Transcript BIRD FLU: A PUBLIC HEALTH CONCERN – WHAT YOU NEED …

CLIMATE CHANGE AND
EMERGING AND RE-EMERGING
DISEASES IN AFRICA
BY
Paa-Kobina TURKSON, BVM. MSc. PhD
PROFESSOR AND VETERINARY EPIDEMIOLOGIST
ANIMAL SCIENCE DEPARTMENT
SCHOOL OF AGRICULTURE
UNIVERSITY OF CAPE COAST, GHANA
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PRESENTATION PLAN
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General overview
Definitions
Emerging and Re-emerging Diseases
Factors influencing Disease Emergence
Impact/Effects of climate on diseases
Conclusions
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Overview I
• The last 200 years
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have seen greater
environmental
change than the last
2000;
The last 20 years
have seen greater
change than the last
200 (Myers and
Tickell, 2001).
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NEWS FLASH!
2010 hits global temperature high
By Richard Black Environment correspondent, BBC News 20 January 2011
• 2010 was the warmest year since global temperature
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records began in 1850 - although margins of uncertainty
make it a statistical tie with 1998 and 2005.
The World Meteorological Organization (WMO) concludes
that 2010 was 0.53C warmer than the average for the
period 1961-90, a period commonly used as a baseline.
The 10 warmest years have all occurred since 1998.
Regions of the world experiencing particularly warm
conditions during 2010 included Africa, southern and
western Asia, and the northern extremities of North
America, including Greenland.
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Overview II
• Recent global research provides evidence of
climate change-related disease outbreaks already
occurring through the spread of different types of
pathogens—viruses, bacteria, fungi and parasites.
• By 2050, 6 billion people around the world will be
at risk to the ‘big 7’ climate-related diseases:
malaria, dengue and other haemorrhagic fever
viruses, schistosomiasis, sleeping sickness, Chagas’
disease, Leishmaniasis and river blindness; 4 of
the big 7 are zoonoses (transmissible between man
and animals) (Benniston, 2002).
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Overview III
• At the moment there is little evidence
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of causal changes in disease
transmission due to climate change
within Africa (Climate Change and Health Initiative 2008).
This lack of evidence does not mean
that these changes do not exist.
Rather, it may reflect the lack of
available epidemiological data as a
result of poor or absent surveillance
data and health information systems.
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Definition of Climate Change
• UNFCCC (United Nations Framework
Convention on Climate Change) definition:
Climate change is a change in climate
attributed directly or indirectly to human
activity that alters the composition of the
global atmosphere and which is in
addition to natural climate variability
observed over comparable time periods.
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Definitions of Emerging Diseases I
• Defined as Emergence of a pathogen in a
human or animal population which is related
to the increase in distribution, increase in
incidence or increase in virulence or other
factors. (Jones et al 2008)
• Emerging infections (EIs) are defined as
“Infections that have newly appeared in a
population or have existed previously but are
rapidly increasing in incidence or geographic
range”
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Definition of Emerging Diseases II
• The term ‘emerging disease’ is broad and in
general, covers any one of three disease situations:
– a known agent appearing in a new geographic
area
– a known agent or its close relative occurring in a
hitherto unsusceptible species
– a previously unknown agent detected for the first
time.
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Emerging Diseases I
• Since 1980, a new disease has emerged on
average every 7 months. (Climate Change and Health
Initiative 2008).
• Majority (60.3%) of 335 Emerging Infectious
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Diseases events between 1940 and 2004 analysed
by Jones et al (2008) were caused by zoonotic
pathogens.
71.8% of these zoonotic EID events caused by
pathogens originated from wild life e.g.. The
emergence of Nipah Virus in Perak, Malaysia and
SARS (Severe Acute Respiratory Syndrome) in
Guandong Province, China.
