I am taking a Veterinary Parasitology class right now and usually cats get low numbers of worms...however, when the worms die they are more likely to pass into the lungs. My notes state that most cats are asymptomatic, but those with clinical signs produce respiratory signs such as coughing and/or dyspnea, or intermittent vomiting that is not associated with eating. A small percentage of cats suffer acute respiratory distress and sudden death, similar to what is observed in cats suffering from asthma or cardiomyopathy. Some cats have signs of weight loss or diarrhea without respiratory signs. Many of these cats appear clinically normal prior to these acute events.

As to a positive antibody test, that does not necessarily mean that the cat has heartworm. This result can indiciate that there is a current adult infection, recently cleared adult infections, ectopic infections (meaning that the heartworm migrated to a spot not normally found in), exposed cats on preventive, or simple exposure of cats to infected mosquitoes.

Nine months ago, one of my cats came back antibody positive for Heartworm..how he got it in Arizona where I have never seen a single mosquito I don't know...My veterinarian gave me HeartGuard (which I needed anyway since I now live in the south), which will cause a slow kill of the heartworms and hopefully, not cause dead worms to move into the lungs. My best suggestion would be to have your vet give this medication...and in six months have the cat retested. I retested Whisper twice six months later and he came back negative. Good luck!