CLIPAR lec #2

Nematodes

Roundworms with a pseudocoelom, complete digestive tract, separate sexes, and no circulatory or respiratory system.

Pseudocoelom

Fluid-filled body cavity not completely lined by mesoderm.

Outer Cuticle

Flexible protective exoskeleton that allows movement and growth through molting.

Separate Sexes

Male and female nematodes are distinct individuals.

Male Nematode Cloaca

Common opening for the reproductive and digestive systems in males.

Spicules

Sclerotized copulatory structures used during mating.

Gubernaculum

Sclerotized guiding structure for spicules.

Soil-Transmitted Helminths (STH)

Intestinal nematodes transmitted through contaminated soil.

Ascaris lumbricoides

Largest intestinal nematode infecting humans.

Ascaris lumbricoides Infective Stage

Fully embryonated egg.

Ascaris lumbricoides Diagnostic Stage

Fertilized or unfertilized eggs in stool.

Ascaris lumbricoides Life Cycle

Egg ingestion → intestinal hatching → liver-lung migration → return to small intestine.

Ascaris Lung Migration

Causes allergic manifestations and eosinophilia.

Ascaris Adult Habitat

Small intestine.

Ascaris Fertilized Egg

Mammillated egg containing developing embryo.

Ascaris Unfertilized Egg

Larger, elongated egg lacking embryo.

Ascaris Embryonation Time

2-3 weeks in soil.

Ascaris Diagnosis

Detection of characteristic eggs in fecal samples.

Ascaris Drug of Choice

Albendazole.

Kato Technique

Qualitative thick smear method using 20-60 mg of stool.

Kato-Katz Technique

Quantitative stool examination method.

Direct Fecal Smear

Less sensitive stool examination method.

Trichuris trichiura

Human whipworm.

Trichuris trichiura Morphology

Thin anterior three-fifths and thick posterior end.

Trichuris trichiura Male Length

30-45 mm.

Trichuris trichiura Female Length

35-50 mm.

Trichuris trichiura Male Posterior End

Coiled with single spicule and retractile sheath.

Trichuris trichiura Female Posterior End

Bluntly rounded.

Trichuris trichiura Adult Habitat

Cecum and colon.

Trichuris trichiura Pathogenesis

Anterior end embeds into mucosa causing inflammation and hemorrhage.

Trichuris trichiura Clinical Manifestations

Bloody diarrhea, abdominal pain, tenderness, rectal prolapse.

Trichuris trichiura Light Infection

Usually asymptomatic.

Trichuris trichiura Symptomatic Infection Threshold

More than 5,000 eggs per gram of feces.

Trichuris trichiura Severe Infection Threshold

More than 20,000 eggs per gram of feces.

Trichuris trichiura Egg Shape

Lemon/barrel-shaped with bipolar plugs.

Trichuris trichiura Egg Measurement

50-54 µm × 23 µm.

Trichuris trichiura Egg Color

Yellowish-brown outer shell with transparent inner shell.

Trichuris trichiura Infective Stage

Embryonated egg.

Trichuris trichiura Diagnostic Stage

Characteristic eggs in stool.

Trichuris trichiura Lung Migration

Absent.

Trichuris trichiura Prevention

Proper fecal disposal, health education, mass chemotherapy.

Strongyloides stercoralis

Human threadworm and only naturally pathogenic Strongyloides species in humans.

Strongyloides stercoralis Habitat

Small intestine.

Strongyloides stercoralis Unique Feature

Autoinfection.

Strongyloides stercoralis Infective Stage

Filariform larva.

Strongyloides stercoralis Diagnostic Stage

Rhabditiform larva.

Strongyloides stercoralis Free-Living Forms

Present in soil.

Strongyloides stercoralis Female Length

About 2.2 mm.

Strongyloides stercoralis Buccal Cavity

Short.

Strongyloides stercoralis Esophagus

Long and slender.

Strongyloides stercoralis Autoinfection

Rhabditiform larvae develop into filariform larvae within host.

Strongyloides stercoralis Skin Manifestation

Pruritic hemorrhagic papules and erythema.

Strongyloides stercoralis Moderate Infection

Diarrhea.

Strongyloides stercoralis Heavy Infection

Cochin-China diarrhea.

Cochin-China Diarrhea

Bloody, watery, intermittent diarrhea caused by severe Strongyloides infection.

Strongyloides Hyperinfection Syndrome

Massive larval dissemination in immunocompromised patients.

Strongyloides Diagnosis

Harada-Mori, Baermann funnel, Beale's string test, duodenal aspiration, small bowel biopsy.

Strongyloides Drug of Choice

Albendazole.

Strongyloides Alternative Drug

Thiabendazole.

Strongyloides Prevention

Footwear use, sanitation, treatment of infected persons.

Hookworms

Skin-penetrating nematodes causing chronic blood loss.

Hookworm Species

Ancylostoma duodenale and Necator americanus.

Hookworm Infective Stage

Filariform larva.

Hookworm Diagnostic Stage

Eggs in stool.

Hookworm Adult Habitat

Small intestine.

Hookworm Skin Manifestation

Ground itch or dew itch.

Ground Itch

Maculopapular skin lesions caused by larval penetration.

Hookworm Lung Migration

Causes minute hemorrhages with eosinophilic infiltration.

Hookworm Major Complication

Iron-deficiency anemia.

Hookworm Hypoalbuminemia

Loss of blood, lymph, and protein.

Ancylostoma duodenale

Old World hookworm.

Ancylostoma duodenale Buccal Capsule

Two pairs of ventral teeth.

Necator americanus

New World hookworm.

Necator americanus Buccal Capsule

Pair of semilunar cutting plates.

Necator americanus Female Length

9-11 mm.

Necator americanus Male Length

5-9 mm.

Necator americanus Male Structure

Caudal bursa used for copulation.

Necator americanus Appearance

Grayish-white, cylindrical, fusiform worm.

Hookworm Rhabditiform Larva

Similar to Strongyloides but larger with longer buccal cavity.

Hookworm Diagnosis

Direct smear, Kato/Kato-Katz, ZnSO4 flotation, FECT, Harada-Mori.

Hookworm Treatment

Albendazole or mebendazole.

Skin-Penetrating Nematodes

Hookworms and Strongyloides stercoralis.

Global Burden of Nematode Infections

Approximately 1.2 billion infections worldwide.

Effects of Chronic Nematode Infection

Growth retardation, iron-deficiency anemia, cognitive impairment.

Mass Chemotherapy Indication for Strongyloides

Community prevalence greater than 50%.

Holomyarian Muscle Arrangement

Somatic muscle cells are small, numerous, and closely packed.

Petechial Hemorrhages

Small mucosal hemorrhages caused by embedded Trichuris worms.

Rectal Prolapse

Severe complication of heavy Trichuris trichiura infection.

Health Education

Essential preventive measure against soil-transmitted helminths.

Sanitary Disposal of Human Feces

Primary control measure for nematode infections.