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Saturday, 03 September 2016 07:55

Never Heard of Black Fever? It’s Killing People All Over the World Featured

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You might expect a disease
that can kill 95 percent of its victims
would be on everyone’s radar.
But in the case of visceral leishmaniasis,
that’s not the case.
Known as Black Fever, the
affliction remains on the World
Health Organization’s list of neglected
tropical diseases. Why?
Well, because it affects “the
poorest of the poor,” said David
Poché, director of field research at
Genesis Laboratories. Transmitted
by adult sand flies that bite cattle
and whose larvae feed on their
feces, it affects 400,000 people
every year and, even with available
treatment, still kills as many as
30,000. (Malaria, by comparison,
was contracted by 214 million people
last year, killing 438,000.)
More than 90 percent of
new VL cases occur in India,
Brazil, Bangladesh, Ethiopia,
South Sudan, and Sudan, but Poché
said the disease is spreading. VL
and other forms of leishmaniasis
are “subtle diseases” that kill untreated
individuals slowly—sometimes
over the course of multiple
years—meaning there’s still “not a
perception of urgency” among infected
individuals and the medical
community, said Mark Wiser, a
professor in Tulane University’s
department of tropical medicine.
Estimating the growth of
VL and other forms of leishmaniasis
is challenging because of its
slow-burn progression as a disease,
as well as its rapid appearance in
specific locations, Wiser said. Although
mortality has decreased in
some areas, recent conflicts in the
Middle East and an increase in
Syrian refugees caused spikes elsewhere.
Poché worked with colleagues
from Texas A&M’s department
of wildlife and fisheries
sciences to study how the insecticide
fipronil can be used to kill the
sand flies that spread VL. Their
findings, published on Thursday in
the journal PLOS Neglected Tropical
Diseases, showed that when
used on cattle, single annual

fipronil treatments could reduce
sand fly populations by more than
90 percent. Using a model, the researchers
showed that monthly
treatments could eradicate the flies
within two years. Their work was
funded by the Bill and Melinda
Gates Foundation.
Because of the lack of information
about the proportion of sand flies
that feed on cattle, and the proportion
of eggs laid in cattle feces,
they had to use a probabilistic
model to study the potential impact
of the insecticide. In their simulations,
they found that the timing of
insecticide application as it related
to the sand fly life cycle was also
important. Sufficient planning
would be needed to apply the insecticide
at the right time to avoid
the compliance issues that prevent
drugs from being effective. The researchers
hope to start a field trial
to gather more data about how
fipronil could limit sand fly populations.
Unfortunately for those affected by
the disease, which causes fever,
weight loss, and anemia, frequent
insecticide treatment of cattle that
live in close proximity might be
too costly.
A drug to treat VL, miltefosine,
was approved by the U.S.
Food and Drug Administration in
2014 and is available at little or no
cost in India—specifically Bihar,
which has a vast majority of that
country’s VL cases, Wiser said.
(The insecticide study’s model was
based on Bihar.) But Poché noted
that in Bihar, one of the poorest
areas in India, testing is costly.
Transportation is an additional barrier,
as is the fact that drugs like
miltefosine have to be taken for 45
to 60 days, said Rajesh Garlapati,
senior vector ecologist at Genesis
Labs.
Once fever goes down, “people
neglect to take the whole course of
treatment. They act as reservoirs
and spread disease,” Garlapati said.
Other leishmaniasis drugs come
with toxic side effects, and the
prospect of developing a more
practical treatment is unlikely,
Wiser said. He contends there is little
incentive for pharmaceutical
companies to invest in the necessary
research.
“Rich people get cancer, so
developing an anti-cancer drug,
you know people can afford to buy
it. If it’s a disease that only poor
people get, it’s a little bit different
story,” he said. “Drug companies
aren’t particularly interested because
the people with the disease
don’t have a lot of money, so they
can’t make a profit on these
things.”

Read 1392 times Last modified on Tuesday, 06 September 2016 15:42

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