Case 4 the First FatalBaylisascarisInfection in Humans: An Infant with Eosinophilic Meningoencephalitis

Abstract

Baylisascaris procyonis, the ascarid of raccoons, causes a characteristic, rapidly fatal eosinophilic meningoencephalitis with ocular involvement in many naturally and experimentally infected aberrant hosts, including monkeys. Warnings that humans are potentially susceptible to the devastating infection have been issued, but an instance in humans has not been recognized. This report describes a boy who died from an eosinophilic meningoencephalitis, which mimicked B. procyonis infection in monkeys. The causative agent was not identified during life. Autopsy showed a systemic larval ascarid infection with massive involvement of the brain. The size and anatomy of the larvae in histologic sections were identical to those recorded for B. procyonis. The larvae were indistinguishable from the B. procyonis larvae observed in histologic sections of experimentally infected monkeys. An indirect immunofluorescence test was positive for B. procyonis. Exposure to raccoon feces was highly likely. The evidence suggests that this is the first recognized B. procyonis infection in humans. Prudent avoidance of exposure to raccoon feces is indicated.

Eosinophil-Associated Inflammation and Elaboration of Eosinophil-Derived Proteins in 2 Children With Raccoon Roundworm (Baylisascaris procyonis)Encephalitis

“…23 In our patients, and other previously described cases of human B procyonis infection, ataxia and related CNS signs were early manifestations. [3][4][5][6][7] Severe white matter changes were also observed by MRI in our patients (Fig 1).…”

“…A complete blood count revealed significant eosinophilia (absolute eosinophil count: 2232/m 3 ; Table 2, Fig 2). A lumbar puncture revealed 121 white cells/mm 3 and 8000 red cells/mm 3 with 4% eosinophils, a protein of 50 mg/dL, and glucose of 52 mg/dL. CSF and blood bacterial and viral cultures were negative.…”

“…The peripheral blood absolute eosinophil count was 2068/mm 3 . CSF analysis revealed 20 white cells/mm 3 and 2 red cells/mm 3 , with 13% eosinophils.…”

“…A complete blood count showed 35% eosinophils (absolute eosinophil count: 7035/m 3 ). A lumbar puncture revealed 6 white blood cells/mm 3 and 1 red blood cell/mm 3 , with 54% eosinophils, 23% lymphocytes, 19% monocytes, and 3% basophils, a protein of 21.9 mg/dL, and glucose of 74 mg/dL (Table 1). CSF Streptococcus pneumoniae antigen, stains for acid-fast bacilli, and cultures for mycobacteria were negative.…”

“…1,2 Neural larva migrans and eosinophilic meningoencephalitis attributable to B procyonis have now been identified in 7 young children, including the 2 reported here. [3][4][5][6][7] We specifically note a novel correlation with elevated cerebrospinal fluid (CSF) levels of major basic protein and the neurotoxic protein eosinophil-derived neurotoxin associated with eosinophilic inflammation in these 2 cases. We hypothesize that the severe neurologic consequences of Baylisascaris encephalitis are attributable, in part, to marked eosinophil degranulation and release of these toxic eosinophil proteins in the central nervous system (CNS) of patients with this disease.…”