Malaria is a Global Problem
After centuries of fighting malaria—and conquering it in much of the world—it is amazing what we still do not know about the ancient scourge, including what determines life and death in severely ill children
in its clutches.
- Investigators are studying malaria survivors and tracking many
other leads in efforts to develop vaccines.
- Most important, proven weapons—principally,
insecticide-treated bed nets, other antimosquito strategies, and new combination
drugs featuring an ancient Chinese herb—are moving to the front lines.
- Malaria not only kills, it holds back human and economic development. Tackling
it is now an international imperative.
A Villain in Africa
- Four principal species of the genus Plasmodium, the parasite that causes malaria, can infect humans, and at least one of them still plagues every continent except Antarctica to a lesser or greater degree.
- Today, sub-Saharan Africa is not only the largest remaining sanctuary of Plasmodium falciparum—the most lethal species infecting humans—but the home of Anopheles gambiae, the most aggressive of the more than 60 mosquito species that transmit malaria to people.
- Every year 500 million falciparum infections kill Africans, leaving one million to two million dead—mainly children.
- In addition, within heavily hit areas, malaria and its complications may account for 30 to 50 percent of inpatient admissions and up to 50 percent of outpatient visits.
- The clinical picture of falciparum malaria, whether in children or adults, is not
- In the worst-case scenario, the disease’s trademark fever and chills are followed
by dizzying anemia, seizures and coma, heart and lung failure—and death.
- Those who survive can suffer mental or physical handicaps or chronic debilitation.
Lessons of History
- Malaria was not always conﬁned to
the tropics—until the 20th century, it
also plagued such unlikely locales as
Scandinavia and the American Midwest.
- The events surrounding malaria’s exit
from temperate zones and, more recently,
from large areas of Asia and South
America reveal as much about its perennial
ties to poverty as about its biology.
- Take, for example, malaria’s ﬂight
from its last U.S. stronghold—the poor,
- The showdown began in
the wake of the Great Depression when
the U.S. Army, the Rockefeller Foundation,
and the Tennessee Valley Authority
(TVA) started draining and oiling thousands
of mosquito breeding sites and
distributing quinine (a plant-based antimalarial
first discovered in South
America) to purge humans of parasites
that might otherwise sustain transmission.
- The TVA engineers who brought hydroelectric
power to the South also regulated
dam ﬂow to maroon mosquito larvae
and installed acres of screen
in windows and doors.
receded, the local economies
- Then came the golden days
of DDT (dichlorodiphenyltrichloroethane).
- After military
forces used DDT powder to aerially
bomb mosquitoes in the malaria-ridden
Paciﬁc theater during World War II,
public health authorities took the lead.
- Five years later selective spraying within
houses became the centerpiece of global
The resistance to malaria requires constant upgrading!
- By 1970, DDT
spraying, elimination of mosquito breeding
sites, and the expanded use of antimalarial
drugs freed more than 500 million
people, or roughly one third of those
previously living under malaria’s cloud.
- Sub-Saharan Africa, however, was
always a special case: with the exception
of a handful of pilot programs, no sustained
eradication efforts were ever
- Instead the availability
of chloroquine—a cheap, man-made relative
of quinine introduced after World
War II—enabled countries with scant resources
to replace large, technical spraying
operations with solitary health workers.
- Dispensing tablets to almost anyone
with a fever, the village foot soldiers
saved millions of lives in the 1960s and
- Then chloroquine slowly began
to fail against falciparum malaria.
- With little remaining infrastructure and expertise
to counter Africa’s daunting mosquito
vectors, a rebound in deaths was
- Along the way, economists learned
their lesson once again.
- Today in many
African households, malaria not only
limits income and robs funds for basic
necessities; such as, food and youngsters’
school fees, it fuels fertility because victims’
families assume they will always
lose children to the disease.
- On the regional
level, it bleeds countries of foreign
investment, tourism, and trade.
- Continent wide,
it costs up to $12 billion a
year, or four percent of Africa’s gross domestic
- In short, in many places
malaria remains entrenched because of
poverty and, at the same time, creates
and perpetuates poverty.
Battling the Mosquito
Some highly intelligent residents of malaria-plagued communities still believe
that an evil spirit or certain foods cause
the illness, a fact that underscores yet another
pressing need: better malaria education.
