Diarrhea in kittens (Proceedings)


Diarrhea is one of the most common concerns of owners with young kittens or teen-aged cats. Often times, diarrhea in kittens can be attributed to dietary changes, parasites or infectious diseases, and these should be the initial focus of any investigation in these young cats.

Diarrhea is one of the most common concerns of owners with young kittens or “teen-aged” cats.  Often times, diarrhea in kittens can be attributed to dietary changes, parasites or infectious diseases, and these should be the initial focus of any investigation in these young cats.  However, once diarrhea becomes chronic in a kitten (e.g. it has been present for more than 3 weeks), dysbiosis will develop that will often only be exacerbated by multiple antibiotics or diet changes.  Thus, a careful approach to diet selection and therapy in these youngsters is needed. The purpose of this talk is to review some of the more common causes of diarrhea in kittens, and to discuss the best approaches for diagnosis and treatment of this diarrhea.  Where appropriate, the role of diet in both diagnosis and therapy of diarrhea will also be reviewed.  

Infectious/parasitic causes of diarrhea


Trichomonosis, caused by Tritrichomonas foetus, has been recently recognized as a pathogen in kittens and adult cats. This is the same protozoal organism that infects cattle, causing early embryonic death, abortion, and pyometra.  However, in cats, the organism infects the large intestinal mucosa and causes chronic large bowel diarrhea characterized by increased mucus, tenesmus, hematochezia and increased frequency of defecation.  Most affected kittens are healthy, alert and active, and the only outward signs of illness are the presence of anal hyperemia or swelling, and painful defecation.  Most infections are diagnosed in young kittens with chronic diarrhea (average age 9 mo), but infection can occur in cats of any age.  Cats that are exposed to the organism are highly likely to become infected, and infection is likely to be persistent.  In a recent study, all 8 cats that were exposed to the trophozoites became infected – the organism was cultured from their feces throughout the 200 days of the study.  However, infection with T. foetus does not necessarily correlate with the degree of clinical signs, as there are many cats that culture positive to the organism but are completely asymptomatic.  The prevalence of this infection in the general population is unknown, but at a large international cat show, 31% of the cats (36/117 cats) were affected.  The infection can be easily misdiagnosed as giardiasis unless the observer is trained to recognize the differences in the two species, and co-infection with Giardia spp. has been documented in 12% of cats.  Infections are most commonly found in young cats from crowded housing conditions (shelters, catteries, rescue groups or cat “collectors”) which may reflect an increased opportunity for exposure or, alternatively, due to environmental stress and immature immune function in young cats. 

Diagnosis of this infection can be made by one of four different approaches.  These are listed in order from relative ease of using the test and expense:  1) direct examination of the feces for the trophozoites, 2) fecal cultures for the organism (using the InpouchTF kit, Biomed Diagnostics, White City, OR), 3) PCR of feces (must be submitted to specific labs, Dr. Gookin's lab at NC State University is the best), and 4) colonic mucosal biopsy.  The fecal smear test has the lowest sensitivity (14%), and errors in diagnosis can be made by inexperienced observers.  However, it is still the easiest and potentially fastest way to make a definitive diagnosis.  The InPouchTF kit is more sensitive than the fecal exam, but takes up to 12 days to grow the organism for diagnosis.  The samples can be sent to lab for culture, or the culture kits can be obtained and used in the practice setting.  Because other trichomonad species can grow in the pouch, PCR testing of the cultured organisms may be needed.  PCR testing is the most sensitive and specific method of diagnosis, but is also more expensive and results take longer to obtain as there are only a few labs that can do this test.

Therapy of cats with trichomonosis is difficult, as there is no readily available, approved drug for the treatment of the infection.  Metronidazole and other antibiotics have been used in both experimentally and naturally infected cats, but are completely ineffective in clearing the infection.  Because members of the nitroimidazole family of antimicrobials would be expected to be effective against trichomonads, other drugs from the family have been tested.  Ronidazole (powder-on feed antibiotic used in treatment of turkey cankor) at a dose of 20-30 mg/kg q24h po for 14 days has been shown to clear the infection in both naturally infected and experimental cases of the disease.  This drug is not approved for use in cats, and is also potentially hepatotoxic and neurotoxic, and thus should be used only in circumstances where the owners understand the risks and a definitive diagnosis has been made.  This antibiotic should not be used empirically to treat cats with undiagnosed diarrhea, as numerous anecdotal reports of neurotoxicity have been reported with its use in cats – especially at doses higher than recommended above or for longer than 14 days.  All other antibiotics and antiparasiticidals, including tylosin, enrofloxacin, azithromycin and fenbendazole, have not been shown to be effective against T. foetus, and in some cats may exacerbate diarrhea by altering the normal flora, or result in delay of clinical remission.  Clinical remission of the diarrhea has been shown to occur in many infected cats, usually by 2 years of age, even if they are not treated.  However, many cats that have this infection are not acceptable indoor pets due to the malodorous feces they produce.  At this time there is no evidence that this organism is zoonotic, but it certainly is infectious to other cats, and thus appropriate infection prevention measures should be instituted. 


