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Herd-decimating parasites

 
 
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Approximately 80% of world livestock are threatened by infestations from ticks or tick-borne diseases.

A vast network of 44 scientists from 24 laboratories in eight Member States of the European Union, nine African and Caribbean countries and which includes more than 150 associated researchers throughout the world aims to combat the ravages to health and the economy caused by the innumerable species of ticks which infest cattle in tropical and sub-tropical countries. Supported by the Union, the ICTTD project is an example of North-South cooperation based on synergies and exchange of expertise.

     

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 research programme.

"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 themselves.

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 participating laboratories.

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.

 
Project
Integrated Control of Ticks and Tick-Borne Diseases

Programme
INCO-DC

Reference
1C18-CT95-009

Contact
Frans Jongejan (coordinator)
Department of Parasitoloogy and Tropical Veterinary Medicine, Faculty of Veterinary, University of Utrecht, Netherlands
Fax : +31-30 2540784
E-mail : f.jongejan@vet.uu.nl
http://www.uu.nl/tropical.ticks

Partners
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

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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.

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