October 2016

Husky with seizures

A one year-old intact male husky was presented to the Oklahoma State University Center for Veterinary Health Sciences (OSU-CVHS)  Emergency facility for seizures that had begun 2 days prior. According to the referring veterinarian, the patient had a history of heavy ectoparasite infestation and was positive for hookworm infection by fecal flotation. The husky tested negative to all analytes on the IDEXX 4DX Snap Plus ELISA.  The dog was admitted to the Intensive Care Unit (ICU), where neurologic signs progressively worsened, with left sided padding of front and hind limbs, ataxia, conscious propioception deficits on all limbs, but deep pain intact noted. Ultimately, the animal coded in the ICU and was humanely euthanized. Grossly, necropsy revealed severe, acute multifocal, locally extensive cerebral hemorrhage with flattening of gyri and cerebellar coning. A sample was taken for histopathology. Microscopic evaluation of brain tissue reveled acute, severe, multifocal, hemorrhagic and necrotizing, neutrophilic meningoencephalitis with intralesional organisms that were 10-20 microns and circular. See below (left). A sample of brain tissue was submitted to the Centers for Disease Control. See resulting indirect immunoflourescence stain of brain tissue below (right).

What is your diagnosis?

Many thanks to Drs.Tony Confer, DVM, PhD, Diplomate ACVP & Rory Chia-Ching Chien, DVM, MSc, Anatomic Pathology Resident at OSU-CVHS who provided the case history and photos. 

Answer

The indirect immunofluorescence assay performed by the CDC confimed the presence of Balamuthia mandrillaris, a free-living amoeba naturally found in the environment. This parasite can cause a rare and serious condition of the brain and spinal cord termed Granulomatous Amebic Encephalitis (GAE) in humans and dogs. Balamuthia lives freely in soil, and also may be present in fresh water. Cysts and trophozoites (the infective form) of the parasite may enter the vertebrate host in various ways, including through nasal passages to the lower respiratory tract or through ulcerated or broken skin.