An Anopheles mosquito at the sting. Credit: prep4md / www.flickr.com
Reading The enemy comes in the night. Then the female mosquitoes of the genus Anopheles seek their victims and suck their blood. They transport a scourge that has accompanied humanity since its earliest times: the deadly parasite Plasmodium, which gets into the bloodstream of the victim via the mosquito bite and is responsible for the infection with the disease malaria. Every year about 1.5 to 2 million people die of the fever. Scientists have always come up with new ideas to stop the deadly disease - despite several hopeful approaches but so far without any resounding success. For decades, chloroquine has been the drug of choice for treating an outbreak of malaria. But in Asia and South America drug resistance developed rapidly. Resistance was also observed in Cambodia in the past year in Cambodia, where the drug Artemisinin has been described as particularly powerful. "By sometimes administering the artemisin derivative alone and not in combination with other medications, it was easier to develop resistance, " explains Johannes Friesen of the Max Planck Institute for Infection Biology in Berlin. There are even multidrug-resistant strains that currently have no effective drug. "Which drugs can replace the Artemisininpräparate is the big question, " says researchers.

Also, the development of a vaccine is extremely difficult for several reasons. First, the life cycle of the parasite is highly complex with a variety of different life stages. In this way, the malaria virus can escape again and again the elimination by the immune system of its host. In addition, there are many different strains of the Plasmodium pathogen worldwide. "If you isolate a strain from Asia, the recognition structures for the immune system are different than for an isolate from South America or Africa, " explains Christian Epp from the Department of Infectious Diseases at Heidelberg University Hospital. The researchers must therefore limit themselves to the few structures that are identical in all pathogens, which makes vaccine development extremely difficult.

Genetically modified or attenuated by radiation pathogens could serve as a live vaccine in the future. "At the moment, this principle is being tested in humans in the first test, which can be very exciting, " explains Epp. Johannes Friesen and his colleagues are also making progress in the fight against the devastating disease. Recently, they were able to immunize mice with live parasites with simultaneous antibiotic prophylaxis in the long term against the parasite infestation. Now the results in the field trial will be confirmed by the distribution of antibiotics.

The most promising candidate for a vaccine so far is the protein "RTS, S". A compound containing this compound is currently in clinical trials. In previous test phases, the risk of malaria in the trial participants was already reduced by 53 percent. Now the scientists are testing the potential vaccine on a large scale. In the final phase, before approval can be sought, the efficacy of the product is studied in two groups of children in Africa. Overall, the vaccination of up to 16, 000 infants and toddlers is planned. If this study is successful, an application for the vaccine for use in children aged 5 to 17 months could be submitted as early as 2012. "RTS, S" is currently the most advanced vaccine being worked on, "confirms Epp. display

"But a moderately effective vaccine would not be a miracle weapon, " explains Friesen. As before, the most effective control strategies are not to let a mosquito bite sting. In recent years, more and more insecticide-treated bed nets have been distributed to the population in malaria areas, posing immense logistical challenges for local health authorities. In addition, the nets must be repeatedly re-impregnated at regular intervals. The WHO also plans to increase the use of the insecticide DDT in the future in order to curb the spread of disease-carrying mosquitoes.

In addition, the early detection of a disease is of utmost importance for the healing success. But the biggest enemy in the fight against malaria remains poverty. "Unfortunately, it is still a social issue to decide whether or not to die of malaria, " explains Friesen. "In the affected areas, people from higher-level backgrounds have better access to healthcare: many poorer people fall victim to the disease because they are simply can not afford the bus to the hospital. "Also missing in many areas of a suitable health infrastructure, also make counterfeit drugs is a major problem.

By ddp correspondent Gwydion Brennan

© science.de

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