So your pet has heartworms. Here’s what to expect during treatment!

Living in southeast Louisiana, we have all had the displeasure of experiencing our local mosquitoes. These little pests are relentless in their drive to get blood meals from any warm-blooded bodies. Not only do mosquitoes take blood from dogs and cats, but they can also transmit a deadly parasite—heartworms. The random mosquito can end up inside the house, so it is important that every pet in the home, whether they go outside or not, is on a heartworm prevention for life starting at about 6 weeks of age to prevent infection.

If your dog or cat is not currently on prevention, thelucy mew best thing to do is to visit your vet for a simple blood test to check the current heartworm status. Dogs and cats that are negative can immediately start the best prevention recommended by their veterinarian. If the test comes back positive, the next step is to schedule treatment. Unfortunately, at this time, there is no safe treatment option for cats. The best thing to do would be continue monthly treatment, and follow the advice of your veterinarian to minimize any clinical signs. Heartworm positive dogs are started on an appropriate monthly prevention, and a treatment protocol is created for each patient, usually based off the standard protocol set by the American Heartworm Society.

At the time of diagnosis, blood work is taken to determine if the patient is healthy enough for treatment. Keep in mind that those tiny worms from the mosquito have traveled from the site of the bite all the way to the heart—they could have done a lot of damage to many organs on the way. Every patient should also have chest x-rays performed to evaluate how much, if any, lung inflammation and scarring is present. Some of this will go away after treatment, but some of the scarring is permanent. Every dog is also started on a month-long course of either doxycycline or minocycline to help remove a bacterial infection on the worms themselves. We need to get rid of that infection in order to weaken the worm before the actual treatment.


Heartworm treatment starts typically starts two months from the time of diagnosis. It consists of 3 deep muscle injections given over the mid-lower back area, on both the right and left sides. The first injection is given two months following diagnosis, and can be done as a day visit. The patient spends the day in the clinic, receives the injection, then goes home the same day. The next two injections are given 4 weeks later. For this visit, the patient should spend the night as the injections must be given 24-hours apart. During the 10 weeks of treatment, it is critical that the patient stay under complete exercise confinement. This means absolutely no running, jumping, playing, off-leash time, walks around the block or rough-housing. As the worms die off, there is an increased risk of creating a blood clot or possible embolism to the lungs. This can become a potential emergency situation, and the risk increases whenever the heart rate increases. Since treatment only kills the adult worms, it is very important to stay on monthly prevention during treatment and every 30 days for the rest of your dog’s life afterwards. Once treatment is complete, your dog will be retested to ensure that the treatment was a success.

If you would like to discuss your pet’s heartworm prevention status, test your pet, or discuss treatment for your heartworm positive dog, we would more than happy to do so at our Community Clinic at the Louisiana SPCA. Please call to schedule an appointment today at 504.363.1333.

Dr. Adrianna Smith has been with the Louisiana SPCA for just over a year; she worked in private practice in Metairie for 3 years before joining our team. She earned her Doctor of Veterinary Medicine degree from Ross University School of Veterinary Medicine. Dr. Smith has one dog, which she adopted from the Louisiana SPCA. If you have any questions for Dr. Smith, email or visit dr-adrianna-smith