My dog is on heartworm preventative. Also, sometimes owners forget to give preventative daily or monthly, sometimes dogs spit them out of may get under dosed due to weight gain. Doing a heartworm test will give you peace of mind in knowing that your pet is healthy. I give my pet heartworm preventative faithfully once a month. We always recommend with all of our surgical procedures a pre-anesthetic profile, post operative pain injection, and surgical fluids to offer optimal care for your pet during any surgical procedures.
Many Northern states stop preventative in the winter because of cold temperatures.
Here in Arkansas we have seen mosquitoes in the winter. The weather here is not cold enough to take a risk of taking your pet off of preventative, or possibly forgetting to get back on preventative once you stop. It improves the temperament of the pet, decreases territorial aggression, helps reduce roaming behavior and reduces the chances of your pet from getting testicular or prosthetic problems or even cancers. Lymes vaccines are recommended because we live in an area where your pet is commonly exposed to ticks which may be likely to be carrying the disease. The only way to prevent risk exposure is to vaccinate yearly.