If you and your canine or feline friend live in an area where mosquitoes are indigenous, your dog or cat is at risk for heartworm infection and heartworm disease. Because the Shelter encourages people to keep their cats indoors only, it is assumed that dogs are much more at risk for this mosquito-borne illness. Still, mosquitoes get indoors. It should be noted that even one adult heartworm in a cat can be life-threatening, and that even in the early stages of infection, a cat's body experiences greater levels of inflammation. It was once thought that feline heartworm infection was roughly 10% of the canine level in any geographic area; new information indicates that as many as 14% of all cats in any geographic area are infected with heartworm, with an average rate of 6%. In fact, research indicates that in areas where heartworm infection is present, the incidence of feline heartworm infection rivals or surpasses that of feline leukemia virus or feline immunodeficiency virus.