INFORMATION ON ENCEPHALITIS LETHARGICA

Encephalitis lethargica is an inflammation of the brain caused by two trypanosomes (microscopic protozoan parasites). The illness, which can be fatal, is transmitted from one infected person to another by the tsetse fly. While it can occur worldwide, encephalitis lethargica is particularly prevalent in Africa.

CAUSES OF ENCEPHALITIS LETHARGICA

The disease is caused by Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. The first species is found in central and West Africa. The infection is unending; it persists for months or years with no display of symptoms. When they do appear, the disease is at an advanced stage and the symptoms are more severe. T. brucei rhodesiense is found primarily in southern and eastern Africa. It causes an infection whose symptoms appear quickly (acute infection). This disease is more severe. Fortunately, the rapid appearance of symptoms offers more of a chance for quick exposure.

Both trypanosomes are transferred to the tsetse fly when the fly obtains a blood meal from an infected person. The trypanosomes then multiply in the blood of the fly, and can be transferred to a susceptible person on whom the fly afterward feeds.

SYMPTOMS OF ENCEPHALITIS LETHARGICA

The early symptoms of the disease include fever, severe headache, joint pain, and swelling of the lymph nodes. These symptoms can vanish and reoccur. Later, symptoms of what is called the neurological phase emerges and often includes the characteristic symptoms of the disease: severe weakness, paralysis of eye muscles, sleepiness, disturbance of the sleep cycle, and a lapse into a deep and incurable coma. Transmission of the trypanosomes across the placenta from a pregnant woman to the fetus can occur. Normally this causes natural abortion or death of the fetus.

TREATMENT OF ENCEPHALITIS LETHARGICA

The choice of treatment depends on whether the disease is found earlier or later in the infection. Early-stage infections can be cured using two drugs; suramine and pentamidine. A contract between the World Health Organization and the drug's manufacturer (Aventis) has guaranteed continued production of the compounds.

Treatment of the presently, neurological symptoms requires a drug that can cross the blood-brain obstruction to reach the parasite. Currently only one drug (melarsoprol) is commercially available. The drug causes harsh side effects and itself has a fatal complication rate approaching 10%. As well, resistance of the trypanosomes to the drug is growing. A second drug (eflornithine) exists, but is not commercially available. It is lively only against Trypanosoma brucei gambiense. There is no vaccine for the disease available till now.