An international team led by Ingrid Felger, from the Swiss Tropical and Public Health Institute in Basel, Switzerland has developed a highly sensitive method for the detection of malarial parasite in blood samples. This quantitative PCR based assay proved to be 10 times more efficient than the current standard assays including microscopy in use for the detection of malaria.
The researchers have targeted two genes with a high copy number for the assay, telomere-associated repetitive element 2 (TARE-2, ~250 copies/genome) and the var gene acidic terminal sequence (varATS, 59 copies/genome) in the malarial parasite genome. Copy number represents the number of locations a given gene is present in the genome. High copy number results in higher gene expression meaning that more molecules are present for the transcript. Exploiting this property of these genes helped researchers reach a limit of detection of 0.03 to 0.15 parasites/micro liter blood.
Researchers analyzed 498 blood samples randomly collected for a malaria survey in Tanzania by three methods. Parasite were detected in 25% of the samples by light microscopy, 50% by 18S rRNA qPCR, and 58% by TARE-2 or varATS qPCR. This method is 10× more sensitive than the conventional 18S rRNA qPCR assay, which targets a gene present at 5–8copies/genome. The sensitivity of the new assay could detect the presence of gametocyte stage of the parasite (the stage of the parasite transmitted in to humans when a mosquito bites) in 40% of the samples that were left undetected by other detection methods.
This new assay is currently available only for the most common malarial parasite P. falciparum. With this new assay, malaria can be detected at the early low-density infection stage where no disease symptoms are observed in patients. This would further help in malaria control and elimination programmes to eradicate the spread of disease.
This study was published in PLOS Medicine.
The original publication can be accessed here: http://bit.ly/1AEEZcB