My dog is old, so I stopped giving heartworm prevention.
Dr Anthony: Not often, but occasionally, I smirk helplessly when my clients say that they have stopped giving heartworm prevention to their old dogs. As we all know, heartworm disease is transmitted by mosquitoes. Being old does not mean that these blood-sucking insects will spare your pets. In the past years, I had diagnosed heartworm disease in a few dogs aged 12, 13, and 16 years old. These dogs presented heartworms which “migrated” from pulmonary artery to right atrium in a phenomenon known as caval syndrome. Imagine these senior dogs enduring the tedious heartworm treatment, which compromises their quality of senior life.
I live in a high-rise condominium. I don’t see mosquitoes in my house.
Prof Malaika: Mosquitoes can enter the house even if it is a condominium. If you take an elevator to reach the upper floor, mosquitoes can follow you from the car park into the elevator and then enter your house! Therefore, there is still a potential for an infected mosquito to bite your dog and cause heartworm disease.
I worry about long-term side effects of the medications.
Prof Malaika: The preventive medicines are known to be safe and very rarely cause side effects. Therefore, it is important to prevent a fatal disease rather than worry about the rare chance of a side effect.
How effective are the medications in preventing the disease?
Prof Malaika: The preventatives are very effective as long as they are given according to the label instructions for that specific product.
Dr Anthony: Adding to that, for instance, imidacloprid/moxidectin also known as Advocate is reported to provide 100% efficacy in preventing heartworm disease.
Standard heartworm treatment versus slow kill treatment
Dr Anthony: The standard treatment comprises of immiticide (melarsomine dihydrochloride) injections, along with monthly heartworm preventatives and doxycycline antibiotic. When the treatment is completed, the worms usually die within 7 to 10 days after the immiticide injection, but their death may take up to 4 weeks. The exact timeline can vary depending on factors such as the severity of the infection, the dog’s overall health, and how the dog’s immune system responds to the treatment.
On the other hand, the slow kill treatment entails only monthly heartworm preventatives, along with doxycycline to gradually eliminate adult heartworms over an extended period. It does not consist of immiticide (melarsomine dihydrochloride).
When do we consider the slow kill treatment?
Prof Malaika: This should only be considered in very sick or old dogs when it may be too risky to treat them with adulticides. Remember, if there is an option to treat with adulticides, that is best because the slow kill is very slow, typically takes 1 to 2 years to clear the adult heartworms and your dog will suffer unnecessarily.
I am honored to have Professor Dr. Malaika Watanabe here to answer some of our questions. Prof. Dr. Watanabe is a renowned veterinary internist, celebrated for her profound expertise in canine and feline infectious diseases, with a special emphasis on parasitic and vector-borne diseases.
