parasites lecture

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)




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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


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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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



ingestioningestion






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ingestioningestion






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


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



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



Adult tapeworm inAdult tapeworm incanids, felids and peoplecanids, felids and people








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Adult tapeworm inAdult tapeworm in

canids, felids and peoplecanids, felids and people







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


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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LL11



ingestioningestion





LL11



ingestioningestion





LL11



ingestioningestion



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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

parasites lecture

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