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Human Intestinal Nematode Infections.pptx
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- 2. OUTLINE • GENERAL CHARACTERISTICSOF NEMATODES • INFECTIVE STAGE/MODE OF TRANSMISION • LIFE CYCLE OF INTESTINAL NEMATODES • CLINICAL FEATURES • LAB DIAGNOSIS • TREATMENT
- 3. GENERAL CHARACTERISTICS OFNEMATODES • They are unsegmented, elongated and cylindrical. • They have separate sexes with separate appearances. • They have a tough protective covering or cuticle. • They have a complete digestive tract with both oral and anal openings. • Majority of nematodes are free living few are parasites of humans, plants or animals. • The nematodes are generally light cream-white colored. • Their life cycle includes: egg, larvae and adult.
- 4. • Intestinal nematodes •Intestinal nematodes with tissue stage • A. Ascaris lumbricoides • B. Hookworms • C. Strongyloides stercoralis • Intestinal nematodes without tissue stage • A. Enterobius vermicularis • B. Trichuris trichuira.
- 5. INTESTINAL NEMATODES WITHTISSUE STAGE • ASCARIS LUMBRICOIDES • These are common roundworms infecting more than 700 million people worldwide. • Morphology: • Male adult worm measures 15-20 cm in length. The posterior end is curved ventrally. • The female worm measures 20-40 cm in length. Its posterior end is straight. • Infective stage and modes of infection: • The egg containing larva when ingested with contaminated raw vegetables causes ascariasis.
- 6. Life cycle: • Ingestedeggs hatch in the duodenum. • The larvae penetrate the intestinal wall and circulate in the blood. • From the heart they migrate to the lungs, ascend to the trachea, descend to the esophagus and finally reach the small intestine to become adult. • The female pass immature eggs which pass to the soil and mature in 2 weeks
- 7. Clinical features • Adultworms in the intestine cause abdominal pain and may cause intestinal obstruction especially in children. • Larvae in the lungs may cause inflammation of the lungs (Loeffler’s syndrome) – pneumonia-like symptom
- 8. Ova of Ascarislumbricoides Laboratory Diagnosis • Examination of stool for eggs by direct saline smear method. • Demonstration of adult worms in stool Treatment • Mebendazole • Albendazole
- 9. HOOK WORMS • Thereare two species of hookworm: • Ancylostoma duodenale • Necator americanus • The adults are found in the small intestines of man. • Mixed infection is common. • Both of the species are found in Ethiopia, but N. americanus is more common. • Ancylostoma duodenale: • Distribution: This species is found in the northern part of the world including China, Japan, Europe, North Africa and Ethiopia. • Necator americanus • Distribution: This species, so called American hookworm, is found in predominantly the tropics.
- 10. LIFE CYCLE • Infectivestage and methods of infection: • The filariform larva infects by skin penetration. • Adult male and female worms live in the small intestine • The female lays eggs which contain immature embryo • When the eggs pass in the stool to the soil and under favorable conditions of temperature, moisture and oxygen, they hatch into larvae, which molt twice and become infective. • When the filariform larvae penetrate the skin, they circulate in the blood, reach the lungs, ascend to the trachea, descend to esophagus to reach the small intestine and become adults
- 11. • Pathogenecity • Adultworms in the intestine feed on blood causing iron deficiency anemia. • The larvae may cause inflammation of the lungs.
- 12. Ovum of hookworm • Diagnosis: Examination of stool by direct saline/Iodine smear to detect the eggs • Treatment :Mebendazole
- 13. STRONGYLOIDES STERCORALIS • Theworms may be present as parasitic in the host or free living in the soil. • Infection: follows skin penetration by filariform larvae.
- 14. Life cycle • Adultmale and female worms live in the small intestine. • After fertilization, the female penetrates the mucosa of the small intestine and lay eggs in the submucosa. • The eggs hatch and the larvae penetrate the mucosa back to the lumen. • If the environmental conditions are favorable, the larvae will come out with the stool to the soil. They transform into adults, which lay eggs, and hatching larvae get transformed to adults and so on. • If the environmental conditions are not favorable, the larvae in the stool will moult and transform into infective filariform larvae, which pierce the intestine (auto-infection). • Larvae penetrating the skin from the soil or by autoinfection are carried by the blood to the lungs, ascend to the trachea, descend to the esophagus and mature in the small intestine
- 15. • Clinical presentation •The patient complains of mucoid diarrhea. • Larvae in the lungs may cause pneumonia. • Disseminated strongyloidiasis: • Multiplicity of symptoms are present due to the injury of other organs by the migrating larvae. Organs such as liver, heart adrenals, pancreas, kidneys, and CNS, etc. may be affected. This is usually seen in immunocompromized individuals.
