22 Scientific American, July 2019
THE SCIENCE
OF HEALTH
Illustration by Celia KrampienIfy Aniebo is an expert in clinical medicine and infectious diseases.
She is a senior research scientist at the Health Strategy and Delivery
Foundation and a Takemi Fellow at the Harvard T. H. Chan School
of Public Health.Genomic
Surveillance
for Malaria
It can flag pathogens long before
patients show up in clinics
By Ify Aniebo
In 2018 the World Health Organization proposed a “10+1” ini-
tiative for malaria control and elimination that targets 10 Afri-
can countries plus India, which together host 70 percent of
global cases. Although this approach is promising, it is missing
an im portant component: genomic surveillance. Drug resis-
tance threatens all of the progress made so far against malaria,
but genomic surveillance can detect resistance years before the
first warning signs appear in clinics. It can answer critical ques-
tions about how resistance emerges and spreads and can help
control the balance of interventions, preserve the useful life of
already existing drugs and ensure effective treatment.
I call on the WHO, global health partners and the malaria
community to incorporate mandatory genomic surveillance by
making it a major intervention in countries that have the highest
malaria burden. This genomic information can help malaria-con-
trol programs use quality data sets for regular monitoring of drug
resistance, provide evidence-based decision-making around
malaria policy and assist in managing the spread of resistance.
The countries most affected by malaria all had a first-line drug
that ended up becoming resistant. In African countries, toward the
end of the 20th century, chloroquine was the drug of choice, but
malaria parasites grew resistant to it. That drug was then replaced
with a combination of pyrimethamine and sulfadoxine in the early
2000s, and resistance again occurred. Now the parasites are becom-
ing resistant to the current first-line artemisinin-based com bination
therapies (ACTs). Artemisinin resistance is conferred by the kelch13
gene, which is located in the propeller region of chromosome 13.
Although mutation in this gene has occurred in Southeast Asia
and is spreading around the region, there are fears that it will also
spread to Africa, as happened with the drugs before ACTs. The
more drugs we use to treat malaria parasites, the more resistant
they become as a result of selective pressure, which creates the
preconditions for resistance. Because we know this biological
response from the parasites is inevitable, we should put in place
measures to track down these changes when they arise: doing so
would help us prevent the spread of the disease, investigate emer-
gence of resistance and subsequently preserve the efficacy of the
current first-line antimalarial treatment.
With advances in genomic technology, scientists have been
able to analyze malaria parasites from the patients carrying them
and the mosquitoes transmitting them. Such analysis has become
a source of relevant information for both drug and insecticide
resistance. Research shows that genomic surveillance has helped
us understand how different mosquito species arise and transmit
malaria to humans, which in turn has led to a better targeting of
interventions as vectorial capacity becomes better understood.
Such surveillance has enabled greater knowledge of changing
transmission intensity and parasite gene flow, including drug-
resistant genes, and has aided in quantifying the risks of import-
ing malaria from a country that is burdened with the disease. But
work using genomic surveillance as a tool has mostly transpired
within the realm of research, with only a few examples of its appli-
cation in the field where malaria burden remains high.
Genomic surveillance has been used in countries that have
eliminated malaria to prevent its resurgence and in countries that
are in a malaria-elimination phase. It should not be any different
for the African countries that have the highest malaria burden.
Lessons learned from poliomyelitis show that genomic surveil-
lance played a huge role in controlling the infection. Public health
officials have been able to use quality data to learn where this
virus emerged from, map the transmission network and deter-
mine where to direct their vaccination efforts.
It is time for genomic surveillance to move from mainly aca-
demic research into the field where malaria deaths occur. I pro-
pose that the WHO should incorporate a new “tool kit” that
includes malaria genomics in its eradication plans. Such a kit
would provide valuable information that would make national
programs fighting the disease, especially in the African countries
included in the 10+1 initiative, far more effective. As with any pub-
lic health crisis, the more we know, the better.Claudia Wallis will return next month.