A new study has shown that an older malaria drug and acommon dye can safelya dn effectively be usedto block the transmission of malaria. The team of researchers from the London School of Hygiene & Tropical Medicine (LSHTM), the Malaria Elimination Initiative (MEI) at the University of California, San Francisco (UCSF) Global Health Group and the Malaria Research and Training Center (MRTC) in Mali, and Radboud Institute for Health Sciences in The Netherlands found that adding Primaquine or Methylene blue to anti-malarials effectively blocks malaria transmission.
There are 5 million new cases of different forms of malaria every year perpetuated through a cycle involving mosquitoes and humans. The cycle begins when an infected mosquito bites a human and transmits the malaria parasites into his/her bloodstream. Most of the parasites replicate as asexual forms in the red blood cells. The rest develop into sexual forms called gametocytes. These gametocytes are responsible for transmitting the malaria back to mosquitoes. The sexual forms of malaria parasites are not killed by antimalarial therapy. Hence, humans can transmit the parasites back to mosquitoes weeks after being successfully treated.
The researchers conducted a Phase 2 trial to compare the effectiveness of the two compounds ( Primaquine and Methylene blue) in preventing gametocyte transmission against treatment as usual in 80 boys and men in Mali with asymptomatic malaria. They found that adding a single 0.25mg/kg dose of primaquine to sulfadoxine-pyrimethamine and amodiaquine, or adding 15 mg/kg of methylene blue each day for three days to dihydroartemisinin-piperaquine, resulted in the near complete blockage of transmission within 48 hours of treatment. Patients who were not given these medications were able to infect other mosquitoes for at least one week after treatment.
“These encouraging results show the potential effectiveness of methylene blue in stopping malaria transmission in its tracks, as well as strengthening the evidence on the optimal use of primaquine. The data add to the body of work suggesting that safe doses of drugs can be added to conventional treatment and that they block transmission at the individual level. The next step is evaluating this approach within communities to see if it can be an additional weapon in the armoury to reduce and eliminate malaria.” Professor Chris Drakeley of the London School of Hygiene & Tropical Medicine (LSHTM) said.