ASCARIASIS 蛔蟲症About 1/4 of the world population is infected

Ascaris lumbricoides 蛔蟲

Infection is world-wide distributioncommon in areas where human feaces

are used as fertilizerChildren are more often and mor heavily

infected than adults

The largest Intestinal NematodeMale:15~31 cm x 2~4 mm Female: 22~35 cm x 3~6 mm

Cylindrical and white to tan with tapered endsThe mouth surrounded by 3 lips

Cuticle has both annulations and striations

FemalesDidephic

Ovaries, oviducts & uteri arein the posterior 2/3

Vulva is located 1/3 from the anterior ens

MalesPosterior end curved

Reproductive tube in the posterior half of the body

Has 2 copulatory spicule

Embryonated egg Eggs in faeces

Unfertilised

Trachea

Ingested

Fertilised

Larva hatchesin intestine

Swallowed

Pharynx

Adults insmall intestine

2-cell stageAdvancedcleavage

Infectivestage (L2)

Diagnosticstages

MAN

EXTERNALENVIRNOMENT

L4

200,000~250,000eggs per day

3~4 wks

Life Cycle of Ascaris lumbricoides

Lungs (L3)

Portal circulation

Pathogensis 致病機轉

Abdominal pain, nausea, diarrhoea and vomitingImpaired absorption (吸收不良)

Malnutrition (營養不良)

Amount of worms infected 感染蟲數Effects of visceral larval migration (VLM) 內臟幼蟲移行Mechanical effects due to adult worms 成蟲機械式傷害Nutritional deficiencies

Larvae migration (幼蟲移行)Mechanical damage (機械式傷害) cause

inflammatory (發炎), bacterial infection (細菌性感染) and hypersensitive reaction 過敏反應

In lung cause Loeffler's syndrome

Coughing, bronchial asthma and pneumonia- like symptoms

Infiltartion of eosinphils, macrophages, and epitheloid cells around the larvae

Allergic reaction consisting of dyspena, a dry or productive cough,transient eosinophilia, wheezing ot coarse rales, fever, and a chest X-ray suggestive of viral pneumonia.

Sputum contain eosinophils, Charcot-Leyden crystal and sometimes larvae

Heavy Infection 重度感染

Pass or vomit of worms 排出或吐出成蟲Intestinal obstruction by worm bolus 腸阻塞Intestinal perforation 腸穿孔Bile duct and pancreatic duct obstruction 阻塞膽管及胰管→ cholangitis 化膿性膽道炎

multiple liver absceses 多發性肝膿腫ascarid chronic pancreatitis 慢性胰臟炎

Can be fatal

Atopic Ascariasis蛔蟲異位感染

Bile ductPancreatic ductLiverPeritoneal cavityKidneyAppendixPleural cavityUpper respiratory tract

Adult in liver

Adult in bile duct

Liver egg granuloma

Fertilized egg 受精卵Unfertilized egg 未受精卵Decorticated egg 去蛋白膜卵

Finding A. lumbricoides eggs in faeces

through the anus or mouth

Identifying A. lumbricoides worms expelled

Laboratory DiagnosisFertilized females lay about 200,000 eggs per day

A. lumbricoides eggs

Embryonated egg 胎蟲卵 (infective)pale yellow or colourlesscontains a larva (R-form, 1st or 2nd stage )

Fertilized egg 受精卵oval or round, 60 x 40 mm, yellowish brown egg shell covered by an uneven albuminous coatcontains a central grandular mass

Unfertilized egg 未受精卵elongated, 90 x 45 mm, darker and more albuminouscontains a central mass of large refractile grandules

Decorticated egg 去蛋白膜卵pale yellow or colourlesssmooth egg shell no albuminous coat

Prevention and Control預防及控制

•Providing and using adequate latrines•Avoding the use of human feaces as fertilizer•Treating infected individuals as part of a control programme especially children

Preventing soil becoming faecally polluted by

•Washing the hands before eating•Avoid the eating of uncooked vegetables, green salads and fruits

Preventing eggs being ingested by

Treatment

Pyrantel pamoatesingle dose, 10 mg/kg, max. 750 mg/adultLevamisolesingle dose, children (5 mg/kg), adult (150 mg)

Mebendazolesingle dose, twice a day, 100 mg/each

Albendazolesingle dose, children from 2~12 yr. (200 mg), adult (400 mg)

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