Pyrexia in Cats

In animals with fever, the hypothalamic set point is elevated, typically by infection, inflammation, neoplasia, or drug administration.¹ This retrospective study of 106 cats with persistent fever (≥102.6°F) evaluated common causes and effective treatment options for feline pyrexia. 

Unlike previous studies that have shown immune-mediated disease to be a common cause of pyrexia in dogs,^2-4 this study showed immune-mediated disease to be an uncommon cause in cats (5.7%); infectious disease was the most common cause (38.7%), followed by inflammatory conditions (17.9%) and neoplasia (12.3%). The most common infectious disease identified was feline infectious peritonitis (20.8%); others included cellulitis and/or otitis media, pyothorax, pyelonephritis and/or UTI, Mycoplasma felis infection, cholangiohepatitis, and abscess. The average length of hospitalization was 5 days. Survival outcome (67%) was comparable to that in a canine study (70%).¹ These results emphasize the importance of infectious disease over immune-mediated disease as a cause of pyrexia in cats.

Key pearls to put into practice:

The hospital in this study actively participates in feline infectious peritonitis research, which could have led to its overrepresentation. Nevertheless, infectious disease remains the most likely cause for feline pyrexia, thereby warranting evaluation.

Treatment before referral was not associated with temperature at presentation or outcome. Importantly, the study supports use of broad-spectrum antimicrobial therapy versus antipyretics, which can increase the risk for side effects, including worsening of infectious disease.

Targeted diagnostics, rather than a myriad of tests (ie, the wide-net approach), should be considered. The initial database should be tailored to the patient’s localizing signs (eg, cytology in cats with effusion, MRI for neurologic signs).