We hear this question quite often here at HappiDog Rescue. Obviously, we want the best for the animals we love and take care of. If you want guidance on this particular subject, here’s a great article from Today’s Veterinary Practice we recommend reading:

I have heard that yearly testing is no longer necessary due to the high efficacy of heartworm preventives. What is your opinion?

It is true that the monthly oral and 6-month injectable preventives are very good. In addition, when inadvertently administered to a dog with microfilaremic heartworm infection, they are safer than the previous preventive (diethylcarbamazine), which produced severe, sometimes fatal, reactions in microfilaremic dogs. Reactions, albeit rare, can occur in microfilaremic dogs that are inadvertently treated, depending on microfilaria numbers and the product used.