7/28/2019 Parasites Lecture
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FoodFood--borne parasitesborne parasites
Andrew S. Peregrine,Andrew S. Peregrine, BVMS, PhD, DVM, DipEVPCBVMS, PhD, DVM, DipEVPC
Department of Pathobiology,Department of Pathobiology,Ontario Veterinary CollegeOntario Veterinary College
Telephone ext. 54714Telephone ext. 54714EE--mail: [email protected]: [email protected]
2.2. ZoonoticZoonotic nematodenematode Trichinella spiralisTrichinella spiralis
Taenia saginataTaenia saginata
Taenia soliumTaenia solium
Diphyllobothrium latumDiphyllobothrium latum
1.1. ZoonoticZoonotic tapewormstapeworms
CestodesCestodes tapewormstapeworms
Morphology of adultMorphology of adultparasite:parasite:
scolex:scolex:-- suckers ?suckers ?
-- rostellumrostellum -- armed/armed/unarmed ?unarmed ?
short, unsegmented neckshort, unsegmented neck
chain of segments = strobilachain of segments = strobila
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CestodesCestodes tapewormstapeworms
Morphology of adultMorphology of adultparasite:parasite: scolex:scolex:
-- suckers ?suckers ?
-- rostellumrostellum -- armed/armed/unarmed ?unarmed ?
short, unsegmented neckshort, unsegmented neck
chain of segments = strobilachain of segments = strobila
TapewormsTapewormsGeneral life cycle:General life cycle:
Definitive host
Intermediate host
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TapewormsTapeworms
General life cycle (1):General life cycle (1):
indirectindirect
--
usually one intermediate hostusually one intermediate host
adult parasite usually in small intestineadult parasite usually in small intestine gravid segments/eggs in fecesgravid segments/eggs in feces intermediate host ingests eggintermediate host ingests egg hexacanth embryohexacanth embryo blood, lymph etcblood, lymph etc
at predilection siteat predilection site infective larvainfective larva
TapewormsTapeworms
TapewormsTapeworms
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TapewormsTapeworms
TapewormsTapeworms
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TapewormsTapeworms
General life cycle (2):General life cycle (2): definitive host infected by ingestiondefinitive host infected by ingestion
of larva in tissueof larva in tissue
scolex attaches to intestinal wall andscolex attaches to intestinal wall andmatures to adult tapewormmatures to adult tapeworm
Zoonotic tapewormsZoonotic tapeworms -- PrinciplesPrinciples
1. People = definitive host:1. People = definitive host: usually host specificusually host specific
people usually eat intermediate hostpeople usually eat intermediate host
pathogenic ?pathogenic ?
2. People = intermediate host:2. People = intermediate host: people usually eat eggs passed in fecespeople usually eat eggs passed in feces
pathogenic ?pathogenic ?
Zoonotic tapewormsZoonotic tapeworms
PeoplePeopleDefinitive IntermediateDefinitive Intermediate
hosthost hosthost
Taenia saginataTaenia saginata 33
Taenia soliumTaenia solium 33 33
DiphyllobothriumDiphyllobothriumsp.sp. 33
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BeefBeeftapewormtapeworm
Taenia saginataTaenia saginata-- peoplepeople
Cysticercus bovisCysticercus bovis-- cattlecattle
Taenia saginataTaenia saginata(adult tapeworm)(adult tapeworm)
found only in peoplefound only in people
lives in small intestinelives in small intestine 33--15 meters in length15 meters in length
1,0001,000--2,000 segments2,000 segments
up to 12 segments shed dailyup to 12 segments shed daily
infected person shedsinfected person sheds 1,000,000 eggs/day1,000,000 eggs/day
life spanlife span -- can be as long as personcan be as long as person
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TaeniaTaeniasaginatasaginata(adult tapeworm)(adult tapeworm)
TaeniaTaeniasaginatasaginata(adult tapeworm)(adult tapeworm)
TaeniaTaeniasaginatasaginata(adult tapeworm)(adult tapeworm)
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TaeniaTaeniasaginatasaginata(adult tapeworm)(adult tapeworm)
Taenia saginataTaenia saginata(beef tapeworm)(beef tapeworm)
Cysticercus bovisCysticercus bovis-- predilection sitespredilection sites --
heartheart massetermasseter musclesmuscles tonguetongue intercostalintercostal musclesmuscles
diaphragmdiaphragm
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Cysticercus bovisCysticercus bovisin USA cattlein USA cattle
T.T. saginatasaginata-- ControlControl
Recognise that:Recognise that:1.1. People infected by ingestion ofPeople infected by ingestion of
parasite cysts in cattle meat.parasite cysts in cattle meat.
