don't panic over heartworm, go to the internet and learn about the bug and how it gets in the dog, there is lot of info on the subject and is easy to prevent and can be cheap using the horse worming med. keep in mind that the mosquito has to be able to maintain a body temp. of over 70 deg. for ten days in a row in order for the microfilia to develop and in most of this country much of the year that is not possible, know your area's temp. once the dog has the bug, you can't kill it yourself. the use of ivermectrin will not kill the present worms but will stop any more from developing and if the case is not too bad, the worms will eventually die on their own. while we need vets, they need money and they love the panic and the economic benefits they create. this subject is serious but easy to control, learn about it before it cost you $1500 of so,. once the bug is in the dog, you have about 30 days to kill it, therefore a dose of ivermectrin every 30 days is the standard. by the way, the med. the vets give you is in fact ivermectrin in chewable. you can divide the dogs weight by the horse allowance to get the dose, probably about 5/8 to 3/4 inch, the efficacy is really high and the risk of overdose is really low. get up to speed on this issue
cheers