A range of diseases can cause rapid or sudden death in cats. This is complicated by the fact that cats will often mask illnesses--even the most serious of conditions--until just before they die suddenly. The humans who love them are left wondering what happened and what could have been done to prevent it.
The most common cause of sudden death in cats is hypertrophic cardiomyopathy. Other syndromes include feline infectious peritonitis (FIP), feline immunodeficiency virus (FIV) and toxoplasmosis, a parasitic disease.
Hypertrophic cardiomyopathy is a hardening and thickening of the heart muscle. It occurs most often in neutered, middle-aged male cats. Symptoms include laboured, open-mouthed breathing, rapid heart rate, vomiting, decreased appetite and blue-tinged gums.
Symptoms of feline infectious peritonitis (FIP) include depressed appetite, weight loss, dehydration and possible ocular lesions. Feline immunodeficiency virus (FIV, or feline AIDS) may not present any symptoms until just before death. Short-term symptoms include diarrhoea, gingivitis, neurological disorders, chronic fever and recurrent bouts of illness
Signs of toxoplasmosis include weight loss, depressed appetite, fever, diarrhoea, vomiting, glaucoma and yellowish gum and skin tones. Cats with heartworm disease may experience coughing, vomiting, weight loss and right-sided heart failure.
Because symptoms of these diseases often do not develop until just prior to death, veterinary treatment may be only supportive. Even when treatment starts at the onset of the first clinical signs, prognosis is often poor.
Humans who have immunosupression or are pregnant should have no contact with toxoplasmosis-infected cats, as the parasite can spread to the human or foetus. The other diseases discussed here cannot be passed to humans.
Veterinary treatment is often difficult due to the rapid onset and similarities of symptoms. A necropsy is often necessary to determine the cause of death.