Eliminating rabies in Estonia

Abstract

The compulsory vaccination of pets, the recommended vaccination of farm animals in grazing areas and the extermination of stray animals did not succeed in eliminating rabies in Estonia because the virus was maintained in two main wildlife reservoirs, foxes and raccoon dogs. These two species became a priority target therefore in order to control rabies. Supported by the European Community, successive oral vaccination (OV) campaigns were conducted twice a year using Rabigen® SAG2 baits, beginning in autumn 2005 in North Estonia. They were then extended to the whole territory from spring 2006. Following the vaccination campaigns, the incidence of rabies cases dramatically decreased, with 266 cases in 2005, 114 in 2006, four in 2007 and three in 2008. Since March 2008, no rabies cases have been detected in Estonia other than three cases reported in summer 2009 and one case in January 2011, all in areas close to the South-Eastern border with Russia. The bait uptake was satisfactory, with tetracycline positivity rates ranging from 85% to 93% in foxes and from 82% to 88% in raccoon dogs. Immunisation rates evaluated by ELISA ranged from 34% to 55% in foxes and from 38% to 55% in raccoon dogs. The rabies situation in Estonia was compared to that of the other two Baltic States, Latvia and Lithuania. Despite regular OV campaigns conducted throughout their territory since 2006, and an improvement in the epidemiological situation, rabies has still not been eradicated in these countries. An analysis of the number of baits distributed and the funding allocated by the European Commission showed that the strategy for rabies control is more cost-effective in Estonia than in Latvia and Lithuania.

Figure 1. Location of rabies cases in Estonia from 2005 to 2010.

Regarding the distribution of rabies cases in 2006, the area vaccinated during the autumn 2005 campaign lies above the blue line with islands.

Figure 2. Tetracycline positivity and seroconversion in foxes and raccoon dogs (200–2010).

The graphs are by age group (adult/juvenile).

Figure 3. Neighbour Joining phylogenetic tree between 18 Estonian rabies virus sequences and 24 references isolates.

The tree is rooted with isolates EU159392 and AF374721, used as outgroup. The phylogenetic analysis was based on the analysis of the first 400 nt of N gene using NJ method. Bootstrap values greater than 70% are shown next to the branches. Abbreviations for the phylogenetic groups (NEE, C, D and E) earlier described by Bourhy et al. and Kuzmin et al. are used in the text. In ◊ are shown the representative sequences of identical nucleoprotein sequences among rabies virus isolates from Estonia.

Figure 4. Evolution of rabies cases from 2003–2010 in Latvia, Lithuania and Estonia.

A special focus is on the 2008–2010 period. The arrows correspond to the different vaccination campaigns.

Figure 5. Location of rabies cases from 2006 to 2010 in Estonia, Latvia and Lithuania.

For each map, representation of areas with and without rabies cases (“buffer” zone of 50 km around each positive case).

Figure 6. Location of oral vaccination “buffer” zones.

Are detailed the “buffer zones between Estonia and Russia (1,521 km² in the North-East and 4,318 km² in the South) and between Estonia and Latvia (3,486 km²) in 2011.