Simultaneous occurrence of inflammatory bowel disease and trichomonosis in a Maine coon cat — A comment

To my learned colleagues,

On reading the article “Simultaneous occurrence of inflammatory bowel disease and trichomonosis in a Maine coon cat” in the March 2022 of The CVJ I have a concern with the conclusion drawn by the authors. I disagree with the diagnosis of idiopathic inflammatory bowel disease (IBD).

Although there is no uniform classification for non-infectious chronic enteropathies in cats, many authors will further classify these disorders as either IBD, food responsive enteropathy (FRE), or small cell lymphoma.

The histopathologic changes in this patient showed evidence of an enteropathy, a lymphocytic erosive enteritis, and lymphoplasmacytic erosive colitis. These findings unfortunately are neither specific nor sensitive for IBD as any source of chronic inflammation may result in similar findings. These findings could be explained due to a long-standing infection with Tritrichomonas or FRE. It is acknowledged in the case report that in previous studies of tritrichomonas infection there were similar histopathologic findings to this case. Even cats without overt gastrointestinal disease may have inflammatory lesions on gastrointestinal biopsies (1).

According to the WSAVA International Gastrointestinal Standardization Group a diagnosis of IBD is defined by meeting five criteria. “i) Chronic (i.e., > 3 weeks) persistent or recurrent gastrointestinal signs. ii) Histopathologic evidence of mucosal inflammation. iii) Inability to document other causes of gastrointestinal inflammation. iv) Inadequate response to dietary, antibiotic, and anthelmintic therapies alone. v) Clinical response to anti-inflammatory or immunosuppressive agents.” (2).

According to this definition this case fails to meet the 3rd criteria, as Tritrichomonas infection is a clearly documented cause of potential gastrointestinal inflammation.

As a diet trial was performed concurrently with both glucocorticoid treatment and ronidazole it is unclear if the clinical improvement seen in this patient is due to diet, glucocorticoids, or treatment of parasitic infection. One could argue the ability for the cat to remain free of clinical signs for four months after the cessation of glucocorticoid therapy would make a diagnosis of FRE and/or a parasitic chronic enteropathy more likely than IBD. A dietary challenge could have been performed to see if resolution of clinical signs, despite cessation of glucocorticoids, is due to dietary therapy or resolution of Tritrichomonas infection. Without this information it is unclear if this patient meets the 4th criteria for diagnosis of IBD.

Unless the clinical signs return with the withdrawal of prednisolone, and a dietary challenge is performed a diagnosis of IBD has not been confirmed in this patient. However, this argument is purely academic as the patient has done well with the described treatments, and I applaud the authors in their thorough approach.