The damage caused by ticks is a scourge
and a major hindrance to increasing livestock production in many
developing countries which suffer from malnutrition, particularly
in Africa. In the case of bovine animals and small ruminants, the
initial economic damage caused by these blood-sucking parasites
is that of anaemia in cattle, accompanied by weight loss which compromises
the profitability of the livestock concerned. What is more, the
scars left by the bites seriously hamper the recovery of the hides.
But there are more serious aspects. Ticks are responsible for transmitting
many diseases, such as theileriosis, babeosis, anaplasmosis, cowdriosis
and other types of dermatophilosis which constitute a heavy tribute
- estimated annually at several billion euros - to be paid by livestock
farmers in tropical and sub-tropical countries. The problem is all
the more complex in that there are about 870 species of these parasites
and the different diseases are spread by specific varieties of them.
At the present time, the main weapon to combat this problem is
essentially the massive use of acaricides. But these products are
toxic, costly and, what is more, and which is very disquieting,
ticks are developing increasing resistance to them. How are we to
defeat adversaries of this kind?
A "multi-species" approach
A number of detailed research projects on the prevention, detection
and treatment of diseases transmitted by ticks have been carried
out in the world, particularly in Europe, very often in partnership
with laboratories in developing countries. "But given the multiplicity
of varieties encountered locally, most of these projects are focused
on the damage caused by a single species of parasite", explains
Frans Jongejan, from the Faculty of Veterinary Medicine in Utrecht
(NL), coordinator of ICTTD European concerted action, launched in
1996 with the support of the INCO (International cooperation) Community
"An integrated approach covering all pathologies and taking
the socio-economic aspects systematically into account was lacking.
But an approach of this kind is indispensable if we want to tackle
more effectively the problems which livestock farmers in the field
face, having to deal with different parasites all at the same time.
Even if you develop a vaccine which protects cattle from one disease
transmitted by a particular tick species, the herdsmen will still
have to continue to use acaricides to combat the others".
Vaccination, detection and comprehension
The ICTTD initiative focuses on three specific themes.
At the prevention level, it is a priority to develop vaccines to
create barriers against both the ticks and the diseases of which
they are the vectors. The effectiveness of the attenuated vaccines
that have already been developed has to be assessed, but, above
all, new concepts must be formulated for inactivated recombinant
vaccines, as must new ways of administering them which are adapted
to livestock farming conditions in developing countries. Another
challenge, particularly for Africa, is to develop multicomponent
vaccines directed against several diseases and against the parasites
A second important area for action is to perfect detection tests.
The use of recombinant DNA techniques to produce standardised antigens
will make it possible to improve the detection of diseases transmitted
by ticks. Diagnostic tests of the ELISA type, applicable to various
pathogenic agents simultaneously, are being developed and validated
with the cooperation of international laboratories and bodies and
will then be transferred and adapted to the requirements of the
The ICTTD network also coordinates epidemiological surveys and
analyses the socio-economic consequences of diseases transmitted
by ticks. The aim is to help devise optimal strategies to combat
these diseases while taking account of the realities of the production
systems into which they must be integrated.
Conclusion in the field
The exchange of knowledge and expertise is the cornerstone of the
ICTTD network which, particularly through exchange visits, brings
scientists from five continents into contact with each other. For
example: a diagnostic test for cowderiosis was developed by the
University of Utrecht. "This was hardly acknowledged,"
notes Frans Jongejan. "Thanks to information exchanges within
the ICTTD, this test is now available to laboratories in developing
countries and we are kept informed of its real effectiveness. In
the long term, if this test proves to be reliable and operational,
the last stage will involve setting up an African company, well
integrated in the local context, and responsible for distributing
the product according to need". This approach would enable
countries in the South to take full charge of the benefits of new
technologies and to become the driving forces of their own development.
Integrated Control of Ticks and Tick-Borne Diseases
Frans Jongejan (coordinator)
Department of Parasitoloogy and Tropical Veterinary Medicine,
Faculty of Veterinary, University of Utrecht, Netherlands
Fax : +31-30 2540784
E-mail : email@example.com
40 scientists from European laboratories (Germany, Austria,
Netherlands, Portugal, United Kingdom, Italy, France, Spain,
Belgium), from Africa (South Africa, Kenya, Zimbabwe, Sudan,
Burkina Faso), from north Africa (Tunisia, Morocco) and from
Guadeloupe are the founding members of the ICTTD network.
More than 150 associate members, from all the continents,
have contributed their support
Amblyomma variegatum - Female tick
(on the left) and Rhipicephalus humeralis - Male tick
(on the right). These are two of the 870 species of ticks which
infest the southern hemisphere in particular.