The role of veterinary The role of veterinary medicine in food safetymedicine in food safety

What is food borne diseasesWhat is food borne diseases

Apply to illnesses in which the onset Apply to illnesses in which the onset follows the ingestion of food containing follows the ingestion of food containing pathogenic microorganism, bacterial pathogenic microorganism, bacterial toxins, toxic chemical compounds. toxins, toxic chemical compounds. Occasionally poisonous plants and Occasionally poisonous plants and animals are encountered.animals are encountered.

Definitions Definitions -- foodbornefoodborneillness:illness:

Infection Infection -- illness caused by illness caused by eating food contaminated eating food contaminated with living pathogenic with living pathogenic agentsagents

Intoxication Intoxication -- illness illness caused by eating food caused by eating food contaminated with toxins contaminated with toxins (poisons) which occur (poisons) which occur naturally in some plant naturally in some plant and animals. Other toxins and animals. Other toxins are waste products of are waste products of microorganisms.microorganisms.

FoodborneFoodborne illness outbreakillness outbreak -- two or two or more cases of a similar illness more cases of a similar illness resulting from ingestion of a resulting from ingestion of a common food.common food.

Why Should We Care?Why Should We Care?

FoodborneFoodborne illness affects 6 illness affects 6 --80 million people per year80 million people per yearCauses 9,000 deaths per yearCauses 9,000 deaths per yearCosts ~ $5 billion per yearCosts ~ $5 billion per year

FOODFOODITITS S

EVERYONEEVERYONESS

BUSINESSBUSINESS

FactsFacts

More than 200 known diseases are More than 200 known diseases are transmitted through food.transmitted through food.

The causes include viruses, bacteria, The causes include viruses, bacteria, parasites, toxins, metals, and prions. parasites, toxins, metals, and prions.

Symptoms of illness range from Symptoms of illness range from gastroenteritis to neurologic, hepatic, and gastroenteritis to neurologic, hepatic, and renal syndromes.renal syndromes.

Foodborne DiseasesFoodborne Diseases Reportable diseases but underReportable diseases but under--estimatedestimated Many pathogens are not reportable (Many pathogens are not reportable (Bacillus, ClostridiumBacillus, Clostridium)) Pathogens can be spread by water, personPathogens can be spread by water, person--toto--personperson A high proportion are caused by unidentified agentsA high proportion are caused by unidentified agents Campylobacter jejuni, Escherichia coliCampylobacter jejuni, Escherichia coli O157:H7, and O157:H7, and

Listeria monocytogenes Listeria monocytogenes were unknown 20 yrs ago.were unknown 20 yrs ago.

International Classification of Diseases (ICDInternational Classification of Diseases (ICD--99--CM) conditionsCM) conditions CholeraCholera Typhoid feverTyphoid fever Campylobacter jejuni/coliCampylobacter jejuni/coli Clostridium botulinumClostridium botulinum Other ClostridiumOther Clostridium Other and unspecified Other and unspecified

bacteriabacteria AmebiasisAmebiasis GiardiasisGiardiasis Other protozoal intestinalOther protozoal intestinal Enteropathogenic E. coliEnteropathogenic E. coli Enterotoxigenic E. coliEnterotoxigenic E. coli Enteroinvasive E. coliEnteroinvasive E. coli Enterohemorrhagic E. coliEnterohemorrhagic E. coli Misc. E. coliMisc. E. coli

Salmonella (nonSalmonella (non--typhoid)typhoid) ShigellaShigella Staphylococcus aureusStaphylococcus aureus Vibrio parahemolyticusVibrio parahemolyticus Yersinia enterocoloiticaYersinia enterocoloitica RotavirusRotavirus AdenovirusAdenovirus Norwalk virusNorwalk virus Other small round structured Other small round structured

virusesviruses CalicivirusCalicivirus AstrovirusAstrovirus EnterovirusEnterovirus Other virusOther virus IllIll--defined intestinal infectionsdefined intestinal infections Other noninfectious Other noninfectious

gastroenteritisgastroenteritis

Mead et al., EID 5(5), Mead et al., EID 5(5), 19991999

Mead et al., EID 5(5), 1999Mead et al., EID 5(5), 1999

HHazard azard AAnalysis and nalysis and CCritical ritical CControl ontrol PPointsoints

HACCP HACCP -- food safety and othersfood safety and others Systematic approachSystematic approach Evaluation of risks Evaluation of risks Design and evaluation of control systemsDesign and evaluation of control systems

