Is heartworm painful?

It’s hard to say in pets whether it is painful. I don't think the worm as it travels itself is necessarily painful, but as they develop these symptoms, discomfort and pain follows. The inflammation that the worm causes can lead to pain as well inside the body.

It’s not painful, per se, but they feel sick, uncomfortable, and they're likely having difficulty breathing. They're not perfusing very well, so they don't feel well. Is it overt pain? I'm not sure.

Is it painful in the sense like you stubbed your toe? No, but is it painful in the sense that if left untreated, it could cause the death of your dog.

Heartworm disease can be painful if the heart is very enlarged or if the migration of the worm suddenly happens and causes some issues in the vessels.

No, as far as we know, heartworm disease is not a painful condition for dogs, thankfully.

Heartworm is not necessarily painful for dogs, but it is uncomfortable. This discomfort is primarily due to the inflammation it causes in the heart and the lungs.