(BPT) - Heartworms are one of the most common - and preventable - threats to pet health. Sadly, owners who think their pets' risk is low may unknowingly be taking a pass on protecting them from heartworms. To help both veterinarians and pet owners better understand this threat, the American Heartworm Society (AHS) periodically conducts nationwide surveys of veterinary practices to see where the heartworms are. From their latest AHS survey, you can learn more about how heartworms spread (yes, mosquitoes are to blame), where heartworm-positive pets are being diagnosed, and why heartworms are now being found in regions once thought to be heartworm-free.