Sleeping sickness

Sleeping sickness refers to several related diseases that cause a deep sleep-like state and coma. Left untreated, it is fatal. The two most common types are East African and West African sleeping sickness with approximately 20,000new cases reported each year. Few cases of the West African strain have everbeen reported in the United States, with 17 cases of the East African strainreported since 1968. The technical name for the disease is trypanosomiasis, because it is caused by a thin, single-cell organism called a trypanosome. This parasite can be transmitted from infected animals to humans by the tsetse fly and, in extremely rare instances, by blood transfusion or organ transplant. The tsetse fly bite is painful, often developing into a red sore, or chancre.

Fever, headache, and chills are the first symptoms, followed by swollen lymphglands, aching muscles and joints, weight loss, skin rash, and extreme fatigue and general weakness. If the disease is not treated, it will progress to the nervous system causing confusion, personality changes, seizures and difficulty walking or talking. Once the parasites attack the brain, they cause deepsleep and coma. A physician can diagnose the disease with a microscopic examination of a patient's blood, spinal fluid, or fluid from a swollen gland. Ifthe wiggling, long-tailed parasite is present, the disease is confirmed andcan then be treated with arsenic-based drugs. Treatment is painful and dangerous (it has a five percent fatality rate), and only effective if begun beforethe nervous system is damaged. Once the deep sleep occurs, there is little chance for a cure and the patient usually dies.

More than one hundred years ago, several noted researchers contributed to theunderstanding of sleeping sickness. In the late nineteenth century, German bacteriologist Robert Koch went to Africa to do research on the disease. Kochwas the first person to study the bacterium that caused anthrax in cattle bygrowing the organism outside the body in blood serum. He also helped developthe use of a gelatin medium for growing bacteria in Petri dishes so they could be more easily studied. Koch went on to isolate the bacteria that caused anumber of important diseases, such as cholera, tuberculosis, and bubonic plague. After careful study, Koch established that sleeping sickness was transmitted by the tsetse fly, just as he had shown that the plague was transmitted by a flea that infested rats. He suggested that these diseases could be foughtby attempting to control the insects that spread them.

David Bruce, an eminent Scottish microbiologist, made the next stride in theunderstanding of sleeping sickness. Bruce led the Royal Society's Sleeping Sickness Commission in Uganda in 1903. This team of scientists was able to prove that the disease was caused by trypanosomes and transmitted by tsetse flies. The final victory in the battle against sleeping sickness was provided by Louise Pearce (1855-1959). An American physician, Pearce joined a group of scientists at Rockefeller Institute charged with finding a drug that would killthe trypanosome organism. She and her partner, Wade Hampton Brown (1878-1942), decided to study chemicals related to Salvarsan--an arsenic-based cure forsyphilis discovered by Paul Ehrlich. In 1919, they isolated a compound latercalled tryparsamide, which was effective against the disease. Pearce tested the chemical in the Belgian Congo (present-day Zaire), where its usefulness was convincingly demonstrated. Since that time, a number of effective drugs have been developed with the ability to destroy the trypanosomes.

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