Heartworm Society recommends year-round prevention and an annual heartworm test.
Treatment for an established infection is long, expensive and risky. Prevention costs a fraction as much.
Intestinal worms
| Worm | How dogs get it | Notes |
|---|---|---|
| Roundworms | From the mother before birth or via milk, or from contaminated soil | Very common in puppies; can infect people |
| Hookworms | Soil, through the skin or mouth; from the mother | Can cause anemia; can infect people |
| Whipworms | Contaminated soil | Eggs survive in soil for years |
| Tapeworms | Swallowing infected fleas or eating prey | Rice-like segments near the tail |
| Giardia (protozoan) | Contaminated water | Diarrhea; not a worm but common |
Signs: diarrhea, vomiting, weight loss, pot belly in puppies, scooting, visible worms. Many infected dogs show no signs.
Prevention: many monthly heartworm preventives also treat some intestinal worms. Pick up poop promptly and have your vet test a stool sample once or twice a year.
Deworming puppies
Veterinary guidelines (such as those from the Companion Animal Parasite Council) generally recommend deworming puppies every 2 weeks from 2 to 8 weeks of age, then starting a monthly preventive that covers intestinal worms. Your breeder or shelter should have started this.
Choosing a preventive
Options include monthly chewables, topical spot-ons, long-acting injections and collars. Some combine flea, tick, heartworm and worm protection. Your vet will help you choose based on:
- Your region's parasites
- Your dog's age, weight, breed and health
- Whether you have cats or small children
- How easy it is for you to remember (monthly vs. long-lasting)
Set a monthly phone reminder, or use our vaccination & parasite schedule tool to generate your reminder dates.
Important: This article is general educational information, not veterinary advice. Every dog is different — always talk to your veterinarian about your own dog's health, diet and treatment. In an emergency, contact your vet or nearest emergency animal hospital immediately.
