Zebra smell in controlling nagana
by Mwangi Mumero
Trypanosomiasis, African’s deadly livestock disease may be managed
through the use of zebra odours, researchers from the International Centre of
Insect Physiology and Ecology (Icipe) and their partners at the University of
Pretoria now report.
Trypanosomiasis can be transmitted from animals to humans. It is known as
nagana in animals and sleeping sickness in humans.
Writing in the PLOS Neglected
Tropical Diseases Journal, the researchers report that zebras, found in
African rangelands produce smells that repel tsetse fly, the main vector for
the diseases.
“Previous research has shown that
tsetse flies avoid, and hardly bite zebras, even though zebras are commonly
present in areas infested by the flies. Until now, the reason for this evasion
has been unclear, with speculations that the zebras’ striped skin is a
contributing factor. However, the zebra stripes are only visible to tsetse
flies at about 5–10 metres. Beyond this distance, zebras appear uniformly grey
to the flies,” explained Olabimpe Olaide, a Nigerian scholar who conducted the
study as part of her PhD research at icipe,
registered at the University of Pretoria.
Found only in Africa, tsetse flies
and the diseases they transmit are one of the major constraints to livestock
and agricultural production, land use, nutrition, incomes, and overall
development in Africa.
Control of the flies with synthetic
insecticides is expensive and harmful to people, livestock and the environment.
According to Ms. Olaide, the study established
that zebras produce certain scents that repel tsetse flies. A blend of three of
these odours enhances the effectiveness of existing tsetse management tools,
including the icipe tsetse repellent
collar technology and traps.
The tsetse fly traps use colour or
smell to attract flies after which they are killed
The highly successful tsetse
repellent collar technology exploits chemical signals obtained from the
waterbuck, an animal that has also been found to repel tsetse flies.
A blend of these chemicals has been
packaged in innovative dispensers which, when worn as collars around the neck
of cattle, essentially make cattle unattractive to tsetse flies.
“In comparison to the waterbuck
repellent, the chemical blend identified from zebras appears to offer a
comparable, longer lasting and more affordable alternative, although this
potential requires further research,” says Baldwyn Torto, Head of icipe Behavioural and Chemical
Ecology Unit, and co-supervisor and mentor of Ms. Olaide.
In recent years, the International
Food Policy Research Institute (IFPRI) has published an atlas indicating the prevalence
of trypanosomiasis across Africa to help curb this menace that kills 3 million
livestock animals annually in the Africa continent.
Known as the Atlas of African
Agriculture Research and Development , it comprises a series of maps
and short analyses on Africa’s diverse agricultural challenges and
opportunities.
Among the key pages is the
illustration containing information on the location of cattle and production
systems.
This information is combined with
the distribution of tsetse fly species in the area to estimate the presence and
absence of trypanosomosis, a parasitic disease transmitted by the tsetse fly.
These maps are a boon to
researchers, farmers and government officials involved in its trypanosomiasis control.
Nagana also affects rural
development and livelihoods more generally by limiting options for mixed
farming and hindering a balanced use of natural resources.
Another related map shows the
estimated benefits to livestock farmers expressed in US $ per square kilometre
if there is total eradication of trypanosomiasis.
According to the maps, benefits in
the Horn of Africa would amount to nearly $2.5 billion, discounted at 10
percent over 20 years to account for the opportunity cost of funds— an average
of approximately $3,300 per square kilometer of tsetse-infested area.
The maps also indicates production
systems- where for instance mixed farming is heavily dependent on the use of
draft oxen in Ethiopia, areas of Sudan and South Sudan where oxen use is much
lower, and the strictly pastoral areas of Somalia and Kenya.
Other than livestock, the atlas
covers seven topics. They include political, demographic and institutional
classifications.
Others areas include the footprints
of agriculture, the the role of water in African agriculture, drivers of change
in African agriculture, access to agricultural trade and human welfare.
By presenting a broad range of
geospatial data and explanatory text, the analysts hope the Atlas will
serve as a reliable and up-to-date guide for informed decision-making, which
can help speed, broaden and sustain Africa’s agricultural productivity.
The 30-plus map atlas is a
collaborative 5 year-work that has included many experts and organisations.
These organisations include the
Australian Centre for International Agricultural Research (ACIAR) and
the UN Food and Agriculture Organization (FAO).
Other partners were McGill
University, HarvestChoice, IFPRI, Welt Hunger Hilfe and Concern
Worldwide. (ends)
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