Emily Bouwer
Animal Health Laboratory, University of Guelph, Guelph, ON.
AHL Newsletter 2024;28(4):28.
A young kitten became the focus of an animal welfare investigation due to a history of intractable diarrhea and emaciation. The owner had reported that they had owned the kitten for approximately two months, and in the two weeks prior to presentation the kitten had stopped eating and drinking. Apart from deworming one month previously, there was no reported medical treatment. On the morning of presentation to the veterinary clinic, the kitten was found to be moving erratically, gasping, and unable to stand. On antemortem physical examination, the kitten was pale, cold, thin, bradycardic and comatose. The kitten was euthanized and subsequently submitted for postmortem examination.
Figure 1. Emaciated and dehydrated kitten.
Figure 2. Perineal fecal soiling and dermatitis
On gross postmortem examination, the kitten was emaciated and dehydrated (Fig. 1). Diarrheic feces soiled the perineum, tail and caudal thighs, and the underlying skin was hyperemic, swollen and coated in purulent exudate (Fig. 2). Internally, the gastrointestinal tract was empty, except for scant grey-brown liquid feces in the colon. The bone marrow was red and gelatinous, and internal fat stores were absent.
At the time of gross post mortem, pooled large intestine and small intestine were submitted for bacterial culture, which isolated 3+ E. coli and 1+ C. perfringens; these were interpreted as normal enteric flora. The C. perfringens enterotoxin ELISA was performed and enterotoxin was not detected. No Yersinia spp., Campylobacter spp., or Salmonella spp. were isolated. Liver was also cultured, and there was no bacterial growth. PCRs were also performed for Giardia spp., Tritrichomonas foetus and feline parvovirus, and all were negative.
Histologic examination was hampered by the degree of autolysis and freeze-thaw artifact, however, in sections of liver there were numerous, randomly distributed and variably sized foci of acute necrosis (Fig. 3). No significant enteric lesions were identified. Because the liver had previously been cultured with no bacterial growth, and subtle faint bacilli could be identified on routine staining, a Steiner stain was performed to identify argyrophilic bacteria. This stain identified large numbers of positive filamentous rod-shaped bacteria within and surrounding areas of acute hepatic necrosis, as expected with Clostridium piliforme infection (Fig. 4).
Figure 3. Liver, H&E stain, 10X. Multiple pale foci of acute hepatocellular necrosis (arrows).
Figure 4. Liver, Steiner silver stain, 40X. Numerous argyrophilic filamentous rod-shaped bacteria at the junction of viable and necrotic tissue.
This combination of characteristic hepatic lesions and positive identification of compatible intralesional bacteria is considered pathognomonic for Tyzzer’s disease, confirming the diagnosis in this kitten. While not a common disease in cats, there are sporadic cases of Clostridium piliforme infection in kittens that can result in the classical triad of lesions including colitis, hepatitis and myocarditis. Perianal dermatitis with intraepithelial bacteria is also reported, but is not a common feature of the disease. The dermatitis is considered to be the result of direct contact with infected feces. While not identified in this case, likely due to the degree of autolysis, the expected histologic lesions in the gastrointestinal tract include neutrophilic crypt abscesses, crypt degeneration and loss, and ulcerative typhlocolitis and proctitis with mixed lymphoplasmacytic and neutrophilic infiltrates. Intraepithelial rods are often difficult to identify with routine staining, and typically require special silver impregnation stains.
C. piliforme is an obligate intracellular bacterium, which renders culture challenging. Isolating the bacteria in cell-free media is impossible, but the bacterium may grow in tissue culture under anaerobic conditions. Molecular techniques are the preferred method of confirming the diagnosis, particularly on antemortem examination. A PCR test can be performed on feces or affected tissues. The Steiner stain is typically more sensitive on formalin-fixed paraffin embedded tissues than the PCR for identifying the bacteria.
In cats, this infection appears to be more common in younger kittens, and is speculated to be related to impaired immune function. In cases of hepatitis or colitis in young kittens, particularly those that have been orphaned or have poor nutritional status, C. piliforme infection should remain a differential diagnosis.
References
1. Fingerhood S, et al. Tyzzer disease in 19 preweaned orphaned kittens. J Vet Diagn Invest 2023 Mar;35(2):212-216.
2. Oliveira ES, et al. Neurologic and cutaneous infection by Clostridium piliforme in a kitten with systemic Tyzzer disease. J Vet Diagn Invest 2023 May;35(3):322-326.
3. Uzal, Francisco. Tyzzer disease in Animals. In: Merck Veterinary Manual. Reviewed/Revised Jun 2021. Accessed November 15 2024. https://www.merckvetmanual.com/digestive-system/tyzzer-disease/tyzzer-disease-in-animals [1].