New combinations of agents based on the oldest synthetic malaria drug, the methylene blue stain, can curb the spread of malaria parasites and make a significant contribution to the long-term eradication called for by the international "Roll Back Malaria Initiative."
In a study on 160 children with malaria in Burkina Faso, specialists in tropical medicine from the Heidelberg University Hospital have shown that in combination with newer malaria drugs, methylene blue prevents the malaria pathogen in infected persons from being re-ingested by mosquitoes and then transmitted to others and is thus twice as effective as the standard therapy. The results of the study were published in May 2009 in the online journal PLoS One.
Malaria is still one of the deadliest tropical diseases. Every year, 300 million people are infected with malaria and more than one million of them die or suffer severe brain damage. Children under five years are particularly susceptible.
Malaria pathogens need humans and mosquitoes
When the Anopheles mosquito bites, the malaria parasites (plasmodia) in the saliva of the mosquito enter the human body, reproduce in liver cells and then attack the red blood cells. This causes severe symptoms such as high fever or anemia; children in particular can even fall into a coma. During reproduction in the human body, some parasites develop into special reproductive cells, gametocytes. If they are ingested by an Anopheles mosquito, they continue to reproduce in the mosquito. The cycle is complete.
The gametocytes are the key for the spread of malaria by the Anopheles mosquito. Common malaria drugs known as artemisinins block reproduction of the parasites in the human body and reduce the number of gametocytes in blood by half. This makes the transmission of the parasite to the mosquito more difficult but does not completely prevent it. "We urgently need alternative therapies that are effective against the gametocytes and thus improve the control of malaria," states Professor Dr. Olaf Müller, Project Head in the Department of Tropical Medicine and Public Health of the Hygiene Institute at the University of Heidelberg.
Methylene blue prevents transmission to mosquitoes
The appropriate component for such an alternative is a proven agent - the methylene blue stain which has been given to malaria patients since the end of the 19th century has proven to be safe, well tolerated, and effective in combination with various malaria medications.