Tickborne Encephalitis Virus, Northeastern Italy

Beltrame, Anna; Ruscio, Maurizio; Cruciatti, Barbara; Londero, Angela; Piazza, V Di; Copetti, Roberto; Moretti, Valentino; Rossi, Paolo; Gigli, Gian Luigi; Scudeller, Luigia; Viale, Pierluigi

doi:10.3201/eid1210.060395

Cited by 11 publications

(7 citation statements)

References 10 publications

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“…In a group of healthy subjects residing in a TBE focus identified recently in the Friuli Venezia Giulia region [Beltrame et al, 2005;Beltrame et al, 2006;Cruciatti et al, 2006] a seroprevalence of 8% has been detected by an ELISA IgG test. None of the subjects were vaccinated in the past for TBE, nor for Yellow fever.…”

Section: Discussionmentioning

confidence: 99%

“…In Italy, indigenous TBE virus infection cases have been recorded only sporadically from 1975 to 2005, in the Toscana region in central Italy [Amaducci et al, 1978], and in the Trento and Belluno provinces in northern Italy [Bassetti et al, 1994;Caruso et al, 1996]. Recently, a new focus of active TBE has been demonstrated in the Friuli Venezia Giulia region [Beltrame et al, 2005;Beltrame et al, 2006;Cruciatti et al, 2006].…”

Section: Introductionmentioning

confidence: 99%

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Humoral immunity in natural infection by tick‐borne encephalitis virus

Venturi

Martelli

Mazzolini

et al. 2009

Journal of Medical Virology

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Tick-borne encephalitis (TBE) virus is one of the most important flaviviruses associated with neurological disease in Europe. Cross-reactive antibodies elicited by different flaviviruses can make difficult the interpretation of ELISA and hemagglutination-inhibition (HI) tests for the diagnosis of TBE. Neutralization tests, which are more specific, are not in common use because they are difficult to perform and standardize. A plaque reduction neutralization test (PRNT), optimized previously in vaccinated children, was evaluated in sera from acute cases of TBE, collected for diagnostic purposes, and from healthy human population and wild ruminants, collected for serosurvey purposes. The PRNT results were compared with the results of ELISA and HI tests. In acute TBE disease, most sera were positive for IgM antibodies by ELISA and with high HI antibody titers; neutralizing antibodies were detected in 71.4% of patients, at a very low titer (1:10 NT(50)) in almost all cases. Seroprevalences of 8% and 6.5% for anti-TBE ELISA antibodies were found in healthy subjects and wild ruminants, respectively. Among anti-TBE positive healthy subjects, a very low 1:10 NT(50) titer was detected in 17.4% of cases, while NT(80) titers ranging from 1:10 to 1:80 were detected in 65.2% of cases. Among wild ruminants, 90.9% of ELISA and HI positive samples showed a positive, >/=1:10 NT(80) titer. In conclusion, neutralization assays can be useful for the diagnosis and serosurveys of TBE.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Humoral immunity in natural infection by tick‐borne encephalitis virus

Venturi

Martelli

Mazzolini

et al. 2009

Journal of Medical Virology

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“…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).…”

