Parasites and the Brain: Neuroinvasion, Immunopathogenesis and Neuronal Dysfunctions

Abstract

Infections of the nervous system by parasites such as protozoa and helminthes still represent a major health problem. Control programs have been efficient in reducing the incidence of some parasitic infections of the nervous system such as American trypanosomiasis (Chagas’ disease). However, this is not the case for other infections such as African trypanosomiasis, cerebral malaria and neurocysticercosis. Human African trypanosomiasis affects more than 300,000 individuals in sub-Saharan Africa (Smith et al. 1998). Malaria may kill between 1.5 and 2.7 million people every year, cerebral malaria being a major cause of death among children in certain regions (Greenwood 1997). Neurocysticercosis is endemic in most developed and developing countries in Latin America, in several countries in Africa and Asia, in certain European countries and, in general, in developed countries with high rates of immigration from endemic areas (Pittella 1997). It accounts for most new-onset epilepsy cases in children and adults in developing countries, which in some regions may range from 10 to 15 patients per 1,000 inhabitants (Mitchell 1999; Román et al. 2000). As a consequence of HIV/AIDS infections and immunosuppressive therapies, toxoplasmic encephalitis has also become prevalent, e.g. a fourth to half the number of adult Toxoplasma seropositive patients with HIV infections may develop toxoplasmic encephalitis (Jones et al. 1996; Mitchell 1999).