Help! My Dog Has Heartworm! (Vet Answered)
This question has been answered by a vet
Veterinarian & Animal Behaviorist
With nearly two decades in veterinary medicine, Dr. Paola brings hands-on experience across multiple species. A graduate of the University of Guadalajara, she specializes in preventive care, animal welfare, and positive reinforcement training.
The Question
“Dear Dr. Paola,
I rescued Benji one month ago from the Humane Society in Palm City, and he was a stray dog. I am very concerned because he has heartworm and they gave us an antibiotic that we should give him for a month and they told us that after that we have to leave Benji there for 2 days, because they have to give him 2 painful injections of arsenic and i can’t see him for 2 days because it will be tough on Benji. We research and find out that the protocol is different.
We took Benji to the Vet, and she told us that after the antibiotics we have to give him one pill of NexGard and wait one month and after that we take him there for the injection and the same day we can pick him up and in case he doesn’t respond well we have to find a clinic and leave him there. This has to be repeated 2 more times because the injections are 3 and not 2 at the same time, like the Humane Society told us.
My heart is sinking because I don’t want him to have pain, anxiety, and feel that we abandon him in the moment that he needs the most. I would appreciate it if you could guide me in this difficult situation, because I don’t know much about it and I don’t want to lose Benji.
He has some good days, but he also has bad days when he doesn’t want to eat anything or drink water, and he is lethargic, which makes me really worried.
Benji is a mixture of Maltese, Westie, and Terrier, and because he was a stray dog, they think that he is 5 or six years old according to his teeth. I appreciate your help.
Sincerely,” – Ines
Quick Info about Benji
Dear Ines,
Thank you for rescuing Benji and for giving him a second chance at a safe, loving life. What you’re going through is incredibly hard, and your concern for his comfort and emotional well-being shows just how deeply you care. Heartworm treatment can be a complicated and emotionally draining process, but you’re absolutely doing the right thing by staying informed and seeking clarity.
Heartworm disease is serious, and treatment must be carefully timed and structured to reduce the risk of complications, especially from the death of adult worms, which can cause dangerous inflammation and blockages in the lungs. The standard protocol recommended by the American Heartworm Society involves a multi-step process: first, a 30-day course of doxycycline, an antibiotic used to target a bacterium that lives within the heartworms called Wolbachia. This initial antibiotic treatment weakens the heartworms and reduces the risk of a severe inflammatory response. Then, after about 30 days, a heartworm preventive like NexGard or a macrocyclic lactone is given to kill immature larvae. One month later, the adulticide treatment begins with a deep intramuscular injection of melarsomine (an arsenic-based drug), followed by two more injections 24 hours apart, about a month later. This multi-step approach is designed to kill the worms gradually, lowering the risk of life-threatening clots and reactions.
It’s true that the injections can be painful, and Benji will need to stay calm and rested. Activity restriction during the treatments is essential to avoid stressing his heart and lungs. Especially after the injections, because as the worms die, they can break up and cause blockages in the lungs if the dog exerts himself too much. The decision to hospitalize a dog or not during these injections depends on their overall health and how they handle the medication. Some clinics prefer to keep dogs overnight for observation, especially after the final two injections. Others may allow discharge on the same day with strict home care instructions. Both approaches can be valid when they are tailored to the dog’s specific condition. Since Benji has already shown signs of lethargy and loss of appetite, it’s very important to report these to your veterinarian. These may or may not be related to the heartworm infection, but they do merit attention before moving forward.
Benji is lucky to have you as his guardian. With patience, close monitoring, and a thoughtful treatment plan, many dogs recover fully and go on to live long, happy lives. Please remember, you’re not alone in this. You’re navigating something challenging, but there are protocols and treatments available, and your love and care are the most powerful tools in helping Benji heal. Thank you again for your kindness in adopting Benji. I admire you.
Sincerely,
– Dr. Paola