As near as I can tell, you're talking about an injection of ivermectin, which is what we typically find in heartworm tablets.
I would need to ring my vet to confirm but I'm certain he uses proheart SR-12 which has an active ingredient of moxidectrin.
There have been reports of some dogs of various breeds reacting badly though my dogs have never shown any adverse signs.
So with the comment that some vets in caring's area don't think it is necessary, I also wonder if their incidence is as high as ours. Some areas of the US are at greater risk than others, and I expect the risks from one country to the next may be different as well.
Kirsten, you are correct. I live in a cooler climate and as such are considered to be at a lesser risk than for example, J's area which has high heat and humidity.
Given that I never know where we may travel with our SD, I personally chose to err on the side of caution and protect him as best I could.
In this country, we have to have blood drawn for a heartworm test either annually or biannually or a vet won't prescribe the medication.
Again, just speaking of my local vets. As long as a dog has been receiving the medication since puppyhood, the vet will administer the medication. However, if the dog (adult) to be treated has never received the medication previously, a blood test would be undertaken first.
I will echo Kirsten in adding a disclaimer. I, also, am not a vet and am only speaking from personal experience.
It is always best to consult your own vet.