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The parasite, called T.b. gambiense, has not had sex for thousands
of years and is now made up entirely of asexual clones descended
from a single ancestor.
"We've discovered that the parasite causing African sleeping
sickness has existed for thousands of years without having sex and
is now suffering the consequences of this strategy," said Willie
Weir, bioinformatician at the University of Glasgow.
"Theoretically ... the predicted consequence of this is that it will
become extinct in the long-term," added Weir, who was lead author of
the study published in the scientific journal, eLife.
Sexual reproduction shuffles up an organism's DNA - the building
blocks of life - creating genetic diversity and eliminating
undesirable mutations, helping a species survive.
"In the near to medium term ... identifying this weakness in the
parasite could help researchers find ways to develop new forms of
treatment for sleeping sickness," Weir added.
The parasite is spread through the tsetse fly, and affects people
living in rural areas in 24 countries in West and Central Africa.
Once a person is infected, it can lie dormant for years before
symptoms start to develop, damaging their nervous system and
eventually causing a coma if left untreated.
The later stages of the disease are treated using chemicals which
are difficult to administer and have potentially dangerous
side-effects. It can be treated more easily if diagnosed early on.
The parasite "jumped" from animals into the human population within
the last 10,000 years, at a time when livestock farming was
developing in West Africa.
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The most recent major outbreak of the disease began in the 1970s and
lasted until the late 1990s.
In 1998, nearly 40,000 cases were reported, but experts estimated
another 300,000 cases were undiagnozed and therefore untreated, the
World Health Organization (WHO) said.
By 2012, the number of new reported infections had dropped to just
over 6,000.
This was similar to numbers in the mid-1960s - some 5,000 cases -
after which surveillance was relaxed and the disease reappeared.
The WHO has targeted it for elimination as a public health problem
by 2020.
(Reporting by Alex Whiting, Editing by Ros Russell; Please credit
the Thomson Reuters Foundation, the charitable arm of Thomson
Reuters, that covers humanitarian news, women's rights, trafficking,
corruption and climate change. Visit news.trust.org)
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