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7/28/2019 Epi 529 Presentation
http://slidepdf.com/reader/full/epi-529-presentation 1/31
Climate Change, Food Safetyand Infectious Diseases
7/28/2019 Epi 529 Presentation
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Outline
Background on Climate Change
Impact of Climate Change on Food Safetyand Health
Addressing Risks
Challenges faced in Climate ChangeEpidemiology
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Climate Change
A statistically significant variation in either the mean
state of the climate or its variability, persisting for an
extended period (typically decades or longer) (IPCC,2007)
May be due to natural internal processes or external
forcings, or persistent anthropogenic changes in thecomposition of the atmosphere or in land use.
Warming of the climate system is unequivocal (IPCC)
IPCC : Intergovernmental Panel on Climate Change
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Image Source: www.whataretheywaitingfor.com/climate-change-affects-us-all.html
Climate Change
Air and Ocean Temperatures
Snow-melts / Rising sea-levels
Frequency of heat waves andextended dry periods
Frequency of heavyprecipitation events
EWE (extreme weather events &stronger storm systems)
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Changes in Temperature - I
Global warming in twophases 1910 – 1940 &1970s –
Increase of 0.550 Celsiussince 1970s
Several thermometermeasurements takenover 7000 stationsworldwide everyday.
Fourth Assessment report of the IPCC
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Changes in Temperature - II
Patterns in temperature trends form 1979 – 2005 Slightly greater rate of warming in the troposphere.More spatially uniform warming in the troposphere while spatial
effects of land warming confined to certain pockets (urban
heat island effect) Fourth Assessment report of the IPCC
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Climate Change and Food Safety
Climate change impacts all sectors of the epidemiologic
triad of disease
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Climate Change and Food Safety
Bacteria,Viruses, Parasitic
Protozoa
Changing patternsof plant and animal
diseases
Harmful AlgalBlooms (HABs)
ToxinogenicFungi
Water qualityand availability
EnvironmentalContaminants
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CC and Bacterial Food Borne Diseases
Fecal /Oral routes
Ingestion of spores throughenvironmental routes
M.C. Tirado et al. / Food Research International 43 (2010) 1745 –
1765
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Bacteria, Viruses and Parasites
Cause contamination at any level of the farm – fork continuum
Contact with human or animal faeces
Contact with infected food handlers
Environmental contamination of air and water
Raw foods Climatic factors that affect their growth or survival :
Temperature, pH, salinity, moisture, oxygen, competitivemicroflora
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Salmonellosis
Salmonella infection causes more deaths than any other food-
borne pathogen in England and Wales
Symptoms - “food poisoning” (gastro-intestinal infection)
In Europe, Salmonella accounts for 71% of all laboratory confirmed
outbreaks of food borne disease
Inappropriate storage and preparation too far in advance
Food sources : Raw/undercooked meat, poultry, eggs, milk
S. Typhimurium and S.Enteritidis account for over 70% of human
infections in Europe
Kovats et al. Epidemiol. Infect. (2004), 132, 443 –
453.
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Temperature and Salmonella
Rate of multiplication of Salmonella is directly associated with
temperature in the range 7.5 – 37oC (in laboratory settings)
Ambient outdoor temperature expected to influence reproduction of Salmonellas
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In Europe, 5 – 10% increase in reported cases of Salmonellosis foreach one degree rise in weekly temperatures above 5oC
An eastern regional gradient observed in Australia for the
notification of Salmonellosis; rates of notification increase withdecreasing latitude and hence increasing average yearlytemperature
Elevated temperatures during the week preceding onset of infectionassociated with increasing notifications of salmonellosis.
Inappropriate storage temperature and food handling may be important factors for transmission
Temperature and Salmonella
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Example: Vibrio in Alaska
Vibrio Parahaemolyticus Leading cause of sea-foodassociated bacterial gastroenteritis in the US.
Found mostly in warm water estuaries
Source : raw or undercooked oysters
Alaskan waters thought to be too cold to support this
species
Between 1995 – 2003, over 400 Alaskan oysters testedfor Vibrio
McLaughlin et al. N Engl J Med 2005 353; 14
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Outbreak of Vibrio Parahaemolyticus on an Alaskan cruise shipin 2004.
62 cases of Vibrio-attributable gastroenteritis
Consumption of raw oysters significant predictor of illness
Oysters harvested from an oyster farm when mean daily water
temperatures exceeded 15o
C (theorized threshold for risk of illness).
Northernmost documented sea food poisoning from oysters(that caused illness due to Vibrio).
Example: Vibrio in Alaska
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Example: Vibrio in Alaska
Mean daily water temperature at the oyster farm
2004 was the only year when the meantemperatures did not fall below 15oC
Mean surface water temp. in Gulf of Alaskain July & August
In 2004, mean temperatures
were over 15oC for a much longer
period and at least 2oC warmer
than previous years
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Toxigenic Fungi and Mycotoxins
Mycotoxins: naturally occurring substances produced bytoxigenic molds that grow on several crops
Aspergillus ochraceus (Ochratoxin A) in coffee and cereal
seeds Fusarium verticillioides (fumonisin B1) in rice Aspergillus flavus (aflatoxin) in maize
Direct human exposure to consumption of contaminated crops
Indirect exposure through animal products from livestock thathave consumed infected crops.
