An unusual sex life may spell the extinction of the deadly African sleeping sickness parasite, which threatens millions of people in West and Central Africa, an international team of scientists said on Tuesday.
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.
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 undiagnosed 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.