Helminthic eosinophilic meningitis: emerging zoonotic diseases in the South.

Today most emerging infectious diseases, such as West Nile virus and severe acute respiratory syndrome (SARS), arise in the natural environment as zoonoses and are often imported into the United States (US). The most common helminthic infections that can cause eosinophilic meningitis (EoM) in the US, neuroangiostrongyliasis and baylisascariasis, share many of the characteristics of emerging infectious diseases. Neuroangiostrongyliasis, a rodent zoonosis caused by the rat lungworm, Angiostrongylus cantonensis, is now endemic in the US following the importation of infected rats on container ships and African land snails, the parasite's intermediate hosts, as biological controls and exotic pets. Baylisascariasis, a raccoon zoonosis, caused by the raccoon roundworm, Baylisascaris procyonis, has extended its US distribution range from suburban neighborhoods in the northern US to the Southeast and West Coast since the 1980s. Both A. cantonensis and B. procyonis are now enzootic in Louisiana and have caused EoM in humans. This review analyzes scientific articles selected by MEDLINE search, 1966-2008, in order to assess the evolving epidemiology of EoM in the US, and specifically in Louisiana; and to alert Louisiana clinicians to populations at increased risk of helminthic EoM as a result of age, ethnicity, lifestyle, food choices, location of permanent residence, or recent travel in the Americas or Caribbean. Most parasitic diseases causing EoM are no longer confined to tropical countries; they are now endemic in the US and in Louisiana and more cases may be anticipated.