A mosquito bite is just a nuisance to most people, but it can kill your dog if the mosquito is carrying heartworm larva, says the American Heartworm Society.

In fact, canine heartworm disease is the biggest killer of dogs in the country, after automobile accidents.Current data shows only about 10 million dogs of the estimated 50 million in the U.S. are protected against heartworms. Until recently, the only preventive treatment required daily dosage but now a new swallowable tablet, available only through veterinarians, needs to be given just once a month.