NEMATODA

NEMATODA

NEMATODES

NEMA: thread EIDOS: form

Nematohelminthes are either : round, cylindrical, spindle shaped.Examples: ENTEROBIASIS = OXYURIASIS ( pin worm)ASCARASIS = round wormANCYLOSTOMIASIS = hook wormTRICHINOSISTRICHURIASIS = whip worm

Intestinal Nematodes

Ascaris lumbricoidesGiant intestinal roundwormWhitish or pinkish wormMore than 1 billion individuals are affected70% from AsiaSoil transmitted helminthPolymyarianSomatic muscles are numerous and project well into the body cavity

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 ).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.

Ascaris lumbricoidesMales = 10-31 cmVentrally curved posterior end with 2 spiculesFemales = 2235cmStraight, conical posterior end

Ascaris lumbricoidesTrilobate lips

The lips of Ascaris lumbricoides The three lips are seen at the anterior end. The margin of each lip is lined with minute teeth which are not visible at this magnification.

Ascaris lumbricoidesUnfertilized eggsNarrowerLongerThin shellRefractile granules are not organizedFound in the absence of males

Ascaris lumbricoidesFertilized eggsThick transparent hyaline shellOvoid mass of protoplasm which develops into larvae at about 14 days

Ascaris lumbricoidesEmbryonated eggsInfective stageEmbryonation occurs in the soil

Life Cycle

1. Site of inhabitation: small intestine 2. Infective stage: embryonated eggs 3. Route of infection: by mouth 4. No intermediate and reservoir hosts 5. Life span of the adult: about 1 year 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 approximately 240,000 eggs per day, which are passed in faeces. When passed, the eggs are unsegmented and require outside development of about three weeks until a motile embryo is formed within the egg.

Ascaris lumbricoidesRetrieved fromhttp://parasitol.wkhc.ac.kr/image/nema/lifeal.JPG Feb. 2008

Pathogenesis There are two phase in ascariasis: 1. The blood-lung migration phase of the larvae: During the migration through the lungs, the larvae may cause a pneumonia. The symptoms of the pneumonia are low fever, cough, blood-tinged sputum, asthma. Large numbers of worms may give rise to allergic symptoms. Eosionophilia is generally present. These clinical manifestation is also called Loefflers syndrome.

2. The intestinal phase of the adults. The presence of a few adult worms in the lumen of the small intestine usually produces no symptoms, but may give rise to vague abdominal pains or intermittent colic, especially in children. A heavy worm burden can result in malnutrition. More serious manifestations have been observed.

ComplicationWandering adults may block the appendical lumen or the common bile duct and even perforate the intestinal wall. Thus complications of ascariasis, such as intestinal obstruction, appendicitis, biliary ascariasis, perforation of the intestine, cholecystitis, pancreatitis and peritonitis, etc., may occur, in which biliary ascariasis is the most common complication.

DiagnosisThe symptoms and signs are for reference only. The confirmative diagnosis depends on the recovery and identification of the worm or its egg. A. Ascaris pneumonitis: examination of sputum for Ascaris larvae is sometimes successful. B. Intestinal ascariasis: feces are examined for the ascaris eggs. (1) direct fecal film: it is simple and effective. The eggs are easily found using this way due to a large number of the female oviposition, approximately 240,000 eggs per worm per day. So this method is the first choice. (2) brine-floatation method: (3) recovery of adult worms: when adults or adolescents are found in feces or vomit and tissues and organs from the human infected with ascarids , the diagnosis may be defined.

Ascaris lumbricoidesTreatmentAlbendazoleDrug of choice400 mg single dose 200 mg for children under 2 year oldMebendazole500 mg single dosePyrantel Pamoate10 mg/kg body weight (max. of 1 g)

Prevention1.Sanitary disposal of faeces.2.Hygienic habits such as cleaning of hands before meals.3.Health education.

Ancylostoma duodenale

Ancylostoma duodenale

Slightly larger than Necator americanusHead curves in the same direction as the curvature of the body

Morphology1. Adults: They look like an odd piece thread and are about 1cm. They are white or light pinkish when living. is slightly larger than.The males posterior end is expanded to form a copulatory bursa.2. Eggs: 6040 m in size, oval in shape, shell is thin and colorless. Content is 2-8cells.

Scanning electron micrograph of the mouth capsule of Ancylostoma duodenale, note the presence of four "teeth," two on each side.

Ancylostoma duodenale

Buccal capsule2 pairs of curved ventral teeth

Ancylostoma duodenale

Copulatory bursa of male

Ancylostoma duodenale - copulatory bursa and spines of male(a side view)

The Morphological Differences between Two species of Hookworms_____________________________________________________ A. duodenale N. americanus______________________________________________________ Size larger smaller______________________________________________________ Shape single curve, looks like C double curves, looks like S ______________________________________________________ Mouth 2 pairs of ventral teeth 1peir of ventral cutting plates____________________________________________________________ Copulatory circle in shape oval in shape Bursa (a top view) (a top view)____________________________________________________________ Copulatory 1pair with separate 1pair of which unite to form spicule endings a terminal hooklet_______________________________________________________ caudal spine present no_______________________________________________________ vulva position post-equatorial pre-equatorial _______________________________________________________

