By Holly Brown, DVM, PhD, DACVP
Viper, a 2-year-old male Bengal cat, was adopted from a breeder and presented to the veterinarian (VCA Metzger Animal Hospital, State College, PA) the following day for a routine examination and neuter. No significant abnormalities were noted on physical examination, and the neuter was performed without any concerns. Before discharge, however, Viper developed diarrhea, and the owner elected to hospitalize him overnight to monitor his stool. The diarrhea persisted, and Viper was prescribed oral metronidazole to administer at home.
Diagnostic Testing, Treatment, and Disease Progression
Viper’s diarrhea continued despite treatment, and at recheck, the veterinarian recommended fecal testing for gastrointestinal parasitism. An in-clinic automated fecal analysis with artificial intelligence (AI) interpretation reported Cystoisospora (coccidia) and Viper was prescribed sulfadimethoxine. The diarrhea persisted intermittently, so the patient returned to the veterinarian for an abdominal ultrasound. Based on observed intestinal wall thickening, the veterinarian suspected inflammatory bowel disease and recommended a hydrolyzed diet and tylosin. Viper’s owner was reluctant to try another antibiotic, and Viper would not eat the recommended food. The owner tried various diets, having some success by adding pumpkin to commercial canned cat food and probiotics.
A few months later, Viper started having malodorous yellow/green watery feces with fresh blood and mucus. Additional diet changes and probiotics were ineffective. The veterinarian recommended another abdominal ultrasound, at which point Viper’s colon wall was observed to have increased in thickness, and tylosin was recommended once again, as well as vitamin B12 injections. After two weeks, the additional therapies had resulted in no improvement.
Repeated fecal testing, performed as routine flotation with manual microscopy, and repeated automated fecal analysis with AI, failed to identify any ova or parasites. Additionally, a fecal sample was submitted to the Antech reference lab for KeyScreen® GI Parasite PCR testing, and Tritrichomonas blagburni was identified (Figure 1).
Focused Treatment and Response
Ronidazole was prescribed to treat the protozoal infection, and the tylosin was discontinued. Viper’s stool quickly improved to a soft consistency with no blood, and by the conclusion of the 14-day course of medication, Viper’s stool had finally become firm. Repeated abdominal ultrasound two weeks after finishing treatment for T. blagburni revealed normal intestinal wall thickness, and repeated KeyScreen® GI Parasite PCR testing came back negative.
Tritrichomonas blagburni is a flagellated protozoal parasite (Figure 2) that lives in a cat’s large intestine, causing inflammation and tissue changes in response to infection. Infection is most common in cats housed in large groups and purebred cats, and many cats may be asymptomatic carriers. The onset of clinical disease is most common in young cats, and the most common clinical sign is chronic diarrhea, which may last for years. The diarrhea may contain blood and/or mucus, and may resolve but relapse later.
Diagnosing T. blagburni infection may be achieved via observation of organisms on fecal smear, by fecal culture, or more sensitively via molecular diagnostic testing. Antech’s KeyScreen fecal PCR screens for 20 parasites including hookworms, roundworms, whipworms, coccidia, and protozoa, like Giardia and Tritrichomonas. In Viper’s case, routine ova and parasite testing via fecal flotation and manual microscopy, as well as automated fecal analysis with AI, repeatedly failed to detect his protozoal infection; KeyScreen® GI Parasite PCR testing was instrumental in achieving the appropriate diagnosis and instituting effective treatment.