Giardia spp. is a frequent cause of diarrhea in cats and kittens, with a prevalence rate reported to be at 4 percent nationally, but the infection rate is much higher in shelters or catteries where it may be nearly 12%.  In many adult cats, Giardia spp. infections are subclinical or transient, but in kittens, infection is classically associated with an acute onset of malodorous, pale, mucoid diarrhea.  The diagnosis is relatively straightforward when the trophozoites or cysts are identified on fresh fecal smears or a flotation.  However, because the cysts are shed intermittently, and they can be misidentified or confused with other fecal artifacts, the sensitivity of this approach is only about 50%.  The sensitivity increases to 90% if zinc sulfate flotation is used to examine 3 separate fecal samples.   The SNAP Giardia test kit (IDEXX laboratories) for detection of Giardia cyst wall protein 1 (GCWP-1) in canine and feline feces has been made available for use as an in house diagnostic test for diagnosis of the infection.  The test has not been performance tested in large numbers of field studies, but the sensitivity has been shown to be > 90% (e.g. like commercial ELISA microplate readers used in commercial labs), and thus the ease, simplicity and cost will make this test a great addition to the veterinarian's diagnostic armamentarium.  Treatment of giardiasis in cats and kittens has not changed drastically for many years, and includes specific anti-protozoal therapy combined with environmental control. Metronidazole, at a dose of 25 mg/kg po q12h for 7 days, continues to be a highly effective therapy for the disease in affected cats.  Fenbendazole has been anecdotally reported to be effective in cats at a dose of 50 mg/kg po q24h for 5 days, but only one clinical study has been reported and in that study the cats were co-infected with cryptosporidium, and the response to treatment was less optimal (50%).  So, the true effectiveness of this drug against Giardia spp. is not known, but it is a reasonable and safe alternative.  Finally, experimentally infected cats were effectively treated with a combination product containing febantel (Drontal Plus, Bayer Animal Health).  In that study, the kittens did not have diarrhea from the giardia infection, but the giardia antigen tests became negative after therapy, suggesting complete removal of the organism.  One note of caution is suggested as this drug is not approved for use in cats, primarily because neurologic signs were observed in some cats when the drug was administered them during initial testing.  Because re-infection is a major cause of persistence or recurrence of infection in a household, cattery, or shelter setting, institution of appropriate environment control measures is essential.  These measures include environmental decontamination (cleaning of all floors, cages, litter pans and surfaces that have been in contact with feces with quaternary ammonium or Clorox containing disinfectants), coat cleaning (bathing or shaving of long haired cats), and isolation of affected animals during the diarrheic phase to prevent infection by co-grooming, etc.  Because this organism is zoonotic, appropriate education about handling of infected cats and kittens is an important aspect of the environmental control procedures implemented.     



Cryptosporidium parvum is a coccidian parasite that infects the microvilli of the intestinal epithelium of kittens and immunosuppressed cats.  The disease caused by this infection can range from an asymptomatic carrier, to mild, transient illness, to prolonged, life-threatening malabsorption syndromes.  The some adult cats, the organism can cause intestinal infiltrates similar to those observed with classic inflammatory bowel disease, and because the organisms are very small, unless special stains are used, may be not diagnosed.  Because cryptosporidiosis has a high prevalence rate in cats (8-87% by serology), diagnosis should be made by detection of the organism in feces using an ELISA test or with immunofluorescence assays on feces.  The organisms can be observed in feces at high power, but they are extremely small (< 4 um), and are easily missed unless special stains or assays using immunofluorescence and careful observation are employed.  Further complicating the diagnosis, the organisms are shed intermittently, and thus, infected cats can often have negative fecal fluorescence exams.  Because cryptosporidiosis is zoonotic, the person handling the needs to use appropriate precautions when handling the infected feces, such as wearing gloves and cleaning any utensils with disinfectants (bleach).   Treatment of kittens infected with cryptosporidiosis is very difficult, as the drugs proported to be effective against this organism are either toxic or ineffective in cats (e.g. paromomycin, nitrazoxanide).  Tylosin, metronidazole and other commonly used antimicrobials are ineffective in eradicating the organism.  They may improve diarrhea if a bacterial component is active, but in most cases they are not helpful. However, azithromycin (dose 5-10 mg/kg po q12h) is effective in humans, and although its effectiveness in cats has only been studied in a small number of kittens, the drug appears to be safe and is reasonably effective.   

