Warning: regulations can damage your health--the case of rabies

Epidemiology and control of fox rabies in Europe

During recent years, most of the research on the control of sylvatic rabies has concentrated on developing methods of oral vaccination of wild rabies vectors. In order to improve both the safety and the stability of the vaccine used, a recombinant vaccinia virus which expresses the immunizing glycoprotein of rabies virus (VRG) has been developed and extensively tested in the laboratory as well as in the field. From 1989 until 1995, several million VRG vaccine doses have been dispersed in western Europe for vaccination of red foxes. In Europe, the use of VRG has lead to the elimination of sylvatic rabies from large areas, which have consequently been freed from vaccination. This may have consequences on the regulation of pets movements within the whole European Union.

Epidemiology and elimination of rabies in western Europe

In recent years, most of the research on the control of sylvatic rabies has concentrated on developing methods of oral vaccination of wild rabies vectors. In order to improve both the safety and the stability of the vaccine used, a recombinant vaccinia virus, which expresses the immunizing glycoprotein of rabies virus (VRG), has been developed and extensively tested in the laboratory as well as in the field. Between 1989 and 1995, several million VRG vaccine doses have been dispersed in Western Europe for the vaccination of red foxes, leading to the elimination of sylvatic rabies from large areas, which have consequently been freed from the need for vaccination. This approach may have consequences for the regulation of pet movement within the whole European Union.

The development and use of a vaccinia-rabies recombinant oral vaccine for the control of wildlife rabies; a link between Jenner and Pasteur

To improve both safety and stability of the oral vaccines used in the field to vaccinate foxes against rabies, a recombinant vaccinia virus, which expresses the immunizing G protein of rabies virus has been developed by inserting the cDNA which codes for the immunogenic glycoprotein of rabies virus into the thymidine kinase (TK) gene of the Copenhagen strain of vaccinia virus. The efficacy of this vaccine was tested by the oral route, primarily in foxes. The immunity conferred, a minimum of 12 months in cubs and 18 months in adult animals, corresponds to the duration of the protection required for vaccination of foxes in the field. Innocuity was tested in foxes, domestic animals, and in numerous European wild animal species that could compete with the red fox for the vaccine bait. No clinical signs or lesions were observed in any of the vaccinated animals during a minimum of 28 days post vaccination. Moreover, no transmission of immunizing doses of the recombinant occurred between foxes or other species tested. To study the stability of the vaccine strain, baits containing the vaccine were placed in the field. Despite considerable variations of environmental temperatures, the vaccine remained stable for at least one month. Because bait is taken within one month, it can be assumed that most animals taking the baits are effectively vaccinated. To test the field efficacy of the recombinant vaccine, large-scale campaigns of fox vaccination were set up in a 2200 km2 region of southern Belgium, were rabies was prevalent. A dramatic decrease in the incidence of rabies was noted after the campaigns. The recombinant is presently used to control wildlife rabies in the field both in several European countries and in the United States.

Field trials of a recombinant rabies vaccine

To improve both safety and stability of the vaccines used in the field to vaccinate foxes against rabies by the oral route, a recombinant vaccinia virus, expressing the glycoprotein of rabies virus (VVTGgRAB) has been developed. VVTGgRAB innocuity was verified in target species and in domestic animals as well as in numerous wild animal species that could compete with the red fox in consuming vaccine baits in Europe. Oral immunization of foxes, by distributing VVTGgRAB vaccine-baits, was undertaken for the whole infected area in Belgium (10,000 km2). Five campaigns of fox vaccination, were carried out from autumn 1989 until 1991. Each time, 150,000 vaccine-baits were dropped by air at a mean density of 15 per km2. These campaigns induced a drastic decrease in the incidence of rabies and the elimination of the disease from 80% of the initially infected area. Regarding the geographical evolution of rabies in Belgium and in adjacent regions in neighbouring countries, new spatial strategies for bait dispersal were planned for 1992, 1993 and 1994: successive confined campaigns were carried out along political borders only. These campaigns induced a new decrease of incidence; no rabid fox could be detected in 1993 in spite of an improved epidemiological surveillance. In 1994, rabies was again confirmed in 13 foxes collected in an area close to the French border. These cases demonstrated the persistence of a border rabies focus and justify further restricted vaccination campaigns.