Scientists
hope the simple solution can help slow the spread of dengue, malaria, Zika, and
other illnesses.
Kampong
Cham, Cambodia—In a backyard lush with mango and papaya trees, an addition to
Touch Sophea’s family was stirring excitement: Several tadpole-size guppies
were doing laps in a large barrel of water.
“They’re
pretty to look at, with so many colors,” said the farmer. The 33-year-old
gathered around the container with her three children, her husband, and her
niece at their home in Kampong Cham province, about 80 miles from Cambodia’s
capital, Phnom Penh.
Fish
often have a spiritual significance in Asian cultures, and in Cambodia, they
are seen as lucky. But these little swimmers, which at about half an inch long
would be tough to spot if they weren’t so active, are not just pets, as
Sophea’s children think of them.
They are
part of a promising one-year trial testing a low-tech innovation against dengue
and other diseases spread by mosquitoes.
The
nonprofit Malaria Consortium is nearing the end of an experiment in Cambodia
that pits a low-tech innovation against a modern problem:
As
climate change has worsened, new regions are seeing more cases of dangerous
illnesses spread by mosquitoes, such as dengue, which is responsible for an
estimated 400 million infections annually, according to the World Health
Organization.
Though
deaths from dengue are on the decline, the illness racks the body with symptoms
including a mild fever, headaches, rashes, and sore muscles and
joints—devastating livelihoods. In deadly cases, dengue causes severe bleeding
and organ impairment.
Infection
numbers have risen, and in 2015 there were more than 3.2 million known dengue
cases across the Americas, Southeast Asia, and Western Pacific, according to
the World Health Organization.
About 70
percent of infections occur in Asia, according to the journal Nature.
Touch Sophea and her children
gather around a barrel containing guppies. (Photo: Amy Fallon)
That high
percentage is why scientists here are exploring simple solutions to some of
medicine’s toughest problems—even as the search continues for cures to dengue
and other mosquito-borne illnesses, such as Zika, malaria, and West Nile.
“There is
an urgent need to find an effective low-cost and home-grown solution,” Jeffrey
Hii, a senior vector-control specialist for Malaria Consortium, told TakePart.
What can
a guppy do? The aim of the pilot, which is funded by the U.K. and German
governments, is for the fish to eat the mosquito larvae that are typically laid
in natural water sources—which are abundant in the tropics—before the insects
grow into adults and spread the disease.
The guppies,
which are indigenous to rice paddies and other of the region’s natural water
sources, are kept in rain barrels that Cambodians have long relied on to hold
water for cooking and cleaning. The barrels are situated near homes and attract
the majority of mosquitoes that carry dengue nearer to humans.
In
Kampong Cham, which has one of the highest dengue incidence rates in Cambodia,
thousands of guppies have been given to about 3,000 households by Malaria
Consortium Cambodia, the organization's local branch, which began its pilot
last October. Each villager is given two guppies, doled out from a school kept
at the local health center, to breed at home. If these swimmers die, villagers
can get more, though guppies typically reproduce within a month.
Dr. Jeffrey Hii.
(Photo: Vanney Keo for Malaria Consortium)
Scores of
community health volunteers, trained by Malaria Consortium Cambodia, are
responsible for distributing the guppies and informing residents about
prevention, including mosquito nets.
Traditionally,
the best ways to reduce dengue have included properly throwing out trash, using
insecticide sprays, coils, vaporizers, window screens, and bed nets, and
wearing long-sleeved clothes.
But
chemical insecticides are costly and require funding, and there is resistance
to them, among other concerns.
Recently,
pesticide sprays targeting Zika mosquitos in South Carolina were blamed for a
massive bee die-off.
While
Malaria Consortium supports some use of pesticides in times of outbreak,
finding natural alternatives is a priority.
Sophea
learned about the trial when a volunteer visited her province, which is home to
nearly 1 million people. The trial’s social mobilization and communication
strategy involved a tuk-tuk, a motorized rickshaw, driving through villages
handing out fliers and informing residents through songs with informative
lyrics.
“This was
an effective and culturally appropriate method to reinforce message using
songs. The songs were liked the most,” Hii said.
For
Sophea, adopting a couple of fish didn’t take much convincing.
“One of
my neighbors had dengue,” said Sophea. “I’m very concerned about my children
contracting it. If they get it, my baby can die in one week.”
