Researched the genetic makeup of the tsetse fly for the first time

Researched the genetic makeup of the tsetse fly for the first time

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Researchers decode the genetic material of the pathogen that causes sleeping sickness

In the tropical regions of Africa, thousands of people develop sleeping sickness (African trypanosomiasis) every year. There is no vaccination against the tropical disease and effective drugs have serious side effects. If left untreated, however, the sleeping sickness is fatal. Researchers are now focusing on curbing the spread of the dangerous pathogen transmitted by the tsetse fly in order to get the disease under control. A group of scientists recently succeeded in decoding the genome of the tsetse fly. As they report in the scientific journal "Science", the nutrient secretion of the larvae is very similar to the breast milk of mammals. So far, the lack of an insect genetic card has been a great difficulty in identifying flies' weaknesses.

Sleeping sickness is transmitted by the tsetse fly The tsetse fly (Glossina morsitans morsitans) is one of the African gnats whose food consists exclusively of the blood of their hosts. One meal is enough to almost double your weight. The flies are considered extremely dangerous because they transmit pathogens that cause sleeping sickness in humans and Nagana disease in animals. The disease progresses in three stages: After the infection, fever, chills, edema, itchy rash and swelling of the lymph nodes appear in those affected after a few weeks. After a few months, the nervous system is attacked, so that sufferers suffer from confusion, seizures, paralysis, and coordination and sleep disorders. If the disease is not treated, the patient falls into a twilight sleep, to which the disease owes its name.

According to the World Health Organization (WHO), sleeping sickness is currently common in 36 African countries. Experts estimate that 20,000 new cases occurred in 2012. Around 70 million people live in the distribution area of ​​the tsetse fly.

No vaccination against sleeping sickness available In contrast to most other insects, tsetse flies give birth to their offspring alive and feed the larvae in the womb with a secretion from the mammary glands. The flies need twelve genes for milk production, which the researchers recently identified. These genes account for more than half of total gene activity, they report in the specialist magazine. A total of 12,000 genes were identified. It turned out that tsetse flies, which perceive their hosts visually and via the smell, and houseflies have a similar vision system. As the researchers write, the genes for the proteins in saliva are particularly interesting because they inhibit blood clotting in their victims.

Almost ten years have taken more than 140 scientists from 18 countries to decode the genetic makeup of the tsetse fly. Among other things, the DNA provides information about the insects' metabolism, their sensory perceptions and their immune system. As there is no vaccination against sleeping sickness and effective drugs have strong side effects, it is difficult to combat the disease, the researchers write. In addition, an increasing number of pathogen strains would develop resistance to the drugs used. That is why the researchers already want to curb the spread of sleeping sickness.

Researchers want to curb the spread of the tsetse fly, but the new results are still not making any groundbreaking progress, Professor Christian Meyer from the Bernhard Nocht Institute for Tropical Medicine in Hamburg emphasizes to the news agency "dpa". "Decoding the genome is basic research." It is certainly conceivable that, thanks to the findings, improved insecticides could be developed, but they would have to be applied across huge areas. "This is logistically not feasible," says Meyer.

Apart from insecticides, another approach, according to the experts, could be to breed genetically modified tsetse flies that cannot reproduce or transmit the pathogen more poorly. But here too there are difficulties in practical implementation. Because the genetically manipulated flies would have to prevail against their natural counterparts in order to eventually displace them. "But they have a disadvantage," said Meyer. Experience with other genetically modified insects has shown that. Environmentalists also criticize such projects that genetically modified animals have a significant impact on the ecosystem and that the ecological consequences are not foreseeable. This could also displace other useful insects. (ag)

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Video: The life cycle of the tsetse fly 1987: Entire title