Other Infectious Causes of Kitten Diarrhea1

Other causes of diarrhea that should be considered in kittens include several viral diseases:  feline panleukopenia virus, hemorrhagic calcivirus, rotavirus, astrovirus, enteric coronaviruses and feline infectious peritonitis.  Feline panleukopenia is the most clinically important intestinal virus of this group, and affects primarily unvaccinated kittens and cats causing fever, depression, anorexia, vomiting and diarrhea.  Diagnosis is usually based on the clinical signs and history, but the canine parvovirus antigen test cross-reacts with the feline virus and thus can be used for confirmation.  Treatment of this and any viral enteritis in kittens is symptomatic and supportive.  Because young kittens are prone to dehydration and hypoglycemia, fluid therapy and nutritional support are key aspects of the supportive care.  Bacterial causes of diarrhea include salmonellosis, campylobacteriosis, clostridial infections, and occasionally yersiniosis, tyzzer's disease (Bacillus piliformis), and colibacillosis.  Diagnosis of bacterial infections causing diarrhea in kittens or cats is very difficult, primarily because pathogens can be isolated in similar rates from both diarrheic and non-diarrheic feces.  Other infectious causes of diarrhea include fungal diseases such as histoplasma, however, these are more likely to occur in adult cats.   Most of the parasitic causes of diarrhea in kittens are typical, e.g. hookworms, roundworms, and strongyloides, and be easily found on fecal flotation, however, therapeutic de-worming should still be performed in kittens that have diarrhea, even if the fecal is negative. 

Anatomic/mechanical causes of diarrhea

The curious and investigative nature of kittens makes particularly at risk of ingestion of foreign substances that may result in the development of diarrhea or vomiting.  In most cases, obstructions or intussusception cause vomiting, but the more distal the problem in the GI tract, the more likely diarrhea may be the primary clinical signs.  The mechanical or anatomic causes of diarrhea to be considered in kittens include developmental abnormalities (e.g. short bowel syndrome), mechanical dysfunction (e.g. obstruction or intussusception), or foreign bodies (e.g. bones, string, plants, hair, etc).  In general, the diagnosis of these conditions will require radiographs or other imaging techniques, but string foreign bodies can occasionally be diagnosed by finding the string entrapped at the base of the tongue or by palpation of the intussusception.  For most of the problems in this category, surgical resolution of the problem is required.   

Nutritional causes of diarrhea in kittens

The use of diet to assist in the management of diarrhea is not a new concept.  Nevertheless, the type of diet used to help manage the problem has become an increasingly complex issue.  In many, if not most cases of simple diarrhea (especially in kittens), the best approach is to feed a highly digestible diet or change the diet to one with fewer additives, flavorings, or other substances than may be associated with food intolerance.  These types of diets are designed to provide food that is easy to digest (moderate to low fat, moderate protein, moderate carbohydrate), may have additives to improve intestinal health (soluble fibers, omega 3 fatty acids, increased anti-oxidant vitamins, etc), and contain no gluten, lactose, food coloring, preservatives, etc.  There are many different brands available that fall under the category “highly digestible”, but, the key is to remember that they are not all alike.  In particular, the protein digestibility of the diet chosen is one of the key factors they may determine the success of the diet.  This information can be difficult to access, but in general, meat source proteins are more digestible than plant source, animal proteins are more digestible than meat by products.  Meat meals are a good source of protein.  Also, to increase digestibility of foods in cats, decrease the number and amount of carbohydrates in the food – a single source carbohydrate food is better than foods with many different sources, highly digestible carb sources are better than complex plant source carbs.  Thus, when one diet from this category not accepted by the kitten, is ineffective, or seems to make the diarrhea worse, you cannot assume that all diets in this category will be ineffective.  The highly digestible diets from different pet food manufacturers have a wide variety of different formulations: different protein and carbohydrate sources, different levels of fat, and a variety of additives designed to promote intestinal health (FOS, MOS, omega 3 fatty acids, antioxidant vitamins, soluble fiber, etc).  If one type of highly digestible diet has been fed for at least 2 weeks with minimal response, then is it entirely reasonable to either try another diet from a different source, or try an entirely different dietary strategy (e.g. high protein/low carb, novel antigen, hydrolyzed, etc).  Another consideration in kittens is that the diarrhea may be due to carbohydrate intolerance or bacterial changes resulting from diet changes.  Thus, feeding a canned food diet, which contains less carbohydrates may result in the resolution of the diarrhea, or addition of probiotics or prebiotics to help influence the microflora are also reasonable therapeutic options. 