General approach allows design of operation General approach allows design of operation specific programsspecific programs Extremely useful for infectious disease control Extremely useful for infectious disease control

programsprograms

Important types of Important types of foodbornefoodbornediseasesdiseases

SalmonellosisSalmonellosisStaphylococcal intoxicationStaphylococcal intoxication

Clostridium Clostridium perfringesperfringesE. coli O157/H7E. coli O157/H7Campylobacter Campylobacter jejunijejuni

Clostridium Clostridium botulinumbotulinumListeriaListeria monocytogenesmonocytogenesVibrioVibrio speciesspeciesViral agentsViral agents

Food frequently involved in Food frequently involved in outbreaks:outbreaks:

MeatMeatPoultry productsPoultry productsDairy productsDairy products

Potato saladPotato saladPastryPastryFish productsFish productsFruitsFruits

Transmissible Spongiform Transmissible Spongiform Encephalopathy (TSE) Encephalopathy (TSE) --

Prion Diseases Prion Diseases

ReviewReview

What are these diseases?What are these diseases?

Transmissible Spongiform Encephalopathy Transmissible Spongiform Encephalopathy (TSE)(TSE) A prolonged incubation period of months or A prolonged incubation period of months or

years a progressive debilitating neurological years a progressive debilitating neurological illness which is always fatalillness which is always fatal When examined by electron microscopy, When examined by electron microscopy,

detergent treated extracts of brain tissue from detergent treated extracts of brain tissue from animals or humans affected by these diseases animals or humans affected by these diseases reveal the presence of scrapie associated reveal the presence of scrapie associated fibrils (SAF)fibrils (SAF)

What are these diseases?What are these diseases?

Pathological changes appear to be mainly Pathological changes appear to be mainly confined to the CNS and/or lymphoid tissue confined to the CNS and/or lymphoid tissue Brian lesions include Brian lesions include vacuolationvacuolation, and , and

astrocytosisastrocytosis Some of these diseases cause no detectable Some of these diseases cause no detectable

immune or inflammatory response in the host immune or inflammatory response in the host which has inhibited the development of a live which has inhibited the development of a live animal diagnostic test. animal diagnostic test.

Human TSE DiseasesHuman TSE Diseases Sporadic CreutzfeldtSporadic Creutzfeldt--Jakob Disease (Jakob Disease (sCJDsCJD)) Is a slow degenerative human disease of the central Is a slow degenerative human disease of the central

nervous system with obvious dysfunction, progressive nervous system with obvious dysfunction, progressive dementia, and vacuolar degeneration of the brain. dementia, and vacuolar degeneration of the brain. Typically, Typically, sCJDsCJD patients are over 50 years oldpatients are over 50 years old It occurs sporadically worldwide at a rate of 1 case per 1 It occurs sporadically worldwide at a rate of 1 case per 1

million people per year. million people per year.

More rare are the related TSE conditions of More rare are the related TSE conditions of GerstmannGerstmann-- StrausslerStraussler syndrome; syndrome; KuruKuru;; Fatal Familial Insomnia. Fatal Familial Insomnia.

vCJDvCJDA new findingA new finding

In 1996, the UK announced the In 1996, the UK announced the identification of 10 cases of a new variant identification of 10 cases of a new variant form of CJD (form of CJD (vCJDvCJD). ). All of the patients developed onset of illness All of the patients developed onset of illness

in 1994 or 1995. in 1994 or 1995.

Where has Where has vCJDvCJD been been detected?detected?

The vast majority of The vast majority of vCJDvCJD cases have cases have been detected in the UKbeen detected in the UK There have been few patients in France, There have been few patients in France,

Ireland, and Italy. Ireland, and Italy. One case of One case of vCJDvCJD has been detected in has been detected in

the U.S. but this case was traced back to the U.S. but this case was traced back to UK as the origin of onset. UK as the origin of onset.

Sporadic CJD vs. Sporadic CJD vs. vCJDvCJD

The affected individuals were much younger The affected individuals were much younger than the than the sCJDsCJD patient (range of 14 to 52 patient (range of 14 to 52 years old). years old). In the variant cases, In the variant cases,

electroencephalographic (EEG) electrical electroencephalographic (EEG) electrical activity in the brain was not typical of activity in the brain was not typical of sCJDsCJD.. A new ELISA capture Ag. can be used to A new ELISA capture Ag. can be used to

differentiate between the two diseasesdifferentiate between the two diseases

Sporadic CJD vs. Sporadic CJD vs. vCJDvCJD Although brain pathology was recognizable as Although brain pathology was recognizable as

CJD, the pattern was different from CJD, the pattern was different from sCJDsCJD, with large , with large aggregates of prion protein plaques. aggregates of prion protein plaques. Epidemiological and case studies have not Epidemiological and case studies have not

revealed a common risk factor among the cases revealed a common risk factor among the cases of of vCJDvCJD. . All victims were reported to have eaten beef or All victims were reported to have eaten beef or

beef products in the last 10 years, but none had beef products in the last 10 years, but none had knowingly eaten brain material. knowingly eaten brain material. One of the affected individuals had been a One of the affected individuals had been a

vegetarian since 1991. vegetarian since 1991.