2.2. Cattle infected by ingestion of eggs inCattle infected by ingestion of eggs infeed/water contaminated with humanfeed/water contaminated with human fecesfeces..
3.3. Treatment will not eliminateTreatment will not eliminateinfections in cattle.infections in cattle.
T.T. saginatasaginata-- ControlControl
1.1. Compulsory meat inspectionCompulsory meat inspection2.2. Thoroughly cook meatThoroughly cook meat
3.3. Prevent contamination ofPrevent contamination ofcattle feed/water withcattle feed/water withhumanhuman fecesfeces
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C.C. bovisbovis-- monitoringmonitoring
Routine postRoutine post--mortem inspection ofmortem inspection ofcattle for parasite cysts:cattle for parasite cysts:
incision/observationincision/observation -- heartheart
-- massetermasseter musclesmuscles
observation/palpationobservation/palpation -- tonguetongue
-- diaphragmdiaphragm
T.T. saginatasaginata-- breaking the cyclebreaking the cycle
Sources of infectionSources of infection ReportsReports
application of sewage sludge to fieldsapplication of sewage sludge to fields 33
leakage of raw sewage on to fieldsleakage of raw sewage on to fields 22
water contaminated with sewage effluentwater contaminated with sewage effluent 11
fecalfecal contamination of feed/water by farm 8contamination of feed/water by farm 8
employeesemployees
dispersal of eggs by birdsdispersal of eggs by birds 11
T.T. saginatasaginata-- breaking the cyclebreaking the cycle
1.1. Educate employees about mode ofEducate employees about mode of
transmission and importance of personaltransmission and importance of personalhygiene.hygiene.
2.2. Provide adequate and convenient toiletProvide adequate and convenient toiletfacilities.facilities.
3.3. Examine employees prior to employmentExamine employees prior to employmentand periodically thereafter.and periodically thereafter.
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T.T. saginatasaginata-- breaking the cyclebreaking the cycle
4.4. Exclude unauthorised personnel fromExclude unauthorised personnel frompremises.premises.
5.5. Maintain animal source and destinationMaintain animal source and destinationrecords.records.
6.6. Periodic assay of water supply.Periodic assay of water supply.
7.7. Use of sewage on land ?Use of sewage on land ?
Infectivity ofInfectivity ofTaenia saginataTaenia saginataeggseggs
temperatures
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Taenia soliumTaenia solium(adult tapeworm)(adult tapeworm)
found only in peoplefound only in people
lives in small intestinelives in small intestine
22--4 meters long4 meters long
800800--1,000 segments1,000 segments
most common in Latin America,most common in Latin America,Africa, India, parts of Far EastAfrica, India, parts of Far East
T. soliumT. solium-- Life cycleLife cycle
1.1. As forAs for T. saginataT. saginata::
ingestioningestion
adult tapeworm in peopleadult tapeworm in people
eggs / segmentseggs / segments
Cysticercus cellulosaeCysticercus cellulosaein pigsin pigs
adultadultTT.. soliumsoliumin peoplein people
T. soliumT. solium-- Life cycleLife cycle
1.1. As forAs for T. saginataT. saginata::
ingestioningestion
adult tapeworm in peopleadult tapeworm in people
eggs / segmentseggs / segments
Cysticercus cellulosaeCysticercus cellulosaein pigsin pigs
adultadultTT.. soliumsoliumin peoplein people
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T. soliumT. solium-- Life cycleLife cycle
1.1. As forAs for T. saginataT. saginata::
ingestioningestion
adult tapeworm in peopleadult tapeworm in people
eggs / segmentseggs / segments
Cysticercus cellulosaeCysticercus cellulosaein pigsin pigs
adultadultTT.. soliumsoliumin peoplein people
T. soliumT. solium-- Life cycleLife cycle
2.2. In additionIn addition::
(a) ingestion of(a) ingestion of T. soliumT. soliumeggseggs
