Page 291 - TBE_Book_V2_2019

Chapter 12b

TBE in France

Yves Hansmann and Aurélie Velay

History and Current Situation

The first human case of tick-borne encephalitis Other wooded regions (Ardennes) were
virus (TBEV) infection in France was reported explored for TBEV in ticks, but without
3
in 1968 in Alsace, an eastern region next to evidence of virus infection.
the German border: a gamekeeper working in
1
a forest near Strasbourg. Between 1970 and Between 1968 and 2018, more than 200
1974, an extensive research survey confirmed human tick-borne encephalitis (TBE) cases
4,5
the presence of TBEV in ticks and rodents in have been described in France. The majority
this French region. Eight percent of adult tick of cases (more than 90%) were diagnosed in
batches collected were infected (Ixodes Alsace. Twenty-two cases were imported,
6
ricinus) by the TBEV. Tick collection occurred in including eight imported cases in 2017.
a forest near Strasbourg, the main city in the Among them, 14 cases came from Germany
region. Nymphs were more rarely infected (after staying in the Black Forest, a mountain-
1
(1.6% of the collected lots). These data were ous area bordering eastern France). The 8
confirmed in 2011 in Alsace in Guebwiller’s other imported cases were acquired in
Valley, a middle altitude forest, with Austria, Finland, Poland, Romania, Russia,
identification of western (European) subtype Slovakia, Sweden, and Switzerland.
TBEV (TBEV-EU). The infection rate still
Among the autochthonous cases, the majority
remains low: TBEV was detected only in the I.
ricinus nymphs (2.48%) that were collected of the patients were infected in Northeastern
during May; however, not in those collected France, especially in Alsace (more than 70% of
during the other spring or summer months. In the autochthonous cases during the five last
a more recent study, Bestehorn et al., years). Although Alsace remains the area with
the highest prevalence of TBE in France, a
collected ticks (953 male, 856 female adult
ticks and 2,255 nymphs) in endemic foci in the secondary hotspot was identified in the Alpine
upper Rhine region in France and Germany region, in a Swiss neighboring area (Savoie and
2
between 2016, 2017 and 2018 by flagging. Haute Savoie) during the last ten years with 8
patients presented with TBE. In 2006, 1
The minimal infection rate (MIR) of the
patient was infected close to Bordeaux (not a
collected ticks in the Foret de la Robertsau
(France) was estimated to 0,11% (1 known endemic area). In 2017 and 2018, 3
nymph/944 ticks). The isolated and sequenced patients infected in Haute Loire (in the
TBEV strain from Foret de la Robertsau (F) is surrounding countryside of Saint Etienne),
making this region a new possible emerging
related to circulating TBEV isolates from
area of TBE.
eastern Bavaria and the Czech Republic. In the
French department Alsace, there are today at
Until 2016, in humans, the annual number of
least two independent TBEV strains cases in France each year ranges from 1 to 12.
circulating: the historical Alsace strain isolated In 2016 we noticed a recrudescence of infec-
in 1971 and the newly identified strain from tion with 29 cases of TBE infection .
5
Foret de la Robertsau.

286