Mosquitoes carrying microscopic heartworm larvae transmit it to vulnerable dogs via biting. A monthly heartworm preventive, in either pill or topical form, can keep your dog free of potentially fatal heartworm disease. There's a reason your veterinarian conducts a blood test on your pet before prescribing preventive medication. If your dog tests positive for heartworm, he needs treatment rather than the preventive. The type of treatment depends on the severity of his infestation.
Your veterinarian will determine the level of your pet's disease -- mild, moderate or severe. A dog with mild heartworm disease may be asymptomatic, while those with symptoms must be stabilized before treatment can start. Symptoms include coughing, lethargy, weight loss and breathing difficulties. Unfortunately, by the time a dog exhibits signs of the disease, it is generally fairly advanced. Stabilization might include intravenous fluid therapy, antibiotics, corticosteroids and vasodilators.
If your dog is diagnosed with mild to moderate disease -- stage one or two -- the standard treatment consists of two intramuscular injections of melarsomine dihydrochloride over 24 hours, or an initial injection followed by the two injections one month later. After any injection, he requires at least a month of confinement and exercise restriction. Melarsomine dihydrochloride, marketed under the brand name Immiticide, eradicates heartworm in approximately 90 percent of treated dogs. If a dog remains heartworm-positive after the treatment, your vet can repeat the therapy four months later.
Slow Kill Method
The Immiticide regimen isn't cheap. One possible alternative for positive, asymptomatic dogs is the "slow kill" method, which consists of giving an ivermectin-based preventive to the dog each month. Because this method doesn't kill adult heartworms, it's really just somewhat better than no treatment. Another drawback is the development of heartworm strains resistant to ivermectin treatment, occurring because the adult heartworms exposed to the slow kill method are producing ivermectin-resistant baby worms, or microfiliaria. If you have financial issues regarding heartworm treatment, speak with your vet. A payment plan or other option is probably a better alternative for your dog than the slow kill method.
Severely Infested Dogs
Dogs severely infested with heartworms might have hundreds of the parasites within them, with substantial, irreparable damage already done to the heart and lungs. If a dog is dying from the infestation from the sudden blockage known as caval syndrome, your vet can attempt to remove the adult worms -- some of which may reach 1 foot in length -- through an incision in the jugular vein. A severely affected dog not yet at death's door might receive Immiticide after symptoms have stabilized.