(b) autoinfection(b) autoinfection
cysticerci in peoplecysticerci in people
human cysticercosishuman cysticercosis
neurocysticercosisneurocysticercosis
Pathogenesis/Clinical signsPathogenesis/Clinical signs
usuallyusually inapparentinapparent in people with adultin people with adulttapewormtapeworm
usuallyusually inapparentinapparent in pigs within pigs with cysticercicysticerci
cysticercicysticerci in people ?in people ? in CNSin CNS epilepsy, seizures, blackouts, vertigoepilepsy, seizures, blackouts, vertigo
in eyein eye loss of visionloss of vision
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T.T. soliumsolium-- EpidemiologyEpidemiology
access of pigs to humanaccess of pigs to human fecesfeces
poor meat inspectionpoor meat inspection
inadequate cooking of porkinadequate cooking of pork
foodstuffs contaminated with humanfoodstuffs contaminated with humanfecesfeces
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T.T. soliumsolium-- ControlControl
meat inspectionmeat inspection
exclude contact of pigs with humanexclude contact of pigs with humanfecesfeces
thorough cooking of porkthorough cooking of pork
deep freezing proceduresdeep freezing procedures
proper standards of personal hygieneproper standards of personal hygiene
Diphyllobothrium latumDiphyllobothrium latum
Human broad tapewormHuman broad tapewormFish tapewormFish tapeworm
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found in people and various animalsfound in people and various animals
lives in small intestinelives in small intestine
largest tapeworm in peoplelargest tapeworm in people
3,000+ segments3,000+ segments
occurs globally, especiallyoccurs globally, especiallyBaltic countries/AsiaBaltic countries/Asia+ Canada+ Canada
Diphyllobothrium latumDiphyllobothrium latum
Diphyllobothrium latumDiphyllobothrium latum
Definitive hostDefinitive host
Adult tapeworm inAdult tapeworm incanids, felids and peoplecanids, felids and people
Eggs in fecesEggs in feces
coracidiumcoracidium
1st Intermediate host1st Intermediate hostCopepodCopepod
coracidiumcoracidium procercoidprocercoid
2nd Intermediate host2nd Intermediate hostFishFish
procercoidprocercoid plerocercoidplerocercoid
Diphyllobothrium latumDiphyllobothrium latum
Definitive hostDefinitive host
Adult tapeworm inAdult tapeworm incanids, felids and peoplecanids, felids and people
Eggs in fecesEggs in feces
coracidiumcoracidium
1st Intermediate host1st Intermediate hostCopepodCopepod
coracidiumcoracidium procercoidprocercoid
2nd Intermediate host2nd Intermediate hostFishFish
procercoidprocercoid plerocercoidplerocercoid
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Diphyllobothrium latumDiphyllobothrium latum
Definitive hostDefinitive host
Adult tapeworm inAdult tapeworm in
canids, felids and peoplecanids, felids and people
Eggs in fecesEggs in feces
coracidiumcoracidium
1st Intermediate host1st Intermediate hostCopepodCopepod
coracidiumcoracidium procercoidprocercoid
2nd Intermediate host2nd Intermediate hostFishFish
procercoidprocercoid plerocercoidplerocercoid
Disease ?Disease ? adult tapewormadult tapeworm vitamin Bvitamin B1212 deficiency ?deficiency ?
Epidemiology:Epidemiology: generally a parasite of people:generally a parasite of people:
ingestion of uncooked fishingestion of uncooked fish
human sewagehuman sewage freshwater lakesfreshwater lakes
animals infected by eating raw fish or fishanimals infected by eating raw fish or fishoffal:offal: dogs, cats, pigsdogs, cats, pigs
foxes, polar bearsfoxes, polar bears
Diphyllobothrium latumDiphyllobothrium latum
sewage disposalsewage disposal adequate cooking of fishadequate cooking of fish
deep freezing of fishdeep freezing of fish
education of publiceducation of public
treatment of infected individualstreatment of infected individuals
role of wild animals ?role of wild animals ?