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Emerging Diseases II
• Of 335 EID events from 1940-2004, the
causes were as follows (Jones et al, 2008):
• Bacteria/ Rickettsia
54.3%
• Viruses/ Prions
25.4%
• Protozoa
10.7%
• Fungi
6.3%
• Helminths
3.3%
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Examples of Recent Emerging Zoonoses
(modified after Brown, 2004)
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Ebola virus
Bovine Spongiform Encephalopathy (Mad Cow)
Nipah Virus
Severe Acute Respiratory Syndrome (SARS)
Alveolar Echinococcosis
Monkeypox
Rift Valley Fever
Highly Pathogenic Avian Influenza (Bird Flu)
“Swine Flu” (H1N1)
Monkey Herpes B virus ( Ghana; January 2011)
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Re-emerging Zoonotic Diseases (After Bengis
et al 2004)
• Viral
• Rabies and related Lyssavirus infections
• Rift Valley Fever
• Marburg Virus
• Bacterial
• Bovine Tuberculosis
• Brucella species in wild animals
• Tularaemia
• Plague
• Leptospirosis
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Emerging Diseases in Farm animals I (After Vourc’h et al 2006)
Emerging Disease (Cause)
Species
Location/Date
Blue tongue (Reoviridae)
Sheep
Mediterranean Basin 1996-2001
Border Disease (Flaviviridae)
Sheep
France 1994
Bovine Leukocyte Adhesion Deficiency
(CD18 gene mutation)
Holstein
cattle
Various countries 1980s
Bovine Spongiform Encephalopathy
Cattle
UK 1980
Complex vertebral malformation
(SLC35A3 gene mutation)
Dairy
cattle
Denmark 2000
Epizootic Rabbit Enteropathy
(Unidentified virus)
Rabbits
Europe 1996
Hendra Disease (Paramyxovirus)
Horses/
Humans
Australia, Papua N. Guinea 1984
Highly Pathogenic Avian Influenza
(H5N1)
Poultry/
Humans
South East Asia, 2003-4. Now a
pandemic
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Emerging Diseases in Farm animals I (After Vourc’h et al 2006)
Emerging Disease (Cause)
Species
Location/Date
Nipah Virus (Paramyxovirus)
Pigs/
Humans
Malaysia and
Singapore 1998
Porcine Dermatitis and Nephropathy
Pigs
Syndrome (Suspected porcine circovirus)
UK 1993
Porcine Reproductive and Respiratory
Syndrome (Arteriviridae)
Pigs
North America
1987
Post-weaning multi-systemic wasting
syndrome (Suspected porcine circovirus)
Pigs
Canada 1990
Rabbit haemorrhagic disease
(Calciviridae)
Rabbits
China 1984
West Nile Fever (Flaviviridae)
Humans/
crows
US 1999
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Causes of re-emergence
• The re-emergence of well-documented
zoonotic diseases appears to be driven by
climatic, habitat and population density
factors that affect hosts, pathogens or
vectors – frequently causing natural
increases and decreases in disease activity in
different geographical areas and over
various periods of time.
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Factors contributing to emergence /re-emergence of
infectious diseases I
Include genetic, biological, and social, political economic factors.
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Microbial adaptation and change
Human susceptibility to infection
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Climate and weather
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Changing ecosystems
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Human demographics and behaviour
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Economic development and land use
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Technology and industry
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Breakdown of public health measures
Poverty and social inequality
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Factors contributing to emergence /re-emergence of
infectious diseases II
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War and famine
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Lack of political will
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Intent to harm (Bio-terrorism)/ Bio-warfare.
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Altered landscape which bring hosts into contact with new
pathogens
Greater population densities which facilitate their rapid
spread
Faster, longer-distance travel and trade which carry diseases
to new populations
Natural disaster or war which disrupt the ability to keep
diseases in check
Climate change, of natural or anthropogenic origin, which
could be a driver to changes in disease dynamics.
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Effect of climate on disease causation I
(CHCD 2008)
• Climate may affect certain pathogens directly.
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Many pathogens must spend a period of time in
the environment to be able to get from one host to
another. During this transit they are exposed to
the weather. The time period can be months /years
(e.g.. Spores causing anthrax) or as short as
seconds or minutes (e.g. human cold and influenza
viruses and rinderpest virus in animals.)
In most cases, climate and weather affect the
ability of the pathogen to survive or reach and
enter a new host and result in seasonality of
certain diseases.
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Effect of climate on disease causation II
• Many pathogens use vectors to facilitate
transmission between primary hosts:
mosquitoes, fleas, ticks, non-biting flies etc.
• Climate often plays a dominant role in
determining the spatial and temporal
distribution of arthropod vectors so that
vector-borne diseases are often climatically
restricted in both time and space.
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Impact of climate on infectious diseases I
(CHCD 2008)
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Climate directly influences the ability for
pathogens and vectors to survive,
replicate, move or attack hosts. For
example
– Vector-borne diseases: malaria,
trypanosomosis, Rift Valley Fever
– Parasites with free-living stages: soil
helminths
– Air-borne parasites e.g. meningitis
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Impact of climate on infectious diseases II
Climate influences ecology which in turn
influences pathogen/vector availability or
host susceptibility. For example
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Excessive rainfall leads to ground saturation
resulting in increased hatching of vectors and
outbreaks of Rift Valley Fever
Food production. Malnourishment often leads
to iron deficiency and can exacerbate anaemia
which is the major cause of death in malaria
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Impact of climate on infectious diseases III
Climate influences human (animal?)
behaviour.