Can cause acute symptoms, death. Carcinogenic, neurotoxic,cytotoxic, immunosuppressive among others.
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Mycotoxins
Interactions between plant and toxigenic molds modified by climate
change : temperature, humidity and precipitation
Moist and humid conditions, after heavy rains – conducive to fungal
growth
Decreased plant health – drought stress, temperature stress,
malnutrition
Outbreaks of acute aflatoxicosis reported in Kenya – 125/337reported cases died from consumption of aflatoxin contaminated
maize in 2004 (repeated outbreaks in ‘05 and ‘06)
Aflatoxin levels in maize were five times the recommended level in
50% of household grain stores in parts of Kenya
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Climate Change and Mycotoxins
2003-04; hot and dry summers in Italy – increased growth of A. flavuson maize crops.
A.flavus has a wide temperature tolerance : 19 – 35oC.
Livestock fed on contaminated maize exposed to high levels of aflatoxin M1.
Contamination of food commodities – peanuts and pistachios.
Heat/drought stress – cracking of peanut pods & hull splitting of pistachios
Unusually warm and humid conditions in Arizona – high levels of aflatoxin contaminated Bt cotton seeds.
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Climate Change Mycotoxin Cycle
R.R.M. Paterson, N. Lima / Food Research International 44 (2011) 2555 –
2566
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Biosynthesis rates and Climate Models
R.R.M. Paterson, N. Lima / Food Research International 44 (2011) 2555 –
2566
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Challenges in predicting Climate Effects:
Vector borne diseases
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Disease episystem – encompasses all biological and environmental
components of a vector borne disease epidemiologic system
Direct effects of climate change on disease triad
Indirect effects mediated through other environmental factors
Complex interplay – presents alternate plausible mechanisms for
increase in vector borne diseases.
Increasing urbanization, lack of public health infrastructure etc.
Challenges in predicting Climate Effects:
Vector borne diseases
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Challenge in gauging climate effects on current or newepisystems.
Paucity of available information on the mechanisms controlling
and influencing specific components of the complex vector–pathogen–host cycle.
Vector competence – needs further study. What are the geneticand environmental effects on vector competence ? Specific genes
critical for vector competence in nature are virtually unknown.
Array of vector competence phenotypes produced by differentgenotypes in various environments - ??
Challenges in predicting Climate Effects:
Vector borne diseases
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Climate and new episystems :
Bluetongue Virus (BVT) in Europe
Disease of ruminants, insect borne
Vector : Midge Culicoides
Rarely causes clinical signs in cattle
Non-tariff trade barriers between BVT-endemic and BVT-free regions.
Virus confined to Australia, Africa and parts of Asia
No efficient treatment. High morbidity in most livestock(Except cattle)
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Unprecedented spread in Europe between 1999-2006
Major outbreaks in Belgium, Netherlands, Germany etc.
Development of new episystems in Europe.
More than 1 million domestic and wild animals becameinfected.
BVT-vaccination programmes launched in Europe
BVT-8 in Northern Europe caused clinical signs in cattle.
Climate and new episystems :
Bluetongue Virus (BVT) in Europe
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Tabachnick W.J., Journal of Experimental Biology, 213 943-954
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Climate Change and BVT expansion ?
Initial entry between 1998-2006, due to expansion of African vector
Culiocides imicola
Higher temperatures in Europe – seven of ten warmest years
between 1958 – 2008 occurred between 1998-2006
Winter of 2006-07 warmest recorded temperatures
Other plausible reasons ?
Environmental / biological / ecological factors ?
What is the reason for vector competence of European Culiocides ?
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Other Plausible Reasons – BVT expansion
Changes in livestock / exotic animal movement in parts of Europe.
Btw 1965 – 1995, increase in animal theme parks, with exoticanimals imported from BVT-endemic regions (France – 200%,Italy – 130%, UK – 110%)
No restrictions to exclude BVT-infected animals.
No BVT testing done, no clinical signs of disease.
Infected livestock = = Infected Culicoides
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Changes in wildlife populations (increase in wild deerpopulations – carriers of midges and ticks). Availability of host.
Coupled with changing forest landscapes.
Changing livestock management practices – 46% increasein number of cows per herd in Italy (2003).
Other Plausible Reasons – BVT expansion
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Unanswered Questions
Is range expansion of African Culicoides a necessary precursor for
expansion of BVT into Europe ? Europe also had other competent
Culicoides vectors
Elevated temperatures in Europe necessary to maintain longertransmission season ?
USA has BVA episystems with prolonged subzero temperatures.
Temperature alone cannot be used to Culicoides populations inEurope.
Temperature – poor predictor of C. imicola populations in Europe
Other BVT episystems around the world relatively stable.