Decoding of tsetse fly genome opens way to new controls
14 July 2014
An international research team from 78 research institutes in 18
countries, has published the DNA sequence of the tsetse
fly, the carrier of the sleeping sickness parasite, following a
10-year project .
The tsetse fly, Glossina morsitans,
transmits the parasite to humans and pets through its bite. It took
ten years of work by some 145 researchers in the consortium to
reveal the genome of the vector fly. They also
determined its genetic structure and the proteins coded by each
gene. Knowing its genome is essential to understanding the biology
of the insect.
A unique insect
The tsetse fly is distinct from all other insects in many ways.
First, compared to other disease vectors among which only the female
bites to feed on blood, both sexes are 'hematophagous'. More
surprising, the fly has a very distinctive reproductive method which
is comparable to that of mammals. It does not lay eggs but gives
birth to developed larva after ten days gestation in its uterus,
during which it feeds its offspring with a milky secretion.
Researchers found a set of visual and odour proteins that seem to
drive the fly's key behavioural responses such as searching for
hosts or for mates. They also uncovered the photoreceptor gene
rh5, the missing link that explains the tsetse fly's attraction
to blue/black colours. This behaviour has already been widely
exploited for the development of traps to reduce the spread of
A neglected disease no longer
Screening and treatment for sleeping sickness, or Human African
Trypanosomaisis (HAT), is costly, difficult, and toxic. Preventing
the disease by developing a vaccine seems difficult because of the
ability of the trypanosome to thwart mammalian immune systems.
Therefore, vector control is currently the only means of breaking
the transmission cycle for the disease.
Gradually, HAT is becoming a less-neglected disease, mobilising
an increasingly large scientific community through studies such as
these. Access to its DNA represents a major scientific advance, and
will accelerate research on its fundamental biology. It opens the
way for new prospects for controlling this vector.
These studies should make new concrete progress possible for the
disadvantaged populations that are the victims of this scourge.
"Tsetse flies carry a potentially deadly
disease and impose an enormous economic burden on countries that can
least afford it by forcing farmers to rear less productive but more
trypanosome-resistant cattle." says Dr Matthew Berriman,
co-senior author from the Wellcome Trust Sanger Institute.
"Our study will accelerate research aimed at
exploiting the unusual biology of the tsetse fly. The more we
understand, the better able we are to identify weaknesses, and use
them to control the tsetse fly in regions where human African
trypanosomiasis is endemic."
"Though human African trypanosomiasis affects
thousands of people in sub-Saharan Africa, the absence of a
genome-wide map of tsetse biology was a major hindrance for
identifying vulnerabilities," says Dr Serap Aksoy, co-senior
author from the University of Yale. "This
community of researchers across Africa, Europe, North America and
Asia has created a valuable research tool for tackling the
devastating spread of sleeping sickness."
International Glossina genome initiative. Genome sequence of
the tsetse fly (Glossina morsitans): vector of African
trypanosomiasis. Science, 2014, Vol. 344 no. 6182 pp. 380-386.
Associated studies can be found on the
Sanger Institute: www.sanger.ac.uk
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