Heartworm Disease

Heartworm is a preventable, but serious and potentially fatal, parasite that primarily infects dogs, cats, ferrets and rare cases have been seen in other species of animals as well. The infection is more prevalent in hotter climates due to the fact that the insect that typically spreads the parasite is the mosquito. It is most prevalent in the southeast of the United States, but there are also cases on both coasts and in between.

The most common thing people say is, “Why is there a need to put my pets on heartworm medications if they do not go outside?” The answer is this, don’t mosquitoes come into your house and bite you? They won’t discriminate between a human or one of your pets. They can be outside OR inside your house.

Let’s start at the beginning. Heartworm disease is a potentially deadly infection, caused by worms (Dirofilaria immitis) that can grow to be as large as 14-inch-long adults. These worms live in the right side of the heart and arteries of the lungs. Pets of any age, species and breed are susceptible to this infection. Heartworm infection can cause potentially serious damage to the arteries, eventually leading to heart failure, and in severe cases, damage other organs such as the liver and kidneys. However, with an easy once a month preventative treatment, heartworm should never get to that point.

Before you start the prevention (which can only be gotten with a prescription from your veterinarian), if your pet is over six months of age, they need to do a simple blood test to make sure the pet tests negative for the heartworm parasite before prevention is started. The reason you can not give it without a test, is if the heartworms have already matured from larvae into adults and are living in your pets heart and/or arteries, the worms will cause a blockage in your pets blood system and/or heart and most likely kill them. You can start heartworm prevention before six months of age because by six months, if your pet is inoculated with the parasite, the worms aren’t adults large and/or mature enough to cause a blockage yet. They can also live for five to seven years in a dog. In cats, it takes about eight months to mature into adult worms that live from two to three years.

Adult female heartworms release their young, called microfilaria, into the animal’s bloodstream. Mosquitoes then become infected with microfilaria while taking a blood meal from an infected animal. During the next 10 to 14 days, the microfilaria mature to the infective larval stage within the mosquito. When the mosquito bites another dog, cat, or other susceptible animal, the infective larvae enter through the bite wound, and that is where the life cycle repeats itself again.

Please remember, each veterinarian has THEIR OWN protocol and you must use the one that your veterinarian uses. They may ask to test your pet every year for heartworm just to make sure as a precaution.

Treatment for heartworm disease is costly and painful for your pet. It requires several painful injections of a strong immiticide that will kill the worms. The injections are usually given in the deep lumbar muscle (lower back) of the animal. The injections are spread out by a few weeks depending on what stage the heartworm infection is. After each injection, the pet must stay in STRICT CAGE REST, short walks, and NO OVER EXERTING themselves for weeks and sometimes months.

All of these things can easily be prevented when using heartworm prevention in the correct way. The main reason for this blog is to explain to you that when your vet asks you about if your pet is on heartworm prevention or not, it is really for their well being. Hopefully this has given you all more information on this deadly parasite. Always remember, please consult with your veterinarian first before giving, stopping, or changing any medications. Until next time!

Rachel Husney, LVT