When an outdoor-access cat goes missing from its home range, this frequently means that something has happened to the cat to prevent it from returning home. Death, injury or illness may all prevent a cat from returning home. When sick or injured, a cat may hide within its home range and may die if not found. This behavior has been observed in both outdoor-access and indoor-only cats. Understanding the frequency of different causes of death in owned cats (particularly sudden death where the owner does not know that the cat is sick or injured), may help us better determine priority areas to search for a missing cat.
Olsen and Allen (2001) conducted a study on sudden and unexpected causes of death for cats in a city of over 200,000 people and surrounding towns in Saskatchewan, Canada. During a 10-year period, one large veterinary facility treated 994 cats of which 79 (8%) were brought in for autopsies by their owners because they died suddenly and unexpectedly. Of these 79 cats, 49 (62%) were outdoor-access, 11 (14%) were indoor-only, and 19 (24%) were unknown.
Table 1 shows the relative frequency of different causes of sudden death. By far the most frequent cause of sudden death (34%) was attributed to trauma caused by road traffic accidents (RTAs). All but two of the RTA deaths were outdoor-access cats, so that means that 51% (25 out of 49 total) of outdoor-access cat deaths were due to RTAs. Other types of death due to trauma were 3 dog bites and 1 gun shot.
Heart disease (20%), primarily hypertrophic cardiomyopathy, was the second most frequent cause of sudden death followed by intestinal disease (8%). Five of the 6 cases of intestinal disease were under six months old and died of enteritis due to feline panleukopenia. Surprisingly, three of these kittens were indoor-only. Respiratory disease accounted for 6% of deaths; three of these cats died of pneumonia and were 2-10 months old. The other two cats died from breathing obstructions.
Urinary tract diseases (5%) were more likely to occur in older cats. Three cats aged 8, 10, and 18 years died of renal disease. One 6 year old cat died of a urethral obstruction. This is unusual only because urinary obstructions usually have visible symptoms such as frequent urination or straining prior to death. Diseases associated with feline leukemia virus (FeLV: 4%) were the last relatively frequent cause of sudden death. All three FeLV-related deaths were outdoor-access cats. The remaining four causes of sudden death all accounted for few cats (1% each). The cause of death could not be determined in 13% of cases.
In this particular study, road traffic accidents accounted for a high percentage of deaths (51% of outdoor-access cats autopsied). This number is even likely to be an underestimate because the data were collected from autopsy reports. If a cat was obviously hit by a car, its owner would probably be less likely to go through the expense of getting the body autopsied. There were also no cases of poisoning or death by predators, besides the three presumed dog bites. However, predator deaths may also be underestimated since these bodies are less likely to be recovered.
Unfortunately, since Olsen and Allen (2001) did not collect data on the entire population of cats in the study area, it is not possible to determine whether certain characteristics (e.g. age, sex, access to outdoors, etc.) may predispose cats to different causes of sudden death. In upcoming blog posts, I intend to focus on the most common causes of sudden death and find out what is known about them. The first paper I’m going to review is a very informative study on the factors that may predispose domestic cats to road traffic accidents.
Olsen, Tammy and Andrew Allen. 2001. Causes of sudden and unexpected death in cats: a 10-year retrospective study. Canadian Veterinary Journal 42: 61-62.