CLIMATE CHANGE AND EMERGING AND RE-EMERGING DISEASES IN AFRICA

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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

• 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 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).

4
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 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 pathogensviruses, 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 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
  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)

• 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
Vourch 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
Vourch et al 2006)
Emerging Disease (Cause) Species Location/Date
Nipah Virus (Paramyxovirus) Pigs/ Humans Malaysia and Singapore 1998
Porcine Dermatitis and Nephropathy Syndrome (Suspected porcine circovirus) Pigs 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.
• Microbial adaptation and change
• Human susceptibility to infection
• Climate and weather
• Changing ecosystems
• Human demographics and behaviour
• Economic development and land use
• Technology and industry
• Breakdown of public health measures
• Poverty and social inequality

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Factors contributing to emergence /re-emergence
of infectious diseases II

1. War and famine
2. Lack of political will
3. Intent to harm (Bio-terrorism)/ Bio-warfare.
4. Altered landscape which bring hosts into contact
   with new pathogens
5. Greater population densities which facilitate
   their rapid spread
6. Faster, longer-distance travel and trade which
   carry diseases to new populations
7. Natural disaster or war which disrupt the ability
   to keep diseases in check
8. 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.
  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)

• 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
• 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.
• 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 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
  vectorborne 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 10-20 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 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 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
Infection Hazards
Health Outcome
Survival/ replication of pathogens in
the environment
Temperature Humidity Precipitation
Consumption of contaminated water
Incidence of mortality and morbidity attributable
to diarrhoea
Contamination of water sources
Consumption of contaminated food
Living conditions (water supply and sanitation)
Contact with infected persons
Contamination of food sources
Food sources and hygiene practices
Vulnerability (e.g. age and nutrition)
Rate of person to person contact
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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

• Changes in the distribution and impacts of the
  vector-borne diseases of man and animals.
• 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
  vector-borne 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

1. Some diseasesbecause of climate changeare
   moving into new areas where people have little
   natural immunity (e.g. schistosomiasis, yellow
   fever, malaria, Chikungunya fever, Onyong-nyong
   fever, Dengue, West Nile.)
2. Water-borne infectious diseases are exacerbated
   by flooding and complicated by inadequate access
   to water by people and animals.
3. 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
  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
  short-term 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.