Heartworm disease is a disease that we see – unfortunately – rather frequently in our patients at Carriacou Animal Hospital. While this disease is severe and if not prevented/treated also fatal, it is easily preventable with a monthly medication.
What are heartworms?
The heartworm disease is caused by a worm-like parasite, called Dirofilaria immitis, that establishes itself within the pet’s heart and is transmitted to dogs – and also to cats – by mosquitos.
Dogs get infected with heartworm larvae, when infected mosquitos carry heartworm larvae and bite the dog. It takes approximately 100 days after infection until the heartworm larvae develop over several stages to mature heartworms and establish within the heart or in the blood vessels to the heart and the lungs. Over another few months, adult female worms grow in size to about 30 cm long, the males to about 23 cm. Eventually they are ready to mate and the females give birth to live young heartworm larvae. Those very small larvae are then distributed in the blood vessels across the whole body. Now is the time, a mosquito gets infected again with young heartworm larvae, when it bites the dog and feeds on its blood and this closes the lifecycle of this parasite.
How do heartworms affect my dog or cat?
Most often symptoms begin to show when the heartworms start clogging up the heart, the lungs and their surrounding blood vessels. Depending on the amount of worms present, the duration of the infection and the individual reaction of the dog to the parasite, symptoms can vary a lot.
In moderate to advanced stages of infection, the dog owner may notice symptoms like exercise intolerance, fatigue, coughing, shortness of breath, breathing noises and decrease in appetite. In very severe stages of the disease the dog may even cough up blood or worms.
Cats can get infected with heartworm, too, but their infection often goes undetected. Cats seem to be more resistant and only show symptoms in the late stages of infection with a heavy worm burden. Coughing and shortness of breath are often the only symptoms and can be confused with feline asthma. The infection can end fatal if left untreated.
Amount of heartworms found in the heart of a fatally infected dog (1,5 years old).
What is the prognosis?
Upon examination and further diagnostic tests, your veterinarian may find other indicators for heartworm disease, such as heart murmurs or other signs of compromised heart and lung functions. In severe infections, your veterinarian may find signs for obstruction of the blood flow due to a large number of worms in the main vein (vena cava) leading to the heart and the right chamber of the heart itself. The outcome for patients with mild and moderate clinical signs is good, when the right treatment is administered. In severe stages of the disease, treatment is sometimes still possible, but it is painful, bears a higher risk of complications – which can be fatal – and is labor intensive and expensive.
How can heartworm disease be prevented?
The best and most effective way to treat heartworm disease is prevention. There are different products available that can be given in tablet form, drops in the food or even spot-ons for the skin. They all have one thing in common: They need to be given regularly once per month to every pet as long as the live. Especially, living in the Caribbean, you need to give your dog or cat the heartworm medication year-round.
So, if you are not giving your dog the specific monthly treatment, already, and/or if you think your dog is showing signs of heartworm disease, please contact us or the veterinarian in your area!
- Dr. Nadine Cerny, June 2020