Roundworms in Dogs & Puppies: 2025 Vet Guide by Dr Duncan Houston 🐾🪱

Hello, I’m Dr Duncan Houston, BVSc. In this detailed 2025 guide, I’ll explain how roundworms—those spaghetti-like parasites—infect dogs and puppies, how they’re treated, and most importantly, how to protect both pets and people from these persistent parasites.

🧬 What Are Roundworms?

Dogs and puppies can be infected with two main types of roundworms:

• Toxocara canis (dog-specific)
• Toxascaris leonina (infects both dogs and cats)

Both worms live in the intestines and release eggs into the dog’s feces. These eggs can survive in the soil for months or even years, becoming a source of infection for other animals—and even humans. 🤢

🦴 How Dogs Get Infected

🐾 Toxocara canis:

• 🍼 Puppies are born infected—larvae migrate through the uterus before birth
• 🥛 Larvae are passed through the mother’s milk
• 🐭 Ingesting infected prey like rodents
• 🌱 Swallowing eggs from contaminated soil or feces

🐾 Toxascaris leonina:

• Only spreads by ingestion of eggs from contaminated environments or prey
• No in utero or nursing transmission

🔄 Life Cycle of Toxocara canis

1. 🐶 An infected dog sheds eggs in its feces
2. ⏳ Eggs develop in soil for 30+ days before becoming infectious
3. 🐾 A new host ingests the eggs → larvae hatch in the intestine
4. 🫁 Larvae migrate through the liver → lungs → coughed up → swallowed again
5. 🧬 Worms mature in the intestine and release eggs, restarting the cycle

Note: Larvae can “hibernate” in tissues for months or years and reactivate under stress, like pregnancy. This is why puppies are nearly always born with roundworms. 🐕👶

🧪 Signs of Roundworm Infection

Some infected dogs show no symptoms. Others may have:

• 💩 Diarrhea or vomiting (worms may be visible)
• 🍝 Worms in vomit or stool (white, spaghetti-like)
• 📉 Weight loss or poor coat condition
• 🪩 Distended “pot belly” in puppies
• 🫁 Pneumonia (from migrating larvae)
• 🚫 Intestinal blockage (rare, but possible)

🧫 Diagnosis

The most common test is a fecal flotation—where stool is examined under a microscope to detect worm eggs. This should be done for:

• 🐶 All puppies (routine screening)
• 🐾 Adult dogs (yearly or as needed)

If your dog vomits a worm, bring it to the vet for identification. 📦

💊 Deworming Treatment

There are many safe, effective dewormers available. Most only kill adult worms, so repeat doses are essential. Options include:

• Fenbendazole (Panacur®)
• Pyrantel pamoate (Nemex®, Heartgard Plus®)
• Milbemycin oxime (Interceptor®, Trifexis®)
• Moxidectin (Advantage Multi®, ProHeart®)
• Selamectin (Revolution®—effective even though not on U.S. label)

🧬 Important Notes:

• Most products do not kill migrating larvae, so multiple treatments are needed
• Some monthly preventives include a dewormer to reduce soil contamination

💡 Always follow your vet’s schedule for repeat deworming. One dose is not enough!

🦠 Why Roundworms Are Dangerous

• 🐕 Intestinal issues, poor growth, and blocked intestines in dogs
• 👨‍👩‍👧‍👦 Zoonotic—humans, especially children, can become infected through contact with contaminated soil
• 🧠 Can cause visceral or ocular larva migrans in humans (worms migrating to organs or eyes)

Prompt treatment and clean-up of feces are critical to reduce public health risks. 🧽

🧼 Environmental Control

• 💩 Pick up and dispose of feces immediately
• 🧽 Wash hands after gardening or handling dogs
• 🚫 Prevent dogs from hunting or eating prey
• 🌳 Avoid letting dogs roam in unknown areas

Roundworm eggs can survive in the soil for years. Prevent contamination before it starts. 🛡️

📋 Summary Table

📲 Final Thoughts

Roundworms are a hidden threat—especially to puppies and young children—but with vigilant care, they are preventable and treatable. Regular fecal testing, timely deworming, and monthly preventives go a long way in protecting your household. If you’re unsure of your dog’s risk or the best deworming schedule, connect with a vet. 🐶🛡️

For 24/7 guidance, medication tips, and personalized treatment plans, use the Ask A Vet app. Our team is ready to help you keep your pets worm-free and thriving. 📱💚