Treatment

• After a dog is diagnosed as positive for heartworm, the owner must make a decision of treatment or no treatment. This can be a very expensive--from $300 to $1200--and painful. The dog is assessed by number of worms present, age, size and health, and whether the owner can contain the dog in a small enclosure such as a crate for an extended period of time.
  
  Three stages of worm must be treated. The worms born from adults are tiny and called microfilariae. These are found in the bloodstream. Larvae that have been picked up by a host mosquito are called L3 and L4. These are found in the skin, as they have not yet migrated to the heart. The L5 or adult worms live in the pulmonary arteries and the heart. The L5 worms are killed with arsenic, while the smaller larvae and microfilariae can be killed with a less toxic compound such as a heartworm preventative. These must be killed first, so they do not become adults during the treatment. There is a waiting period of three to four months between killing the L3, L4 and microfilariae and killing the adult worms.
  
  Veterinarians often administer melarsomine dihydrochloride. This is injected deep in the muscle of the lower back. Pain medication is used for the discomfort around the injection site. If two doses are required, a second injection is given the next day on the other side of the lower back. A third dose may be given one month later as two injections one day apart.
  
  Treated dogs must be confined for one month. Confinement is total. No walks, no running, nothing that would increase the heart rate of the treated animal.