Sudden Death in Cats
Question: Dear Dr Richards,
It's me again. In someone else's name again, I know, sorry. But she's desperate. She found her cat dead this morning, on his favorite place like he was only asleep. The evening before, he was normal and acted as usual, nothing suspicious. We already agreed on the suggestion of poison being impossible. What could it be, he was vaccinated and in good shape. Please help her, she hates that uncertainty!
Kindest regards, Anna
The most common causes for sudden death in cats are cardiomyopathy and heartworm disease. Both of these disorders can cause death with almost no warning at all. We have had a client whose cat went to jump from the couch to a chair near it and landed in the chair, dead. This cat had about four heartworms in the pulmonary arteries when we did a post mortem examination. As far as our client could tell, her cat was normal right up to the time that it died. Other clients have had similar experiences with cats who have had cardiomyopathy, although none quite this dramatic. It seems odd that these disorders can be serious enough to cause death while not causing any warning symptoms but it really seems to be the case at times. Cardiomyopathy is probably the leading cause of anesthetic deaths in cats and most of the time the affected cats have no signs that are detected prior to the anesthetic crisis.
There are many other possible problems, though. Cats probably occasionally are born with defects that can lead to sudden death, such as aneurysms that may suddenly rupture. Toxin exposure sometimes occurs without the cat owner being aware of it. Application of a dog flea control product containing permethrin sometimes results in accidental poisoning, although most cats do show clinical signs prior to the time that they die with this particular toxic exposure.
Sometimes, there are signs of a serious illness that are subtle enough that veterinary clients, or even veterinarians, miss them. Toxoplasmosis, feline infectious peritonitis, feline leukemia virus, hemobartonellosis, liver failure, chronic kidney failure and other diseases usually cause recognizable symptoms but in rare instances there are not clear-cut clinical signs and death appears to occur suddenly.
The only really good way to try to figure out the cause of a sudden death is a post-mortem examination. For people who are really bothered by not knowing what happened, making plans to have a post-mortem examination in advance of the time when their pets die can provide answers, which is comforting in the long run for many people.
Mike Richards, DVM 10/1/2001
Question: Hi there, I am a subscriber. I found your article interesting on young vets getting out of school. Although I'm a teacher, I remember how hard it was getting started after having to spend 6 years in University and pay student loan debts. I can't imagine regarding vet school and then having to cover overhead costs. I really think pet health insurance that is available her in Canada is a "godsend". It has helped my dog trememendously who's had to have knee surgery twice (ligament tear).
I have two questions. For the spca shelter I have been fostering two week old kittens who are now 3 weeks old (I've had them for 1 1/2 weeks now). They are healthy and strong and eat quite a bit now. However, last night when I went to go feed them, one was very limp and seizuring. I feed them every 3 hours and the 3 hours previous she had been absolutely fine and was even playing with her brother. When I rushed her into an animal emergency clinic, they decided to euthanize her as she was obviously very ill. I am very upset as I care for all the little creatures that I foster, and just wondered what you thought could have happened. I was too upset last night to ask the Doctor, but the spca staff said that this just happens sometimes.
Question: There are several possible causes of sudden death in young kittens but in the three to six week age range the most common causes of death are reported to be the infectious diseases.
The most common parasitic problem causing death at this age is probably toxoplasmosis. It is usually necessary for the mother to become infected during the pregnancy for the kittens to develop signs this early but that has been documented to occur and is supposed to be a pretty common cause of kittens seizuring and developing rapidly fatal pneumonias in the neonatal period. Our experience with this is that usually more than one kitten in the litter is affected but that it can be a small percentage of the litter. Roundworm migrations can cause seizures and death but I think the kitten is a little young for this effect.
The most common bacterial cause of death in this age range may be Bordetella infection, although I am not sure of that. It is supposed to be pretty common in shelter environments and can cause rapidly developing pneumonia in kittens in the 3 week to 8 week old age range. It would seem likely that some of the other kittens would be infected but there can be variations in the immune status of kittens in the same litter, making it possible for only one kitten to show signs. Mycoplasmal pneumonia and chlyamdiosis can occur in young kittens, as well.
Viral illness is also possible. Feline herpes virus, calicivirus and feline leukemia virus are all possible problems in this age range. Panleukopenia (feline distemper) can also occur in kittens this young but it has become uncommon to see this disease, probably due to the vaccination of so many more cats than in the past.
Since several of these illnesses are pretty common in shelter situations and since it is difficult to raise orphaned kittens and for cost considerations, it is unusual for people to pursue post mortem examinations to determine a specific cause when kittens in this age range die, so there are likely to be other problems that occur that we do not have much information about.
Dr Mike Richards, DVM 7/5/2001
Question: I was so grateful to find some information on sudden death, because on Sunday, August 6th, my healthy 2 and 1/2 year old British Blue died suddenly. He showed no signs of any illness. He was in his Sherpa bag, we were bringing him back home from our Summer place and he started to struggle. We stopped to check why he was moving around and I put my hand on the back of his neck and he let out a cry and went limp. It took all of 30 seconds. Needless to say, my husband and I are devastated and we felt so helpless. We got him to our vet within 10 minutes, but it was clear he was already gone. The vet seem quite confident in saying that it would have to have been some sort of heart condition that had gone undetected and it was the only explanation. I was somewhat satisfied by her assurances, but I can't stop reliving the incident and trying to figure out what could have gone wrong, and could I have done anything to prevent it. We plan on getting another British Shorthair next year (we love the breed and their loving and loyal temperament) but I'm scared. Just a little background - Chad traveled with us almost every weekend - he loved to be with us and would get into his bag to go the country willingly and would sit quietly during the entire trip. Sometimes he would like to sit on my lap and watch the passing scenery. He adapted immediately to the new environment - he was never skittish or restless - he basically took over and sometimes it seemed he was annoyed when we were back in the City - he loved the freedom of all the windows to look out of. When he took him outside into the yard - he was never out of our sight for even a second. He usually would sit on the dock with us and just watch life. He was not at all interested in chewing any plant life, and was very picky about his food and never picked up any thing off the floor to eat, etc. Obviously, one of my fears was poisoning, but the vet told me he would certainly have shown some signs of sickness if that were the case; i.e.. vomiting. But he was his normal active self Sunday morning, ate his breakfast (he ate Iams) and had his Spring water and acted perfectly normal for the 1 3/4 drive back to the City.
