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Human sleeping sickness, the age-long disease that has defied several interventions,

is closer to being checked as African researchers recently announced improved techniques to control the disease.

In a study recently
carried out in Burkina Faso and Cote d’Ivoire, African scientists show
that by mimicking odours in cows, pigs and humans and using them to
bait Tsetse flies (the vector harbouring the trypanosomes which causes
sleeping sickness), they can increase the number of flies attracted to
a trap and the number of kills.

The scientists figure that this is a sure way to break the transmission of the disease from fly to man.

An associate
professor of the Community and Primary Health Department of the
University of Lagos, College of Medicine, Bayo Onajole, says although
using odour baits to kill tsetse flies is not a new method, “ it can
help in preventing transmission.”

He adds that, “For
the control of vector-borne diseases, it is always advised to use an
integrated approach such as having a high index of suspicion of
patients, presenting with symptoms, treating with drugs and detecting
approaches targeted at the environment,” he said.

Human sleeping
sickness is caused by African trypanosomiasis and this is harboured in
Tsetse flies of various species. Tsetse flies (Diptera:

Glossinidae) infest
approximately 10 million km2 of sub-Saharan Africa where they transmit
trypanosomes, which cause sleeping sickness. The most dangerous species
(called Glossinidae Palpalis), which occur in West Africa, accounts for
97 per cent of total reported cases.

Age-long challenges

According to the
World Health Organisation, sleeping sickness threatens up to 60 million
people in 36 countries of sub-Saharan Africa and affects 50,000 to
70,000 people each year. Only a small fraction of these countries are
under surveillance with regular examination, or have access to a health
centre that can provide diagnostic facilities, or are protected by
vector control interventions. In Nigeria, the disease is common in the
northern parts of the country especially amongst cattle-rearers, in
savannah and riverine areas.

The researchers
also said that one of the major challenges of controlling the diseases
for over 80 years has been the cost and logistical difficulty of
managing fly control programmes.

“There are no
vaccines or prophylactic drugs available to prevent the disease, which,
once it has been contracted, is treated with curative drugs that often
prove ineffective because of emerging disease resistance in the
trypanosomes,” the authors said in the PLoS Journal of Neglected
Diseases where the research was published last month.

“These drugs can
often have unpleasant and sometimes fatal side effects. Prospects for
development of effective vaccines or prophylactic drugs are poor.”

Vaccine prospects

Another step that
could help control the disease is developing a vaccine. A Nigerian
scientist, Jonathan Nok, last year won the Nigeria Liquefied Natural
Gas (NLNG) Prize for his work in discovering the gene responsible for
the creation of Sialidase (SD),

an enzyme which
causes sleeping sickness (Trypanosomiasis). Mr. Nok, a professor of
Biochemistry and the Dean of the Faculty of Science, Ahmadu Bello
University, says the breakthrough is significant as it will form the
baseline for developing DNA-based vaccines against Trypanosoma, a
predominantly African problem.

Way forward

The researchers
find that this kind of vector control in the management of the disease
has done little over the past 80 years and to overcome this, they are
trying to develop cost-effective insecticide-treated targets by
identifying chemicals that will increase the number of flies that will
be lured to a target and killed.

Commenting on the viability, one of the co-authors of the study, Michael Lehane says,

“We are aiming to test the technology in the field in the near future,

and assessing the
impact in the epidemiology, as well as in the socio-economics of the
intervention areas. Until then, it is difficult to state the specific
value of this approach to the control of the disease. This opens the
way for further work to identify the attractants present in these
natural odours that can then be simply and cheaply incorporated into
targets to reduce the cost of control,” reads the study.