第二讲Nematode线虫
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(2) 3 pharyngeal glands open into the buccal cavity and pharyngeal cavity, secrete acetylcholine esterase and proteinases
Hookworm
1. Morphology
2) Egg: 64-75μm by 34-40μm 1-8 cells or an embryo Shells are thin and hyaline.
♀: the posterior end is cone-shaped
♂: elliptic and fan-shaped (copulatory bursa)
Hookworm
1. Morphology
1) Adults
Characteristics of copulatory spicules
Hookworm
Introduction to Nematodes
1. Morphological characteristics
4) Body wall (3) Musculature Polymyarian (多肌型): roundworm Meromyarian (少肌型): pinworm Holomyarian (细肌型): whipworm
1. Location: small intestine
infective egg through mouth
2. Infective stage: 3. Way of infection: 4. Larva migration: Intestine
circulatory
respiratory
intestine
Ascaris lumbricoides
5. Epidemiology
1) Epidemiological characteristics and epidemic conditions
Source of infection Way of transmission Susceptible population
Ascaris lumbricoides (roundworm)
1. Morphology
1) Adult: (1) The largest nematode in human intestine, ♀, 20-35 cm long, may reach 49 cm; ♂, 15-31 cm.
Ascaris lumbricoides
Hookworm
1. Morphology
1) Adults: small nematode, about 1.0 cm in length Appearance: A. duodenale “C” shaped N. americanus “S” shaped
Hookworm
1. Morphology
1. Morphology
1) Adult
(2) Head: one dorsal and two ventrolateral lips, buccal cavity, fine denticles, papillae and cephalic sensors.
ቤተ መጻሕፍቲ ባይዱ
Ascaris lumbricoides
Ascaris lumbricoides
5. Epidemiology
2) Factors causing extensive distribution of the infection (2) Factors from man a. Poor sanitation b. Vegetable contaminated c. Others
invertebrates (worms) which may crawl by their muscle contraction.
Introduction to Nematodes
1. Morphological characteristics
1) Typical nematodes are elongated, cylindrical, bilaterally symmetrical. 2) Dioecious
6. Prevention and treatment
Ancylostoma duodenale Necator americanus
(hookworm)
Worldwide distribution Intestinal parasites Causing host blood loss (anemia)
Introduction to Nematodes
2. Life cycle:
1) Egg
Egg – larva – adult
Eggshell: (light microscopy) proteinaceous layer, chitinous, embryo membrane. (electron microscopy) vitelline layer (fertilization membrane), chitinous
lipid layer
Introduction to Nematodes
2. Life cycle:
Egg – larva – adult
2) Larva: Fine cylindrical in shape
Molting: Larvae form a new cuticle and shed the old one.
Hookworm
2. Life cycle
(7-8d)
24h
Summary of life cycle
1. 2. 3. 4. Location: small intestine Infective stage: filariform larvae Infection way: through skin Larva migration:
2) Factors causing extensive distribution of the infection (1) Factors from the worm: a.200,000 eggs daily/per female b. Egg resistance c. Life cycle is direct (geonematode)
or wandering)
Ascaris lumbricoides
3. Pathogenesis
(3) Complications
a. Biliary ascariasis b. Intestinal penetration c. Intestinal obstruction
Ascaris lumbricoides
1. Morphology
1) Adult
(3) ♀: The posterior end is straight. ♂: The posterior end curves ventrally, with a pair of copulatory spicules.
Ascaris lumbricoides
4. Diagnosis
1) Etiological examination (病原学检查） Direct fecal smear:
1 smear, 80% positive; 3 smears, 95%.
2) Why can not we detect any egg in a few cases ?