Section: Introductionmentioning

confidence: 90%

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

Carpi

Bertolotti

Rosati

et al. 2009

Journal of General Virology

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Tick-borne encephalitis (TBE) is a severe disease that has been endemic in north-east Italy since 1992. Over the past two decades, there has been an increase in the number of human cases reported in many European countries, including Italy. To assess the current TBE infection risk, questing ticks were collected from known TBE foci, as well as from a site in northern Italy where no human infections have been reported previously. A total of 1739 Ixodes ricinus (1485 nymphs and 254 adults) was collected and analysed for TBEV prevalence by a real-time RT-PCR targeting the 39 untranslated region. Phylogenetic analyses of the partial envelope gene were conducted on two newly sequenced TBE virus (TBEV) strains and 28 previously published sequences to investigate the genealogical relationships of the circulating TBEV strains. These phylogenetic analyses confirmed a previous report that the European TBEV subtype is the only subtype circulating within the TBE foci in north-east Italy. Interestingly, nucleotide sequence analysis revealed a high degree of divergence (mean 2.54 %) between the TBEV strains recovered in the Italian province of Trento, despite the circulation of a single TBEV subtype. This elevated genetic variability within a single TBE focus may reflect local differences in the longstanding evolutionary dynamics of TBEV at this site relative to previously characterized sites, or more recent and continuous reintroduction of various TBEV strains. INTRODUCTIONTick-borne encephalitis virus (TBEV) is a zoonotic arbovirus of significant medical importance in both Europe and Asia, causing 4500 and 11 000 cases, respectively, of human encephalitis annually (Randolph, 2006). The ecology of TBEV involves a rodent-tick transmission cycle where uninfected ticks acquire TBEV from infected ticks while co-feeding on the same competent reservoir host, mostly small mammals of the genus Apodemus (Labuda et al., 1993(Labuda et al., , 1997. The non-viraemic transmission among co-feeding ticks represents the major amplification route for TBEV, which contributes to the local specificity of infection risk and the heterogeneity of the spatial distribution of endemic sites (Randolph et al., 1999). Additionally, systemic viraemia in rodents is not sufficient to ensure TBEV transmission to ticks, as the virus itself causes a high mortality rate in the host before ticks are presented the opportunity to complete a blood meal (Randolph et al., 1996). Furthermore, the distribution of endemic tick-borne encephalitis (TBE) sites can also be influenced by multiple abiotic and biotic factors, which affect tick abundance, tick phenology, tick infestation prevalence and tick human contact rate, as well as differences in surveillance efforts (Randolph et al., 2008).TBEV belongs to the genus Flavivirus and its genome consists of a single-stranded, positive-sense RNA of approximately 11 kb, which encodes a polyprotein that is cleaved by cellular and viral proteases into three structural -the capsid, membrane and envelope proteins -and seven non-st...

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“…The disease is not notifiable in the country but individuals with TBE can be reported at the regional level, where they are classified as 'viral meningitis and encephalitis' (notifiable diseases, class 2). Although the extent of affected areas in Italy is not well defined, the regions of the north east appear to be those where cases have been documented, as suggested by case series of TBE published in the last decade [7][8][9][10]. However, to the best of our knowledge, systematic information on the occurrence of persons with TBE is lacking even in these affected areas of Italy, and both the incidence rates (IR) and the geographical distribution of persons with the disease have been mostly derived from international literature or reports of aggregated cases [6].…”

Section: Introductionmentioning

confidence: 99%

Tick-borne encephalitis in north-east Italy: a 14-year retrospective study, January 2000 to December 2013

Rezza¹,

Farchi²,

Pezzotti³

et al. 2015

Eurosurveillance

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Italy is considered at low incidence of tick-borne encephalitis (TBE), and the occurrence of human cases of TBE appears to be geographically restricted to the north east of the country. However, most information to date derives from case series, with no systematic data collection. To estimate incidence rates (IR) and spatial distribution of TBE cases, we conducted a retrospective study in north-eastern Italy. Data were collected through the infectious disease units and public health districts of three regions (Friuli Venezia Giulia, Trentino Alto Adige and Veneto) between 2000 and 2013. Overall, 367 cases were identified (IR: 0.38/100,000). The cases' median age was 56 years and 257 (70%) were male. Central nervous system involvement was reported in 307 cases (84%). Annual fluctuations in case numbers occurred, with peaks in 2006 and in 2013, when 44 and 42 cases were respectively observed. A strong seasonality effect was noted, with the highest number of cases in July. In terms of geographical location, three main endemic foci with high TBE IR (>10/100,000) were identified in three provinces, namely Belluno (Veneto region), Udine (Friuli Venezia Giulia) and Trento (Trentino Alto-Adige). When investigating the whole study area in terms of altitude, the IR between 400 and 600 m was greater (2.41/100,000) than at other altitudes (p<0.01). In conclusion, the incidence of TBE in Italy is relatively low, even considering only the three known affected regions. However, three endemic foci at high risk were identified. In these areas, where the risk of TBEV infection is likely high, more active offer of TBE vaccination could be considered.

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Tickborne Encephalitis Virus, Northeastern Italy

Cited by 11 publications

References 10 publications

Humoral immunity in natural infection by tick‐borne encephalitis virus

Humoral immunity in natural infection by tick‐borne encephalitis virus

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

Tick-borne encephalitis in north-east Italy: a 14-year retrospective study, January 2000 to December 2013

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