- Nevertheless, long before Ronald
Ross and Giovanni Batista Grassi learned
in the late 19th century that mosquitoes
transmit malaria, savvy humans were
devising ways to elude mosquito bites.
- Writing almost five centuries before the
common era, Herodotus described in
The Histories how Egyptians living in
marshy lowlands protected themselves
with fishing nets: “Every man has a net
which he uses in the daytime for fishing,
but at night he finds another use for it: he
drapes it over the bed. . . . Mosquitoes
can bite through any cover or linen blanket
. . . but they do not even try to bite
through the net at all.”
- Based on this
passage, some bed-net advocates view
nets steeped in ﬁsh oil as the world’s earliest
- It was not until World War II, however,
when American forces in the South
Paciﬁc dipped nets and hammocks in five
percent DDT, that insecticides and textiles
were formally partnered.
- After public
opinion turned against DDT, treating
bed nets with a biodegradable class of
insecticides—the pyrethroids—was the
logical next step.
- It resulted in a breakthrough.
- The ﬁrst major use of pyrethroid-treated nets paired with antimalarial
drugs, reported in 1991, halved
mortality in children younger than ﬁve
in the Gambia, and later trials, without
the drugs, in Ghana, Kenya.
- With wide enough
use, whole families and communities
beneﬁted from the nets— even people
who did not sleep under them.
- Insecticide-treated bed nets also
- They work only if malaria
mosquitoes bite indoors during
sleeping hours—a behavior that is not
- Nets make some sleepers hot, discouraging
- Until recently, when PermaNet
and Olyset—two long-lasting pyrethroid-impregnated nets—became
available, nets had to be redipped every six to 12 months to remain effective.
- In addition,
at $2 to $6 each, nets with or without
insecticide are simply unaffordable
for many people.
- Insecticide resistance could also undermine
nets as a long-term solution:
mosquitoes genetically capable of inactivating
pyrethroids have now surfaced
in several locales, including Kenya and
southern Africa, and some anophelines
are taking longer to succumb to pyrethroids,
a worrisome adaptive behavior
known as "knockdown resistance".
precious few new insecticides intended
for public health use are in sight
(largely because of paltry economic incentives
to develop them), one solution
is rotating other agricultural insecticides
Some malarial specialists advocate use of DDT for home spraying to fight mosquitoes.
- Decoding the olfactory clues
that attract mosquitoes to humans in the ﬁrst place is another avenue of research
that could yield dividends in new repellents.
- For the time being, old fashioned,
indoor residual spraying with
DDT remains a valuable public health
tool in many settings in Africa and elsewhere.
- Applied to surfaces,
DDT is retained for six months or
- It reduces human-mosquito contact
by two key mechanisms—repelling
some mosquitoes before they ever enter
a dwelling and killing others that perch
on treated walls after feeding.
Treating the Sick
- Anti-mosquito measures alone
cannot win the war against malaria—
better drugs and health services are also
needed for the millions of youngsters
and adults who, every year, still walk the
malaria tightrope far from medical care.
- Some are entrusted to village herbalists
and itinerant quacks.
- Others take pills of
unknown manufacture, quality, or efficacy (including counterfeits) bought by
family members or neighbors from unregulated
- In Africa, 70 percent
of antimalarials come from the informal
private sector—in other words, small,
roadside vendors as opposed to licensed
clinics or pharmacies.
- Despite plummeting efficacy, chloroquine,
at pennies per course, remains
the top-selling antimalarial pharmaceutical
that is drunk by Africans.
- The next
most affordable drug in Africa is sulfadoxine-pyrimethamine, an antibiotic that interferes with folic acid synthesis by the parasite.
- Unfortunately, P. falciparum
strains in Africa and elsewhere
are also sidestepping this compound as
they acquire sequential mutations that
will ultimately render the drug useless.
- Preventing, as opposed to treating,
malaria in highly vulnerable hosts—primarily
African children and pregnant
women—is also gaining adherents.
More investments in the fight against malaria are needed
- Once again the world is coming
to terms with the truth about malaria:
the ancient enemy still claims at least one
million lives every year while, at the
same time, imposing tremendous physical,
mental and economic hardships.
- Given our current tools and even more
promising weapons on the horizon, the
time has come to fight back.
- This is an ancient disease that is both preventable and curable, but it still claims at least one million lives every year.
Extensive information about mosquitoes
and their behaviors is available here with special illustrations for greater understanding.