Background: The cerebrospinal fluid (CSF) of healthy cats presents up to 5 cells/]mu L, with predominance of mononuclear cells and the presence of more than 1% eosinophils is rare and should always be considered an abnormal finding. There is no consensus on the term eosinophilic pleocytosis, as it is used to indicate the presence of more than 10 eosinophils/mu L or more than 10% of the total leukocytes. The increase in eosinophils in the CSF may result from infectious, inflammatory, neoplastic and idiopathic diseases. The objective of this paper is to report a case of marked pleocytosis in CSF, with 84% eosinophils, probably due to toxoplasmosis, in a cat with paraparesis and diffuse spinal pain. Case: A mixed breed female cat, neutered, adult and domiciled in a rural area was presented due to gait abnormalities in the pelvic limbs that started one day before presentation. The general physical examination was unremarkable. On neurological examination it was observed asymmetric deficit of postural reactions in pelvic limbs, patellar reflex normal to increased and pain elicited on palpation of the thoracic and lumbar spine. Based on these findings, the neurological syndrome was classified as thoracolumbar, but with diffuse pain, and the main differential diagnoses were inflammatory/infectious and neoplastic diseases. The leukogram showed eosinophilia and the serum biochemistry showed no significant changes. Serological assays for feline immunodeficiency virus and feline leukemia virus were negative. Analysis of cerebrospinal fluid (CSF) identified marked pleocytosis with 84% eosinophils and increase in protein concentration. Myelography showed no compressive or expansive changes. Fungal culture for CSF cryptococcosis was negative. Serum immunofluorescence antibody titer for Toxoplasma gondii (IgG) was 1:256. There was a marked improvement after treatment with sulfametoxazole/trimethoprim and pyrimethamine and after 3 weeks of treatment, there was almost complete recovery of neurological signs and after 9 months the cat was neurologically normal. Discussion: The most common causes of acute-onset thoracolumbar spinal cord syndrome in cats, with diffuse pain on spinal palpation, are meningomyelitis of inflammatm/infectious origin, such as feline infectious peritonitis (FIP) and neoplasms such as lymphoma. Other meningomyelitis of inflammatory origin, such as infectious and immune-mediated meningomyelitis of unknown origin are considered uncommon in cats. Although the clinical, systemic and neurological signs of HP and toxoplasmosis may have similarities, in the present case HP was not considered responsible for the observed signs, as the evolution of the case and the analysis of the CSF tend to be different. The peripheral eosinophilia, the cytological analysis of the CSF, characterized by marked eosinophilic pleocytosis, associated with a positive titer for toxoplasmosis, good response to treatment and improvement in the neurological condition, with survival for more than 9 months after treatment, rules out the possibility of HP. Neurological signs observed in the absence of systemic signs are more common in cases of protozoan reactivation, which probably occurred in the present case. The possibility of toxoplasmosis in the patient in this report was reinforced by the fact that the animal came from a rural area. Eosinophilia of CSF is most commonly associated with parasitic infections, although it can be caused by a variety of infectious agents, but in the cat of the present report, the marked eosinophilic pleocytosis was likely due to toxoplasmosis, which is a rare occurrence in this specie. In conclusion, toxoplasmosis should be considered in the differential diagnosis of focal spinal cord lesions in cats. The identification of laboratory findings as well as the appropriate therapy favored the good evolution of the condition.
