History of Discovery

            Canine heartworms were first discovered in 1856 on the southeast coast of the United States.  An infection by the same agent was then discovered in cats in the 1920’s.  However, it was not until 1952 that a human infection by Dirofilaria immitis was documented in America.  Since then, most diagnoses of a case have been in the United States and Canada.  In South America, discovery of the dog parasite was first made in 1847; however, a report was not published until 1875.  The first human case took place in Brazil in 1887 along with the first feline case in 1921.

            There has been evidence for the existence of the agent for many centuries.  In 1586, Chez Iean Wolfe made this sketch of a “monster” found inside the heart of a horse, later identified as D. immitis.

Figure 2: Monstrous creature found inside horse heart in 1586. 23