Introduction to Nematodes
1. Morphological characteristics
3) Protocoelom (pseudocoelom)
Introduction to Nematodes
1. Morphological characteristics
4) Body wall (1) Cuticle (角皮): buccal capsule, papillae, copulatory birsa, etc. (2) Hypodermis: cellular or syncytial
skin circulatory respiratory intestine
3. Pathogenesis
1. Pathogenesis of the larvae
(1) Dermatitis (“ground itch”)
due to working in farmland, contacting with the soil Susceptible locations: between fingers and toes
1) Adults Buccal capsule
A. duodenale: 2 pairs of ventral teeth N. americanus: 1 pair of ventral semilunar cutting plates
Hookworm
1. Morphology
1) Adults
1. Morphology
1) Adult Internal structure: Function of glands:
(1) A pair of cephalic glands open into cephalic sensors, secrete anticoagulant and acetylcholine esterase.
3) Pathogenesis of adult worms
(1) Nutrition robbing and mucosa damage (2) Effects of toxin and allergen (3) Complications (due to the habits of worms’ penetrating
(2) Symptoms caused by larva migration
from pulmonary capillaries to alveoli a dry cough, sore throat, severe hemorrhage, etc
3. Pathogenesis
2. Pathogenesis of the adults
Ascaris lumbricoides
3. Pathogenesis
1) About 85% of ascariasis cases are symptomless 2) Pathogenesis of larva migration
Mechanical trauma: Clinical manifestation: cough, fever, etc.
1. Morphology
2) Egg
Fertilized eggs: 45-75μm by 35-50μm Unfertilized eggs: 88-94μm by 39-44μm
Ascaris lumbricoides
2. Life cycle
Ascaris lumbricoides
Summary of the life cycle
4 molts, 4 larval stages
2. Life cycle:
Egg – larva – adult
3) Types of life cycle
(1) No intermediate host (direct) geonematodes (2) Requiring intermediate hosts (indirect), bionematodes
Nemathelminthes – Nematodes (threadworm) Platyhelminthes-flatworms (Cestodes,Trematodes) Acanthocephala- spiny- or thorny-headed worms
are multicellular
Nematode (线虫)
Ⅰ. Ⅱ. Ⅲ. Ⅳ.
Introduction to helminth and nematode Round worm Hook worm Pinworm
Introduction to helminthes
1. Definition: Helminthes 2. Classification
Hookworm
1. Morphology
2) Egg: 64-75μm by 34-40μm 1-8 cells or an embryo Shells are thin and hyaline.
♀: the posterior end is cone-shaped
♂: elliptic and fan-shaped (copulatory bursa)
Hookworm
1. Morphology
1) Adults
Characteristics of copulatory spicules
Hookworm
Introduction to Nematodes
1. Morphological characteristics
4) Body wall (3) Musculature Polymyarian (多肌型): roundworm Meromyarian (少肌型): pinworm Holomyarian (细肌型): whipworm
1. Location: small intestine
infective egg through mouth
2. Infective stage: 3. Way of infection: 4. Larva migration: Intestine
circulatory
respiratory
intestine
Ascaris lumbricoides
5. Epidemiology
1) Epidemiological characteristics and epidemic conditions
Source of infection Way of transmission Susceptible population
Ascaris lumbricoides (roundworm)
1. Morphology
1) Adult: (1) The largest nematode in human intestine, ♀, 20-35 cm long, may reach 49 cm; ♂, 15-31 cm.
Ascaris lumbricoides
Hookworm
1. Morphology
1) Adults: small nematode, about 1.0 cm in length Appearance: A. duodenale “C” shaped N. americanus “S” shaped
Hookworm
1. Morphology
1. Morphology
1) Adult
(2) Head: one dorsal and two ventrolateral lips, buccal cavity, fine denticles, papillae and cephalic sensors.
ቤተ መጻሕፍቲ ባይዱ
Ascaris lumbricoides
Ascaris lumbricoides
5. Epidemiology
2) Factors causing extensive distribution of the infection (2) Factors from man a. Poor sanitation b. Vegetable contaminated c. Others
invertebrates (worms) which may crawl by their muscle contraction.
