If Baxter had the misfortune of being bitten by the wrong mosquito, he's at risk for heartworm infection. These nasty parasites take up residence in your pup's heart, and if untreated, lead to death. The best cure for heartworm depends on your dog, as well as the parasite and degree of infection.
Before deciding on the appropriate treatment, your vet will consider Baxter's age, size and overall health. The vet will look for the presence of microfilariae -- heartworm offspring -- and may use ultrasound to determine the gender and number of parasites Baxter's hosting. The degree of damage they've inflicted, as well as how long he's been infected, also affect the course of action.
The Food and Drug Administration, or FDA, approves of one drug -- melarsomine dihydrochloride, or Immiticide -- to eliminate adult heartworms in dogs. Immiticide is injected into a dog's lumbar muscles, usually in a series of three injections. During this phase of treatment, adult worms die and work their way through your pup's system. The potential danger of a clump of worms clogging one of Baxter's major arteries means he should be on very restricted exercise during this time; in fact, he should be confined to a kennel and taken out only for bathroom breaks. Other possible side effects include fever, cough and the occasional nosebleed -- which you should report to your vet. After 16 weeks, all adult parasites should be dead, as confirmed by a negative heartworm antigen test.
If Baxter's heartworm test shows the presence of microfilariae, he'll need a microfilaricide. Some vets prefer to go after the offspring first, but generally treatment takes place three to six weeks after the adulticide treatment is complete, when the adult worms are dead and unable to produce microfilariae. The FDA hasn't approved medication specifically to act as a microfilaricide; however, veterinarians routinely use ivermectin or milbemycin to do the job; selamectin and moxidectin are also used. Hospitalization during this treatment phase is normal so the dog can be observed for potential adverse reactions to the death of microfilariae, such as diarrhea, vomiting and lethargy. Your vet may decide to administer a heartworm preventive instead of using a microfilaricide, knowing it will take up to nine months for the microfilariae to die.
If a dog is critically ill or severely infected, the vet may decide surgical removal is warranted. Though it sounds like a major undertaking, surgical removal of heartworms is not very invasive. An incision is made in the neck over the jugular vein while the dog's heavily sedated or under general anesthesia. The vet uses special instruments to remove the worms one by one.
Your vet may decide to wait a bit before beginning Baxter's treatment; if that's the case, your pup's activity will be severely restricted. During this time, the vet may prescribe preventive medication to keep new worms from developing. Heartworms contain Wolbachia, organisms living in the heartworm that protect the parasites. The antibiotic doxycycline kills Wolbachia, weakens and sterilizes heartworms and minimizes the risk of poor reactions to treatment. Currently, no alternative or holistic treatments for heartworm treatment exist.
When the vet's sure Baxter's heartworm-free, your pup can take one of several heartworm preventives on the market. Options include monthly topicals, daily and monthly chewables and pills and an injectable. When one of these is given consistently as directed, you can be confident Baxter's protected against this dangerous parasite.
- American Heartworm Society: Canine Heartworm Disease
- 2ndChance.info: What to Do When Your Dog Has Heartworms
- WebMD: Treating Heartworm Disease in Dogs
- Healthy Pets: Heartworm Drug Shortage Prompts Use of Cheaper, Safer Therapy
- Michigan State University: Canine Heartworm Disease
- American Heartworm Society: Current Canine Guidelines for the Prevention, Diagnosis, and Management of Heartworm (Dirofilaria immitis) Infection in Dogs [PDF]
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