Both the American Heartworm Society (AHS) and the Companion Animal Parasite Council (CAPC) have recently acknowledged the possibility that heartworms are growing resistant to commonly prescribed preventive drugs.
Per DVM Newsmagazine:
“CAPC Executive Director Michael Paul and AHS President Wallace Graham cited the interest and need to explore this issue in greater detail to find out why a population of animals in the Gulf region tested positive for heartworm infection, despite being on heartworm prevention.”
And according to Dwight Bowman, M.S., Ph.D. in his Veterinary Practice News article:
“… from the point of view of the dog and cat, health care now is similar to that of people after World War II when penicillin and related antibiotics jumped onto the scene and provided a remarkable method of combating bacteria. Life is good!”