Heartworm disease, caused by Dirofilaria immitis, is a serious and potentially fatal condition affecting dogs, cats, and ferrets. The American Heartworm Society (AHS) strongly recommends year-round prevention using FDA-approved medications to protect pets from this devastating parasite. Below, we provide a detailed breakdown of heartworm preventives available for dogs, cats, and ferrets, including their effectiveness against other parasites, administration methods, and key considerations for pet owners.
Why Year-Round Prevention Matters
Heartworm disease is transmitted through the bite of an infected mosquito. While mosquitoes are more active in warmer months, indoor pets are also at risk due to the presence of mosquitoes inside homes. Year-round prevention ensures continuous protection and eliminates the risk of missing a dose, which could leave pets vulnerable to infection.
Heartworm Preventives for Dogs
Heartworm preventives for dogs come in three primary forms: oral tablets/chews, injectables, and topical spot-on treatments. Each method has its advantages, and the choice often depends on pet preferences, lifestyle, and veterinary recommendations.
1. Oral Administration (Monthly Tablets and Chews)
Oral preventives are highly effective and often preferred for their ease of use. Many also provide broad-spectrum protection against other intestinal parasites.
| Drug | Trade Name(s) | Treats Heartworm (Larvae) | Additional Parasites Treated | Minimum Age/Weight | Safe for Breeding/Lactation | Food Allergen Considerations |
|---|---|---|---|---|---|---|
| Ivermectin + Pyrantel Pamoate | HEARTGARD® Plus (Boehringer Ingelheim), Tri-Heart® Plus (Merck), Iverhart Plus® (Virbac) | ✅ | Hookworms, Roundworms | 6 weeks/no minimum weight | ✅ (HEARTGARD® Plus, Tri-Heart® Plus) | Beef, Pork Liver |
| Ivermectin + Pyrantel Pamoate + Praziquantel | Iverhart Max® (Virbac), IMECTRO® (Ceva) | ✅ | Hookworms, Roundworms, Tapeworms | 8 weeks/6 lbs | ❌ Not Evaluated | Pork Liver, Artificial Beef |
| Milbemycin Oxime | Interceptor® (Elanco), MilbeGuard® (Ceva) | ✅ | Hookworms, Roundworms, Whipworms | 4 weeks/2 lbs | ✅ | Beef |
| Milbemycin Oxime + Praziquantel | Interceptor® Plus (Elanco) | ✅ | Hookworms, Roundworms, Whipworms, Tapeworms | 6 weeks/2 lbs | ❌ Not Evaluated | Chicken |
| Milbemycin Oxime + Lufenuron | Sentinel® Flavor Tabs (Merck) | ✅ | Fleas, Hookworms, Roundworms, Whipworms | 6 weeks/2 lbs | ✅ | Artificial Beef, Pork/Soy |
| Milbemycin Oxime + Lufenuron + Praziquantel | Sentinel® Spectrum® (Merck) | ✅ | Fleas, Hookworms, Roundworms, Whipworms, Tapeworms | 6 weeks/2 lbs | ❌ Not Evaluated | Beef |
| Milbemycin Oxime + Spinosad | Trifexis® (Elanco) | ✅ | Fleas, Hookworms, Roundworms, Whipworms | 8 weeks/5 lbs | ⚠️ Use with Caution | Artificial Beef, Pork Liver/Hydrolyzed Soy |
| Moxidectin + Afoxolaner + Pyrantel | NEXGARD® PLUS (Boehringer Ingelheim) | ✅ | Fleas, Ticks, Hookworms, Roundworms | 8 weeks/4 lbs | ❌ Not Evaluated | None |
| Moxidectin + Sarolaner + Pyrantel Pamoate | Simparica® Trio (Zoetis) | ✅ | Fleas, Ticks, Hookworms, Roundworms | 8 weeks/2.8 lbs | ❌ Not Evaluated | Pork |
| Moxidectin + Lotilaner + Praziquantel + Pyrantel | Credelio Quattro™ (Elanco) | ✅ | Fleas, Ticks, Hookworms, Roundworms, Tapeworms | 8 weeks/3.3 lbs | ❌ Not Evaluated | Meat Allergen Free |
2. Injectable Administration (Every 6 or 12 Months)
Injectable preventives provide long-lasting protection and are ideal for pet owners who struggle with monthly compliance.
| Drug | Trade Name(s) | Treats Heartworm (Larvae) | Additional Parasites Treated | Minimum Age/Weight | Safe for Breeding/Lactation |
|---|---|---|---|---|---|
| Moxidectin | ProHeart® 6 (Zoetis) | ✅ | Hookworms | 6 months/5 lbs | ✅ |
| Moxidectin | ProHeart® 12 (Zoetis) | ✅ | Hookworms | 12 months/5 lbs | ✅ |
3. Topical Administration (Monthly Spot-On)
Topical treatments are applied directly to the skin and are a great option for pets who refuse oral medications.
