* Parasitism: One organism (the parasite, in this case, the heartworm) benefits at the expense of the other (the host, the dog).
* Heartworm's Benefit: The heartworm thrives in the dog's blood vessels, particularly the heart and lungs. It reproduces and spreads within the dog's body, ultimately causing significant harm.
* Dog's Harm: The dog suffers from a range of severe health problems due to the heartworm infestation, including:
* Heart failure: Heartworms block blood flow and damage heart tissue.
* Lung damage: Worms obstruct blood vessels and can lead to inflammation and fluid buildup in the lungs.
* Other health issues: Weakness, coughing, difficulty breathing, and even death.
Therefore, the relationship is not mutually beneficial. The heartworm benefits at the dog's expense, making it a parasitic relationship.