Trichinella spp. biomass has increased in raccoon dogs (Nyctereutes procyonoides) and red foxes (Vulpes vulpes) in Estonia

Background: Raccoon dogs and red foxes are well-adapted hosts for Trichinella spp. The aims of this study were to estimate Trichinella infection prevalence and biomass and to investigate which Trichinella species circulated in these indicator hosts in Estonia. Methods: From material collected for evaluating the effectiveness of oral vaccination program for rabies eradication in wildlife, samples from 113 raccoon dogs and 87 red foxes were included in this study. From each animal, 20 g of masseter muscle tissue was tested for the presence of Trichinella larvae using an artificial digestion method. The Trichinella larvae were identified to species level by multiplex polymerase chain reaction method. Results: The majority of tested animals were infected with Trichinella spp. The parasite species identified were T. nativa and T. britovi. The apparent infection prevalence was 57.5% in raccoon dogs and 69.0% in red foxes, which were higher than previous estimates. In addition, the larval burden had also increased in both hosts. We estimated that in 2011-2012, the Trichinella spp. biomass was more than 15 times higher in raccoon dogs and almost two times higher in red foxes than in 1992-2000 (based on mean larval burden), and almost 20 times higher in raccoon dogs and almost five times higher in red foxes than in 2000-2002 (based on median larval burden). Conclusions: Raccoon dogs and red foxes are relevant reservoirs for Trichinella spp. in Estonia. The biomass of Trichinella circulating in sylvatic cycles was substantial and had increased: there is substantial infection pressure in the sylvatic cycle.Peer reviewe

Eliminating Rabies in Estonia

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

Bait uptake and seroprotection rates in foxes and raccoon dogs from 2006 to 2010.

<p>TC: tetracycline.</p><p>CI: Confidence Interval.</p><p>Ab positive sera: rabies antibody titer by ELISA≥0.5 EU/mL.</p><p>Tetracycline, used as a biological marker, was sought in the lower jaw of the foxes and raccoon dogs killed in vaccinated zones. The number of positive samples out of the total samples and the positivity percentage for tetracycline are reported by target species (red fox and raccoon dog).</p><p>Sera were analysed with an indirect ELISA kit (Platelia Rabies II kit, Biorad). A threshold seroconversion of 0.5 EU/mL was adopted.</p

Location of rabies cases in Estonia from 2005 to 2010.

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

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

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

Number of rabies cases from 2000 to May 2011 in the main species in Estonia.

<p>*up to end of May 2011.</p

Characteristics of rabies virus isolates included in the phylogenetic analysis.

<p>(NEE = North Eastern Europe, D = centre of the European part of Russia, E = North-Western part of Russia).</p

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

<p>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. <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001535#pntd.0001535-Bourhy1" target="_blank">[20]</a> and Kuzmin et al. <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001535#pntd.0001535-Kuzmin1" target="_blank">[21]</a> are used in the text. In ◊ are shown the representative sequences of identical nucleoprotein sequences among rabies virus isolates from Estonia.</p

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

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

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

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