Adverse reactions to food

Food sensitivity and food intolerance are the most common adverse reactions to food in cats.  Food allergy or hypersensitivity is an adverse reaction to a food or food additive with a proven immunologic basis – and is often associated with both GI and skin changes.  Food intolerance is a non-immunologic, abnormal physiologic response to a food or food additive – and is by far the most common reason for food related diarrhea in cats. Food poisoning, food idiosyncrasy and pharmacologic reactions to foods also come under this category of adverse reactions to food.  The specific food allergens that cause problems in cats have been poorly documented, with only 10 studies describing the clinical lesions associated with adverse food reactions.  In these reports, over 80% of the reported cases were attributed to beef, dairy products or fish in cats.  The incidence of food allergy versus food intolerance in cats is unknown and even less is known about food allergy in kittens. The diagnosis of both food sensitivity and intolerance is based upon a dietary elimination trial.  The major difference between these two types of adverse food reactions is the length of time on the diet that is required to achieve a response (cats with food sensitivity require 6-12 weeks on the elimination diet before an improvement will be seen).  Alternatively, in cats with food intolerance, resolution of signs usually occurs within days of the diet change (unless there is concurrent bacterial floral disruption or other factors influencing the response).   There are a variety of commercially available and homemade elimination diets, as well as diets formulated with hydrolyzed proteins, that may be used in cats with suspected food sensitivity or intolerance.  The key is to select a diet that has a novel (or alternatively a hydrolyzed) protein source (based on a careful dietary history), that is balanced and nutritionally adequate (commercial diets are best for this), however, homemade elimination diets may be needed to find an appropriate test diet.  If a homemade diet must be used for long term therapy, a complete and balanced diet containing the necessary protein sources should be formulated by a nutritionist.  Nutritional consultation services are available in many locations, and can be found by searching the internet.  In most kittens, food related causes of diarrhea appear to be caused by food intolerance rather than a true food sensitivity, thus, avoiding the offending food is the most effective therapy and will result in complete resolution of signs.  Further, a shorter term trial is needed to determine if that diet choice is appropriate – most kittens will respond within 2 -3 weeks. 

Finally, some cats with diarrhea will respond to placing them on a high protein, low carbohydrate diet (canned growth or diabetic formula foods).  The reason why cats respond to these diets is not completely known, but may be related to carbohydrate intolerance or to changes in the bacterial flora that result from some foods.  While this hypothesis remains to be proven in cats and kittens, there is increasing anecdotal evidence that in kittens and adult cats with idiopathic diarrhea, feeding a canned diet containing high protein and low carbohydrate content is beneficial.  This may be beneficial for a variety of reasons, but is a prudent therapy option.  Obviously, all cases of diarrhea in kittens or cats will not resolve by use of dietary manipulation alone, but in many of these cats dietary therapy is an important component of therapy that should be carefully considered and implemented, and adjusted to meet the needs of the pet and its situation.


Marks SL, Willard MD.  Diarrhea in Kittens.  In, August, JR (Ed), Consultations in Feline Internal Medicine, vol 5. Elsevier, St. Louis, MO., pp 133, 2006.

Marks SL, Cheney JM, Taton-Allen GF, et al:  Prevalence of enteric zoonotic organisms in cats.  J Am Vet Med Assoc 216: 687-92, 2000.

Marks SL, Kass PH, Melli A.  Evaluation of zinc sulfate fecal flotation and two immunoassays for the detection of Giardia duodenalis in naturally infected kittens.  J Vet Int Med 18: 388 (abstract), 2004.

Gookin JL, Stebbins ME, Hunt E, et al.  Prevalence of and risk factors for feline Tritrichomonas foetus and Giardia infection. J Clin Microbiol 42: 2707-10, 2004.

McReynolds CA, Lappin MR, Ungar B, et al:  Regional seroprevalence of Cryptosporidium parvum specific IgG of cats in the United States.  Vet Parasitol 80: 187-90, 1999.

Roudebush, P.  Adverse reactions to foods:  Allergies versus intolerance.  In, Ettinger SJ, Feldman EC (eds) Textbook of Veteinary Internal Medicine, 6th ed., Elsevier, St. Louis, MO, pp 153, 2005.

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