Almost half of the world’s population is at risk of malaria infection, with children and pregnant women at the highest risk of getting sick and dying from the disease. Current methods to detect this potentially deadly infection rely on obtaining an invasive blood sample, and each test has significant limitations that restrict their utility.
In new research published in Nature Communications, Yale School of Public Health epidemiologist Dr. Sunil Parikh, MD, MPH, and colleagues from the University of Arkansas for Medical Sciences and Cameroon, present a new noninvasive test that could dramatically alter the global malaria testing landscape by providing reliable, safe, and sensitive testing to low- and middle-income countries that have been plagued by the deadly mosquito-borne disease.
Best of all, the new test is capable of detecting malaria without taking a single drop of blood.
The test is performed using a device called a Cytophone that applies targeted lasers and ultrasound to detect malaria-infected cells circulating in the bloodstream, said Dr. Jillian N. Armstrong, a former PhD student in Parikh’s lab and one of the study’s lead authors. About the size of a table-top printer, the initial Cytophone prototype can determine whether infection is present within minutes via a small noninvasive probe that is placed on the back of a person’s hand above a targeted vein.
Shimmering crystals
The Cytophone’s noninvasive detection is possible, Armstrong said, because when infected with malaria parasites, red blood cells accumulate a by-product called hemozoin, an iron crystal. These nanocrystals in the infected cells have unique magnetic and optical properties that absorb more energy than normal hemoglobin when they pass through a laser, which makes it possible for the Cytophone probe to detect the infected cells.
In tests with 20 adult patients diagnosed with symptomatic malaria in Cameroon, the Cytophone was able to detect malaria infections with 90% sensitivity and 69% specificity, as good, and in some instances better than, the current gold standards for malaria testing. Current malaria tests require drawing blood from patients and special laboratory equipment.
“Our study showed that the Cytophone was safe and had comparable diagnostic performance to current point-of-care options when compared to highly sensitive quantitative PCR as the gold standard,” Armstrong said.
Our study showed that the Cytophone was safe and had comparable diagnostic performance to current point-of-care options when compared to highly sensitive quantitative PCR as the gold standard.
Dr. Jillian N. Armstrong, study author
Precise detection
The Cytophone was conceived by bioengineer Vladimir P. Zharov, who led a research team from the University of Arkansas that initially created the technology to detect cancerous melanoma cells in the circulatory system. Zharov’s team developed this portable prototype for malaria detection and Zharov shares co-senior authorship of the current study with Parikh.
When used for malaria testing, the Cytophone successfully detected Plasmodium falciparum, the most common and deadliest species of malaria parasite.
Parikh said he was particularly excited by the Cytophone’s ability to also detect less common Plasmodium species, which are driving increased infections in some countries. This is because all species of human malaria produce hemozoin nanocrystals during infection. During clinical testing in Cameroon, one person in the population sample was infected with a different species of parasite and the Cytophone successfully detected the infection.
“That was a really exciting proof of concept with the first generation of this platform,” said Parikh, who has been conducting malaria research in Africa for over 20 years. “I think one key part of the next phase is going to involve determining and demonstrating whether or not the device can detect and distinguish between other species.”
The device also detected the decline of parasite presence when patients were retested after treatment. The results confirmed the Cytophone was sensitive enough to be able to detect both high and low levels of parasites in infected blood.
Collaboration key
In discussing the study, Parikh and Armstrong praised the work of their Cameroonian collaborators, who they said were instrumental in testing the device during the COVID-19 pandemic.
“The trainees in Cameroon were amazing and enabled us to test this device with little advanced training”, said Parikh.
Armstrong described Professor Yap Boum II, director of the Medicine Sans Frontiers Epicenter in Cameroon’s capital city of Yaoundé and another co-senior author of the study, as the “driving force” of the project, continuing testing in Cameroon when the rest of the international team was forced to stay home due to COVID-19 restrictions.
“I believe that these kinds of transdisciplinary projects between engineers and epidemiologists are crucial to reduce the global burden of disease,” Armstrong said.
Through this collaboration, the team aims to continue working on a new generation of Cytophones that they anticipate will be even more sensitive, more advanced, and potentially battery powered.
Alongside other innovations, the team hopes that the device, through further development, will not only be available for use in high endemic settings such as Cameroon, but also for quick tests in areas where malaria is not as prevalent.
“You could also imagine this device being used in a setting where you want to screen large numbers of individuals quickly - where malaria is actually not very prevalent - and you want to pick it up as a screening tool to avoid having large numbers of people get a blood finger prick,” Parikh said.
Malaria continues to be a major global health problem, with a quarter of a billion cases and over 600,000 deaths estimated to occur annually. The World Health Organization has set a goal of reducing malaria cases by at least 90% globally and to eliminate malaria from 35 countries by 2030. The Cytophone technology offers an exciting new point-of-care diagnostic tool with potential to assist in this effort by improving detection of malaria cases and helping to initiate treatment.
Research excellence
The new malaria test is the latest in a long line of transformative malaria research being conducted at YSPH. In recognition of the school’s strength and expertise in this area, the National Institutes of Health earlier this year named Parikh a co-principal investigator of a new International Center of Excellence in Malaria Research (ICEMR) in Burkina Faso. Burkina Faso has the 6th highest burden of malaria worldwide despite aggressive deployment of multiple different prevention measures. Parikh will share leadership of the ICEMR with Prof. Roch Dabiré, PhD, Regional Director of the Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso, and Prof. Brian Foy, PhD, a professor of microbiology, immunology, and pathology at Colorado State University.
Yale School of Public Health Associate Professor Dr. Amy Bei, PhD, is a co-investigator at the new center. Her primary research focus is Plasmodium and the intersection of population genetics, genomics, molecular genetics, epidemiology, and immunology. Bei’s work includes the study of malaria vaccine candidates and the functional consequences of naturally arising diversity. She has several ongoing research projects in Senegal in addition to many active collaborations in sub-Saharan African countries in both East and West Africa.
Parikh and Bei convene a larger multidisciplinary team of malaria and mosquito specialists affiliated with the Yale Institute for Global Health who comprise a faculty network known as MalarYale. Team members are leading projects in nearly a dozen countries, including Africa and South America, focused on all malaria species. The goal of MalarYale is to foster collaboration within Yale and beyond, and to tackle problems in malaria where multifaceted approaches are needed.
Other members of the network include Dr. Choukri Ben Mamoun, PhD, a professor of medicine (microbial diseases) and of microbial pathogenesis; Dr. Erol Fikrig, MD, Waldemar Von Zedwitz Professor of Medicine (Infectious Diseases), and professor of epidemiology (microbial diseases) and of microbial pathogenesis; Dr. Joseph Vinetz, MD, professor of medicine (infectious diseases), anthropology, and epidemiology (microbial diseases); and Dr. John Carlson, PhD, professor of molecular, cellular and developmental biology.