About a month and 1/2 ago, he was lying in bed with me and I was rubbing his back, when he let out a yell and jumped off the bed. I noticed we was limping. Because it seemed related to my touching his back, I was alarmed. (I had a diabetic cat who eventually went limp in his back legs due to infection). I took him to his vet and had him examined and had x-rays. I made it clear what had precipitated his problem and expressed concern that he hurt his back. The doctor said while it wasn't apparent on the x-ray, it was possible that he had a condition called anterial patella luxation (sp?) and suggested surgery if it did not improve. While he continued to limp, he didn't seem to be in any pain. I had a friend, who is a vet (who is also holistic and a chiropractor) examine him, and after a full exam seemed to think that the limping was possibly his hip and suggested I take him to an orthopedist. I then took him to Animal Medical Center in New York to a orthopedic surgeon recommended to me as one of the best. This surgeon suggested that his problem was not bad enough to warrant surgery and he should be rested and do a "wait and see". That seemed like the right thing because within days he was perfectly fine - no limp - jumping around again and playing like a kitten. The reason I bring this all up is because I read about blood clots - Is it possible that that's what happened to cause the weakness in the back legs and it wasn't an injury at all? I'm afraid of that possibility because it makes me feel that his death could have prevented. But if three doctors examined him and no one detected a problem with his heart, how could I have known? I know at least the first two listened to his heart (the third time, my husband took him) I don't know if you'll be able to offer me any insight, but the grief is overwhelming and I can't seem to stop asking why? I'm afraid that if I question the three doctors he saw just last month, that they'll be more concerned with protecting their own reputations if they missed something. I do not want to assign blame as I know that it won't change things. Is sudden cardiac arrest a reality, or did I do something wrong? After his "knee" problem, his vet suggested he trim down - he was getting close to 12 pounds. We switched his diet to Iams light and supplemented with a tablespoon of Spot's Stew (all natural w/veggies) every morning. Was this a mistake? Is light food wrong for a 2 and 1/2 year old? His weight was still a healthy 11 pounds. I'm sorry this is so long, but I'm still reeling from shock and disbelief.
Answer: The two most common causes of sudden death in cats, in our practice, are cardiomyopathy and heartworm disease. I think that together they account for over 90% of the sudden death cases in which we have done post-mortem exams. So I would be most suspicious of a heart problem, too.
I do think that the limping seen a little over a month ago could have been due to a blood clot but it is also entirely possible that it was not. I have to admit here that I don't usually consider cardiomyopathy as a cause of lameness unless there is a heart murmur. Unfortunately, not all cats with cardiomyopathy have heart murmurs. I read an post on the Veterinary Information Network by Dr. Kittleson, who is a well known authority on cardiomyopathy about a sudden death in a cat that he had done an ultrasound exam on one month previously that did not show cardiomyopathy. On the post-mortem exam it was possible to diagnose the condition, though.
The prognosis for cats whose cardiomyopathy shows up due to blood clots causing obvious problems is poor, even with treatment. Most cats with this particular presentation for cardiomyopathy live less than a year after diagnosis and most live fewer than five or six months. It is a tough condition to diagnose and a tough condition to treat.
Weight loss usually helps with heart disease and with lameness from arthritis so I don't think that the dietary change was likely to be a causative factor in the sudden death.
I tried to check and see if British Shorthairs were prone to cardiomyopathy but I did not find any literature suggesting this was the case.
This is a condition that makes veterinarians feel pretty helpless, too. In cats that do not develop heart murmurs, there may be no clue, or only very subtle clues, that a heart problem exists. It is a frustrating and humbling disease for veterinarians so I know that it must be even more frightening and confusing for pet owners.
It would take bad luck to have this occur in more than one cat in a household.
If you need more specific information I will try to find it for you.
Mike Richards, DVM 8/16/2000
Question: I'd like to pose a question about our cat, Mookie, who up and died while we were petting him this past Sunday.
I've searched the web and all pet sites about SUDDEN DEATH and have found this "affliction" only in the context of heartworm. I wonder if you have other ideas on this? Mookie was a healthy active 11-year-old Manx. All shots up to date. No lethargy or appetite suppression. He was purring one moment and the next he let out a blood-curdling scream, then died.
Thanks in advance.
Real "sudden death" is an unusual occurrence. As you noted, it can happen in cats infected with heartworms. It is also reported to occur in cats as the result of cardiomyopathy. This disorder can be very insidious and may not be detected prior to death. Cats probably get aneurysms that rupture, although I have only seen one report on these. Anything that causes thromboembolism can cause sudden death -- this can be seen as the result of cancers, blood clotting disorders, cardiomyopathy, trauma and other disorders. Low serum potassium can lead to sudden death, as can high serum potassium -- but usually there are other signs of illness making the process seem a lot less sudden in retrospect.
I am sorry to hear about Mookie. It is unfortunate but without a necrospy (autopsy) exam it is not possible to tell you what might have happened. It is hard when things like this can't be resolved.
Mike Richards, DVM 4/12/99
Last edited 02/16/07
Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...