Heartworm Positive Dogs are in the Doghouse

Written by Logan Lewis, CCAS contributing editor

Dogs that are heartworm positive are now facing an even bigger challenge: the lab that produces the life saving drug, Immiticide, has gone out of business. The U.S. has been experiencing shortages of the prescription medication since 2011, but by the close of 2013, the technical difficulties of manufacturing the drug overwhelmed the need, and only a small percentage of heartworm-positive dogs will have access to the much needed medicine while the supplier company, Merial, imports limited quantities from their European supplier. 

Treating heartworm-positive dogs with Immiticide (an injectable drug administered by a veterinarian) has long been considered the golden standard of heartworm treatment because it is the only drug that can kill adult heartworms. The administration of the injection is often referred to as the “fast kill” version of heartworm treatment for dogs due to the relatively short amount of time it takes for the medication to start working. 

The miracle drug, which is injected near the spinal cord, does not come without side effects, one of which is painful administration to the dog and adverse side effects such as gagging and coughing while the worms slowly die and exit the body. 

With the alarmingly low production of Immiticide, veterinarians will only be allowed limited quantities and are encouraged to save these reserves for only the most desperate cases while Merial, the company that supplies and sells the drug, works out the manufacturing problems with their supplier. Although Merial is receiving minimal supplies from Europe, the expiration date is shorter than the type produced in the U.S., which is causing yet another hurdle for vets to overcome. 

However, there is another treatment of heartworms in dogs referred to as “slow-kill” method, which is the monthly administration of heartworm medicine (that specially contains Ivermectin). This method is not preferable to many pet owners and veterinarians mainly because the medicine can take up to 1 to 2 years to kill the adult heartworms (although it is successful in killing heartworm larvae). By that time, it may be too late for older or severely infected dogs. For younger dogs, however, this may be the best (and perhaps only) treatment. Unfortunately, physical activity aggravates the problem, so owners with heartworm positive dogs will need to monitor the dog’s activity. 

Ideally, every dog over 6 months of age should be on heartworm preventative year-round (especially in the south) so that heartworms can altogether be avoided. It is now more important than ever to be vigilant about administrating your dog’s heartworm preventative once a month, every month, year-round so that they can live a long and happy life free from heartworms and the problems that are caused by the medication’s shortages.