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Malaria control success in Africa ‘at risk from spread of multi-drug resistance’

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New research sheds light on how resistance is emerging in different locations and moving across Africa.

Undated handout photo issued by University of Edinburgh of a malaria-spreading mosquito

Malaria control in Africa is at risk from the spread of multi-drug resistance, scientists say.

A genomic study of malaria parasites on the continent found the genetic features of Plasmodium falciparum parasites that inhabit different regions of Africa.

This included the genetic factors that create resistance to anti-malarial drugs.

The research sheds new light on how resistance is emerging in different locations and moving across Africa, putting previous progress at risk.

Malaria remains a global problem, with the deadliest parasite species P. falciparum prevalent across sub-Saharan Africa.

Between 2000 and 2015, an ongoing drive to eliminate the disease saw worldwide malaria deaths drop from 864,000 to 429,000 per year.

In 2015, 92% of global malaria deaths were in Africa, with 74% of these occurring in children aged five or under.

However, the research published in the Science journal indicates that if new forms of treatment are not developed, this progress may be at risk.

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It comes from the first network of African scientists, the Plasmodium Diversity Network Africa (PDNA), to work with genomic tools to study the diversity of malaria parasites across the continent.

They studied the genetic diversity of P. falciparum populations endemic to several countries in sub-Saharan Africa, including Ethiopia and Ghana.

The study found P. falciparum parasites are genetically distinct according to which region of Africa they are found.

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Researchers also discovered that the regional populations are sharing genetic material in all directions.

This includes genes that can confer resistance to anti-malarial drugs, with new types of drug resistance emerging in different parts of Africa.

Human migration, including that resulting from colonial activity, is thought to have played a part in the evolution of the parasites.

Professor Abdoulaye Djimde, Wellcome International Fellow at the Wellcome Sanger Institute, said: “Contrary to previous studies, we identified distinct Western, Central and Eastern populations of P. falciparum, as well as a highly-divergent Ethiopian population.

“Genetic material originating from all directions was shared by all populations, indicating that the flow of genes is multi-directional, as opposed to unidirectional from east to west as previously thought.

“This is crucial information for understanding how resistance to malaria drugs is developing in Africa.”

Samples of P. falciparum were collected from 15 African countries by PDNA and their genomes sequenced at the Wellcome Sanger Institute as part of the MalariaGEN data-sharing network.

Scientists said that most concerningly, strong genetic signatures were detected on chromosome 12 in P. falciparum samples from Ghana and Malawi.

This raises the possibility that recent evolution of the parasite could compromise the effectiveness of artemisinin-based combination therapies (ACTs).

ACTs combine multiple anti-malarial drugs in one treatment to overcome resistance to one or more individual drugs.

First author Dr Alfred Amambua-Ngwa said: “Whatever the historic factors affecting the flow of genes between the distinct P. falciparum populations, the multi-directional flow we’ve identified raises the prospect of continental spread of resistance to artemisinin-based combination therapies, which could arise from anywhere in Africa.

Genomic surveillance, and on a large scale, is going to be vital to track the emergence and spread of resistance to combination therapies.”

In a separate study in the same journal, scientists report on the first detailed map of individual malaria parasite behaviour across each stage of its life cycle.

The result is the Malaria Cell Atlas, which gives the highest resolution view of malaria parasite gene expression to date and monitors how individual parasites change as they develop in both the mosquito and human host.

Dr Virginia Howick, joint first author from the Wellcome Sanger Institute, said: “We’ve created an atlas of gene activity that spans the complete life cycle of the malaria parasite.

“This is the first atlas of its kind for a single-cell organism.

“The malaria parasite’s life cycle is key to research into this disease and the Malaria Cell Atlas will help us truly understand the parasite in order to effectively control malaria.”

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