In my introductory blog, I mentioned that I was treated with Revolution for ear mites and fleas. This medication however, is also labeled for prevention of heartworm disease… Which gives me an excellent segue to my next topic: heartworm disease.
Heartworms have been traditionally associated with cardiopulmonary in dogs. The name of the actual parasite is Dirofilaria immitis and it needs two hosts to complete its lifecycle: the mosquito and the dog. Here’s a very basic overview of this life cycle in the dog:
- An infected mosquito with L3 larvae bites a dog
- The L3 larvae enter the dog’s skin and develops to an L4 larvae. It will live in the skin for a few months while developing to an L5 larvae.
- L5 larvae are young adult worms that are ready to migrate to the heart where they typically live in the pulmonary artery.
- Once in the heart, these worms grow larger and mate, thereby producing L1 larvae which are transmitted to mosquitoes when they feed.
The L1 larvae develop into the L2 and L3 larvae in the mosquito. And it starts all over again.
Depending on how many worms a dog has in his heart, the clinical signs can vary. This disease can cause right-sided heart enlargement, pulmonary hypertension, increased tendency to form blood clots, exercise intolerance and chronic coughing. If a worm migrates into the vena cava, it can cause death.
(Ok, that was a lot of information on dogs which is painful for me. I want to talk about cats.)
Cats do, in fact get infected with the heartworm parasite. The disease just looks different in cats because cats do not typically develop as many adult worms the way dogs do. Instead of developing symptoms associated with heart disease, cats more often develop lung disease. Cats have a very strong immune reaction to heartworm larvae, therefore less than 25% of the larvae make it to adulthood in the heart. There are two phases that heartworms can cause respiratory symptoms in cats: L5 reaching the pulmonary arteries and/or adult worms dying. Both of these phases cause a lot of inflammation which causes difficulty breathing. This is know as HARD or Heartworm-Associated Respiratory Disease. HARD can look very similar to asthma and often requires a similar treatment. In some cases, feline heartworm disease can cause death.
The best to deal with HARD is to avoid it altogether. In other words, heartworm preventatives are very effective at preventing this potentially devastating disease. There are many products available for this purpose: Heartgard, Revolution, Interceptor, to name a few. My personal preference is Revolution because it is applied topically….and I HATE pills.
So there it is…the HARD Facts. There is much more information from other sources about this topic. I have just included the basics due to space and due to my pending nap schedule.