Diarrhea is one of the most common health problems of kittens and young cats. Common causes include dietary change and infectious disease. The diagnostic plan can be divided into 1st tier and 2nd tier tests:
Direct fecal smears
Giardia fecal antigen
T. foetus testing (large bowel diarrhea)
Response to treatment with a broad spectrum dewormer such as fenbendazole
Clostridium enterotoxin (large bowel diarrhea)
Fecal culture (small bowel diarrhea)
Cryptosporidium testing (small bowel diarrhea)
Comprehensive fecal examinations are critical for diagnosis. Fecal specimens for examination should always be fresh (< 1 hour old). Fecal flotation techniques are best for common nematode ova, coccidia oocysts and Giardia cysts. Gravitational flotation is widely used but is less efficient than centrifugation flotation for detection of parasites shed in low numbers. Therapeutic deworming with a broad-spectrum product should be performed even if no parasite ova are found.
Direct fecal smears (fecal wet mount) should always be performed to detect Giardia and Tritrichomonas trophozoites as well as Campylobacter. Fecal/rectal cytology smears can be examined for Clostridium endospores and Campylobacter. If neutrophils are present, culture for Campylobacter, Clostridium or Salmonella may be warranted.
Selected Infectious Causes of Diarrhea
Giardia spp. are flagellate protozoans found in the intestinal tract of humans and many animal species worldwide. The trophozoite is the active, motile form found in the intestinal tract. The cyst is the environmentally resistant stage responsible for transmission when ingested via contaminated fomites, food, or water. Giardia infection may cause acute diarrhea in kittens characterized by pale malodorous feces, sometimes containing mucus. Infections in adults may be asymptomatic.
Diagnosis of Giardia has traditionally relied upon microscopic identification of cysts or trophozoites in feces, but sensitivity is low (85.3%). A single negative test cannot rule out infection. A higher sensitivity (97.8%) can be achieved by using a centrifugation flotation technique for cyst detection in combination with a patient-side Giardia immunoassay kit (SNAP Giardia, IDEXX Laboratories).
The primary goal of treatment is to stop diarrhea and reduce or eliminate cyst shedding, especially since the infection is zoonotic. Elimination of infection is not always possible. Treatment options include metronidazole (25 mg/kg, PO, BID for 7 days) and fenbendazole (50 mg/kg, PO, SID for 3–5 days). Cysts can be inactivated on contaminated surfaces by thorough cleaning followed by steam cleaning or quaternary ammonium products (1 minute contact time).
Tritrichomonas foetus is a flagellated protozoan found in the distal ileum and colon. T. foetus infection is most common in young cats (< 2 years) in population-dense environments such as shelters and catteries. Prevalence of infection ranges from 10–31%, depending on the population sampled and the diagnostic tests employed. Presumably, trichomonads are transmitted among cats via feces in the litter box and are ingested from the paws and hair coat during grooming. Trichomonads do not forms cysts, unlike Giardia, and so cannot survive prolonged periods in the environment.
Infected cats often have chronic waxing and waning, malodorous large bowel diarrhea, but asymptomatic carriers have also been documented. The diarrhea is semi-formed to liquid and is often described as 'cow patty' in consistency and may contain mucus or fresh blood. Increased frequency of defection, flatulence and tenesmus may also be seen. Severely affected cats may dribble feces and have perineal inflammation. Infected cats generally maintain good body condition and a normal appetite.
T. foetus cannot be diagnosed with routine techniques such as fecal flotation. Fecal samples for analysis should be freshly voided or collected with a fecal loop, free of cat litter and kept at room temperature. Samples may also be collected via saline flush of the colon. Only grossly abnormal fecal samples should be tested and antibiotic therapy should be stopped one week before samples are collected. T. foetus infection may be diagnosed by several methods: fecal smear (cheapest, least sensitive), fecal culture (most time-consuming), or PCR (most expensive, but most sensitive).
T. foetus trophozoites look similar to Giardia and misdiagnosis is not uncommon. Key morphologic features distinguish the two pathogens. T. foetus has a single undulating membrane, a single nucleus, and the organism moves with a rigorous forward motion. Giardia has characteristic 'owl eyes', a concave ventral disc and a 'falling leaf' motion.
