Infectious diseases of the nervous system:
Pathogenesis and worldwide impact

In comparison to studies on infectious diseases of the nervous system in western societies, studies on such diseases in the developing world have been relatively neglected. This is paradoxical as neurotropic pathogens are frequent in the developing world and contribute significantly to human suffering and disease burden. More over living with neurological handicap and /or cognitive dysfunction is likely to have an impact on socio-economic development. To our knowledge this topic has not been covered by a meeting in a broad, comprehensive way. Therefore we propose to hold a Conference on “Infectious Diseases of the nervous system: pathogenesis and world impact”. Such a conference should advance knowledge in the field and promote exchanges between medical research centers in developing and tropical regions.

While viral encephalitis and bacterial meningitis are actively being studied in the US and other developed countries, less attention is paid to often fatal nervous system (NS) invasion caused by neurotropic viruses, parasites and mycobacteria that represent important health problems in tropical regions. The 27-year old AIDS epidemic which originated from Africa is a haunting example of unabated viral spread between continents, affecting both poor and affluent societies. With increasing manifestations of climate changes affecting our planet, pathogens spread by insect vectors may change in their reproductive cycle and move to other regions of the world. In addition, there are newly emerging viral infections able to spread to the nervous system. Also, because of increased opposition to vaccination in both developing and western countries, infections by poliovirus and measles virus are re-emerging in some areas.
Because of the absence of HIV or malaria vaccines, tuberculosis meningitis and cerebral malaria take a heavy toll among children and, when they survive, may cause neurological sequels affecting motility, sensory organs and mental function. In addition, malaria and/or HIV contracted during pregnancy can cause premature birth and impairment of cognitive development. Cysticercosis-induced epilepsy, on the other hand comes with its stigma, sleep disturbances and difficult schooling. At the early stages of HIV infection in young adults, the virus often enters the nervous system and persists there. While combined antiretroviral therapy has decreased the occurrence of AIDS dementia, HIV-associated neurocognitive disorders are still observed today in a substantial proportion of AIDS patients. Moreover, AIDS induces other neurotropic “common” pathogens such as Cryptococcus neoformans and JC papova virus to become unleashed, causing respectively meningitis and Progressive Multifocal Leuko-encephalopathy responsible for 3-4% of AIDS deaths. In sub-Saharian Africa, Human African Trypanosomiasis (HAT), transmitted by tsetse flies, threatens millions of people and patients show profound disturbances of sleep cycles together with sensory signs and lack of coordination before going into coma and dying if untreated. Mycobacterium leprae which invades nerves, causing sensory loss, still affects many thousands of people each year. Fortunately, several types of acute viral encephalitis (such as Japanese and West Nile encephalitis transmitted by mosquitoes) are on the way to become preventable by safe vaccines. In contrast, many deadly cases of rabies still occur in Africa, India and China in spite of well known strategies to avoid such human loss. These examples are but a few indicating how neurotropic infectious agents have such a profound impact on neural cell function causing either a fatal outcome or debilitating, prolonged neurological impairment. It seems particularly important to develop therapies for neurological diseases that affect young victims and result in long lasting disease burden and impact on society. Therefore, a conference addressing the mechanisms of these diseases is warranted.
The list of relevant diseases considered comprises:

• (1) Cerebral malaria, which accounts for a substantial proportion of malaria deaths (estimated to 2 million of the 300 to 500 millions cases per year);
• (2) Neurocysticercosis, the most common cause of epilepsy in the developing world;
• (3) Sleeping sickness ( Human African Trypanosomiasis) which is re-emerging in sub-Saharian Africa;
• (4) CNS viral infections: West Nile encephalitis, Japanese encephalitis and measles encephalitis. Poliomyelitis resurging in Angola and Sudan;
• (5) Bacterial meningitis and cerebral tuberculosis, whose fatality rate can reach 15-50% among children;
• (6) Leprosy, still affecting hundreds of thousands of people each year in the world;
• (7) Human Retroviral Infections: Tropical spastic paraparesis (HTLV1), HIV-associated Neurocognitive Disorders (the exact frequency of which among the over 40 millions people infected in the world is not known) and HIV-associated brain infections such as Progressive Multifocal Leuko-encephalopathy;
• (8) Rabies, still spreading to humans in Africa, India (over 25,000 deaths per year in this country alone) and China.