Researchers found that eradicating malaria may be more challenging than previously believed. Such premise was derived from the findings of a new study saying that most childhood malarial infections in endemic areas are relapses rather than new infections.
Controlling and eliminating malaria have been significantly hard for endemic nations because the hypnozoite reservoir of parasites which cause the disease - Plasmodium vivax (P. vivax) and Plasmodium ovale (P. ovale) - are undetectable. This is because P. vivax can can conceal itself in the liver after the clearing of the primary infection. The hidden parasite can be dormant and unidentified for a couple of months or years, before it reactivates to continue, not start, infectious processes.
The new study conducted by international researchers aims to identify the impacts of relapses to the malarial infection and disease spread in children residing in Papua New Guinea.
The authors involved 524 children, aged 5-10 years old, who live in an area where P. falciparum and P. vivax are recognized to be continuously present at high rates. Fifty percent of the participants received anti-malaria treatment against infections in the blood and liver stages (primaquine group). The rest of the subjects were administered with blood-stage plus placebo treatment (placebo group).
The findings of the study showed that within eight months of follow-up, children in the primaquine group had a lesser risk of carrying at least one P. vivax or P. ovale parasite via a highly advanced molecular method, compared to those in the placebo group. The primaquine group also exhibited reduced risk of having at least one clinical P. vivax episode and were also found to not typically have P. vivax sex cells.
As per the results of the trial study, the authors estimate that about four out of every five P. vivax infections in malarial-hyperendemic areas are due to relapses. The rate for P. ovale cases rooted from relapses is estimated to be three out of five. With this, the authors said that relapses are essential factors to consider in effectively controlling malaria spread.
"These findings highlight the importance of developing new anti-hypnozoite drugs and MDA programs that target areas and risk groups with confirmed local transmission of P. vivax to achieve global malaria control and elimination," the authors wrote.
The study was published in the Public Library of Science (PLOS) Medicine on Oct. 27, 2015.
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