New evidence shows potential of two drugs to block malaria transmission

February 6, 2018, University of California, San Francisco
Credit: CC0 Public Domain

An international team of researchers has shown that two different compounds-one, an older malaria drug, the other a common laboratory dye with known antimalarial properties-can safely and effectively be added to treatment regimens to block transmission of the most common form of malaria in Africa.

This development could help reduce the spread of P. falciparum malaria, including its drug-resistant forms, thus speeding progress toward elimination of the disease.

"Although these two drugs have been around for more than half a century, this is the first time that the exciting and impressive effects of each of these drugs on have been so clearly demonstrated in a comparative study," said Roly Gosling, MD, PhD, a professor of epidemiology and biostatistics at UC San Francisco (UCSF). "Now we can say that the effectiveness of common malaria drugs used for seasonal malaria chemoprevention can be improved, with the potential of removing the threat of malaria to many millions of people across West Africa."

Malaria has several different forms and is perpetuated through a cycle in which it is passed from mosquitoes to humans and back again. When a person is bitten by an infected mosquito, malaria parasites travel through the liver to the bloodstream, where they circulate for several weeks. The majority of parasites replicate into asexual forms in red blood cells, which cause the symptoms of malaria when they burst. But a small percentage develop into male and female cells, called gametocytes, which play an important role in transmitting the disease back to mosquitoes.

Since these gametocytes are not killed by the anti-malarial drugs used to treat P. falciparum, the most common form of malaria found in Africa, people can continue to transmit the infection to mosquitoes for weeks after they've been treated, unless something is added to the treatment regimen to block their transmission.

The study, published Tuesday, Feb. 6, 2018, in The Lancet Infectious Diseases, tested the safety and efficacy of primaquine, which has been used for decades years to treat another form of malaria, called P. vivax, and a laboratory dye called , which has been in use for nearly a century to distinguish dead from living cells. When injected into the bloodstream, methylene blue also acts as an anti-malarial agent. Researchers found that each of these compounds, when added into different anti-malarial , blocked the P. falciparum 's gametocytes from passing from infected humans into mosquitoes that bit them.

"The results are very promising," said Teun Bousema, PhD, associate professor of Radboud Institute for Health Sciences, in The Netherlands. "We found that adding either of these drugs to antimalarial medicines already in use ensured that patients were no longer able to pass the disease back on to mosquitoes."

The researchers conducted a Phase 2 trial to compare the effectiveness of the two compounds in preventing gametocyte transmission against treatment as usual in 80 boys and men in Mali with asymptomatic malaria. They found that adding a single dose of primaquine to sulfadoxine-pyrimethamine and amodiaquine treatment or adding three doses of methylene blue to dihydroartemisinin-piperaquine treatment resulted in the near complete blockage of transmission within 48 hours.

"Patients who were not given these medications were able to infect mosquitoes for at least one week after treatment," said Alassane Dicko, MD, PhD, professor of Public Health at the Faculty of Pharmacy, Medicine and Dentistry of the University of Science, Techniques and Technologies of Bamako in Mali.

The researchers said the findings could help countries moving towards to rapidly reduce population-level transmission of the disease, but formal trials are needed to confirm the optimal scenarios in which these drugs can be used, and how their use could be integrated with other strategies and tools.

"The next question is when primaquine versus methylene blue should be adopted for rollout," said Ingrid Chen, PhD, an assistant professor of epidemiology and biostatistics at UCSF. "From a practical standpoint, primaquine is available as a single dose, while methylene blue requires three doses, and it also gives urine a blue color, which would require a greater degree of community sensitization prior to use."

Explore further: Methylene blue die kills in vivo malaria parasites at speed not seen before

Related Stories

Methylene blue die kills in vivo malaria parasites at speed not seen before

February 6, 2018
Research shows that the dye methylene blue is a safe antimalarial that kills malaria parasites at an unprecedented rate. Within two days, patients are cured of the disease and no longer transmit the parasite if they are bitten ...

Mini-primaquine does help stop people infecting mosquitoes with malaria

February 2, 2018
A single dose of primaquine is thought to stop people with P. falciparum malaria infecting mosquitoes, which could help bring down malaria transmission. In this Cochrane Review update prepared by an international team of ...

Cochrane Review on primaquine to prevent malaria transmission

July 3, 2014
Researchers from the Cochrane Infectious Diseases Group, hosted at LSTM, conducted an independent review of the effects of adding a single dose of primaquine (PQ) to malaria treatment to prevent the transmission of the disease.

Low-dose treatment may block malaria transmission

November 14, 2013
Lower doses of the antimalarial drug primaquine are as effective as higher doses in reducing malaria transmission, according to a study published today in Lancet Infectious Diseases by London School of Hygiene & Tropical ...

Experts discover ways to tackle drug resistant parasites that cause the killer disease malaria

December 11, 2017
A new analysis of all relevant previously published clinical data shows how parasites causing malaria become resistant to a commonly used treatment for malaria in travelers.

Recommended for you

Marker may help target treatments for Crohn's patients

October 16, 2018
Crohn's disease (CD), a chronic inflammatory condition of the intestinal tract, has emerged as a global disease, with rates steadily increasing over the last 50 years. Experts have long suspected that CD likely represents ...

Polio: Environmental monitoring will be key as world reaches global eradication

October 15, 2018
Robust environmental monitoring should be used as the world approaches global eradication of polio, say University of Michigan researchers who recently studied the epidemiology of the 2013 silent polio outbreak in Rahat, ...

Study traces hospital-acquired bloodstream infections to patients' own bodies

October 15, 2018
The most common source of a bloodstream infection acquired during a hospital stay is not a nurse's or doctor's dirty hands, or another patient's sneeze or visitor's cough, but the patient's own gut, Stanford University School ...

Researchers make essential imaging tests safer for people at risk of acute kidney injury

October 15, 2018
Every year, millions of people undergo medical tests and procedures, such as coronary angiography, which use intravascular contrast dyes. "For the majority of patients, these are safe and necessary procedures. However, about ...

Do not give decongestants to young children for common cold symptoms, say experts

October 11, 2018
Decongestants should not be given to children under 6—and given with caution in children under 12—as there is no evidence that they alleviate symptoms such as a blocked or runny nose, and their safety is unclear, say ...

New techniques can detect Lyme disease weeks before current tests

October 11, 2018
Researchers have developed techniques to detect Lyme disease bacteria weeks sooner than current tests, allowing patients to start treatment earlier.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.