Control:Control:
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TrichinellaTrichinellaspiralisspiralis
I say we do it . and trichinosis be damned
Trichinella spiralisTrichinella spiralisDisease = trichinosis/trichinellosisDisease = trichinosis/trichinellosis
InfectionInfection ingestion of parasitisedingestion of parasitisedmuscle cellmuscle cell
predation, cannibalism,predation, cannibalism,carrion feedingcarrion feeding
Wide host range:Wide host range: pigs, wild pigs, rodents,pigs, wild pigs, rodents,
polar bears, seals,polar bears, seals,
bears, wolves, foxes,bears, wolves, foxes,peoplepeople
T. spiralisT. spiralis-- Life cycleLife cycle
adult + mate (~ 2 days)adult + mate (~ 2 days)
female invades mucosafemale invades mucosa
LL11
skeletal muscle cells (nurse cells)skeletal muscle cells (nurse cells)
LL11 released in small intestinereleased in small intestine
ingestioningestion
LL11 in skeletal muscle cellsin skeletal muscle cells
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T. spiralisT. spiralis-- Life cycleLife cycle
adult + mate (~ 2 days)adult + mate (~ 2 days)
female invades mucosafemale invades mucosa
LL11
skeletal muscle cells (nurse cells)skeletal muscle cells (nurse cells)
LL11 released in small intestinereleased in small intestine
ingestioningestion
LL11 in skeletal muscle cellsin skeletal muscle cells
T. spiralisT. spiralis-- Life cycleLife cycle
adult + mate (~ 2 days)adult + mate (~ 2 days)
female invades mucosafemale invades mucosa
LL11
skeletal muscle cells (nurse cells)skeletal muscle cells (nurse cells)
LL11 released in small intestinereleased in small intestine
ingestioningestion
LL11 in skeletal muscle cellsin skeletal muscle cells
T. spiralisT. spiralis-- Life cycleLife cycle
adult + mate (~ 2 days)adult + mate (~ 2 days)
female invades mucosafemale invades mucosa
LL11
skeletal muscle cells (nurse cells)skeletal muscle cells (nurse cells)
LL11 released in small intestinereleased in small intestine
ingestioningestion
LL11 in skeletal muscle cellsin skeletal muscle cells
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Larvae in muscle cells:Larvae in muscle cells: may remain infective for yearsmay remain infective for years
very resistant, includingvery resistant, includingputrefactionputrefaction
Adults (small intestine):Adults (small intestine): 1.01.0 3.0 mm3.0 mm
very short livedvery short lived
T. spiralisT. spiralis-- CharacteristicsCharacteristics
Maintained in pigs by:Maintained in pigs by: feeding pigs flesh of infected pigsfeeding pigs flesh of infected pigs
tail bitingtail biting
rats in piggeriesrats in piggeries
probably
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raw/undercooked pork, bear, seal orraw/undercooked pork, bear, seal orbiproductsbiproducts-- smoking, drying, curing ?smoking, drying, curing ?-- horse meat (Europe)horse meat (Europe)
thermal death point ~ 59thermal death point ~ 59ooC for 10 minC for 10 min-- microwave ?microwave ?
larvae in pork killed @larvae in pork killed @ --2020ooC for 3 daysC for 3 days
larvae in bears withstandlarvae in bears withstand --2020ooC for 6C for 6monthsmonths
Human trichinosisHuman trichinosis
Human trichinosisHuman trichinosis most cases = asymptomaticmost cases = asymptomatic
Abdominal syndromeAbdominal syndrome -- early (several days):early (several days):-- abdominal painabdominal pain-- diarrheadiarrhea-- nauseanausea
General syndromeGeneral syndrome -- later (weeks, months):later (weeks, months):-- fever, chillsfever, chills-- edema around eyesedema around eyes-- myalgia, laboured breathingmyalgia, laboured breathing
Fatal dose ~ 5 larvae/g body weightFatal dose ~ 5 larvae/g body weight
Human trichinosisHuman trichinosis
Diagnosis:Diagnosis:-- clinical signsclinical signs
-- larvae in muscle biopsylarvae in muscle biopsy-- history of eating raw/undercooked meathistory of eating raw/undercooked meat
-- eosinophiliaeosinophilia
-- rise in antibody titrerise in antibody titre
Treatment:Treatment:-- anthelmintic + antianthelmintic + anti--inflammatoriesinflammatories
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Ethnic groups at riskEthnic groups at risk
Traditionally:Traditionally: Germans, PolishGermans, Polish
Recently:Recently: southsouth--east Asian refugees,east Asian refugees,especially Laotiansespecially Laotians+ Cambodians+ Cambodians
Northerners:Northerners: InuitInuit-- bear meat, walrus meatbear meat, walrus meat
meat inspection:meat inspection:-- microscopic examination of diaphragmmicroscopic examination of diaphragmmuscle + antibodymuscle + antibody--ELISAELISA
persuade public to cook fresh pork/porkpersuade public to cook fresh pork/porkproducts !!products !!
cook/freeze ready to eat products forcook/freeze ready to eat products forspecified timesspecified times
waste food must be boiled before fed towaste food must be boiled before fed topigspigs
eliminate rats/wildlife fromeliminate rats/wildlife from piggeriespiggeries
Control of trichinosisControl of trichinosis