Toxoplasmal meningoencephalitis in a 14 week-old shelter cat with presumed feline infectious peritonitis.

Toxoplasmal meningoencephalitis is a sporadic condition that is often misdiagnosed antemortem, frequently resulting in euthanasia especially in resource-limited settings. Here we report a case of a 7-week-old female domestic shorthair cat from an animal shelter who presented in a compromised condition and continued to display clinical signs consistent with a "failure to thrive" kitten. Weight loss and decreased activity were observed, and later on, neurological dysfunction became apparent. Based on clinical signs, non-effusive feline infectious peritonitis (FIP) was strongly suspected. Other possible conditions, such as a portosystemic shunt or toxoplasmosis, were also considered. Due to a poor prognosis, euthanasia was elected. Molecular testing at necropsy revealed no evidence for feline coronavirus infection; however, histopathological examination of the brain tissue revealed disseminated necrotizing meningoencephalitis with the presence of Toxoplasma gondii bradyzoites and tachyzoites, which was further confirmed by PCR and sequence analysis. In hindsight, it became clear that the kitten's failure to thrive was due to severe neurological compromise caused by overwhelming toxoplasmosis infection. This report underscores the diagnostic challenges associated with feline neurological disorders.