Download Climate changes and effects on vector borne-diseases and

Infectious diseases - how may
climate change influence
epidemiology?
• Ann Albihn,
• National Veterinary Institute, Uppsala
• www.sva.se
Albihn, Rossby Centre Day 2013, May 7, SMHI, Norrköping
The influence of CC on infectious diseases is
well documented
Klimat- och sårbarhetsutredningen 2005-2007
HÄLSOEFFEKTER AV EN KLIMATFÖRÄNDRING I SVERIGE
En nationell utvärdering av
hälsokonsekvenser hos människa och djur.
Risker, anpassningsbehov och kostnader
En rapport utarbetad för Klimat- och sårbarhetsutredningen
SOU 2007:60
Bilaga B34
Schmallenberg virus affect ruminants
• A surprisingly quick spread of VBD
• Transmission from mother to
foetus
• Cows may deliver dead or
malformed offspring
• In the end of 2011 in Germany,
France, Netherlands,...
• In 2012 further spread also to Swe
• Swedish survey of farm based milk
containers in May 2012 only 1
pos., in Nov 72 % of 723 pos
• Virus detected also in
• midges (Culicoides spp.)
• aborted lambs and calves
• wildlife
Zoonotic diseases may infect
both humans and animals
• 70% of all human infections
• 14 milj humans/year die
• More difficult to control than
”human only diseases”
Infectious diseases are spread by....
•
Water
•
Vector animals
•
Feed, soil
•
Contact
•
animal – animal
•
animal – human
•
Air
What kind of diseases?
•
Endemic diseases
•
•
Salmonella, Cryptosporidia, TBE
Exotic diseases
•
RVF, WNF, Schmallenberg virus
Ecosystem changes influence infectious diseases
Diseases that are transmitted by the environment or by
wild animals or use these as vectors or reservoirs
•Epidemiology, geographical distribution, seasonality and
prevalence may be affected.
•Biodiversity decline
•Damage for wildlife populations
Vectors transmit diseases between individuals and species
•Arthropod vectors - flies,
mosquitoes, sandflies,
ticks, midges...
•Highly sensitive to
climatic conditions as
temperature and humidity
•Distribution of vectors
will shift particularly at
their latitudinal and
altitudinal limits
Reservoir or host animals
www.vpe.slu.se
•Length of the vegetation period
- Exposure period prolonged
•Heat stress
-Changed behavior
-Immuno-suppressed
H. Fogelfors 2008.
Institutionen för växtproduktionsekologi
Secondary effects of CC may contribute to
an increased risk for infectious diseases
1961-90
~2085A2
temp > 5oC
(Fogelfors et al.,2008)
Waterborne infections and CC
Increased risk for contamination of water, soil and crop
• Flooding or irrigation with contaminated water
• Increased transportation of surface water and
pathogens from e.g. grassing land
• Sewage treatment plants has to low capacity to
treat water from e.g. heavy rain or instant snow
melting
• Increased water temperatures is favourable for
some pathogens
VTEC-disease in Halland 2005
• Serious gastrointestinal
disease as may cause deaths
• > 100 diseased humans
• On field lettuce crop
• Irrigated just before harvest
and packing
• Heavy rainfall and surface runoff from grassing land
• Contaminated river
• VTEC isolated from cattle,
lettuce and humans but not
from the river
Some arthropod
vectors travel by
the wind over long
distances
Geografic
location
Population
Individual
Temperature
Life cycle
Reprod. rate
metabolism
Biting rate
Vector competence
Active season
Exposure
period
A. Albihn, 2010
Population
density
Moisture
Vegetation
Predators
Host animal
Disease reservoir
Intermediate host
Dead-end-hosts
Pathogen
Presence
Serotype
Incubation time
Asian tiger mosquito (Aedes albopictus)
• A “multi-competent” vector
• Likes long-distance travelling
in used tires
in plants
• Is easily detected on arrival
(beautiful and aggressive)
Distribution of the Asian tiger mosquito
Photo: Eric Blomgren
Originated i south-east Asia
Distributed world-wide during the
last 40 years
Stegomyia albopicta / Asian tiger mosquito
Infection landscapes, 2011
Distribution of the Asian tiger mosquito
and the global transportation system
Eric Blomgren, SVA
The Common Tick - Ixodes ricinus
Changed distribution to higher latitudes and in
central Europe also to higher altitudes
A higher population density of ticks is experienced
Vector for e.g.
•Borrelia/Lyme disease
•Babesios
•Anaplasmos
•Rickettsia
•Tick-borne encephalitis (TBE)
Borreliosis/Lyme diseases
•
•
•
•
Tick-borne (Ixodes spp.)
Temp., humidity, vegetation
Rodents are reservoir species
Deer, humans and others
are mostly ”dead end host”
West Nile fever
Reservoar: Birds
Vector: Mosquitos Culex
& Aedes
West Nile virus
Diagnosed in New York 1999
1999
West Nile virus
2000
West Nile virus
2001
West Nile virus
2002
West Nile virus
2003
West Nile virus
2009
Conclusions 1
• CC cause changes in the
environment and in ecosystems
• Complex and dynamic
interaction between CC,
ecosystems,vectors, pathogens,
animals and humans
• Changes awaited in
geographical distribution,
seasonality, prevalence of VBD
• Lessons learned in other regions
must be adapted to local
conditions
• Necessary to pool cross-border
efforts to control VBD
Conclusion 2
For endemic infections For exotic infections
e.g. VTEC, salmonella, eg. Schmallenberg,
WNF, blutongue,
CC influence mainly due
to increases surface CC influence mainly due
run-off and flooding to influence on vectorand reservoir animals.
These animals are in
large dependent on
temperature,
precipitation, and
vegetation