Heartworm is a parasitic disease primarily affecting dogs, and occasionally, ferrets and other animals. While cats can be infected with a related parasite called feline heartworm, it's much less common than in dogs and doesn't typically cause serious health issues.
If you're worried about a kitten's health, it's best to contact your veterinarian. They can diagnose any potential problems and provide the appropriate treatment.
Please avoid giving any medication or treatment to a kitten without consulting a veterinarian.