Diarrhea in a cat

Our question today comes from Tina N. who says "I have two male cats, one five and the other two years of age. Both were adopted, the youngest about nine months ago. Both cats eat the same food, but the five year old always has soft or runny, sometimes bloody, stools. The younger cat always has a firm stool. What could be the cause of this?"

There are a number of reasons why Tina's cats may show such different consistency in their stools, even when they eat the same food. Tina did not indicate if this problem only started after the younger cat joined the household, but if so, he may have brought some extra baggage with him in the form of parasites. Of the parasitic causes of diarrhea, coccidiosis is the most common in cats and dogs.. The parasite is transmitted when infective oocysts are ingested from the environment and they invade the lining of the intestinal tract. The source of the infective oocysts may have been from the younger cat. Quite often cats and dogs seem to develop a tolerance to the coccidia and show no symptoms, especially in mature animals. In the case of Tina's older cat, if he was not exposed to the parasite when he was younger, he would not have developed this tolerance. Symptoms seen in coccidiosis include mild to severe diarrhea, sometimes with blood. We tend to think that if we don't see any parasites in our pet's stool they are not infected, but in the case of coccidia, they are much too small to be seen with the naked eye. Your veterinarian will have to perform a fecal floatation test (see our last issue for more information on this test procedure) to detect the parasites. One caution here is that often the numbers of coccidia in the stool are small and repeated tests may have to be conducted to find them.

Other parasites might be the cause here, such as Giardia, Cryptosporidia and similar organisms. These are less likely, though, since cats are generally asymptomatic while dogs develop sometimes severe diarrhea.

Another possibility we might consider could be the food itself, but in Tina's cat's case it is unlikely because while diarrhea may result, blood in the stool would be very rare from this cause. But certainly you would want to try at least a few different cat foods to see if the diarrhea will respond to a change in diet. Speaking of diets, although many cats love milk and cream, this will often result in diarrhea if they are not accustomed to dairy products. My cats all just adore cheese in any form but they do not have problems with it because they receive it on a fairly regular basis.

Other causes of the diarrhea Tina reports might include Feline Lymphocytic-Plasmacytic Enteritis which causes both diarrhea and vomiting and the more common Feline Lymphocytic-Plasmacytic Colitis. However, these are much less common than an intolerance to the particular diet ingredients or coccidia infection.

The bottom line here is to observe your pets. If they are showing signs of dehydration or they are losing enough blood to make their gums pale, take them to your veterinarian for an examination and a more definite diagnosis. Occasional diarrhea, even with tiny amounts of blood, in a otherwise healthy cat or dog is not cause for panic, but do continue to observe them for additional signs.