| Drug | Trade Name(s) | Treats Heartworm (Larvae) | Additional Parasites Treated | Minimum Age/Weight | Safe for Breeding/Lactation |
|---|---|---|---|---|---|
| Moxidectin + Imidacloprid | Advantage Multi® (Elanco), Barrier® (Aurora), IMOXI™ (Vetoquinol USA), PARASEDGE™ Multi (Virbac), Midamox™ (Norbrook) | ✅ | Fleas, Hookworms, Roundworms, Whipworms, Ear Mites, Mange Mites | 7 weeks/3 lbs | ❌ Not Evaluated |
| Selamectin | Revolution® (Zoetis), Paradyne® (Vethical), Senergy™ (Virbac), Selarid™ (Norbrook), Revolt™ (Aurora) | ✅ | Fleas, Ticks, Ear Mites, Mange Mites | 6 weeks/no minimum weight | ✅ |
Heartworm Preventives for Cats
Cats are equally susceptible to heartworm disease, though their symptoms and treatment differ from dogs. Prevention is critical, as there is no approved treatment for heartworm infection in cats.
1. Oral Administration (Monthly Tablets and Chews)
| Drug | Trade Name(s) | Treats Heartworm (Larvae) | Additional Parasites Treated | Minimum Age/Weight | Safe for Breeding/Lactation | Food Allergen Considerations |
|---|---|---|---|---|---|---|
| Milbemycin Oxime | Interceptor® (Elanco), MilbeGuard® (Ceva) | ✅ | Hookworms, Roundworms | 6 weeks/1.5 lbs | ❌ Not Evaluated | Beef |
2. Topical Administration (Monthly Spot-On; Bravecto PLUS is Every 2 Months)
| Drug | Trade Name(s) | Treats Heartworm (Larvae) | Additional Parasites Treated | Minimum Age/Weight | Safe for Breeding/Lactation |
|---|---|---|---|---|---|
| Moxidectin + Imidacloprid | Advantage Multi® (Elanco), Barrier® (Aurora), IMOXI™ (Vetoquinol USA), PARASEDGE™ Multi (Virbac), Midamox™ for Cats (Norbrook) | ✅ | Fleas, Hookworms, Roundworms, Ear Mites | 9 weeks/1.5 lbs | ❌ Not Evaluated |
| Moxidectin + Fluralaner | Bravecto® PLUS (Merck) | ✅ | Fleas, Ticks, Hookworms, Roundworms | 6 months/2.6 lbs | ❌ Not Evaluated |
| Esafoxolaner + Eprinomectin + Praziquantel | NEXGARD® COMBO (Boehringer Ingelheim) | ✅ | Fleas, Ticks, Hookworms, Roundworms, Tapeworms | 8 weeks/1.8 lbs | ❌ Not Evaluated |
| Selamectin | Revolution® (Zoetis), Paradyne® (Vethical), Revolt™ (Aurora), Senergy™ (Virbac), Selarid™ (Norbrook) | ✅ | Fleas, Ear Mites, Mange Mites | 8 weeks/no minimum weight | ✅ |
| Selamectin + Sarolaner | Revolution® Plus (Zoetis) | ✅ | Fleas, Ticks, Hookworms, Roundworms, Tapeworms, Ear Mites | 8 weeks/2.8 lbs | ❌ Not Evaluated |
Heartworm Preventives for Ferrets
Ferrets are also vulnerable to heartworm disease, and prevention is essential for their health.
Topical Administration (Monthly Spot-On)
| Drug | Trade Name(s) | Treats Heartworm (Larvae) | Minimum Age/Weight | Safe for Breeding/Lactation |
|---|---|---|---|---|
| Moxidectin + Imidacloprid | Advantage Multi® (Elanco), Midamox™ for Cats (Norbrook) | ✅ | 2 lbs | ❌ Not Evaluated |
Key Considerations When Choosing a Heartworm Preventive
- Pet’s Lifestyle: Outdoor pets or those in mosquito-prone areas may benefit from broad-spectrum preventives that also target fleas and ticks.
- Allergies: Some preventives contain food allergens (e.g., beef, pork, chicken). Always check the ingredient list if your pet has known allergies.
- Breeding or Lactation: Not all preventives are safe for pregnant or nursing pets. Consult your veterinarian for appropriate options.
- Administration Preference: Choose a method that fits your pet’s routine (e.g., oral tablets for easy dosing, topicals for pets who refuse pills).
- Veterinary Guidance: Always consult your veterinarian before starting any preventive regimen, especially for puppies, kittens, or pets with health conditions.
A dog wearing an orange knitted hat, symbolizing the need for year-round protection
The Importance of Compliance
Missing even a single dose of heartworm preventive can put your pet at risk. Set reminders to administer preventives on time, and never skip doses, even in colder months. The American Heartworm Society provides educational resources, including posters and social media tools, to help pet owners stay informed.
Conclusion
Heartworm disease is a preventable tragedy. By choosing the right preventive and staying consistent, you can safeguard your pet’s health and avoid the devastating consequences of infection. Consult your veterinarian to determine the best option for your dog, cat, or ferret, and commit to year-round protection.
For more information, visit the American Heartworm Society or download their Printable Preventive Chart.
References
- American Heartworm Society. (2025). Heartworm Preventives Chart. Retrieved from heartwormsociety.org