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Cold weather leads to closer contact and
higher transmission of influenza virus.
Extreme weather events leads to population
displacement and disruption of sanitation and
water/food supplies, a pre-disposition for
pathogens spread by faecal/oral route.
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OIE confirms impact of climate change on
animal diseases in a world-wide study.
• “More and more countries are indicating that climate
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change has been responsible for at least one emerging or
re-emerging disease occurring on their territory. This is a
reality we cannot ignore…” Dr Bernard Vallat , DG, OIE.
Of 126 OIE's Member Countries and Territories who took
part in a study in 2006, 71% stated they were extremely
concerned at the expected impact of climate change on
emerging and re-emerging diseases.
58% identified at least one emerging or re-emerging
disease on their territory that was believed to be
associated with climate change.
The three animal diseases most frequently mentioned
were: Bluetongue, Rift Valley fever and West Nile fever.
The majority of countries also consider that human
influence on the environment has an impact on climate
change and therefore on the emergence or re-emergence
of animal diseases.
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Some Effects of Climate Change on Infectious
Diseases of Animals in Africa (Baylis 2006)
• Moisture-sensitive diseases will be affected,
including anthrax, blackleg,
dermatophilosis, haemorrhagic septicaemia,
PPR, haemonchosis and vector–borne
diseases. These diseases may decline in some
areas and spread to others.
• Increase in Fascioliasis due to F. hepatica in
Central, East and parts of West Africa;
decline in Fascioliasis due to F. hepatica and
F. gigantica in northern and southern
Africa, depending on measures to preserve
water supplies.
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Some Effects of Climate Change on Infectious
Diseases of Animals in Africa (Baylis 2006)
• Possible increase in frequency of epidemics
of diseases linked to El Nino Southern
Oscillation (i.e. Rift Valley fever, Blue
tongue)
• Possible increases in pathogen transmission
between wildlife and livestock.
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Examples of climate-disease links (After Baylis, 2007)
Anthrax
• Worldwide zoonosis
• Spores remain infective for 1020 years in pasture.
• Temperature, RH and soil
moisture affect spore
germination
• Heavy rainfall stirs up dormant
spores.
• Outbreaks often associated
with alternating heavy rainfall
and drought, and high
temperatures
Spotted hyena eating a zebra
dead from anthrax, Ethosha
Park, Namibia
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Examples of climate-disease links
(After Baylis,
2007)
Fascioliasis (liver fluke)
• Caused by the Fasciola, a
trematode/fluke
• Of economic importance to
cattle and sheep producers
in many parts of the world.
• Associated with
environmental conditions
favouring the intermediate
snail host. Eg. low lying
wet pasture, areas subject
to periodic flooding, and
temporary or permanent
bodies of water
Liver fluke life cycle
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Examples of climate-disease links
(After Baylis, 2007)
African horse sickness
• Lethal infectious disease of
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horses
Caused by a virus
transmitted by Culicoides
biting midges.
Large outbreaks of AHS in
the Republic of South Africa
over the last 200 years are
associated with the
combination of drought and
heavy rainfall brought by
the warm-phase of the El
Niño Southern Oscillation
(ENSO)
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Some Effects of Climate Change on Infectious
Diseases of Humans in Africa (Baylis 2006)
• Uncertain impact on acute respiratory
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infections
Possible increase in cholera in response to
more coastal flooding
Increased impact of diarrhoeal diseases
Greater areas of risk of vector-borne diseases
such as Rift Valley Fever, dengue,
leishmaniasis, schistosomiasis, malaria, West
Nile Fever.
Uncertain effect on meningococcal meningitis,
filariasis, trypanosomosis.
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Pathways for Weather to Affect Health:
Diarrhoeal Diseases (After Ebi, 2006)
Distal Causes
Proximal Causes
Temperature
Humidity
Precipitation
Survival/ replication Consumption of
of pathogens in the
contaminated water
environment
Living conditions
(water supply and
sanitation)
Food sources and
hygiene practices
Infection Hazards Health Outcome
Contamination of
water sources
Consumption of
contaminated food
Contamination of
food sources
Contact with
infected persons
Rate of person
to person contact
Incidence of
mortality and
morbidity
attributable
to diarrhoea
Vulnerability
(e.g. age and
nutrition)
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Potential Health Effects of Climate
Variability and Change (After Ebi, 2006)
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Examples of links between climate, animal health and
human health in Africa. I
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Changes in the distribution and impacts of the
vector-borne diseases of man and animals.
