Recently Reemerging Helminthic Infections Causing Eosinophilic Meningoencephalitis: Neuroangiostrongyliasis, Baylisascariasis, and Gnathostomiasis

Today most emerging infectious diseases, such as sudden acute respiratory syndrome (SARS) and novel influenza A H1N1 (swine flu), arise in the natural environment as zoonoses and are distributed by international commerce and travel. The helminthic infections that can cause eosinophilic meningoencephalitis (EM), such as neuroangiostrongyliasis, baylisascariasis, and gnathostomiasis, share these characteristics of emerging infectious diseases. Neuroangiostrongyliasis, a rodent zoonosis, is now endemic in the United States (US) following the introduction of giant African land snails as biological controls and exotic pets. Baylisascariasis, a raccoon zoonosis, has extended its US distribution range from the northern US to the southeast and west coast since the 1980s and was exported to Japan in the exotic pet trade. Gnathostomiasis, a zoonosis of wild carnivores, has been recently recognized as an emerging cause of EM in returning travelers to the United Kingdom (UK). This review analyzes scientific articles selected by PubMed and Medline search engines, 1966–2009, in order to assess the evolving epidemiology of these three examples of recently reemerging helminthic infections causing EM worldwide in order to compare their epidemiology, clinical manifestations, diagnoses, and management outcomes and to alert clinicians to populations at increased risk of helminthic EM as a result of age, ethnicity, lifestyle, food choices, location of permanent residence, or recent international travel.