Heartworm Disease: It Hurts. It kills. It is costly and traumatic to treat.
Banfield, The Pet Hospital, Omaha, Nebraska
Many vets, as well as the American Heartworm Society (www.heartwormsociety.org), are recommending heartworm prevention year-round for all dogs, no matter what part of the country they live in, because it does exist everywhere; many people travel with their Pets; and the weather that contributes to mosquito prevalence is variable.
Heartworm disease tends to primarily be a disease found in canines. Thanks to advances in medicine, Pet owners should not have to worry about the horrible toll Heartworm disease can take, as long as they follow the appropriate preventive measures. In Nebraska it is recommend pups get their heartworm “treat” once a month and getting a heartworm test once a year.
Heartworm disease is caused by a parasite— a big white worm that starts off tiny enough to live in a mosquito. The mosquito bites a dog; the larvae travel to his or her heart and pulmonary vessels, grow into a huge mass of wriggling pasta-like worms, and cause considerable damage to the cardiac and respiratory systems, including coughing, lethargy, and often sudden death.
When I was practicing in Colorado, I had a shepherd mix as a patient. She was in for her annual exam—check-up, vaccines and a heartworm test. Her heartworm test came back positive. Her owners had spent all they had on her routine care and couldn’t afford several hundred dollars to treat her.
Every vet I know goes through the following two struggles when clients need to make a financial decision about their Pet’s life. It is how we end up with most of our Pets and it is how many of us run ourselves out of business. 1) I was not in a position to adopt the dog. 2) I could not afford to treat her any more than her family could. All I could do is walk through this time with them. After several agonizing weeks, they decided to have her euthanized to spare her inevitable future pain, and to prevent the disease from being spread to others.
Let me say that every other heartworm case I have ever had has had a happy ending. It is treatable, today more so than ever. Long ago, the disease was treated surgically— vets would remove the worms from the pulmonary vessels and heart with a hook. Sort of barbaric, yes, but the 50% or so who survived did well. Then a drug was discovered that was incredibly toxic to the Pet, but would kill heartworms, and survival rates went way up. Now, we use a series of two injections of a newer, safer drug. Pets are usually hospitalized for treatment and it is still hard on them, but in the long run, they do great.
Find out when your dog’s last heartworm test was. If it was not in the past year, get it scheduled. It will take all of 15 minutes to have blood drawn and get a result back. Get out your new calendar, and write, “Give heartworm medication” on such and such date. Or better yet, take the cute little reminder sticker out of your box of heartworm preventive and put it on the calendar. Then, do that for every month. Every time you come to a sticker day, give the preventive. If you do not live in Nebraska, call your veterinarian, ask what he or she does with their own Pets, and follow that schedule.
I would like nothing more than to hear you to sound a little bit bored when I call you each year to say your Pet’s test was negative. In fact yawn as you answer and say (like you said the year before and will say the next), “Well, yeah, I figured.”
For what it’s worth, my two dogs, Ebony and Noodle, get their heartworm prevention monthly and a yearly test. Sometimes I forget to tell my husband when their tests are negative, but if I do tell him, he sounds a little bored and says, “Well, yeah, I figured.”

I have heard that in the cold months that it is better to discontinue monthly treatments as it is toxic to the dog’s liver ad not necessary due to the lack of mosquitos, is there any validity to this?
May 24th, 2009 at 1:38 pmHi! The medication in heartworm preventatives is a very low dose of Ivermectin (Heartgard and Wormshield) or another medication that is very safe for dogs given once a month. In fact, these drugs are sometimes used for other conditions in much higher doses with very good results. To prevent heartworm disease, we only need a dose high enough to kill the microfilaria, the immature stage that is transmitted from the mosquito to the pet’s bloodstream. This is safe for your pet’s liver and other internal organs, so please do not discontinue heartworm preventative for fear of hurting your pet! The damage done my heartworms is extensive and sometimes fatal! Some pet owners choose not to give prevenative over the winter, because heartworm disease needs a mosquito to be transmitted, and mosquitoes cannot live in temperatures below freezing. Have your veterinarian help you decide if seasonal prophylaxis is an option, and if so, when you should stop and restart preventative. Also remember if you travel with your pet, to consider the weather where you will be!
May 27th, 2009 at 1:30 pm