Feline Diarrhea: Tritrichomonas and Giardia

                                          By:  Loren W. Noblitt, DVM, MS

Few conditions are more frustrating for veterinarians (and owners) than feline diarrhea.  I know that I always cringe a little inside when I'm confronted with these cases.  Primary causes of diarrhea, like gastrointestinal inflammation, infection, dietary changes, and cancer should all be considered, as well as secondary causes like liver, metabolic, and pancreatic disease.  The first diagnostic step (if the answer isn't obvious) is to obtain baseline blood work (CBC/Chemistry/Thyroid level), a fecal sample, and a urine sample.  Sometimes, a gastrointestinal (GI) blood profile test is indicated on a case-by-case basis.

In the infectious category, usually the cause will be related to bacterial infection, either from stress (immunosuppression that allows low level anaerobic, "bad" bacteria to thrive), dietary indiscretion (introduction of "bad", foreign bacteria either from human food, trash, feces, or an animal carcass), or a very recent food change (malabsorption, food intolerance, or digestive problems).  When treatment for these more common causes fails to yield resolution of diarrhea, or if the diarrhea has been a chronic longterm issue for your cat, the veterinarian likely will discuss Tritrichomonas foetus (T. foetus) and Giardia.

T. foetus and Giardia are both protozoal diseases, meaning that they are neither bacteria nor virus, but rather a life-form in-between (so to speak); they are both transmitted by the fecal-oral route (through direct contact with feces), and Giardia can be found in unclean water.  Let's now discuss the salient features of each of these pathogens, focusing on risk factors, diagnosis, and treatment.

T. foetus is an emerging parasite in the feline world, however, it was first discovered in cattle as a cause of abortion (thus the species name: 'foetus'), and is spread as a venereal disease amongst cattle. Surveys have suggested that approximately 1/3 of all purebred cats are infected. It is rarely tested for and may be responsible for many of the cases of chronic diarrhea (e.g. inflammatory bowel disease) in cats.  A T. foetus organism looks very similar to Giardia so if viewed by in a fecal smear a misdiagnosis of Giardia is common. Fecal floats and Giardia snap tests are insensitive to it. T. foetus is a fragile organism whose life span out of the body is normally less than an hour. This lack of hardiness is due to the fact that T. foetus cannot form a cyst.  If T. foetus dries out, if it is refrigerated, or if it experiences temperatures above 105°F, it will die.  Good News!!! 

The protozoan lives in the intestinal lining of the large bowel.  It causes "cow pie" like stool that is often gassy and malodorous. The health of the cat is not usually adversely affected.  Cat breeders have commented that in symptomatic cats that the smell of the stool is a significant clue of an infection. It is important to note that an infected cat may or may not have clinical signs of tritrichomoniasis.

T. foetus is typically transmitted by an infected cat to other cats sharing the same litter box. Currently, the preferred and most reliable test to confirm diagnosis is a PCR test using the cat's stool sample.  Follow this link to see video of T. foetus and Giardia in action (Quicktime required): http://www.ncsu.edu/project/cvm_gookin/Tfoetusvideo.mov

Treatment of the T. foetus  infection is difficult due to drug resistance. Traditional antiprotozoal drugs such as Panacur and Metronidazole do not alleviate the symptoms, and as mentioned above, often is the first indicator that T. foetus infection may be present. Some antimicrobial drugs have been shown to improve symptoms but do not eradicate the parasite.  Ronidazole has had good efficacy in eradiation of the parasite in cats but has the potential for a variety of side effects, most notably, neurological side effects.  During treatment, the cat should be engaged in play activity regularly to ensure they are not experiencing neurological side effects, or motor skills impairment.  Two weeks of ronidazole, dosed at 30 mg/kg, once daily, is currently the recommended dosage. Care should be exercised (wearing gloves) while handling ronidazole, which can be toxic to humans.

During treatment, the cat should be keep isolated from other cats as to prevent the spread of T. foetus to another cat. Your cat should be fed a prescription high fiber food to help clear the organisms from the colon and to help heal the colon cells.  A common GI diet remedy in cats (boiled chicken breast and white rice) may be highly beneficial during and after treatment.

Treatment with ronidazole has shown good efficacy, and some positive results may be achieved after just two to three days of treatment, but completion of the two week cycle of drugs to avoid the risk of recurrence.  It is essential that a PCR test be conducted after treatment to verify that the organism has been completely eradicated.  It is also recommended that a follow-up test be performed a few months after the first.  Interestingly, cats that carry T. foetus and are not treated, usually cure themselves of the parasite within 2 years.

                                                                   
                                                    Giardia, in its motile Trophozoite form (above and below)

Photos courtesy of:  http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Giardiasis_il.htm

 

Giardia is a single-celled protozoan that affects the intestinal tract of mammals and usually causes diarrhea and can cause vomiting.  Definitive diagnosis comes from an enzyme-linked immunosorbant assay (ELISA) test using a stool sample.  Dogs and cats can become infected when they swallow Giardia that may be present in stagnant puddles of water or unclean drinking water. It is primarily contracted from the stool of infected animals, both wild and domestic.  Having giardiasis for a long time can cause weight loss, generally poor condition, and even death when the disease is serious. You might notice blood in your cat's stool from irritation that the Giardia parasite causes to the lining of the small and large intestines; however, many cats infected with Giardia do not show any signs of disease. The best way to prevent Giardia infection is to make sure that your cat has a safe, clean drinking water supply.  It is important not to allow cats to drink water from areas where other animals have left their feces.  Pick up soiled litter left by your cat or cats daily and place it in the trash.  Take care not to track animal feces into your house or environment where the cat will be.

The best treatment for Giardia is a six day course of an antiparasitic medication called Panacur (Fenbendazole), and on days #3 and #6 of the treatment, use wet wipes or soap and water to thoroughly clean your cat's rear end and tail.  This will cut down on the number of Giardia cysts that stick to the hair and will help prevent your cat from re-infection by normal cat grooming behaviors.  Bleach (diluted 1:20) or Lysol spray should be used to clean the litter boxes (allowing 10 minutes of good contact time before wiping), as these are both quaternary amines that are able to destroy the Giardia cyst lifeforms.  Importantly, a stool sample should again be checked in 1 month after the treatment was started to make sure the giardiasis is cured. 

As a veterinarian, I am often asked the question, "Can my cat (or dog) get Giardia from my dog (or cat)?"  The answer is Yes.  Either.  We typically recommend treating all the animals in the household when one animal is identified as being a Giardia carrier. 

Also of note, there is a chance that humans can be harmed by the same Giardia that affects their pets, but zoonotic infection (infection passed from animal to human) is extremely rare in this particular case.  It is likely that most people become infected with Giardia passed by other people rather than Giardia from pets.  Be sure to avoid contact with feces by using gloves, a bag over your hand, or a scooping device.  Also, be sure to thoroughly wash your hands after picking up feces.