TSE Diseases in AnimalsTSE Diseases in Animals

Bovine Spongiform Encephalopathy Bovine Spongiform Encephalopathy Chronic Wasting DiseaseChronic Wasting Disease ScrapieScrapie Transmissible Mink EncephalopathyTransmissible Mink Encephalopathy

TSETSEss in animals and menin animals and men

Animals

Humans

Scrapie

CWDTME BSE

FSE

Sporadic CJD

Kuru, Fatal Familial Insomnia

vCJD

??

The agentThe agent

The agent is smaller than most viral particles The agent is smaller than most viral particles and is highly resistant to heat, ultraviolet light, and is highly resistant to heat, ultraviolet light, ionizing radiation, and common disinfectants ionizing radiation, and common disinfectants that normally inactivate viruses or bacteria that normally inactivate viruses or bacteria Has not been observed microscopically. Has not been observed microscopically.

The agentThe agent

Three main theories on the nature of Three main theories on the nature of the agent have been proposed: the agent have been proposed: An unconventional virusAn unconventional virus A prion or abnormal partiallyA prion or abnormal partially--

proteinaseproteinase KK--resistant protein, devoid resistant protein, devoid of nucleic acid, capable of causing a of nucleic acid, capable of causing a cell to produce more abnormal proteincell to produce more abnormal protein A A virinovirino or "incomplete" virus composed or "incomplete" virus composed

of naked nucleic acid protected by host of naked nucleic acid protected by host proteins. proteins.

The Infectious AgentThe Infectious Agent

The proposed infectious agent of BSE The proposed infectious agent of BSE is the altered forms of PrP (Prion is the altered forms of PrP (Prion protein) : protein) : PrPPrPscsc (Scrapie(Scrapie--specific specific isoformisoform of PrP)of PrP)

There are at least 20 known mutations There are at least 20 known mutations of PrP geneof PrP gene

Characteristics of Characteristics of PrPPrPscsc

Resistant to Resistant to proteinasesproteinases, e. g. , e. g. proteinaseproteinase KK Not inactivated by radiation, formalin, or Not inactivated by radiation, formalin, or

organic solvents with extremes of pHorganic solvents with extremes of pH Can cross 0.2 Can cross 0.2 m filtersm filters Highly resistant to heat (> 100Highly resistant to heat (> 100C)C)

Inactivation of Inactivation of PrPPrPscsc

Chemical inactivation :Chemical inactivation : 1 ML 1 ML NaOHNaOH at 55 at 55 CC Chlorine bleach at 20,000 Chlorine bleach at 20,000 ppmppm

Heat inactivation :Heat inactivation : Wet sterilization at Wet sterilization at 133133 C for 20 min. at C for 20 min. at

3 bar3 bar

Bovine SpongiformBovine SpongiformEncephalopathy (BSE) Encephalopathy (BSE)

What do we know?What do we know?

Number of BSE cases in the world

182779

1070 707 688 421220 176

90 7443

11 105 3 3 2 2 2

1 1 1 11

10

100

1000

10000

100000

1000000

UK

Repu

blik o

f Irela

ndFr

ance

Portu

gal

Switz

erlan

dGe

rman

ySp

ainBe

lgium Ita

lyNe

therla

nds

Slowa

kiaDe

nmark

Japa

n

Czec

h Rep

ublik

Polan

d

Liech

tenste

inLu

xemb

urg

Slove

niaGr

eece

Austr

iaFin

land

Israe

l

country

l

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o

o

f

c

a

s

e

s

Background and HistoryBackground and History

No cases of BSE have been confirmed in the No cases of BSE have been confirmed in the U.S.A. despite 10 years of active U.S.A. despite 10 years of active surveillance. surveillance.

BSE pathogenesisBSE pathogenesis

Experimental oral exposure(1, 10 or 100g @ 4 months of age)

Some infectivity detectedin the distal ileum region(6 - 18 months of age)

Late incubation and clinical phase(at least 32 months p.i.)

Incubation

No infectivity detected- muscle tissue, milk- blood, periph. nerves- spleen, lymphatic tissue- brain, spinal cord- distal ileum etc.

