Ascaris communcicable disaeas

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NEMATODES

Ascaris Lumbricoides


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NEMATODES (Round Worms) Ascaris lumbricoides(roundworm), Trichinella spiralis(trichinosis), Trichuris trichiura

(whipworm), Enterobius vermicularis(pinworm), Strongyloides stercoralis(Cochin-china

diarrhea),

Ancylostoma duodenaleand Necatoramericanes(hookworms)


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Nematodes or roundworms are among the

most abundant animals on earth - over

500,000 species have been described.

Majority of nematodes are free-living in

every conceivable habitat.


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Characteristics of the PhylumNematoda


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Characteristics of the Phylum Nematoda

Reproductive system

consists of tubular organslying in the pseudocoelom.

MALE nematodes are

generally smaller in size.


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Characteristics of the PhylumNematoda

FEMALE nematodes arelarger in size. The femalereproductive organs aredoubled.


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Characteristics of the Phylum NematodaNematode development is similar in all nematodes.

Consists of 4 larval (=juvenile) stages between the egg andadult. Each stage is separated by a molt of the cuticle.

M1 M2 M3 M4

Egg L1 L2 L3 L4 Adult

Larval stages may be passed within the egg, free-living in soil,parasitic in an intermediate host, or parasitic in definitive

host.


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Ascaris Lumbricoides

o Ascaris lumbricoides , common sayinground worm of man, is the largest of theintestinal nematodes parasitizing humans.

o It is the most common worm found in

human.o It is worldwide in distribution and most

prevalent through out the tropics, sub-

tropics and more prevalent in thecountryside than in the city.


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Ascaris lumbricoides.The incidence is over 1500 millioninfections annually. Of these cases, about210 million are symptomatic. In some

rural settings with poor sanitation,perhaps half the children of 2-12 yearshave ascariasis.Then many of them willalso have trichuriasis and various of other

chronic illnesses.


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I. Morphology

Adult: The adults are cylindrical in shape,creamy-white or pinkish in color. The female averages 20-35cm in length, the

largest 49cm.

The male is smaller, averaging 15-31cm inlength and distinctly more slender than thefemale.

The typical curled tail with a pair sickle like

copulatory spines. On the tip of the headthere are three lips, arranged as a Chineseword .


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They have a complete digestive tract.

Reproductive organs are tubular. male

has a single reproductive tubule. The

female has two reproductive tubules and

the vulva is ventrally located at the

posterior part of the anterior 1/3 of

the body.


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Adult worm of A. lumbricoides


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Ascaris lumbricoides

Female

Male


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Ascaris lumbricoidescont.

Female

vagina

genital pore

uterus

gut

oviduct


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Ascaris lumbricoidescont.

seminal vesiclesperm duct

testes

gut

Male


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Lumbricus

A Worms Death


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Lumbricuscont.

clitellum


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Lumbricuscont.

spermathecae

gizzard

seminal vesicle

crop

septa


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Lumbricuscont.

nephridium

ventral nerve cord

Intestine with chlorogogue cells

septum


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The lips of Ascaris

lumbricoides The three lipsare seen at the

anterior end.The margin ofeach lip is linedwith minute

teeth which arenot visible atthismagnification.


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Egg: There are three kinds of the eggs.They are fertilized eggs, unfertilizedeggs and decorticated eggs. We usually

describe an egg in 5 aspects: size, color,shape, shell and content.


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1. Fertilized eggs: broad oval in shape,

brown in color, an average size 6045m. The shell is thicker and consists ofascaroside, chitinous layer, fertilizing

membrane and mammillated albuminouscoat stained brown by bile. The content isa fertilized ovum. There is a new-moon(crescent) shaped clear space at the

each end inside the shell.


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FertilizedAscaris

Egg

A fertilized Ascaris

egg, still at theunicellular stage, asthey are whenpassed in stool.


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2.Unfertilized egg: Longer and slender than

a fertilized egg. The chitinous layer andalbuminous coat are thinner than those ofthe fertilized eggs without ascarosideand fertilizing membrane. The content is

made of many refractable granulesvarious in size.


