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Epidemiologyand Control of
ZoonoticInfections
www.freelivedoctor.com
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EPIDEMIOLOGICAL TRIAD
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Epidemiology of Zoonoses
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Human environment interaction
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1 Zoonosis Intro & TSE
2 Rabies
3 Classic Zoonoses
4 Bioterrorism5 Vector-borne Diseases
6 Parasitic Zoonoses
7 Emerging Zoonoses
8 Foodborne Illnesses
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Introduction to Zoonoses
Definition
Importance
Etiologies
Animal Examples
Transmission Routes
Life Cycles
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Zoonoses
From the Greek:
Zoon: Animal
Noson: Disease
Diseases and infections which are naturally
transmitted between vertebrate animals andhumans
- WHO 1959
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Zoonoses
Does NOT include
Fish and reptile toxins
Allergies to vertebrates
Diseases in which animal-derived food serves as a
vehicle (e.g. hepatitis A contaminated deli meat)
Experimentally transmitted diseases
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Zoonoses
> 750 zoonotic diseases
60% of US Household have 1 pet
Multiple pets in the home
Human-animal bond
Exotic species as pets
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Zoonoses: Common Diseases
Frequency (CDC, 2003)
Salmonella 39,919
Lyme disease 18,991
West Nile (CNS) 2,862
Trichinosis 4
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Zoonoses
Spectrum of Disease Severity
Death = rabies
Severe illness = plague
Chronic illness = Q-fever
Mild illness = psittacosis
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Importance of zoonoses
Economics Zoonotic disease are expensive
Rabies post-exposure prophylaxis
GI illness due to Salmonella or Campylobacter lost
productivity, medical costs
Import/Export
BSE restriction on cattle
Avian Influenza restriction on chicken
Travel/Globalization
Decreased transit time - SARS
Remote area accessibility
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Zoonoses: Importance
Surveillance
Animals are sentinels
Prevention and Control
Animal = key component
Complications (e.g. Lyme disease)
Unknown reservoirs (e.g. Ebola)
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Zoonoses: Etiologic Classification
Viral
Bacterial
Parasitic
Mycotic
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Zoonoses: Viral Examples
Colorado tick fever Japanese encephalitis
Ebola Monkeypox*
Equine encephalitides(WEE, EEE, VEE)
Nipah*
Hantaviruses Rabies*
Hendra* Rift Valley fever
Herpesvirus B West Nile virus*
Influenza Yellow fever
* indicates covered in lectures
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Zoonoses: Bacterial Examples
Anthrax* Plague*
Brucellosis* Psittacosis*
Campylobacteriosis* Q fever*
Cat-scratch disease* Relapsing fevers
Leptospirosis* Salmonellosis*Listeriosis* Tularemia*
Lyme disease* Yersiniosis
* indicates covered in lectures
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Zoonoses: Parasitic Examples
PROTOZOAL HELMINTHIC
Trypanosomiasis Baylisascariasis*
Babesiosis Cysticercosis
Cryptosporidiosis* Hydatidosis
Leishmaniasis Schistosome dermatitis
Giardiasis* Trichinosis*
Toxoplasmosis* Visceral larva migrans
and toxocariasis*
* indicates covered in lectures
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Zoonoses: Mycotic Examples
Aspergillosis
Blastomycosis
Cryptococcosis*
Dermatophytosis*
HistoplasmosisSporotrichosis
* indicates covered in lectures
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Zoonoses: Animal Species
Dogs & Cats
Rabies
Roundworm
Ringworm Lyme Disease (dogs only)
Cat Scratch Disease (cats only)
Food Animals Salmonella
E.coli
Brucellosis
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Zoonoses: Animal Species
Birds:
Psittacosis
West Nile
Cryptococcus
Reptiles, Fish, &Amphibians
Salmonella
Mycobacterium Wild Animals
Hantavirus
Plague
Tularemia
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Routes of Transmission
Direct
Droplet or Aerosol
Oral
Contact
Indirect
Foodborne
Water-borne Fomite
Vector-borne
Environmental
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Zoonoses - Life Cycle
ORTHOZOONOSES/DIRECT ZOONOSES
May be perpetuated in nature by a single
vertebrate species
E.g. rabies, brucellosis, anthrax
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Zoonosis: Rabies Life Cycle
Virusinoculation
(bite)
Salivary
gland
excretion
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Zoonoses - Maintenance Cycle
CYCLOZOONOSES
Requires more than one vertebrate
species but no invertebrate host
Most are cestodiases (tapeworm
diseases)
Taenia saginata and T. solium require man to
be one of vertebrate hosts
Others, such as hydatidosis, man is
accidentally involved
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Life Cycle:
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Zoonoses - Life Cycle
METAZOONOSES
Require both vertebrates and invertebrates to
complete transmission
All arboviral infections
West Nile virus, Saint Louis encephalitis
Some bacterial diseases
Plague, many rickettsia Some parasitic diseases
Leishmaniasis, schistosomiasis
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Zoonoses: Metazoonoses
Invertebrate Host: Mosquitoes Vertebrate Host: Birds
Incidental Hosts:
HUMANS, horses, amphibians, other mammals
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Risk Factors
Companion Animal
Dogs & roundworm
Rats & Rat Bite Fever
Occupational
Animal control workers & rabies
Wildlife biologists & hantavirus
Foodborne
Raw meat & E.coli
Unpasteurized dairy & Listeria
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Risk Factors
Recreational Activities
Camping & Lyme disease
Farm Settings Sheep & Q-fever
Cattle & Cryptosporidium
Travel
Malaysia & Nipha
Australia & Hendra
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FOOD-BORNE DISEASES
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Introduction
Causes of food-borne
diseases/illnesses:1. Chemical toxins (residues)2. Biotoxins endotoxins & exotoxins
3. Infectious agents exogenous &endogenous (zoonoses)
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Introduction contd
endotoxins & exotoxins
lipopolysaccharide (LPS) : proteinpart of bacterium : extracellular
no toxoid : toxoidlow potency : high potency
low specificity : high specificity
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Mode of action of some
bacterial toxins
S. aureusA(alpha-toxin)
E. coliB(shiga toxin)
C. botulinumC(exo-enzyme)
33
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Introduction contd
Food hygiene vs food safety
food hygiene microbiological safety offoodfood safety abscence of
chemicals/residues Not necessary to have sterile
food
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Prevention of food-borne diseases Organisms -
characteristics1. where from2. types & strains
3. behaviour in food4. survive or are killed by
measures to inactivate
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Prevention of food-bornediseases, contd
Food characteristics
Water activity (aw), pH andtemperature
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What influences occurrence of
food-borne diseases/illnesses? Food source
Food storage
Food preparation
Food handlers
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What influences occurrence of
food-borne diseases/illnesses?