- 16. Rhabidiform larva ofStrongyloides stercoralis • Diagnosis - Detection of rhabditiform larvae of strongyloides in stool. • Treatment: Thiabendazole
- 17. INTESTINAL NEMATODES WITHOUTTISSUE STAGE • ENTEROBIUS VERMICULARIS (PIN WORM OR THREAD WORM) • Enterobius vermicularis is a small white worm with thread-like appearance. • The worm causes enterobiasis. Infection is common in children. • Morphology • Male: The male measures 5 cm in length. • Female: The female measures 13 cm in length. The posterior end is straight. • Infective stage • Infection is by ingestion of eggs containing larvae with contaminated raw vegetables. • Mode of infection • By direct infection from a patient (Fecal-oral route). • Autoinfection: the eggs are infective as soon as they are passed by the female worm. If the hands of the patient get contaminated with these eggs, he/she will infect him/herself again and again. • •
- 18. Life cycle • Adultworm lives in the large intestine. • After fertilization, the male dies and the female moves out through the anus to pass its eggs on the peri-anal skin at night. The egg contains larva. • When the eggs are swallowed, they hatch in the small intestine and the larvae migrate to the large intestine to become adult
- 19. Clinical presentation • Themigration of the worms causes allergic reactions around the anus and during night it causes nocturnal itching (pruritus ani) and enuresis. • The worms may obstruct the appendix causing appendicitis.
- 20. Laboratory diagnosis ovum ofEnterobius vermicularis • Peri-anal swab: The peri-anal region is swabbed with a piece of adhesive tape (cellotape) hold over a tongue depressor. • The adhesive tape is placed on a glass slide and examined for eggs. • The swab should be done in the early morning before bathing and defecation. • Eggs in stool: Examination of the stool by direct saline smear to detect the egg: this is positive in about 5% of cases because the eggs are glued to the peri-anal skin. • Treatment:Mebendazole
- 21. TRICHURIS TRICHIURA (WHIPWORM) • Infective stage and mode of infection • Infection is by ingestion of eggs containing larvae with contaminated raw vegetables. • Life cycle: • Ingested eggs hatch in the small intestine and the larvae migrate to the large intestine to become adult. • After mating, the female lays immature eggs, which pass with the stool to the soil and mature in 2 weeks
- 22. • Symptoms • Thepatient complains of dysentery (blood and mucus in stool together with tenesmus). • Rectal prolapse is also possible.
- 23. Laboratory diagnosis ova ofTrichuris trichiura • Finding of characteristic eggs. The egg of trichuris is barrel- shaped, • The shell is thick with a one mucoid plug at each pole. • Treatment: Mebendazole
- 24. Prevention and controlof intestinal nematodal infections •Surveillance and Monitoring •Regular surveys to track prevalence and intensity. •Monitoring drug efficacy and resistance. •Health Education •Community awareness on transmission and prevention. •School-based programs combining deworming + hygiene education. •Personal Hygiene •Handwashing with soap before meals/after defecation. •Washing fruits/vegetables; safe food handling. •Wearing footwear to prevent hookworm infection. •Chemotherapy (Mass Drug Administration – MDA) •Periodic deworming with albendazole or mebendazole. •Target groups: school children, preschool children, women of reproductive age. •Sanitation and Environmental Control •Use of toilets/latrines to prevent soil contamination. •Safe water supply and proper waste disposal.
- 25. Exercise • List thegeneral characteristics of nematodes • What are soil transmitted nematodes, give examples • What are intestinal nematodes, give examples • discuss the soil transmitted nematodes • discuss intestinal nematodal infections • List the neglected tropical nematodal infections • Discuss the infective stages and mode of transmission of intestinal nematodes • Discuss the life cycle of intestinal nematodes • Discuss the laboratory diagnosis of nematodal infections • Discuss the treatment, prevention and control of nematodal infections