Leishmania amastigotes in the central nervous system of a naturally infected dog.

A 4-year-old male Labrador Retriever dog was presented with a 10-day history of tetraplegia, depression, and absent postural reflexes. The cerebrospinal fluid was positive for Leishmania spp. DNA. At necropsy, a 2-cm long mass was observed adhered to C(7) and C(8) left spinal nerves. Microscopically, nerve fiber destruction together with mixed inflammatory infiltration was observed in the spinal nerves. Cervical spinal cord sections showed multifocal, diffuse granulomatous inflammation in the white matter. In the brain, perivascular infiltrates were observed in some areas together with subtle pallor of the parenchyma. Immunohistochemistry for Leishmania infantum confirmed the presence of amastigotes in the spinal nerves, spinal cord, brain parenchyma, and choroid plexuses. The current study describes the presence of Leishmania amastigotes in nervous tissue inciting radiculoneuritis, myelitis, and mild meningoencephalitis, suggesting a likely route by which L. infantum amastigotes reach and affect the central nervous system parenchyma.