Even the most beloved pets can be plagued by pests like heartworms, fleas, and ticks. Some pests carry serious diseases that also affect people.

“These parasites aren’t just a threat to your pet; they’re a health risk to everyone in your home,” says jme Thomas, executive director of Motley Zoo Animal Rescue in Redmond, WA.

If you just adopted a dog or are thinking about it, here’s how to keep the whole family healthy and safe.

What Is Heartworm Disease?

Dogs get heartworms when they’re bitten by an infected mosquito.

“The worms travel though the bloodstream, harming blood vessels and vital organs as they go,” explains Hyunmin Kim, DVM, director of veterinarians at the American Society for the Prevention of Cruelty to Animals (ASPCA) Community Medicine. In time, they cause lasting damage to your dog’s heart, lungs, and arteries.

Treatment of Heartworm Disease

The usual treatment for heartworms is a drug called melarsomine. Your vet gives it to your dog in a series of shots. The medicine can be dangerous, Thomas says, and the entire treatment process is “difficult, distressing, and costly.”

Among other things, your dog must stay quiet or crated for months. Heartworms break into pieces as they die and may block a blood vessel if your dog is too active.

“This is stressful for both people and the animals themselves, who just want to run and play, so prevention should be a priority,” Thomas says. “Depending on the severity of the damage, some pets with heartworms may need to be euthanized, so it’s important to recognize your responsibility in keeping them safe.”

Prevention of Heartworm Disease

“Heartworm infection is almost entirely preventable,” says Gail Hansen, DVM, a veterinarian with the Humane Society Veterinary Medical Association.

“Preventive care is as important for your new puppy or dog as it is for the rest of your family. It’s important to find a veterinarian in your area and establish a relationship early on, before you have an emergency.”

Your vet should test your dog for heartworms every year, she says, and you should use a heartworm preventive year-round. Preventives come in several forms:

• Chewable pills
• Topicals
• Six-month or 12-month shots

Many heartworm pills and topicals protect against other parasites, too, including fleas, ticks, intestinal worms, and ear mites.

“Whether you choose pills or topicals may depend on your vet’s recommendation,” Thomas says. “They can decide what will be best based on your pet’s needs, your location, and the combination of medicines to avoid any contraindications.”

What Are Fleas?

Fleas are more than a nuisance. They’re blood-sucking parasites that can cause trouble for you and your canine companion. Flea bites often itch, which can be intense for dogs with an allergy to flea saliva. Constant chewing and scratching to relieve the itch can cause hard-to-treat skin infections, sores, and hair loss.

A severe flea infestation may lead to anemia, especially in puppies. If not treated quickly, anemia can be fatal.

Fleas are small and hard to see, but flea dirt is a telltale sign. This is flea poop made of dried blood. It looks like black crumbs in your dog’s fur. Dogs who have fleas may have tapeworms, too. They often get tapeworms when they swallow an infected flea. “If you see fleas, flea dirt, or tapeworms -- they look like orzo in your dog’s stool -- you have to take care of both,” Thomas says.

Treatment of Fleas

Your best bet is to talk to your vet. Prescription products can kill fleas quickly and safely -- sometimes in as little as 30 minutes. Flea combs and over-the-counter flea shampoos are also options. Run any off-the-shelf shampoo past your vet to make sure it’s safe.

Prevention of Fleas

“There are lots of effective flea and tick preventives, but there are also many products on the market that are ineffective,” Hansen says. “Your veterinarian can help you find the best product for you, your dog, and your household.”

She says it’s important to follow the label instructions when you apply or give any preventive product and that your dog’s age, size, breed, and overall health matter.

“If you or your pet show any sign of a bad reaction to preventive treatments, including excessive scratching, skin redness, swelling, vomiting, or any abnormal behavior, contact your veterinarian and the manufacturer,” Hansen says.

“Also, be aware that some products can harm the environment, so know how to use and dispose of them properly.”

Thomas says flea collars and treatments you buy at the grocery store aren’t always safe. Ask your vet which ones they recommend.

What Are Ticks?

Like fleas, ticks are parasites that feed on blood. They can spread many debilitating illnesses, including Lyme disease and Rocky Mountain spotted fever. In the past, ticks that transmit these diseases were found in the Northeast and Midwest, but they’re now seen in many other parts of the country.

You should take tick bites seriously, no matter where you live.

Treatment of Tick Bites

The antibiotic doxycycline is the main treatment for both Lyme disease and Rocky Mountain spotted fever.

Still, the decision to treat your dog is tricky. Dogs who don’t have protein in their urine or symptoms like swollen lymph nodes or arthritis usually don’t need antibiotics. If your vet suggests them, find out why. Even after treatment, the bacteria that cause Lyme disease stay in your dog’s body and can cause a relapse. Keep an eye out for symptoms that come back.

Prevention of Tick Bites

You have to be vigilant about ticks, Hansen says.

“After taking your dog for a walk, especially in grassy or wooded areas, check carefully for ticks, particularly on your dog’s head, neck, ears, and feet,” she says.

“Don’t put anything on a tick that has started feeding to try to get it to release itself. This can be harmful to your pet and won’t dislodge the tick. Use tweezers placed close to the skin, and pull the tick straight out,” she says.

Getting the whole tick is key, Thomas explains.

“The head is where the diseases and toxins come from, so removing the body but leaving the head is a problem.”

She adds that “it’s a good idea to save the tick, so your vet can be aware of the type and any particular concerns.”

There’s also a vaccine for Lyme disease in dogs. It’s not 100% effective and doesn’t protect against Rocky Mountain spotted fever and other illnesses. It’s usually recommended for dogs who spend a lot of time outdoors in places where ticks are common. Your vet can tell you if it’s right for your furry friend.

“In all, there’s no one perfect way to treat all of these nasty parasites,” Thomas says. “Preventing them is always far better for both your health and that of your pet.”