The only drug therapy shown to have efficacy against T. foetus is ronidazole. Ronidazole is not approved in most countries for use in companion animals and is typically banned for use in food animals due to concerns that it is carcinogenic in humans. The recommended dose is 30 mg/kg, PO, SID for 14 days. The drug is rapidly and well absorbed from the gastrointestinal tract and has a long half-life, which predisposes some cats to neurotoxicity. Clinical signs include lethargy, inappetence, ataxia and seizures. Signs typically resolve if the drug is withdrawn immediately, but they may worsen before they improve and costly intensive care may be required for recovery. To lessen the risk of neurotoxicity, the ronidazole dose should be based on a current, accurate body weight.
Cryptosporidium felis is an obligate intracellular parasite infecting the small intestine. Infective oocysts are ingested from contaminated feces during grooming of contaminated body parts and from contaminated food and water. The prepatent period is 3 to 6 days and the oocysts are infective as soon as they are shed, making this a very contagious disease. Clinical signs in kittens range from mild, self-limiting to chronic intermittent small bowel diarrhea. Severe diarrhea with weight loss and anorexia may also occur.
C. felis may be diagnosed by fecal flotation if there are large numbers of oocysts but this test is often negative due to intermittent shedding. The small size of the oocyst makes microscopic identification difficult. A modified Ziehl-Neelsen acid fast stain of a thin fecal smear may help in the identification of the oocysts. Immunofluorescent antibody and PCR testing are available from some laboratories.
There are no completely effective and safe treatments for C. felis. Azithromycin (7–10 mg/kg, PO, BID for at least 10 days) appears safe, but efficacy is unknown. Paromomycin, an oral aminoglycoside, may be effective but reported adverse effects include acute renal failure and deafness. Nitazoxanide is approved for treatment in humans. The administration of nitazoxanide to cats at 25 mg/kg, PO, BID for at least 5 days and up to 28 days may be effective but the drug commonly causes vomiting and foul smelling diarrhea.
Environmental control of C. felis is difficult as the oocysts are extremely hardy. They are resistant to chlorination and most disinfectants. The parasite is difficult to filter from water due to its small size and survives treatment at municipal water treatment facilities. Steam cleaning of housing and utensils may be beneficial and oocysts are susceptible to 5% ammonia solutions if the contact time is eighteen hours.
Diagnosis of bacterial diarrhea in kittens is problematic because many agents are routinely isolated from healthy cats. Diarrhea caused by Salmonella or Campylobacter should be considered in kittens living in high density environments, those fed raw meat diets, and those with systemic illness (fever, dehydration, leukocytosis). Antibiotics are often injudiciously administered without a valid diagnosis. Indiscriminate antibiotic usage can lead to alterations in the commensal intestinal microflora and exacerbation of diarrhea or development of antibiotic resistance.
In most cases of simple diarrhea, a highly digestible diet (moderate to low fat, moderate protein, moderate carbohydrate) is recommended. These diets may also contain substances to improve intestinal health (e.g., soluble fibres, omega-3 fatty acids, anti-oxidants, etc.) and do not contain gluten, lactose, colourings and preservatives. Meat source proteins are more digestible than plant source. A single source carbohydrate diet is more digestible than one with multiple sources. If one highly digestible diet is ineffective or not accepted, another should be tried. Canned high protein, low carbohydrate diets will be effective in some cases.
Probiotics such as Enterococcus faecium and Lactobacillus acidophilus may influence the gut microflora by inhibiting pathogenic microorganisms or by immune enhancement. They are generally recommended for otherwise healthy kittens and cats (with an intact mucosal barrier) with acute or chronic diarrhea due to parasitism, viral or bacterial infection, weaning, or dietary change. In one study, the percentage of shelter cats with diarrhea for more than 2 days was significantly lower when treated with E. faecium SF68 (FortiFlora) versus a placebo. In most countries, there are no quality control regulations for probiotics so that only brands with proven efficacy should be used.
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