Epi 529 Presentation

7/28/2019 Epi 529 Presentation

http://slidepdf.com/reader/full/epi-529-presentation 1/31

Climate Change, Food Safetyand Infectious Diseases



Outline

Background on Climate Change

Impact of Climate Change on Food Safetyand Health

Addressing Risks

Challenges faced in Climate ChangeEpidemiology



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



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)



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



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



Climate Change and Food Safety

Climate change impacts all sectors of the epidemiologic

triad of disease



Climate Change and Food Safety

Bacteria,Viruses, Parasitic

Protozoa

Changing patternsof plant and animal

diseases

Harmful AlgalBlooms (HABs)

ToxinogenicFungi

Water qualityand availability

EnvironmentalContaminants



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



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



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.



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



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



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



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).





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



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.



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



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.



Climate Change Mycotoxin Cycle

R.R.M. Paterson, N. Lima / Food Research International 44 (2011) 2555 –

2566



Biosynthesis rates and Climate Models

R.R.M. Paterson, N. Lima / Food Research International 44 (2011) 2555 –

2566



Challenges in predicting Climate Effects:

Vector borne diseases



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.





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 - ??





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)



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



Tabachnick W.J., Journal of Experimental Biology, 213 943-954



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 ?



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



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



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.

Epi 529 Presentation

Documents

Transcript of Epi 529 Presentation