Sequencing a Vampire
More effective methods for controlling tsetse flies – which stalk humans and livestock across sub-Saharan Africa, carrying fatal parasitic infections – are urgently needed. Fortunately, the recently completed genome sequence of the tsetse provides several clues that could transform research and improve disease-control efforts.
NEW HAVEN – Human African trypanosomiasis (HAT) – also known as sleeping sickness – has long plagued rural sub-Saharan African populations. A parasitic infection, it is often fatal when left untreated. And treatment is complex, requiring the kind of highly skilled medical staff that is difficult to find in the affected areas. The parasites that carry the infection – Trypanosoma brucei gambiense in central and western Africa and T. b. rhodesiense in eastern Africa – are transmitted through the bite of an infected tsetse fly (Glossina morsitans morsitan).
In the early twentieth century, HAT epidemics decimated populations in many parts of Africa. Though the systematic screening and treatment of millions of people dramatically reduced disease transmission in the 1930’s, the relaxation of such efforts allowed HAT to reemerge in the 1950’s and 1960’s, reaching epidemic levels by early 1990’s. A World Health Organization campaign finally got the disease under control by 2008, with only about 10,000 people contracting it each year. But millions remain at risk.
Clearly, tsetse flies pose a serious danger in the areas that can least afford or access treatment. And the threat is not limited to humans. African animal trypanosomiasis, or nagana, is caused by the parasites Trypanosoma congolense, T. vivax, and T. brucei – all of which are transmitted by the tsetse fly.