After 10 years of research and 366 million letters of code, an international group of researchers have deciphered the genetic code of the tsetse fly (Glossina morsitans). ITM’s Prof. Jan Van Den Abbeele led the work on the fly’s salivary gland genes. The results of this titanic project involving over 140 scientists, half of whom are from Africa, appeared in the leading scientific journal, Science, in April of 2014.
The tsetse fly is the major vector of African trypanosomiasis. The disease is also known as ‘sleeping sickness’ in humans and ‘nagana’ in animals. The number of reported new cases of sleeping sickness has steadily decreased in recent years in Sub-Saharan Africa, dropping for the first time below 10,000 new cases in 2009. Trypanosomiasis is far more widespread in cattle, however, causing about 3 million animal deaths and an estimated loss to African agriculture of around 3.5 billion euros per year. Clearly, this has a profound effect on the development of the African continent.
Tiny fly still in the running a century on
Back in 1904, the New York Times published an article entitled “Thousands Killed by a Tiny Fly”, predicting that trypanosomiasis was “likely to be ended by the investigation of experts”. Yet, more than 110 years later, Trypanosomiasis persists, mainly because the trypanosome parasite continues to outsmart its pursuers. As the trypanosome parasite is able to evade the mammalian immune system, there is little hope of preventing this disease through the development of a vaccine. Therefore, researchers focus much of their attention on keeping the pathogen carrier, the tsetse fly, in check.
Cracking the code
The newly acquired access to the fly’s complete genetic information will accelerate research on the tsetse fly’s basic biology and how it interacts with the trypanosome parasite and with the human and animal host.
“Completing the tsetse fly’s biological puzzle will help us to gain the upper hand against trypanosomiasis”
“We have all the pieces of the tsetse fly’s complex biological puzzle, which is to be completed in the decades ahead, through targeted experimental work. It will allow us to improve current tsetse control methods and develop new strategies that are more effective and cost less, ” according to Prof. Van Den Abbeele who led the ITM team that focused on the gene coding for the tsetse fly’s salivary proteins, which are crucial for the fly to blood-feed efficiently and for the trypanosome parasite to become infective whilst inside the fly.
The research project started in 2003 when the International Glossina Genome Initiative was established with seed funds from the WHO. The 10 million euro project was funded through multiple channels, including the WHO’s Special Programme for Research and Training in Tropical Diseases.
The scientists primarily focused on the protein-coding genes that make up the tsetse fly: the basic components that allow a tsetse fly to function biologically. Initially, they determined the code of millions of tsetse fly DNA fragments using multiple sequencing techniques. Subsequently, these fragments were assembled to construct the full fly genome. The scientists then identified protein-coding genes and mapped them to the tsetse genome. This was accomplished using computer programmes that “read” the sequence and compare the massive amounts of sequence data from the genome with that from other annotated organisms (mainly from the fruit fly) to predict gene structure and function. These predictions were then added to the publicly available tsetse genomic database at www.vectorbase.org.