Heartworm infection in the South can affect up to 50% of adult dogs in some shelters. Although heartworm infection is considered a treatable condition in most dogs, resources for treatment, including time and veterinary costs, frequently lead to euthanasia of infected shelter dogs.

The situation has become even more dire since the onset of limited availability of Immiticide, the only drug approved for the treatment of canine heartworm infection.  

It is possible that Immiticide may become completely unavailable at some point. The American Heartworm Society has issued guidelines for the management of dogs in the absence of Immiticide.