Asleep all day, awake all night

Trypanosomiasis is a particularly cruel disease. Fever, headaches, and joint pains are the initial symptoms, but they gradually get more severe as the parasites move into the blood and lymphatic systems. First the lymph nodes swell to a large size. Then, if left untreated, the disease gradually overcomes the sufferer's defences and the symptoms get more severe, often leading to anaemia as well a range of endocrine, cardiac and kidney disorders.

The parasites eventually pass through the blood-brain barrier and the disease enters the second "neurological" phase, which gives African sleeping sickness its name. Beset by confusion and loss of coordination, the patient's sleep cycle gradually becomes unbalanced.

Fatigue alternates with manic episodes until the sleep pattern is practically reversed; the patient sleeps during the day and suffers from insomnia at night. Without treatment, the disease is fatal.

"There are very few drugs that are currently available to treat these diseases," says Best, who also points out that nearly all of drugs that are available were developed decades ago. These drugs have side-effects, many of them quite severe, and several are highly toxic in their own right.

One example is the organo-arsenical melarsoprol (or Arsobal), which is the current treatment for African sleeping disease. Melarsoprol kills about 10-20 per cent of the people who take it, so it's almost as bad as the disease itself.

Such treatments are also elaborate in nature, which severely hampers the ability of health organisations to go out into the field and treat the disease effectively, especially in impoverished regions. Melarsoprol, for instance must be given intravenously over several days.

"Trying to give such a treatment intravenously to people who are hospitalised in a developing country is really not cost effective, and it's very difficult to do," Best says.

"What we're trying to develop is a simple pill that a patient can take maybe once or twice that completely eradicates the disease. That will allow aid agencies to go out there and treat large numbers of people cost-effectively, which at the moment they can't do."