Can Heartworm Be Passed Between Dogs?

Q. My 3-year-old Boxer was diagnosed with heartworms. I just acquired another Boxer, and wondered if this is communicable between the dogs.

A. Heartworm can be passed from dog to dog, but not from direct contact. A mosquito must bite your infected dog, then come back at a later time (after the heartworm has gone through a developmental stage in the mosquito), and bite your other dog.
 
In general, this would be unlikely. However, your uninfected dog should get a heartworm test to make sure he doesn’t already have the disease, then you can put him on a monthly heartworm preventive.
 
All dogs that live in areas with mosquitoes should take a heartworm preventative all year long, even if there are no mosquitoes in the cold season.