The pup's vet visit should also be for the purpose of getting a heartworm "preventative" or a prescription for a heartworm "preventative". The "preventatives" kill immature heartworms and thereby "prevent" adult heartworms. The term "preventative"...

i give Kaydee what the vet recommended (heart guardplus) but i have known some people that give the horse wormer Ivermec to their dogs instead of the heart guard.... when i asked the vet he kinda rolled his eyes and gave an answer kind of like "hmm yeah well... its ok BUT... this is better"...