Microbiologists are dissecting the breath of patients infected with malaria in search of a new kind of diagnostic test. MICHELLE ROBERTS writes
People with malaria give off a distinctive “breath-print” that could be used as a test for the disease, according to American scientists.
They had already tried out a crude prototype breathalyser in Africa, a tropical medicine conference heard.
The test was reasonably good at detecting cases in children, but needs developing to become a routine device.
One of the odours it sniffs out is identical to a natural smell that attracts insects that spread malaria.
Pine trees and conifers emit these terpenes to summon mosquitoes and other pollinating insects, say the researchers, from Washington University in St Louis.
They believe people with malaria who have this odour in their breath may also attract mosquitoes and infect more of the biting insects, which can then spread the disease to other people that they bite.
Although the test needs perfecting, it could offer a new cheap and easy way to help diagnose malaria, Prof Audrey Odom John and colleagues say.
The prototype breath test detects six different odours or volatile organic compounds to spot cases of malaria.
The researchers tried it on breath samples from 35 feverish children in Malawi, some with and some without malaria.
It gave an accurate result in 29 of the children, meaning it had a success rate of 83%.
This is still too low for the test to be used routinely, but the researchers hope they can improve its reliability and develop it into an off-the-shelf product.
Simple, rapid blood tests for malaria are already available, but they have limits, say the Washington University researchers.
Testing blood can be expensive and technically challenging in rural settings.
A non-invasive method of detection that does not require blood samples or technical expertise could be of great benefit.
Prof James Logan from the London School of Hygiene and Tropical Medicine said: “The rapid detection of asymptomatic malaria is a challenge for malaria control and will be essential as we move towards achieving the goal of malaria elimination. A new diagnostic tool, based on the detection of volatiles associated with malaria infection is exciting.”
He said more work was now needed to see if it could be made into a reliable test.
The findings are being presented at this year’s annual meeting of the American Society of Tropical Medicine and Hygiene.
Scientists have developed a breathalyser test for malaria, in an advance that could fast-track efforts to eliminate the disease.
Missouri biologists have road-tested a technique that senses the parasite in samples of ¬infected people’s breath. The ¬results, outlined at a conference in Baltimore, build on an Australian discovery that malaria sufferers exhale high levels of certain chemicals.
The test could accelerate ¬diagnosis because the chemicals spike at very early stages of infection, when other techniques can fail to detect the parasite.
The new approach also offers a cheap alternative to lab-based DNA or blood analyses and to finger-prick tests which can ¬diagnose malaria in the field, but lack sensitivity and are losing reliability as the parasites mutate.
“The malaria parasite has been outwitting human interventions for thousands of years,” said Patricia Walker, president of the American Society of Tropical Medicine and Hygiene, which is hosting the conference. “We need innovative collaborations between biologists and ¬engineers to develop new tools that give us the upper hand.”
The team, from Washington University in St Louis, trialled the technique on 35 patients in a Malawi children’s clinic. Half had already tested positive to malaria in blood-based tests.
Sealed breath samples were flown to Missouri for lab analysis, which correctly diagnosed 83 per cent of the children. The team is working on refinements to boost the test’s accuracy, and a method to roll it out in the field.
This would probably involve “compact electronic noses” which can detect and analyse specific sets of odours. Similar “eNoses”, some small enough to attach to insects, are already used to detect chemical spills and graffiti spray paint, and are being developed to sniff out bombs and diagnose tuberculosis.
In 2015, a CSIRO-led team revealed it had discovered spiking levels of nine chemicals in the breath of adults deliberately ¬infected with low-level malaria during a drug trial. Lead researcher Amalia Berna subsequently joined the Washington University team, and the two institutions have collaborated in research funded by a $US1 million ($1.3m) grant from the Bill and Melinda Gates Foundation.
CSIRO lead investigator Stephen Trowell said rapid and ¬reliable diagnosis was crucial to wipe out malaria once and for all. He said researchers had “got very close” using the insecticide DDT and the anti-malaria drug chloroquine, but a smattering of undiagnosed patients had gone untreated and allowed the parasite to re-establish itself.
New evidence shows that malaria parasites can alter patients’ breath to attract mosquitos and drive disease transmission. Researchers have used this information and identified other biomarkers of infection to develop a malaria breath test that was highly accurate in diagnosing pediatric patients, according to data presented today at the American Society of Tropical Medicine and Hygiene Annual Meeting.
Although previous research has shown that malaria parasites can manipulate host odors to enhance Anopheles attraction, this is the first time that it has been confirmed in a real-world setting, according to Chad Schaber, PhD student at Washington University in St. Louis, and colleagues.
During a recent investigation, Schaber and colleagues examined breath samples of 35 children aged 3 to 15 years with (n = 17) or without (n = 18) malaria infection who received care at a pediatric center in Lilongwe, Malawi. The participants provided breath samples by blowing into a balloon-like bag. The samples were then transferred to a tube and sent to a lab at Washington University for review. Blood samples were also obtained to confirm malaria diagnosis.
Schaber reported that patients with malaria had significantly higher levels of mosquito attractants known as terpene compounds. These compounds — 3-carene and alpha-pinene — were associated with a high specificity (greater than 94%) and moderate sensitivity (41%-53%) in predicting malaria infection.
“The terpene is probably a survival mechanism for the parasite, but this compound also might be useful in boosting the effectiveness of mosquito traps used in malaria control efforts,” lead investigator Audrey R. Odom John, MD, PhD, associate professor of pediatrics, infectious diseases, at Washington University School of Medicine in St. Louis, said in a press release.