Order Oxyurida Order Oxyurida

• Enterobius vermicularisEnterobius vermicularis– PinwormsPinworms

– EnterobiasisEnterobiasis

• Large esophageal bulbLarge esophageal bulb• Sharp, pointed tailSharp, pointed tail• Alae at anterior endAlae at anterior end• CosmopolitanCosmopolitan• Common in peopleCommon in people• Relatively unpathologicalRelatively unpathological

• Direct life cycleDirect life cycle• Adults live in ileocecal Adults live in ileocecal

region of intestine region of intestine (wander throughout gut)(wander throughout gut)

• Feed on bacteria and Feed on bacteria and organic material from organic material from cellscells

• At night, females At night, females migrate to anus and lay migrate to anus and lay eggs (up to 16,000 each)eggs (up to 16,000 each)

• Embryonates within 6 Embryonates within 6 hours hours

• Infection via ingestion of Infection via ingestion of embryonated eggsembryonated eggs

• Or may hatch on Or may hatch on perianal folds and perianal folds and wander up intestinewander up intestine

Symptoms and PathologySymptoms and Pathology

• 1/3 asymptomatic1/3 asymptomatic

• PruritusPruritus

• Lesions from feeding not significantLesions from feeding not significant– Secondary infections can occurSecondary infections can occur

• Itching can lead to secondary infectionsItching can lead to secondary infections

Pinworm NeurosisPinworm Neurosis

• NervousnessNervousness– Fidgeting, restlessness, irritable, nail biting, Fidgeting, restlessness, irritable, nail biting,

nose pickingnose picking– Due to toxemia and damage of epitheliumDue to toxemia and damage of epithelium

• ChildrenChildren

• ParentsParents– Obsessive cleaningObsessive cleaning

DiagnosisDiagnosis

• Scotch tape testScotch tape test

• Flashlight testFlashlight test

• MebendazoleMebendazole

• Treat entire familyTreat entire family

Diagnosis ofDiagnosis of Enterobius vermicularis Enterobius vermicularis DIAGNOSIS -

Use of double-stick tape on a tongue depresser.

This is pressed against the perianal folds where eggs will stick to the tape.

Tape is then stuck onto a microscope slide and examined for eggs.

 

Enterobius vermicularisEnterobius vermicularis

Almost anybody can become infected with this parasite. No social class is exempt. These parasites soon become "family affairs".

Once one person, usually a child becomes infected, other family members will undoubtedly also become infected.

 

EpidemiologyEpidemiology

• Very ProlificVery Prolific

• Eggs build up fastEggs build up fast– Clothing and beddingClothing and bedding– Eggs very light and floatEggs very light and float– Easily distributed Easily distributed

• Eggs viable for up to a Eggs viable for up to a weekweek

Prevention and ControlPrevention and Control

• Not very seriousNot very serious

• Good hygieneGood hygiene

Order TrichiuridaOrder Trichiurida

Order TrichiuridaOrder Trichiurida

• Trichuris trichiuraTrichuris trichiura– WhipwormWhipworm

• Trichinella spiralisTrichinella spiralis

Trichuris trichiuraTrichuris trichiura

• 30-50 mm30-50 mm• Long esophagus Long esophagus

surrounded by stichocytes surrounded by stichocytes (glands) (glands) – StichosomeStichosome

• Single gonadSingle gonad• Males have single spiculeMales have single spicule• Eggs have characteristic Eggs have characteristic

shape 50-54 X 22-23 shape 50-54 X 22-23 μμmm

• Direct Life CycleDirect Life Cycle• Adults live in Adults live in

cecum and cecum and ascending colonascending colon

• Release eggs with Release eggs with fecesfeces

• Eggs embryonate Eggs embryonate in soil (21 days)in soil (21 days)

• Eggs ingestedEggs ingested• HatchHatch• Juveniles enter Juveniles enter

crypts of crypts of LieberkLieberküühnhn

Crypts of LieberkCrypts of Lieberküühnhn

Tubular glands at base of villi

• Juveniles enter Juveniles enter crypts of crypts of LieberkLieberküühn hn (large intestine)(large intestine)

• Penetrate cellsPenetrate cells• As they grow, As they grow,

tunnel in tunnel in epithelium. epithelium. Posterior end Posterior end enters lumenenters lumen

• MatingMating• Egg productionEgg production

Symptoms and PathologySymptoms and Pathology

• Most symptom-lessMost symptom-less• > 100 worms> 100 worms

– Heavy infections common (200 to over 1000 worms)Heavy infections common (200 to over 1000 worms)

• DysenteryDysentery• AnemiaAnemia• Growth retardationGrowth retardation• Finger clubbingFinger clubbing• Reduce cognitive function in children Reduce cognitive function in children

Trichuris trichiuraTrichuris trichiura

• WWorms cause loss of muscle tone in wall of rectum and it everts out the anus; whipworms are often seen attached to the rectal tissue

Trichuris trichiuraTrichuris trichiura

• Rectal prolapseRectal prolapse

Symptoms and PathologySymptoms and Pathology

• Anterior end buried in mucosaAnterior end buried in mucosa– Physical damagePhysical damage– FibrosisFibrosis– Chronic hemorrhage Chronic hemorrhage anemia anemia

DiagnosisDiagnosis

• Look for eggs in fecesLook for eggs in feces• Adult wormsAdult worms• Frank blood in fecesFrank blood in feces• Treatment difficultTreatment difficult• MebendazoleMebendazole

EpidemiologyEpidemiology

• CosmopolitanCosmopolitan

• PrevalencePrevalence– SE U.S. 20-25% in childrenSE U.S. 20-25% in children– U.S. 1.2%U.S. 1.2%

