Baylisascaris procyonis: an emerging helminthic zoonosis

Abstract

Baylisascaris procyonis, a roundworm infection of raccoons, is emerging as an important helminthic zoonosis, principally affecting young children. Raccoons have increasingly become peridomestic animals living in close proximity to human residences. When B. procyonis eggs are ingested by a host other than a raccoon, migration of larvae through tissue, termed larval migrans, ensues. This larval infection can invade the brain and eye, causing severe disease and death. The prevalence of B. procyonis infection in raccoons is often high, and infected animals can shed enormous numbers of eggs in their feces. These eggs can survive in the environment for extended periods of time, and the infectious dose of B. procyonis is relatively low. Therefore, the risk for human exposure and infection may be greater than is currently recognized.

Figure 1

Biopsy-proven Baylisascaris procyonis encephalitis in a 13-month-old boy. Axial T2-weighted magnetic resonance images obtained 12 days after symptom onset show abnormal high signal throughout most of the central white matter (arrows) compared with the dark signal expected at this age (broken arrows).

Figure 2

Cross-section of Baylisascaris procyonis larva in tissue section of brain, demonstrating characteristic diagnostic features including prominent lateral alae and excretory columns.