Human infections caused by the Raccoon roundworm, Baylisascaris procyonis

Abstract

Raccoons are the natural host of the roundworm, Baylisascaris procyonis, a zoonotic nematode parasite capable of causing severe human ocular and neurologic disease. Although a rare human infection, baylisascariasis is increasingly being recognized as a significant public health problem, especially in young children less than 4 years old. Large numbers of raccoons are frequently found living in urban and suburban environments, where they thrive because of easily accessible food and shelter. Transmission of the parasite occurs through the inadvertent ingestion of B. procyonis eggs, which are shed in the feces of infected raccoons. Groups of raccoons typically defecate in common areas called latrines, where large numbers of environmentally resistant eggs accumulate. Once released in the intestinal tract, B. procyonis larvae migrate extensively and aggressively in tissues, causing an intense eosinophilic inflammatory reaction. The larvae have a noted tendency to invade the eye (causing ocular larva migrans [OLM], spinal cord, and brain (causing neural larva migrans [NLM]). Infections in humans can be difficult to confirm, and [OLM], spinal cord, and brain (causing neural larva migrans [NLM]). Infections in humans can be difficult to confirm, and diagnosis is typically arrived at by exclusion of other known causes of OLM and NLM. There is no effective cure for human infection. Steroids and anthelmintic agents are usually employed for symptomatic treatment, but their efficacy is controversial. Preventing the establishment of raccoon latrine sites in areas where humans live is of paramount public health importance.