Infectivity ONLY in- brain, spinal cord- dorsal root ganglia- distal ileum (some)

GENESIS OF BSE

Naturally we are ruminants but with their modern technologies we became half-carnivores eating

scrapie (PrPsc)* infected MBM**Can you imagine that ???

* PrPsc is altered form of prion protein PrP

** MBM : meat and bone meals mostly prepared from waste of scrapie

infected sheep or BSE infected cows

According to their mistakes, I am now a mad cow !!!

MAIN CLINICAL SIGNS

Behavioral changes Nervous appearance Loss of weight Reduce milk production

BSE and BSE and vCJDvCJD----Human Health Human Health ConcernsConcerns

Research reported in late 1996 and 1997 Research reported in late 1996 and 1997 has found evidence to further support a has found evidence to further support a causal association between causal association between vCJDvCJD and BSE. and BSE. Two significant studies published in the Two significant studies published in the

October 2, 1997 edition of Nature lead to October 2, 1997 edition of Nature lead to the conclusion that BSE agent is highly the conclusion that BSE agent is highly likely to be the cause of likely to be the cause of vCJDvCJD. .

BSE and CJDBSE and CJD----Human Health Human Health ConcernsConcerns

It was concluded, based on current data It was concluded, based on current data and in the absence of any credible and in the absence of any credible alternative, the most likely explanation was alternative, the most likely explanation was that the cases were linked to exposure to that the cases were linked to exposure to BSE before the introduction of control BSE before the introduction of control measuresmeasures

How Is BSE Currently How Is BSE Currently Diagnosed? Diagnosed?

There is no test to detect the disease in a live There is no test to detect the disease in a live animal. animal. Microscopic examination of brain tissue at Microscopic examination of brain tissue at

necropsy is the primary laboratory method necropsy is the primary laboratory method used to confirm a diagnosis of BSE.used to confirm a diagnosis of BSE. ImmunohistochemistryImmunohistochemistry and and immunoblottingimmunoblotting

are used. are used. There are also several techniques used to There are also several techniques used to

detect the partiallydetect the partially--proteinaseproteinase resistant form resistant form of the prion (of the prion (PrPPrPscsc) protein. ) protein.

ImmunohistochemistryImmunohistochemistry (IHC)(IHC)

Specific PrPScstaining

- since ~ 93/94- time consuming- SE -> 100 %- SP ~ 100 %

CNS tissue for BSE screeningCNS tissue for BSE screening

brain

obex region

spinal cord Brainstem of a cattle

collected with asharp spoon throughthe Foramen magnum

HistopathologyHistopathology

Spongiform changes (holes)

- time consuming- SE < 100 %- SP < 100 %

When do the current tests work?!When do the current tests work?!

Early Early Typical

InfectionClinical BSE

Histology

PrPSc detectionPrPScExposure

LateIncubation time Clinical disease

Typical slaughterage for beef cattle

How effective is our current How effective is our current surveillance system in surveillance system in

detection cases if the disease detection cases if the disease is in the USA?is in the USA?

If the disease is low in its prevalence (1 per If the disease is low in its prevalence (1 per 100,000 animals) then our system is not 100,000 animals) then our system is not sufficient to detect casessufficient to detect cases

Why is the USA TSE situation Why is the USA TSE situation better than in UK?better than in UK?

Scrapie program Scrapie program ---- prevalence of Scrapie is prevalence of Scrapie is lower than in the UKlower than in the UK The ratio of sheep to cows in the USA is much The ratio of sheep to cows in the USA is much

lower than in the UKlower than in the UK The use of animal protein as supplement to The use of animal protein as supplement to

dairy or beef cattle is lower than in Europe or the dairy or beef cattle is lower than in Europe or the UKUK The existence of surveillance systems for other The existence of surveillance systems for other

diseases so that cases would be detected in the diseases so that cases would be detected in the early stage.early stage.

Chronic Wasting Disease in Farmed Elk

(1996-2000)

Dr. Beth Williams, Wy. Vet. Diagnostic lab

Chronic Wasting Disease in Free-ranging

Deer and Elk(1981-2000)

Dr. Beth Williams, Wy. Vet. Diagnostic lab

North PlatteRiver

LaramieRiver

Denver

Fort Morgan

Cheyenne

South PlatteRiver

Fort Collins

10050km

Laramie

Estes Park

Wheatland

WYOMINGCOLORADO

NEBRASKA

Chronic Wasting Disease in Free-ranging

Deer and Elk

Dr. Beth Williams, Wy. Vet. Diagnostic lab