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3. Decorticated eggs: Bothfertilized and unfertilized eggssometimes may lack their outer

albuminous coats and arecolorless.
http://www.cdfound.to.it/hTML/asc4.htm


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II Life Cycle

1. Site of inhabitation: small intestine

2. Infective stage: embryonated eggs

3. Route of infection: by mouth

4. No intermediate and reservoir hosts5. Life span of the adult: about 1 year


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This worm lives in the lumen of small

intestine, feeding on the intestinal contents,where the fertilized female lays eggs.

An adult female can produce approximately240,000 eggs per day, which are passed infeces.

When passed, the eggs are unsegmentedand require outside development of about

three weeks until a motile embryo is formedwithin the egg.


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After the ingestion of embryonated eggs incontaminated food or drink or from

contaminated fingers, host digestive juicesacts on the egg shell and liberate the larvainto the small intestine.

These larvae penetrate the intestinal

mucosa and enter lymphatics andmesenteric vessels. They are carried by circulation to the liver,

right heart and finally to the lungs where

they penetrate the capillaries into thealveoli in which they molt twice and stayfor 10-14days and then they are carried,


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or migrate, up the bronchioles, bronchi, and

trachea to the epiglottis.When swallowed, the larvae pass down into

the small intestine where they develop intoadults.

The time from the ingestion of embryonatedeggs to oviposition by the females is about60-75 days.

The adult worms live for about one year. Theascarid life cycle is as the following diagram.


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Ascaris lumbricoidesworms have a reputationfor wandering, and often do so if the bodythey are in-the host-is ill or taking certainmedications.

Adult roundworms sometimes spontaneouslyexit the host through the anus, mouth, ornose.

They are found in the bathtub, toilet bowl, indiapers, or even on the pillow upon waking.


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III. Pathogenesis

There are two phase in ascariasis: 1. The blood-lung migration phase of thelarvae: During the migration through the lungs,the larvae may cause a pneumonia. Thesymptoms of the pneumonia are low fever,cough, blood-tinged sputum, asthma. Largenumbers of worms may give rise to allergic

symptoms. Eosionophilia is generally present.These clinical manifestation is also calledLoefflers syndrome.


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2. The intestinal phase of the adults. Thepresence of a few adult worms in the lumen

of the small intestine usually produces nosymptoms, but may give rise to vagueabdominal pains or intermittent colic,especially in children. A heavy worm burden

can result in malnutrition. More seriousmanifestations have been observed.Wandering adults may block the appendicallumen or the common bile duct and evenperforate the intestinal wall.


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Thus complications of ascariasis, such asintestinal obstruction, appendicitis, biliaryascariasis, perforation of the intestine,

cholecystitis, pancreatitis and peritonitis,etc., may occur, in which biliary ascariasisis the most common complication.


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Iii. Diagnosis The symptoms and signs are for reference only.

The confirmative diagnosis depends on therecovery and identification of the worm or its egg.1. Ascaris pneumonitis: examination of sputum for

Ascaris larvae is sometimes successful.2. Intestinal ascariasis: feces are examined for

the ascaris eggs.(1) direct fecal film: it is simple and

effective. The eggs are easily found using thisway due to a large number of the femaleoviposition, approximately 240,000 eggs per wormper day. So this method is the first choice.


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(2) brine-floatation method:

(3) recovery of adult worms: whenadults or adolescents are found infeces or vomit and tissues and organsfrom the human infected withascarids , the diagnosis may be

defined.


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Ascaris

W


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AscarisWorms in Intestine


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V. Epidemiology World wide distribution, very common in China,

especially in the countryside.

Factors favoring the spread of the

transmission:1. Simple life cycle.

2. Enormous egg production ( 240,000 eggs/ day/

female ).


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3. These eggs are highly resistant to

ordinary disinfectants( due to the

ascroside). The eggs may remain viable for

several years.

4. Social customs and living habits.

5. Disposal of feces is unsuitable.


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VI. Prevention and Treatment

1.Treatment to ascariasis:Mebendazole,

Albendazole and Levamizole are effective.

2.Sanitary disposal of feces.

3.Hygienic habits such as cleaning of hands

before meals.

4.Health education.


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Ascaris communcicable disaeas

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