• 902 million infected worldwide902 million infected worldwide

ProlificProlific

• Females produce 3,000-20,000 eggs per dayFemales produce 3,000-20,000 eggs per day

• Sensitive to environmental conditionsSensitive to environmental conditions– High rainfallHigh rainfall– Moisture retaining soilMoisture retaining soil– ShadeShade– Warm climateWarm climate

EpidemiologyEpidemiology

• Ingest Eggs with Juveniles!Ingest Eggs with Juveniles!– Very similar to Very similar to AscarisAscaris epidemiology epidemiology

Trichinella spiralisTrichinella spiralis

• Males 1.5 mm, Females 3 Males 1.5 mm, Females 3 mmmm

• Short esophagusShort esophagus

• StichosomeStichosome

• PsuedobursaPsuedobursa

• No copulatory spiculeNo copulatory spicule

• Single gonadSingle gonad

• Uterus contains fully Uterus contains fully developed eggsdeveloped eggs

Trichinella spiralisTrichinella spiralis

• Parasites of carnivorous mammals Parasites of carnivorous mammals • Causes Trichinosis Causes Trichinosis • Unusual life cycleUnusual life cycle

– Same individual host is both definitive and intermediate Same individual host is both definitive and intermediate hosthost

– Adults in small intestineAdults in small intestine

– Juveniles inside muscle cellsJuveniles inside muscle cells• Largest intracellular parasiteLargest intracellular parasite

• Def. host is infected Def. host is infected by ingesting juveniles by ingesting juveniles in the muscle of other in the muscle of other hostshosts

• Juveniles enter Juveniles enter intestinal mucosaintestinal mucosa

• 4 molts4 molts

• GrowthGrowth

• CopulationCopulation

• Within 32 hours Within 32 hours after ingestionafter ingestion

Adults in small intestineAdults in small intestine

• Thread throughout Thread throughout intestinal cellsintestinal cells

• Females release Females release juveniles into mucosajuveniles into mucosa

• Thousands over 4-16 Thousands over 4-16 weeksweeks

• Juveniles enter Juveniles enter hepatoportal systemhepatoportal system

• Carried to liver, Carried to liver, heart, lungs, then heart, lungs, then arterial systemarterial system

• Distributed Distributed throughout bodythroughout body

• Penetrate cells of Penetrate cells of skeletal muscleskeletal muscle

• Grow to about 1 mmGrow to about 1 mm

• Infective in 4-6 weeksInfective in 4-6 weeks

• How do the juveniles fit inside a muscle How do the juveniles fit inside a muscle cell?cell?

• How do juveniles survive inside a muscle How do juveniles survive inside a muscle cell?cell?

Nurse CellNurse Cell

• Juveniles take over cell Juveniles take over cell – Redirect cell activities to their survivalRedirect cell activities to their survival

• Alter gene expressionAlter gene expression– From a contractile fiberFrom a contractile fiber– To a cell that nourishes the wormTo a cell that nourishes the worm

• Cell becomes encapsulated with Cell becomes encapsulated with collagencollagen

• Blood vessels form around the cellBlood vessels form around the cell• Juveniles arrest developmentJuveniles arrest development• Live for months-years and up to 39 Live for months-years and up to 39

yearsyears• Die from calcificationDie from calcification

Which muscles?Which muscles?

• CommonlyCommonly– EyeEye– TongueTongue– MasticatoryMasticatory– DiaphragmDiaphragm– IntercostalsIntercostals– Heavy muscles of arms and legsHeavy muscles of arms and legs

Diagnosis and TreatmentDiagnosis and Treatment

• Most cases go undetectedMost cases go undetected• Difficult to diagnoseDifficult to diagnose• Symptoms are vagueSymptoms are vague• Difficult to find juveniles in tissueDifficult to find juveniles in tissue

– Muscle biopsyMuscle biopsy

– But too lateBut too late

• No treatment to kill parasitesNo treatment to kill parasites– Shielded from drugsShielded from drugs

• Treat symptomsTreat symptoms

EpidemiologyEpidemiology

• CosmopolitanCosmopolitan– Circumboreal (northern areas of North America and Circumboreal (northern areas of North America and

Eurasia)Eurasia)– Less common in tropical areasLess common in tropical areas

• Common in U.S.Common in U.S.– 1940-1950 high prevalence1940-1950 high prevalence– Decreased until 1980Decreased until 1980– Asian immigrants consuming raw porkAsian immigrants consuming raw pork

• Transmission cyclesTransmission cycles– Domestic Domestic – SylvaticSylvatic

Domestic CycleDomestic Cycle

RAT PIGRAT

Cannibalism Scavenging

Eats rats

Raise pigs Create rat habitat Keep infection cycle going

Feed garbage to pigs

Scavenging, Eating human garbage Humans

Eat undercooked

pork

PIG

Nip tails

DEAD END

Sylvatic CycleSylvatic Cycle

Sylvatic CycleSylvatic Cycle

• Humans less commonly involvedHumans less commonly involved

• Hunting and eating wild gameHunting and eating wild game

Control and PreventionControl and Prevention

• Cook meat thoroughlyCook meat thoroughly– PorkPork– Wild gameWild game

• Raw sausage is delicacyRaw sausage is delicacy– Mixture of different animalsMixture of different animals

• Freeze meat Freeze meat – -15 C-15 C

Has trichinosis caused us to modify our Has trichinosis caused us to modify our behavior?behavior?

• Cook pork thoroughlyCook pork thoroughly

• Pork uncommon in fast food restaurantsPork uncommon in fast food restaurants