Prevalence of tick‐borne encephalitis virus in Ixodes Ricinus from a novel endemic area of North Eastern Italy

Abstract

In Alpine area of extreme North Eastern Italy the first autochthonous case of TBE was reported in 1998 and was followed by 45 cases during the period 2001-2007, thus defining this area as definitely endemic. An ecological survey evaluated the tick density and the Tick-borne encephalitis virus (TBEV) infection prevalence in tick collected in selected sites. In addition, TBE strains were characterized by sequencing and phylogenetic analysis. Overall, 2,361 ticks (2,198 nymphs and 163 adults) of the Ixodes ricinus L. species collected during 2005 and 2006 were examined. Five samples were positive for TBEV, corresponding to an overall prevalence rate of 0.21%. When analyzed by place, TBEV was discovered in three sites where the highest tick density was found. The difference of prevalence between high and low density areas tested to be statistically significant (P = 0.028). Phylogenetic analysis showed that four sequences clustered with the Neudoerfl prototype, while the other clustered with the Isosaari 17 strain and with a number of Slovenian isolates. In addition, a sequence detected in archival samples from one human case segregated with another variant, namely the Swedish Torö strain.

Prevalence and genetic variability of tick-borne encephalitis virus in host-seeking Ixodes ricinus in northern Italy

“…The Bayesian phylogenetic analyses provide results that are consistent with those of previous studies, indicating that the new Italian TBEV sequences generated here belong to the European TBEV subtype (Hudson et al, 2001;D'Agaro et al, 2009). Interestingly, we found a substantial amount of genetic divergence between these Italian TBEV sequences, despite both the relatively short E gene sequence fragments analysed and the restricted geographical range (Trento province only).…”

“…Furthermore, the incidence of TBE in these regions has increased from 0.06 to 0.88 cases per 100 000 inhabitants in the same time frame (Rizzoli et al, 2009). Importantly, TBEV has been isolated and identified in most of the regions where human cases have been reported (Hudson et al, 2001;Beltrame et al, 2006;Cruciatti et al, 2006;Floris et al, 2006;D'Agaro et al, 2009). However, previous studies undertaken primarily in the Veneto and Trentino regions have shown a lower prevalence of TBEV in Italian tick populations compared with other European sites where TBEV is endemic (Hudson et al, 2001), whilst phylogenetic analyses indicate that only strains of the European subtype very similar to the Austrian Neudoerfl strain have been found in Italian TBEV populations (Hudson et al, 2001;Floris et al, 2006;D'Agaro et al, 2009).…”

“…In particular, two possible evolutionary constraints affecting the genetic diversity of TBEV are the combination of the tick's long lifespan and its infrequent feeding (only three blood meals per generation), which imply a limited viral replication rate in ticks per tick generation, and the necessity for TBEV replication in two very distantly related biological systems (Marin et al, 1995;Weaver, 2006;Gould & Solomon, 2008). Previous molecular epidemiological studies suggest that TBEV has evolved slowly while spreading towards the north and west (Zanotto et al, 1996;Gould et al, 2003), and within-subtype observations suggest that the European subtype in particular has levels of low genetic diversity (Han et al, 2001;Haglund et al, 2003;D'Agaro et al, 2009). The majority of phylogenetic studies of TBEV have analysed the envelope glycoprotein (E) (Haglund et al, 2003;Melik et al, 2007; Suzuky, 2007).…”

Fencing and mowing as effective methods for reducing tick abundance on very small, infested plots

“…The study was carried out in a mountain area of northeastern Italy, where both Lyme borreliosis and TBE are endemic (D'Agaro et al, 2009;Nazzi et al, 2010). Climate is cool temperate, with annual precipitations around 2800 mm per year and an average annual mean temperature around 11 • C. Vast mixed woodlands cover most of the area and some open meadows are located around villages.…”

Scientific Opinion on the Role of Tick Vectors in the Epidemiology of Crimean-Congo Hemorrhagic Fever and African Swine Fever in Eurasia

“…"Annales ofAgricultural and Environmental Medicine 16,[211][212][213][214][215][216][217] 110 "Bitam I, Parola P,Matsumoto K, Rolain J M, Baziz B, Boubidi S C, Harrat Z, Belkaid M and Raoult D, 2006. " Occurrence of Borrelia burgdorferi sensulato in Ixodes ricinus and Dermacentor reticulatus ticks collected from roe deer and deer shot in the south-east of Poland.…”