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MALARIA: The quest for effective detection of co-infections

18 Dec 2023
MALARIA: The quest for effective detection of co-infections
A snip from the PLOS Neglected Tropical Diseases journal with inset of Ifakara Health Institute scientist Brian Tarimo who contributed to the study. GRAPHIC | IFAKARA/KMC

A group of scientists have called for continued efforts to improve diagnostics in a new malaria study, emphasizing that recognizing the shortcomings in existing assays to detect co-infection is an essential first step.

Hailing from research and academic institutions in the USA and Africa, the scientists challenge previous assumptions about the uncommonness of malaria co-infections, suggesting that such incidences are more common than previously believed.

Two parasites studied
The recommendations are based on their study, which was published on the PLOS Neglected Tropical Diseases journal this month, where they investigated two different parasites that cause malaria – Plasmodium ovale curtisi (Poc) and Plasmodium ovale wallikeri (Pow). The two parasites’ cases of co-infection within human and mosquito hosts have been rarely studied.

“Recognition of the limitation of current assays for detecting co-infections and continued development of better, more facile diagnostics will improve our ability to understand whether and how these two species potentially differ in their epidemiology, biology, and clinical manifestations,” wrote the scientists.

Co-infection detection
To detect co-infection, the scientists modified existing “real-time PCR assays” and created an algorithm to detect mixed Poc/Pow infections. They then applied these assays to field-collected samples from Tanzania and Cameroon, including human blood and mosquito midguts.  

The results detected both Poc and Pow in roughly 10% of human P. ovale blood-stage infections, and surprisingly, in a majority of blood-fed mosquitoes. 

“The real-time PCR approach described here (in the study) represents an efficient method for detecting mixed Poc/Pow infections in both human clinical blood samples and mosquito midguts. Mixed Poc/Pow infections were commonly detected in mosquito midguts, and were also detected, albeit to a lesser degree, in both human dried blood spots and leukocyte-depleted blood samples. This suggests that the extent of mixed Poc/Pow infection may be greater than previously appreciated.”

Use of the PCR approach
Following these findings, the scientists recommend the use of a real-time PCR approach to identify the natural occurrence of mixed Poc/Pow infections in human and mosquito hosts as scientists continue with efforts to improve diagnostics.

“The described real-time PCR approach can be used to identify the natural occurrence of mixed Poc/Pow infections in human and mosquito hosts and reveals that such co-infections and co-transmission are likely more common than appreciated.”

USA, Africa scientists in the study
The study was led by Varun Potlapalli and Jessica Lin from the University of North Carolina School of Medicine, USA with contributions from Meredith Muller, Yu Bin Na, Danielle Williams, Oksana Kharabora, Srijana Chhetri, Mei Liu, Kelly Carey-Ewend, Feng-Chang Lin, Jonathan Juliano and Jonathan Parr – all from the same institute.

Other contributors include Billy Ngasala from the Muhimbili University of Health and Allied Sciences (MUHAS), Tanzania; Innocent Ali from the University of Dschang, Cameroon; Derrick Mathias from the University of Florida, USA; and Brian Tarimo from Ifakara Health Institute, Tanzania.

Read the publication here.