With
about three-quarters of those infected with dengue not showing signs, some
health experts have labeled it a silent disease. In July, Cambodia’s government
warned of a rise in dengue—it typically occurs in outbreaks every three to five
years—with more than 1,000 additional cases in the country in about a year.
Officially
there were more than 15,000 cases and 38 deaths in 2015 across the country of
about 15 million people, but Malaria Consortium Cambodia says the real figures
are much higher.
As she
watched the barrel’s waters on an August day, peeping at the guppies darting
back and forth, Sophea said she couldn’t wait to see them hatch even more
hungry fish.
“Before
there were many mosquitoes, during the day and night, but now there’s less, and
the kids can play around the house,” she said. Sophea also knows to watch for
early symptoms of dengue, because she was told by health volunteers to be alert
to a high fever, headaches, vomiting, and rashes.
The pilot
ends in November, after which the government could include it in its health
policy. In November the consortium plans to prepare policy recommendations,
which could include expansion to more provinces. With government approval, the
nonprofit would continue the work.
One local
government official is impressed with one facet. Dr. Hay Ra, Kampong Cham
dengue supervisor, praised the guppy program for being inexpensive.
But, Ra
said, “we don’t know yet if the community will accept the guppy fish forever,
if they will keep them for a long time. If it’s successful, the program can be
applied in the whole country.”
He said
weather patterns had affected the spread of dengue in Cambodia.
“Climate
change is a big problem,” said Ra. “The number of larvae can increase, and the
mosquitoes can increase. If we don’t prevent dengue, many people will die.
Prevention is very important.”
While the
guppies are being used in the first-of-its-kind trial in Asia, scientists
thousands of miles away on another continent have come up with a surprising
possible protection against malaria.
Sleeping
with a chicken next to one’s bed, or suspending a live chicken in a cage, could
guard against the disease, researchers at the Swedish University of
Agricultural Sciences and Addis Ababa University in Ethiopia have discovered,
according to a trial published in Malaria Journal in July.
The study
was conducted in Ethiopian villages and found that Anopheles arabiensis, one of
the main mosquito species spreading malaria in sub-Saharan Africa, according to
the World Health Organization, was repelled by chicken odor. The mosquito
accounts for nearly 90 percent of malaria cases. Although it’s early days, the
research could pave the way for a chicken-scent repellent being introduced on
the market.
“In terms
of really low-tech innovations, keeping a chicken indoors shouldn’t be very
expensive,” lead researcher Rickard Ignell, from the Swedish University of
Agricultural Sciences, told TakePart. “It’s a matter of persuading people to do
it.”
Ignell said
in several villages across Africa that his team worked in and visited, many
households kept their livestock inside but usually in a separate room next
door.
(Photo: Vanney Keo for
Malaria Consortium)
He
stressed it was still important that households use bed nets and sprays to
decrease the presence of mosquitoes indoors.
“This
could potentially be used all around the world where there’s malaria. Now we’ve
only done it for one species of malaria mosquitoes. We still need to check if
other mosquitoes will behave the same,” Ignell said.
Beyond using
animals to police mosquito populations, the plant world may offer another
solution to decreasing malaria transmission, researchers in West Africa have
found.
The
Anopheles mosquito’s fondness for natural sources of plant sugar, such as
nectar, fruits, and tree sap, can be used to reduce its ability to transmit
malaria via certain plants, researchers in Burkina Faso found.
Their
study, published in the PLOS Pathogens medical journal in August, showed that a
mosquito’s ability to transmit malaria decreased if it fed from the plant
Thevetia neriifolia, known as yellow oleander. Other plants increased the
insect’s ability to transmit illness.
“What we
are really aiming for now is testing a wider range of plant species, trying to
find one or two that are attractive to mosquito vectors, that completely stop
transmission,” researcher Thierry Lefèvre told TakePart. “Then what we imagine
is to foster the planting of such species.”
Some
existing malaria control methods, such as bed nets and indoor spraying, have
faced resistance, so both low- and high-cost solutions were needed, said
Ignell.
“To
introduce new control methods, especially low-tech technologies, it is
important that researchers working with mosquitoes work closely with social
scientists, who have better tools and are more skilled to interact with
villagers in the affected communities,” he said.
In Asia,
Malaria Consortium hopes the current focus on Zika can be used to improve
dengue control.
“We hope
that the global attention can draw more attention to the urgent need to control
one of the fastest-growing infectious diseases in the world that has been
largely overlooked by the international community, a potentially fatal disease
infecting millions per year,” Hii said.
Amy
Fallon
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