− | The risk of Dirofilaria immitis infection is greatest in outdoor dogs and cats. Animals of any age may be affected, but infections are most common in 3 to 8 year old dogs. Medium and large breeds are predisposed. | + | The risk of Dirofilaria immitis infection is greatest in outdoor dogs and cats. Dogs of any age may be affected, but infections are most common in 3 to 8 year old dogs, and medium and large breeds are over-represented<sup>merck, fmc</sup>. In cats, there are no breed or age predispositions, but males are more frequently affected<sup>fmc</sup>. |