Heartworms are a deadly parasite that are spread by mosquitoes. If there are mosquitoes living in your area (welcome to the south), then your pet is at risk of acquiring heartworms.
Dogs are the normal host for heartworms, though some cats and ferrets can also be infected.
Heartworms are spaghetti size worms that live in the heart of animals infected with heartworms. These worms eventually cause heart and lung damage that leads to death. The worms will produce small babies (called microfilaria), that circulate throughout the dogs bloodstream. When a mosquito bites a dog with heartworms, it will suck up blood along with the baby heartworms. When the mosquito bites a second dog, the baby heartworms are transmitted into the second dog. These eventually end up in the heart where they start their damage. These worms will then start producing babies, and the process continues.
The treatment for heartworms is a 10-12 week process that consists of arsenic injections. This treatment can be both toxic and expensive.
What heartworm preventative does is that it destroys the baby heartworms before they can make it to the heart. We will start puppies on heartworm preventative at 7 weeks old and keep them on it for life. It is given year round in the south because we can have mosquitoes flying around at Christmas time.
There are many options for heartworm preventative, ranging from monthly oral to topical treatments. Dogs over 6 months old can also be given a multi-month injection.