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Climate change and biodiversity loss as
drivers for zoonotic diseases emergence in
the Alps: the case of tick- borne encephalitis
Fondazione Edmund Mach San Michele all’Adige (I)
Annapaola Rizzoli, DVM, PhD
Roberto Rosà, Heidi Hauffe, Markus Neteler,
Valentina Tagliapietra, Daniele Arnoldi, Francesca Cagnacci
Global Change and
the World's Mountains
Perth, Scotland, 26-30 September 2010
Tick-borne encephalitis in Europe
•Tick-borne encephalitis virus (TBEV) is a single-stranded RNA virus that
belongs to the genus Flavivirus
•Three subtypes: W European (WE), Siberian (SIB), and Far Eastern (FE)
• Transmitted to humans mostly through the bite of an infected tick of the
Ixodes species, primarily I. ricinus (European subtype) or I. persulcatus
(Siberian and Far Eastern subtypes).
• The prevalence of TBE increased
by almost 400% in the last 30 years (14,000 cases/year)
• TBE is endemic in temperate regions
of Europe and Asia but new foci are discovered
• Evidences of altitudinal shift in many regions
Network of independent but synergistic biological and non-biological factors Examples of data from Estonia, Latvia, Lithuania, Slovenia and Czech Republic.
Reduced
industrial
pollution
Global brightening ??
Environmental
awareness? Socio-economic
transition
20
40
60
80
100
19
70
19
80
19
90
20
00
In
du
str
ial
em
plo
ye
es,
In
du
str
ial
ou
tpu
t,
% o
f p
re
-1
99
0 l
eve
l
employees
LT
output LV
Regeneration of
shrubs Increase in rodent
populations
(transmission hosts)
Decline of
agriculture
0
10
20
30
40
50
19
70
19
80
19
90
20
00
% o
f to
ta
l
na
tio
na
l la
nd
are
a
wooded LV
field crops LV
20
40
60
80
100
19
70
19
80
19
90
20
00N
atio
nl
ca
ttle
he
rd
,
% o
f m
ea
n f
or 1
98
6-8
8
SI
CZ
LV
Increased co-feeding
transmission of TBEV
More infected ticks
Sumilo D, Randolph SE, et al PLoS ONE (2007) e500
More hosts
for adult ticks
More ticks
0
20
40
60
80
100
19
70
19
80
19
90
20
00
Ad
ult
tic
ks ,
May
LV
0
5
10
15
20
19
70
19
80
19
90
20
00
Roe d
eer
&
wild b
oar/
1000 h
a LV
0
5
1 0
1 5
2 0
1970
1980
1990
2000
CZ
Sudden increase
in Spring temperature
-2
0
2
4
6
8
1970
1980
1990
2000
Mean
dail
y m
ax t
em
p ES 1.Mar-20.Apr
4
8
12
16
20
24
1970
1980
1990
2000
21-30.Apr
Higher
unemployment
More wealth
& leisure
0
5
10
151
97
0
19
80
19
90
20
00
% u
nem
plo
ym
en
t
CZ
SI
Greater human
exposure to ticks
in forests?
Higher TBE incidence
0
20
19
70
19
75
19
80
19
85
19
90
19
95
20
00
20
05
0
20
40
60
19
70
19
80
19
90
20
00
0
20
19
70
19
80
19
90
20
00
CZ
SI
LV
TB
E c
ases/1
00,0
00 p
op
ula
tio
n
Šumilo D, Randolph SE et al (2008) Revs Med Virol
Courtesy: Sarah Randolph
Ecological factors
R0
Ecological factors affecting
TBEv circulation within natural foci
Range of observed
host density
Key hosts threshold density and TBE persistence
TBE model
Parameter estimates obtained from Trentino data and from literature
Ro
e d
eer
den
sity
(h
a-1
) –
Lo
g s
cale
1 10 100
0.001
0.01
0.1
1
10
Rodent density (ha-1) – Log scale
0.1
R0 < 1 R0 > 1 R0 = 1
Threshold density and a positive effect
of deer density on tick
abundance
“Diverting” effect’ of deer
Threshold density of competent
rodent hosts
N
T
LN
NL
LNNL
NL
L
TBEgd
kkLHcmR
)/1(111
,0
Complex dynamics in time and space
Upsurge of TBE in northern Italy
Graph showing numbers of mean annual incidence (n. of cases/100.000 inhabitants)
and annual TBE confirmed human cases in the positive provinces
Changes in climate
• Increase of Avg.yr.Tmin on a 50yr
period was 0.75 °C
• Increase of Avg.yr.Tmax on a 50yr
period was 1.7 °C
• Decrease of Avg.yr.prec on a 50yr
period was -180mm
MAP of TBE positive and TBE negative provinces
Trends in annual total precipitation (top), annual minimum (middle)
and maximum (bottom) daily air temperature in the TBE-negative provinces (left panels)
and TBE-positive provinces (right panels) in northern Italy from 1950 to 2006
(Rizzoli et al., Plos one, 2009)
Changes in deer abundance
Changes in roe deer density in provinces TBE positive (Trento
and Belluno) and TBE negative (Sondrio)
0
1
2
3
4
5
6
7
1953
1965
1969
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
Trento
Belluno
Sondrio
Boxplot of mean values of coppice to high forest ratio (cop.hfor)(left panel)
and mean values of roe deer abundance (right panel) in TBE positive and TBE
negative provinces of northern Italy (Rizzoli et al., Plos one, 2009)
Changes in forest cover and structure
- 14% of the total wooded areas increased
from 1950 to 2002
- Major increase in
- high stand mixed forest (184%)
- broad leaf coppices (359%)
- total mixed coppices (154%)
Mean coppice and high forest cover recorded in TBE-negative provinces (left panel)
and TBE-positive provinces (right panel) (Rizzoli et al., Plos one, 2009)
Conclusion
Protection from natural hazards, including infectious diseases, and health
protection are considered among the most relevant services provided by mountain
ecosystems;
Global changes, including the invasion by alien species, are favouring the
emergence of several animal and zoonotic diseases in world’s mountains;
Habitat changes and biodiversity loss favor TBD’s emergence: TBD’s pathogens
circulation is in fact supported mostly by generalist species (rodents, large game
species, I. ricinus)
Urgent need to better understand the effects of multi-trophic interactions under a
global change scenario across altitudinal gradients
Emerging diseases in mountains should be addedd to the “emerging
themes” to be covered by integrated research strategies because of their
dramatic impact on well being and economy
Acknowledgements
The Reseach Fund of
the Autonomous
Province of Trento
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