Heartworm in dogs – Signs, causes, what you need to know
by Ontario SPCA and Humane Society | General Pet Care | February 26, 2021
Recently, we shared a story with our donors about a dog named Boxer who came into our care with heartworm, a serious health condition that can result in severe lung disease, heart failure, and sometimes, even death.
Heartworm can be difficult and time-consuming to treat, which is why we’re overjoyed that Boxer is now settling in with his new furr-ever family who will be giving him the proper care he needs for the rest of his life. In this blog we’re going to answer commonly asked questions about heartworm in dogs – signs, causes, treatment and more.
Heartworm in dogs
You’ve found the perfect dog who is looking for a loving forever home – but she is recovering from heartworm. Or maybe you’ve heard of this illness and worry about your pet getting sick.
Did you know that heartworm is both preventable and is often treatable, if necessary? Prevention of heartworm is always preferable to treatment as it is safer, simpler, and less costly.
How does a dog get heartworm?
Mosquitoes play a critical role in the transmission of heartworm disease. As such, risk is especially high during mosquito season and along waterways where mosquitoes frequent.
A mosquito feeds on an infected animal (such as another dog) and picks up an immature stage of heartworm called microfilaria. This immature stage matures within the mosquito to an infective stage. The mosquito then goes on to bite a dog and pass along this infective stage, which matures further over six to seven months into adult heartworm within that dog.
Adult heartworms can live for up to five to seven years in a dog. Dogs can be re-infected even if they already have heartworm, which means that they can have more and more heartworms build up in their body if not treated.
What are the signs of heartworm disease?
Clinical signs of heartworm disease can include cough, shortness of breath, exercise intolerance, lethargy, reduced appetite, and weight loss. Severe cases may result in heart failure, which can present as a swollen belly and legs, due to fluid build up.
It’s important to note that just because a dog with heartworm disease may not be showing clinical signs, it doesn’t mean they don’t have significant disease and damage present. Contact your veterinarian if you have any concerns about your pet’s health.
Can it be passed to other dogs? To me?
Heartworm disease is not spread directly from dog-to-dog or from dog-to-human. Heartworm disease in humans is rare.
Do dogs ever fully recover from heartworm?
Dogs can be successfully treated for heartworm. However, there is a risk of long-term damage to their heart, lungs, and blood vessels. Other vital organs, such as their liver and kidneys, can also be affected if heartworms have blocked blood flow and oxygen delivery to these areas. Some recovered dogs may also require supportive therapy through the form of medication and diet, for life.
What’s involved in treating heartworm?
There are a number of stages involved in heartworm treatment, which will depend on the treatment plan decided on by your veterinarian. Your veterinarian will stage your dog’s heartworm disease using various tests, such as blood work and x-rays. A specific treatment plan tailored to your dog will be developed by your veterinarian, with the aim to stabilize your dog and reduce treatment complications.
Heartworm treatment traditionally involves a monthly heartworm preventative in the form of an oral or topical medication. The purpose of which is to kill immature heartworms and help to prevent new heartworm infections. Bacteria within the heartworms that helps heartworm survive and reproduce, will be killed using a specific antibiotic prescribed by your veterinarian.
Your veterinarian will administer a series of injections of a specialized drug to kill your dog’s adult heartworms (immiticide) over a number of months. A steroid is often prescribed alongside these immiticide injections to support your dog as the heartworms are killed and broken down in your dog’s body. Your veterinarian may recommend that your dog stay at the clinic for close monitoring after these injections. This is so that additional supportive therapies can be administered if needed.
An absolutely essential component of heartworm treatment is exercise restriction before, during, and in the weeks and months after heartworm treatment is complete. Exercise can worsen heartworm damage and complications can also arise as your dog’s body works to clear dead heartworms. The American Heartworm Society has a great resource for battling boredom during cage rest here.
There is currently no vaccine available to prevent heartworm disease. However, there are preventatives available, once a month topical or oral. There’s also an injectable preventative that can provide prevention for up to six months. Consult your veterinarian for the best prevention plan for your pet.
I’m thinking about adopting a dog with heartworm, what should I know?
Consult your veterinarian before considering adopting a dog with heartworm disease to make sure you appreciate the personal commitments involved.
Three cheers for the volunteers!
Three cheers for the volunteers! Keep doing wonderful work, thank you!