Heartworm Prevention for Dogs and Cats: What Owners Need To Know

Heartworm disease is spread by mosquitoes and can be life-threatening. Dogs need testing and consistent prevention because adult heartworms can damage the heart and lungs. Cats can develop severe lung disease, and there is no approved adult-heartworm treatment for cats.

What symptoms or causes should I watch for?

• Mosquito transmission: A mosquito bite can transmit immature heartworms to dogs or cats.
• Dog testing: Dogs are commonly tested before starting or restarting prevention after a lapse.
• Cat differences: Cats may have respiratory disease from even a small number of worms.
• Prevention class: Many preventives use macrocyclic lactone drugs, but products vary by species and label.
• Missed doses: Gaps in prevention can allow infection before owners see any signs.

What can I safely do at home right now?

• Check prevention history: Write down product name, last use, and any missed months.
• Ask about testing: Do not restart after a long lapse without veterinary guidance.
• Use species-labeled products: Dog and cat heartworm products are not interchangeable.
• Control mosquitoes: Reduce standing water and use prevention even for mostly indoor pets where recommended.
• Keep reminders: Calendar reminders help prevent missed monthly or scheduled products.

When is this an emergency?

Go to an emergency veterinary clinic now if you notice:

• Coughing, fainting, trouble breathing, collapse, or severe weakness.
• A dog with a long prevention lapse or unknown testing history.
• A cat with sudden coughing, wheezing, vomiting, or breathing effort.
• Using a product meant for another species or weight range.
• Positive heartworm test or suspected medication reaction.

What will my veterinarian check?

Your veterinarian may recommend antigen testing in dogs, additional testing when results conflict, and prevention based on age, species, travel, local risk, and prior product history.

How can I reduce the risk next time?

Use a veterinarian-approved prevention plan year-round or as locally recommended, and keep testing current when your clinic advises it.

Related veterinary guides

• Intestinal Parasites in Dogs and Cats: Signs and Prevention
• Puppy First Vet Visit: What Should You Expect?
• Kitten First Vet Visit: What Should You Expect?
• Senior Dog Checkup: What Should Be Included?

References

• American Heartworm Society - Heartworm Basics
• FDA - Keep the Worms Out of Your Pet's Heart
• Pets & Parasites - CAPC Pet Owner Resources

Disclaimer: This article is for educational and informational purposes only. It does not constitute medical advice, does not establish a vet-client-patient relationship, and should not replace an in-person evaluation by a licensed veterinarian.