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

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.

Neurological complications of tick borne encephalitis: the experience of 89 patients studied and literature review.

Tick borne encephalitis (TBE) is an acute febrile syndrome that can be complicated with neurological symptoms ranging from mild meningitis to severe encephalomyelitis. The causative agent is a virus belonging to the family of flaviviruses. We have collected a series of 89 patients and compared the clinical course with the main data of the literature of TBE. This review in addition describes the clinical manifestations associated with TBE infections, the main molecular-biological properties of these viruses, and the different factors that define the incidence and severity of disease who are frequently situated in the age group young/adult with a social harm and functional non-negligible. This review also contains diagnostic elements and neuropathological features typical of this infection and a brief summary of vaccination against TBE.

Persistence of immunity to tick-borne encephalitis after vaccination and natural infection.

Long-term persistence of immunity was assessed in 66 patients who had contracted tick-borne encephalitis (TBE) and in 126 subjects who had completed primary TBE immunization using a conventional three-dose schedule from 3 to 8 years earlier. Immunity was tested in the subjects stratified by age as follows: ≤40 years (N = 37); 41-60 years (N = 100); and over 60 years (N = 55). Antibody levels decreased significantly with increasing age in the vaccinated cohort by comparison with the individuals who had previously contracted TBE. Consistently higher geometric mean antibody levels were found in the patients infected naturally. When the vaccinated subjects were compared, subjects ≤40 years old had significantly higher antibody levels than either of the older groups. Analyzing immunity to TBE over time revealed a remarkable (50%) decline in seroprotection rates in the vaccinated group at 50 months of follow-up, while stable, high levels persisted in all subjects after natural TBE infection. In the vaccinees over 60 years old, the TBE antibody levels reached 60% at 60 months, and 20% at 70 months of follow-up; in contrast, in the 41-60-year-old group, the antibody levels remained high for 70 months, and then fell rapidly. For people aged <60 years old, booster doses are recommended every 5 years after the fourth dose of vaccine, which should be administered 3 years after primary immunization. In subjects aged 60 years or older, booster doses should be given every 3 years.

Humoral immunity and correlation between ELISA, hemagglutination inhibition, and neutralization tests after vaccination against tick-borne encephalitis virus in children.

Vaccination against tick-borne encephalitis (TBE) virus is the measure of choice for disease control in endemic areas, as no treatment is available. In Italy, the province of Belluno is one of the most active TBE virus infection foci. In this study sera were examined from vaccinated children living in areas around Belluno in order to monitor the immune response after anti-TBE vaccination. For the assessment of neutralizing antibodies, a plaque reduction neutralization test (PRNT) was optimized and the correlation between enzyme-linked immunosorbent assay (ELISA), hemaglutination inhibition (HI), and neutralizing antibodies titers was evaluated. All children had high serum levels of TBE IgG in ELISA test after the vaccination, in agreement with previous studies. HI and PRNT titers ranged between very low and high levels. A good correlation between HI and PRNT titers, and with IgG ELISA titers, was observed. PRNT is an useful assay for monitoring protective immunity after the completion of anti-TBE vaccination. This type-specific assay is an important tool for differential diagnosis in cases where the presence of cross-reactive antibodies due to other flavivirus infections or vaccinations cannot be excluded.

Anti-tick-borne encephalitis (TBE) virus neutralizing antibodies dynamics in natural infections versus vaccination.

Tick-borne encephalitis (TBE) virus infection elicits a life-long lasting protection. However, little is known about the neutralizing antibodies titres following natural infection. In this study, subjects with past TBE disease (n = 62) were analysed for the presence and titre of anti-TBE neutralizing antibodies, and compared with a vaccinated cohort (n = 101). Neutralizing antibody titres were higher in individuals with past TBE and did not show an age-dependent decrease when compared with vaccinees.