Introduction to Nematodes
1. Morphological characteristics
1) Typical nematodes are elongated, cylindrical, bilaterally symmetrical. 2) Dioecious
6. Prevention and treatment
Ancylostoma duodenale Necator americanus
(hookworm)
Worldwide distribution Intestinal parasites Causing host blood loss (anemia)
Introduction to Nematodes
2. Life cycle:
1) Egg
Egg – larva – adult
Eggshell: (light microscopy) proteinaceous layer, chitinous, embryo membrane. (electron microscopy) vitelline layer (fertilization membrane), chitinous
lipid layer
Introduction to Nematodes
2. Life cycle:
Egg – larva – adult
2) Larva: Fine cylindrical in shape
Molting: Larvae form a new cuticle and shed the old one.
Hookworm
2. Life cycle
(7-8d)
24h
Summary of life cycle
1. 2. 3. 4. Location: small intestine Infective stage: filariform larvae Infection way: through skin Larva migration:
2) Factors causing extensive distribution of the infection (1) Factors from the worm: a.200,000 eggs daily/per female b. Egg resistance c. Life cycle is direct (geonematode)
or wandering)
Ascaris lumbricoides
3. Pathogenesis
(3) Complications
a. Biliary ascariasis b. Intestinal penetration c. Intestinal obstruction
Ascaris lumbricoides
1. Morphology
1) Adult
(3) ♀: The posterior end is straight. ♂: The posterior end curves ventrally, with a pair of copulatory spicules.
Ascaris lumbricoides
4. Diagnosis
1) Etiological examination (病原学检查） Direct fecal smear:
1 smear, 80% positive; 3 smears, 95%.
2) Why can not we detect any egg in a few cases ?
Introduction to Nematodes
1. Morphological characteristics
3) Protocoelom (pseudocoelom)
Introduction to Nematodes
1. Morphological characteristics
4) Body wall (1) Cuticle (角皮): buccal capsule, papillae, copulatory birsa, etc. (2) Hypodermis: cellular or syncytial
skin circulatory respiratory intestine
3. Pathogenesis
1. Pathogenesis of the larvae
(1) Dermatitis (“ground itch”)
due to working in farmland, contacting with the soil Susceptible locations: between fingers and toes
1) Adults Buccal capsule
A. duodenale: 2 pairs of ventral teeth N. americanus: 1 pair of ventral semilunar cutting plates
Hookworm
1. Morphology
1) Adults
1. Morphology
1) Adult Internal structure: Function of glands:
(1) A pair of cephalic glands open into cephalic sensors, secrete anticoagulant and acetylcholine esterase.
3) Pathogenesis of adult worms
(1) Nutrition robbing and mucosa damage (2) Effects of toxin and allergen (3) Complications (due to the habits of worms’ penetrating
(2) Symptoms caused by larva migration
from pulmonary capillaries to alveoli a dry cough, sore throat, severe hemorrhage, etc
3. Pathogenesis
2. Pathogenesis of the adults
Ascaris lumbricoides
3. Pathogenesis
1) About 85% of ascariasis cases are symptomless 2) Pathogenesis of larva migration
Mechanical trauma: Clinical manifestation: cough, fever, etc.
1. Morphology
2) Egg
Fertilized eggs: 45-75μm by 35-50μm Unfertilized eggs: 88-94μm by 39-44μm
Ascaris lumbricoides
2. Life cycle
Ascaris lumbricoides
Summary of the life cycle
4 molts, 4 larval stages
2. Life cycle:
Egg – larva – adult
3) Types of life cycle
(1) No intermediate host (direct) geonematodes (2) Requiring intermediate hosts (indirect), bionematodes
Nemathelminthes – Nematodes (threadworm) Platyhelminthes-flatworms (Cestodes,Trematodes) Acanthocephala- spiny- or thorny-headed worms
are multicellular
Nematode (线虫)
Ⅰ. Ⅱ. Ⅲ. Ⅳ.
Introduction to helminth and nematode Round worm Hook worm Pinworm
Introduction to helminthes
1. Definition: Helminthes 2. Classification