Time-temperature abuse
Infected food handlers orinadequate hygiene during handlingof food
Consumption/use of unsafe foodsources
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Types of illnesses/diseases
Upper GIT nausea & vomiting
Lower GIT cramps & diarrhoea
Neurological signs
General symptoms
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Types of illnesses/diseases
Upper GIT signs
Nausea, retching, vomiting, abdominal pain,diarrhoea & prostration
S. aureusand its toxins
B. cereusand its toxin
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Types of illnesses/diseases
Lower GIT signsLower abdominal cramps & diarrhoea
Clostridium perfringens, Bacilluscereus
Salmonella, Shigella, ETE. coli,Yersinia enterocolitica,Campylobacter jejuni, Vibrio cholera
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Types of illnesses/diseases
Lower GIT signs, continued
Lower abdominal cramps & diarrhoea
Giardia intestinalis
Cryptosporidium parvum
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Types of illnesses/diseases
Neurological signsVisual disturbances, vertigo, tingling
sensation & paralysis
Clostridium botulinum
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Types of illnesses/diseases
General symptomsFever, chills, malaise, prostration, aches,swollen lymph nodes
S. typhi, L. monocytogenes, C. jejuni Hepatitis A
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Risks of contracting food-borne disease depend on:
Host susceptibilityAge
General health
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Infective dose
Frequently exptrapolated
Feeding studies (healthy, young adultvolunteers)
Estimates (data from outbreaks)
Worst case estimates
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Risk assessment
variable infective doses
Interaction food substrate &environment
pH susceptibility
Type and strain
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Control of food contamination
Micro-organisms in food & water
shellfishfruits & nuts
beanswatermelons
spices & herbsvegetables
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Control of food contamination
Infection of animals milk,eggs or meat
Contaminated skins and guts
- slaughter & dressing
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Pathogenic Bacteria
1
C. botulinum, C. perfringens - Soil, hide, faecal material
Staphylococcus aureustoxin - Human (nostrils and hands)
Listeria monocytogenes - Soil, hide, faecal material
Campylobacter spp. - GIT(esp. poultry)
E. coliO157:H7 - GIT
Salmonella spp. - GIT / Hide
Yersinia enterocolitica - GIT
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Control of food contamination
Ideal = growing & harvesting stages
But world is not sterile
Prevent, reduce or limit by:
Not allowing products from clinically illanimals to enter food chain
Classical meat inspection - gross
HACCP - microscopic
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The chain of production from farm to fork of foodfrom animals
Production
Processing
Final preparationand cooking
Farm, Feedlot, Fishing site
Slaughter Plant, Cannery,Packer, Food Factory
Final Kitchen:commercial,institutional or domestic
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The chain of production from farm to fork -
prevention can occur at each step
Production
Processing
Final preparationand cooking
Feed, water, manure treatment,biosecurity, probiotics, vaccines
HACCP, slaughter hygiene,pathogen reduction andelimination (pasteurization,irradiation)
Cooking, preventingcross-contamination,worker education and handwashing
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Prevention of Food Poisoning
WHO ten golden rules Food processed for safety
Thoroughly cook Eat immediately
Store carefully
Reheat thoroughly
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Prevention of Food PoisoningWHO ten golden rules contd
No contact between raw & cooked
Wash hands
Keep food preparation surfaces clean
Protect from pests
Use potable water
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Food-borne disease outbreaks
& food spoilage
Contamination with undesirable
micro-organisms Unacceptable levels of micro-
organisms
Treatment did not result ininactivation
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Food-borne disease outbreaks
& food spoilage
Preventing/limiting contamination Preventing/limiting spread
Preventing growth
Preventing survival of organisms& persistence of metabolites
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Microbiological/chemical hazards
Micro-organisms part of nature
Chemicals many are man-made Micro-organisms change numbers
Uneven distribution in food
Clinical symptoms acute Variable consumer susceptibility
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