Ancylostoma duodenale

Filariform larvainfective stage to humans

Ancylostoma duodenale

OVABluntly rounded endsSingle, thin transparent hyaline shellUnsegmented during oviposition2-8 cell stages in fresh feces

Life Cycle

1. Final host: man 2. Inf. Stage: Larva 3 or filariform larva 3. Inf. Route: by skin 4. Food: blood and tissue fluid 5. Site of inhabitation: small intestine 6. Life span: Ad 15years, Na 3-7years 7. Blood-lung migration: skin, cavum, right heart, lungs

Life cycle of hookworm

Ancylostoma duodenalePathogenesis and Clinical Manifestations

Pathology of hookworm infection involvesThe skin, at the site of entry of filariform larvaMaculopapular lesions ground itch or dew itch(The larvae penetrating the skin cause allergic reaction, petechiae or papule with itching and burning sensation)Itching, edema, erythema leading to papulovesicular eruption lasting for 2 weeks

The lung, during larval migrationBronchitisPneumonitis Loeffier's syndrome: cough, asthma, low fever, biood-tinged sputum or hemoptysis, chest-pain, inflammation shadows in lungs under X-ray. These manifestations go on about 2 weeks.

The small intestine, the habitat of the adult wormAbdominal painSteatorrheaDiarrhea with blood and mucusEosinophilia ( 30% to 60%)

Adults in intestinal mucosa

Necator americanusAncylostoma duodenale

EpidemiologyOver 900 million people infectedAssociated anemia causes 50,000 deaths annuallyAncylostoma duodenaleNecator americanus

Ancylostoma duodenale

Prevention and ControlSanitary disposal of human faecesWearing of footwearHealth educationTreatment of infected individualsMass chemotherapy when prevalence is greater than 50%Protection of susceptible individuals throughImproved diet to prevent malnutrition

Ancylostoma duodenale

DiagnosisDirect fecal smear only for heavy infectionsKato Technique Increases detection rateKato Katz MethodQuantitative diagnosis

Zinc Sulfate CentrifugationFormalin Ether Concentration Harada-Mori Allow hatching of larvae from eggs on strips of filter paper with one end immersed in water

Ancylostoma caninumAncylostoma brazilienseAncylostoma caninumDog hookwormAncylostoma brazilienseCat hookworm

Both cause creeping eruptions

Ancylostoma duodenale

TreatmentAlbendazoleDrug of choiceOvicidal and larvicidal400 mg single dose in adults and children over 2 years oldAvailable in chewable tablets or suspensionNot recommended for pregnant womenMebendazole500 mg single dose in adults and childrenNot recommended for children below 2 years old

Trichuris trichiura

Trichuris trichiura

WhipwormSoil transmitted helminthOften observed occuring together with Ascaris lumbricoides due to similarities in transmission and mode of distribution

Adultos machos Trichuris trichiura

Trichuris trichiuraAnterior three-fifths long and whip-likePosterior two-fifths is thick and fleshyInhabit the large intestineInsert into the intestinal wall of the caecum in a pin-fashion

Male30-45 mmCoiled posterior endSingle spiculeRetractile sheathFemale35-50 mmBluntly rounded posterior endCan produce over 60 million ggs in an average life span of 2 years

Trichuris trichiuramachohembra

Trichuris trichiuraOvaPassed out together with faecesEmbryonation in the soil (2-3 weeks)Protuberant bipolar mucus plugsFootball in shape

Trichuris trichiuraPathogenesis & Clinical ManifestationsTrichuriasisPetechial hemorrhages predisposing to amoebic dysenteryOver 5,000 eggs /g of stool: symptomaticOver 20,000 eggs/g : severe diarrhoea or dysenteric syndrome

Clinical CourseLight infection: Asymptomatic.Middle infection: Clinical manifestations are usually abdominal pain, anorexia, diarrhoea and constipation.Heavy infection: Bloody diarrhoea, emaciation and rectal prolapse may occur (in malnourished children)

Adultos Trichuris trichiuria en mucosa intestinal

Adultos Trichuris trichiuria en mucosa intestinal

Adultos Trichuris trichiuria en mucosa intestinal

Trichuris trichiuraRectal prolapse during heavy infection

Trichuris trichiura

Trichuris trichiuraDiagnosisDirect fecal smearKato Thick smearKato KatzConcentration TechniquesZnSO4 Formalin Ether

Trichuris trichiuraEpidemiologyDistributed in warm. Moist areas of the world20% 30% prevalence in temperate countries60% - 85% in tropical countriesChildren 5 to 15 years of age are frequently infected

Trichuris trichiuraTreatmentMebendazoleDrug of choice500 mg single dose in light infections2 3 days of consecutive treatment for moderate and heavy infectionsContraindicated during early pregnancy and in hypersensitivityAlbendazole400 mg single dose Contraindicated during pregnancy

Oxantel plus pyrantel pamoate: dosage is 10 to 12mg/kg body weight as a single dose. Heavy infections, treatment may be repeated for 2-3 times.Iron: addition in blood stream helps to solve iron deficiency and rectal prolapse.

Prevention and controlTraining adults and children in proper sanitary disposal of faeces and washing of hands is necessary.Treating water sources before use.Avoid living in overcrowded places and using human faeces as fertilizer on farms.

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