Prevent a broken heart: The deal with heartworms

One of the most common discussions I have with pet owners is about heartworm disease and prevention. Since April is the National Heartworm Awareness month, Dr. Smith and I decided we would devote the next columns to heartworm disease, prevention, and treatment.

Our climate here in the Gulf South is perfect for breeding mosquitos. These annoying biting insects breed rapidly in standing water in warm weather. Unfortunately for our dogs and cats, heartworms are transmitted by mosquitos, and thus heartworm disease is extremely common in this area. When a mosquito bites a dog that is infected with heartworms, it takes in some of the heartworm larvae circulating in the infected dog’s blood. These larvae go through several life stages within the mosquito and then are passed on to the next dog when the mosquito takes a meal. These microscopic larvae migrate into the bloodstream and make their way to the heart, and more specifically, to the arteries leading from the heart into the lungs. These pulmonary arteries are the preferred home of heartworms and once in the pulmonary arteries, they mature into adult worms.


The adult worms in the pulmonary arteries cause inflammation and damage to these blood vessels, as well as damage to the lungs and heart. Left untreated, heartworm disease can cause permanent damage to these organs, heart failure, or even sudden death. These worms, or parts of worms, can also act as emboli in the lungs, blocking blood vessels and causing severe coughing, difficulty breathing that may require hospitalization, or even death. Dogs can develop a condition called caval syndrome in which the heartworms obstruct the valves in the heart and cause sudden heart failure and commonly death.

The good news is that, in dogs, heartworm disease can be treated, and more importantly, it can be prevented. Prevention of heartworm disease should start early, and can begin as early as six weeks of age. There are a bewildering number of products on the market for prevention of heartworm disease. There are tablets and flavored chews meant to be given orally. If your pet is a picky eater, then there are topical products. Most of these products must be given once monthly to be effective. One product, ProHeart 6, is an injection that can prevent heartworm infection for 6 months. This is great for owners whose lifestyle makes it challenging to give a medication every 30 days regularly, or who, like me, tend to be a little forgetful. Your veterinarian can help you figure out which product is best for you and your pet.

solar2.JPGHeartworm disease affects cats as well, but unfortunately there is no treatment for heartworm disease in cats. Therefore, preventing your cat from becoming infected with heartworms in the first place is extremely important. There are oral and topical products on the market for cats and all must be given every 30 days. Signs of heartworm infection in cats are predominantly respiratory, such as difficulty breathing or coughing. For cats, sudden death may be the only indication that a cat was infected.

Decreasing your pet’s exposure to mosquitos can help. Cleaning up any standing water in your yard removes mosquito breeding sites. Keeping your pets indoors at prime mosquito feeding times, dusk and dawn, can also help. Some flea products such as Vectra3D may have some mosquito repellant capability. Frequently, owners mistakenly believe that pets kept entirely indoors do not need heartworm prevention. While their exposure risk may be reduced compared to that of a pet who lives outside, it is not fully eradicated as mosquitos can find their way into even the best-screened houses. ALL PETS, regardless of whether they live indoors or outdoors, should be on regular heartworm prevention every single month.

Heartworm prevention does require a prescription from a veterinarian. Your vet will likely perform a simple blood test to check your pet for heartworms before writing a prescription. Heartworm disease can be devastating to your pet’s health and is so simple to prevent. Talk to your veterinarian to learn how to protect your pet from heartworm disease.

The Louisiana SPCA is devoted to finding loving homes for heartworm positive dogs. When you give to the Heartworm Fund, you give a new life to an animal in need. During the month of April, if you donate to the fund, you’re entered for a chance to win a year of heartworm prevention for your pet!

Dr. Sarah Reardon has been a veterinarian with the Louisiana SPCA for 3 years. She earned her Doctor of Veterinary Medicine degree from LSU School of Veterinary Medicine. Dr. Reardon has 3 dogs, all Louisiana SPCA rescues. If you have a question for Dr. Reardon, email or visit dr-sarah-r-1