Scientists have mapped the genetic code of the tsetse fly, the insect responsible for African sleeping sickness. They said the findings could lead to better repellents and control efforts and boost vaccine research.
The World Health Organization reports African sleeping sickness occurs in 36 sub-Saharan countries. The bite of a tsetse fly transmits parasites that could eventually reach the central nervous system causing confusion, sensory problems and poor coordination. It also disrupts the sleep cycle giving the disease its name.
The WHO said drug treatment is “complex,” but without it the disease is usually fatal. Efforts to control tsetse populations brought the number of new cases below 10,000 for the first time in 2009. In 2012, just over 7,200 new cases were reported.
Serap Aksoy is a professor of epidemiology of microbial diseases at the Yale School of Public Health. She and her colleagues in the U.S., Africa and elsewhere began searching the tsetse fly’s DNA for its genetic code 10 years ago. The WHO provided initial funding. In all, the project cost $10 million.
“The genetic code is the blueprint of the fly that is responsible for making all the proteins that are involved in all of its functions, essentially. These are involved in every aspect of the fly’s essential structure and function. They’re basically the parts list that an organism is made from,” said Aksoy.
African sleeping sickness is the name given when the disease affects people. When found in animals it’s called Nagana.
“Sleeping sickness, along with Nagana, have hindered public health and development of agriculture in Africa for centuries. This is a very neglected disease and hence limited amounts of research funds have gone into the study of this insect and this disease. So, we’re really excited that this will be a breakthrough for control,” she said.
The genome could help researchers better understand just how functions within the tsetse fly work.
She said, “These included, for example, olfaction, which determines smell. What we call gustation, which is taste, vision, reproduction, digestion, blood feeding, immunity and symbiosis. So, these were the kind of things, which we felt represented bottlenecks in [the] fly’s biology. And as we decoded the genome we particularly looked for proteins involved in these processes.”
Olfaction is important, for example, because one of the best ways to control the flies is with traps. These traps use different scents to attract them.
“There are many such traps that have been developed for tsetse flies. But they are not necessarily all efficient at the same rate and not available for some of the important species that transmit the human disease. Scientists can now make better traps that would be more efficient in attracting flies or they can make repellents that may be put on animals on people,” she said.
Aksoy said it’s not clear whether the research could lead to better treatment drugs. But, she says, the information could help vaccine development. She added the research has led to the training of many young African scientists, who will further study the tsetse fly genome.
Genome research currently is underway for other parasitic diseases, including leishmaniasis, trypanosomiasis and Chagas.