The Cause of Sleeping Sickness 1902 – The Tsetse Fly

Journalist Melody Peterson describes sleeping sickness as "a disease more deadly and terrifying than its name" . 

"Yellowish-brown flies inject deadly parasites into their human victims. As the parasites multiply, their human hosts appear to go mad. Victims become confused, stumble and stammer."

African trypanosomiasis is another name for sleeping sickness, which is transmitted by the parasite Trypanosoma brucei, a flagellated protozoan living in the blood of a host bitten by the tsetse fly. The disease is endemic in parts of Africa. In the first stage of the disease:

• The person experiences fever and joint pain. 
• The parasites invade the bloodstream and lymphatic system, causing the lymph nodes to swell. 
• When the parasite enters the brain, the victim's sleep becomes irregular.
• They lose bladder control.
• They become difficult to awaken and die.

Trypanosoma brucei is divided into two subspecies: Trypanosoma brucei gambiense (TBG) and Trypanosoma brucei rhodesiense (TBR) 

• TBG is widespread across a large area of Central and West Africa and is a more slowly developing, more chronic form of the disease. 
• TBR is more common in East and Southern Africa and is more likely to infect various mammals. TBR is a more aggressive parasite, causing all stages of sleeping sickness to develop rapidly, and if the victim is not treated promptly, they usually die within a year.

In 1901, more than 250,000 people died when sleeping sickness broke out in Uganda. 

In 1902, Scottish microbiologist David Bruce became one of the first people to identify conclusively both the causative agent (a flagellate) and the carrier (a fly). A few years later, German scientist Paul Ehrlich and Japanese physician Kiyoshi Shiga developed an arsenic-containing treatment called atoxyl. However, the treatment could cause patients to go blind. 

Today, depending on the stage of the disease and the form of the parasite, treatments may include pentamidine, suramin, melarsoprol and/or eflornithine.

Image: The parasite Trypanosoma brucei gambiense seen under a microscope 

Historical figures mentioned in the article: Paul Ehrlich (1854–1915), David Bruce (1855–1931), Kiyoshi Shiga (1871–1957)

• Previous topic: Inherited Metabolic Diseases 1902 – Genetic Disorders
• Next topic: Vascular Surgery 1902 – Successfully Suturing Blood Vessels