For the first time explored the genetic material of the tsetse fly

Researchers decipher genome of the pathogen of sleeping sickness

04/25/2014

In the tropical regions of Africa, thousands of people suffer from sleeping sickness every year (African trypanosomiasis). A vaccine against the tropical disease does not yet exist and effective drugs have serious side effects. Left untreated, however, sleeping sickness is deadly. Researchers are now focusing on curbing the spread of the dangerous pathogen transmitted by the tsetse fly to get the disease under control. Recently, a group of scientists succeeded in deciphering the genome of the tsetse fly. As in the trade magazine „Science“ report, the nutrient secretion of the larvae closely resembles that of mammalian breast milk. So far, the lack of a genetic map of the insect has represented a great difficulty in identifying flaws in the flies.

Sleeping sickness is transmitted by the tsetse fly
The tsetse fly (Glossina morsitans morsitans) is one of the African biting flies whose food consists exclusively of the blood of their hosts. A meal is enough to nearly double your weight. The flies are considered highly dangerous because they transmit pathogens that cause sleeping sickness in humans and the Nagana plague in animals. The disease occurs in three stages: After the infection occur in those affected after a few weeks, fever, chills, edema, itchy rash and lymphadenopathy. After a few months, the nervous system is attacked, causing people suffering from confusion, seizures, paralysis, coordination and sleep disorders. If the disease is not treated, the patient falls into terminal sleep in a twilight sleep, the disease is due to their name.

According to the World Health Organization (WHO), sleeping sickness is currently prevalent in 36 African countries. According to expert estimates, 20,000 new cases occurred in 2012. Around 70 million people live in the spread area of ​​the tsetse fly.

No vaccination against sleeping sickness available
In contrast to most other insects, tsetse flies give birth to their offspring and feed the larvae in the womb with a secretion from mammary glands. For milk production, flies need twelve genes, which the researchers recently identified. These genes account for more than half of the total gene activity, they report in the journal. Overall, 12,000 genes could be identified. It turned out that tsetse flies, which perceive their hosts visually and through the smell, and houseflies have a similar visual system. As the researchers write, in particular the genes for the proteins in the saliva are interesting, since they inhibit the blood coagulation in their victims.

For almost ten years, more than 140 scientists from 18 countries needed to decipher the genome of the tsetse fly. Among other things, the DNA provides information about the metabolism of insects, their sensory perceptions and their immune system. Since there is no vaccine against sleeping sickness and effective drugs have strong side effects, it is difficult to fight the disease, the researchers write. In addition, more and more pathogen strains would develop resistance to the drugs used. Therefore, the researchers already want to curb the spread of sleeping sickness.

Researchers want to curb the spread of tsetse fly
However, the new results do not bring any groundbreaking progress yet, emphasizes Professor Christian Meyer from the Bernhard Nocht Institute for Tropical Medicine in Hamburg to the news agency „dpa“. „Decrypting the genome is basic research.“ Although it is quite conceivable that improved insecticides could be developed thanks to the findings, but they would have to be spread across huge areas. „That's logistically impossible“, so meyer.

Apart from insect venoms, another approach according to the expert could be to breed genetically modified tsetse flies that could not reproduce or transmit the pathogen more effectively. But even here there are difficulties in the practical implementation. Because the genetically manipulated flies would have to prevail against their natural conspecifics to eventually displace them. „But they are more of a disadvantage“, so meyer. This has shown the experience with other genetically modified insects. Environmentalists also criticize such projects, that genetically modified animals significantly affect the ecosystem and the ecological consequences are not foreseeable. So other beneficial insects could also be displaced. (Ag)