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

Contacts

annapaola.rizzoli@iasma.it