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Wildlife vaccination against rabies in difficult and emergency situations and its potential impact on the environment

Contract nr: FAIR-CT97-3515
Project nr: 3515
Project type: SC
Starting date: 01/03/1998
Duration: 42 months
Total cost: 1,446,100 EUR
EC Contribution: 1,187,000 EUR
Scientific Officer: Isabel MINGUEZ-TUDELA
Research topic: Animal health

Sylvatic rabies has been partly eliminated from large parts of several Member States through the oral immunisation of foxes, but a dramatic increase in fox population densities renders a complete eradication of the disease more difficult. It is more likely that there will be an irrepressible come-back of the disease in the future, in areas freed from the disease just a few years ago. This threat comes from remnant foci centralised in rabies-free areas and from non-Member States, where rabies remains present or is on the increase. Selvatic rabies is an economic problem.

It has an impact on welfare, and constitutes a hindrance to free movement within the EU. The main organisations in charge of the control of rabies in five European countries and one laboratory of animal ecology are proposing the development and testing of appropriate counter measures, to replace the currently used - and often inefficient - classical methods of oral vaccination of foxes. Information on the possible negative impact of rabies elimination must also be obtained, which includes a significant increase in the fox population. While several European teams are now organising extensive field trials aimed at vaccinating fox cubs, nothing is known about the immunological competence of fox cubs. Other new measures in practice consist of increasing the density of baits deposited, or vaccinating the same areas twice within a short time.

These measures multiply the cost of rabies control. This project includes three trials on fox cubs, including vaccination of pregnant vixen, and subsequent testing on fox cubs, whether vaccinated or not. One must also determine the stability of vaccines in use. In fact, huge amounts of vaccines are made of viruses that are very temperature-sensitive. In most European countries, no titre control is carried out after vaccine distribution. Well standardised protocols will be organised in each partner country, which should provide clues as to the origin of some failures currently seen. It is also important to define the optimum density of baits that need to be deposited, in correlation to fox density.

We will organise a specific field protocol in two Member States in areas inhabited by various fox population densities, and three different densities of baits will be distributed. The prerequisite for this protocol is to define a common method for indexing fox density. In order to do this we will:

1) set up one or two abundance indexes of fox density that will be easy to record by veterinary services;
2) calibrate these indexes with more elaborate methods in order to correlate them with real (fox) density.

Double short-delayed oral vaccination protocols will be tested on caged adult foxes, to verify that they provide a booster response significantly more protective than one single vaccination, and the most appropriate time between the first and second distribution of baits will be determined. It is impossible to compare national or regional vaccination programs because:

1) areas are not characterised with the same index or with correlated indexes of fox density;
2) even if the sampling of fox sera is consistent in areas, the ELISA methods in use in the Member States give very divergent results.

We want to identify the main factors that influence efficacy of vaccination programmes. In order to compare the increase in the ratio of immunised foxes between areas vaccinated after campaigns, therefore, we will standardise and calibrate an ELISA test for fox serum samples taken in the field. Using this standardised ELISA test, sera will be re-tested to allow a retrospective analysis of the density and type of vaccine bait used, dates of campaigns, and methods of deposit. Using this newly calibrated index of fox density and ELISA methods, an evaluation of the ongoing vaccination campaign will then be carried out. The relation between fox density, control methods and rabies advance or elimination will be investigated using mathematical models. The results will allow the development of a computer programme package ready for use by veterinary units. There is no common tool for the molecular characterisation of rabies strains currently employed in the surveillance and control of rabies in the EU.

An objective of this proposal will be to do this in one laboratory, in order to identify both the geographical and the species origin of isolates from remnant or unexpected focii. The main possible negative impact of the increase of fox density is a greater risk of the transmission of Alveolar echinococcosis to humans. Methods for determining the frequency in fox faeces of the causative agent of this disease (Echinococcus multilocularis) will be developed. This project will be carried out over a three-year period. All results will be delivered to veterinary units involved, then published in international scientific journals. The benefit expected from this project will be to optimise the use of current funds already allocated by the EU for oral vaccination of foxes. No commercialisation will be considered from the results obtained.

Coordinator details
F-54220 Malzeville
Tel.: +33 3 83 29 89 50
Fax: +33 3 83 29 89 59


    University of Berne
    Institute of Veterinary Virology
    Laenggass Str 122
    CH-3012 Bern
    Tel.: +41 316 31 23 78
    Fax: +41 316 31 25 34

  • Paul-Pierre PASTORET
    Université de Liège
    Boulevard du Colonster 20
    B-4000 Liège
    Tel.: +32 4 366 42 60
    Fax: +32 4 366 42 61

  • Patrick GIRAUDOUX
    Université de Bourgogne
    F-21011 Dijon
    Tel.: +33 3 80 39 62 28
    Fax: +33 3 80 39 62 31

  • Franco MUTINELLI
    Istituto Zooprofilattico Sperimentale delle Venezie
    Via Romea 14/A
    I-35020 Legnaro
    Tel.: +39 04 98 07 03 06
    Fax: +39 04 98 07 05 70

  • Hartmut SCHLUTER
    Bundesforschungsanstalt fuer Viruskrankheiten der Tiere
    Seestrasse 55
    D-16868 Wusterhausen Dosse
    Tel.: +49 339 798 00
    Fax: +49 339 798 020

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