It's a bit confusing because they are advertised as preventatives but while they prevent your dog from contracting heartworm disease what they are actually doing is killing any heartworm larvae they may already have in their system. The medication works 45 days backwards
. Therefore, I give my dogs their heartworm medication every 45 days. I start their medication 45 days after the temperature is about 50 degrees at all times
. Technically they say 57 degrees but I don't want to take chances so I am conservative on that end.
Here is an excellent detailed explanation:
Heartgard Plus, Ivermectin and the others all have additional dewormers that kills other types of worms they might have like roundworm and whipworm. Since my dogs (Chama, to be exact, b/c she is a poop eater) have only once tested positive for other worms I do not use the products with additional dewormers. Instead I take in a stool samply yearly and have it checked for parasites. If they have them, I treat them for those specific worms. That way I am not given them unnecessary medications.
For those of you who don't know me, I'm one of those all natural types.
Unlike many people who treat their animals holistically, I do use heartworm preventative. However, since it is poison, I use it as infrequently as is still effective in killing the heartworm larvae. That means that I give 3, and occassionally 4 (depending on the weather), doses a year. I also test my dogs yearly for heartworm, instead of every 3 years like some people do.