Sleeping sickness

Picture courtesy of the Wellcome Images Collection

  • a disease caused by the Trypanosoma brucei parasite 
  • affects the central nervous system and causes changes of behaviour, confusion, sensory disturbance, and disturbance of the sleep cycle
  • also infects farming cattle, with estimated economic damage of US$ 4.75 billion per year1

Human African trypanosomias (HAT) – also known as sleeping sickness – is caused by infection with one of two subspecies of Trypanosoma brucei, a protozoan parasite. The World Health Organization (WHO) estimates that 65 million people are at risk of infection,2 with 20,000 new cases annually. However, the true burden of HAT is hard to assess due to difficulties in diagnosis and remoteness of some affected areas. 

Most trypanosomes are transmitted by tsetse flies3 that inhabit much of mid-continental Africa. While HAT is caused by T.b. gambiense and T b. rhodesiense, the remaining tsetse-transmitted trypanosomes primarily affect animals and cause African animal trypanosomiasis (AAT), also known as Nagana. This disease is found in 37 countries, across about one-third of Africa's total landmass. It causes serious economic losses in livestock4  from anemia, loss of condition and emaciation. 

Of note, another form of trypanosomiasis that occurs mainly in Latin America causes Chagas disease.

Although T. b. gambiense and T.b. rhodesiense have different rates of disease progression, both will initially cause fever and headaches. In the second stage, parasites will invade the central nervous system and cause neurologic dysfunction. Symptoms include the breakdown in sleep–wake patterns that lend the disease its common name. 

There is no vaccine against HAT, and all persons diagnosed with HAT should receive treatment.  The specific drug and treatment course depends on the causative subspecies and the stage of the disease. However, the current treatments are old and unsatisfactory5 for many reasons, including costs, growing resistance and difficulty in administration. The PDE4NPD consortium therefore aims to find and develop novel drugs against HAT that may also be used to treat AAT. 

References and further reading

  1. Food and Agriculture Organization of the United Nation; PAAT The Disease
  2. World Health Organization; HAT fact sheet
  3. Centers for Disease Control and Prevention; African Trypanosomiasis Fact Sheet
  4. The Center for Food Security & Public Health; African Animal Trypanosomiasis
  5. Brun et al.; Development of novel drugs for human African trypanosomiasis; Future Microbiol 2011