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Diseases such as malaria, Rift Valley fever,
African horse sickness, and bluetongue vary
considerably with seasonal and longer-term
climatic variations.
Climate change is said to directly contribute to
changes in the geographic distribution of vectorborne diseases such as malaria and epidemics of
meningococcal meningitis and Rift Valley fever
and cholera in previously unaffected areas.
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Examples of links between climate, animal health
and human health in Africa. II
2. Some diseases—because of climate change—
are moving into new areas where people have
little natural immunity (e.g. schistosomiasis,
yellow fever, malaria, Chikungunya fever,
Onyong-nyong fever, Dengue, West Nile.)
3. Water-borne infectious diseases are
exacerbated by flooding and complicated by
inadequate access to water by people and
animals.
4. Droughts force peoples and their livestock to
move, potentially exposing them to different
environments with health risks to which they
have never been exposed.
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Conclusion I
• CHCD 2008 stated that “The emergence of
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infectious diseases and their spread and
impact, relate to how pathogens interact with a
complex of social, technological and
environmental processes.
These processes are highly interdependent,
non-linear and often context-specific. They
operate over varied and sometimes
overlapping temporal and spatial scales.
Some disease drivers and effects involve shortterm shocks- as in an ecosystem switch that
triggers a sudden epidemic outbreak- while
others involve longer-term trends and stresses.
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Conclusion I continued
• Disease responses themselves can feed back to
shape these dynamics- either positively, for
instance where the disease is brought under
control, or in less intended ways- for instance
where drugs contribute to emerging pathogenic
resistance.
• Understanding emerging infectious diseases thus
requires an appreciation of such complex social,
technological and environmental dynamics.”
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Conclusion II
Matthew Baylis (2006) argues that
• “There is considerable uncertainty arising
from the many, often conflicting, forces that
climate imposes on infectious diseases, the
complex interaction between climate and other
drivers of change and uncertainty in climate
itself.
• Effects of climate change that act indirectly on
infectious diseases, via effects on other drivers,
are particularly hard to predict.
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Conclusion II continued
• Nevertheless, there is a consensus that some, and
possibly many infectious diseases of animals, humans
and plants will be affected by climate change.
• Many of the diseases we commonly face are kept at
least partly in check by lifestyles, behaviours, farming
systems or control measures that we have learned to
use, sometimes over millennia, to help keep us, our
livestock and our crops healthy.
• By contrast, when a new disease emerges or a familiar
disease spreads to a new region, there is a long lead-in
time before we know its significance and how it can be
controlled or avoided.”
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Conclusion III
• Need for closer collaboration between veterinary,
medical and environmental sciences to improve
disease surveillance and control relating to climate
change, as this is lacking in many countries.
• Rudolf Virchow said “Between animal and human
medicine there are no dividing lines. The object is
different but the experience obtained constitutes the
basis of all medicine.”
• Underscores the concept of or movement for
“One world, one health”
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Acknowledgements
• I acknowledge with gratitude the use of
information from various authors and
particularly work by Matthew Baylis of
Liverpool University and the Climate and
Health Challenge Dialogue 2008. They made
my work easier.
• I thank the organisers for the opportunity given
me for this presentation.
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THANK YOU
FOR YOUR ATTENTION
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Impact of climate change on African Agriculture
(After Chemnitz and Hoeffler 2011)
Effects are at two levels
• Biophysical
Include changes in crop-growing conditions and animal
productivity as a result of rising temperature and highly
variable precipitation
• Socioeconomic
– Falling incomes from agriculture
– Higher risks and greater vulnerability in the rural
population due to changes in their cultural and
economic livelihoods
– Risk of rural areas sliding deeper into poverty
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Impact of Climate on Livestock-Keeping I
• According to Spore (August 2008),
climate change in Africa may modify
the distribution and nutritional quality
of forage plants, factors that will
influence milk production and
production. Nutrition-related diseases
may therefore become important.
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Impact of Climate on Livestock-Keeping II
• Climate change will also influence the type of
livestock species kept. “If the climate becomes
hotter and drier, goats and sheep will take
precedence over cattle and chickens which are
very sensitive to heat. The humid zones will in
turn become more suited to poultry and large
livestock especially in high altitudes. But, if
rainfall increases in these areas, goats and
chickens will become more attractive options”
(Spore 2008). This may influence the types of
diseases that will have to be handled.
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