Dog owners know that heartworms can be deadly to your pet and prevention is necessary. Heartworms can ONLY be spread by mosquitoes and if you have an indoor dog, they are still at risk. Heartworms can lead to death or a very expensive treatment, that's why monthly medication (like Heartgard) can save your dogs life.
You've probably heard of Cesar Millan, professional dog handler and trainer. Here are his myths and facts about heartworms. http://www.cesarsway.com/Heartgard/Heartworm-Disease?utm_content=Heartworms+in+Dogs%3A+Myths+vs.+Facts&utm_campaign=&utm_source=Twitter&utm_medium=Twitter%3A+cesarmillan