class nematoda. general characters cylindrical round worms with tapering ends separate sex, the...
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General characters• Cylindrical round worms with tapering ends• Separate sex, the female is usually larger than
the male• No intermediate host• Infective stage: embryonated egg• Body is usually tapered to a pointed posterior
end, and to a rounded anterior end• They are classified into 2 main categories
according to their primary location in the body: Intestinal nematodes Tissue nematodes (filariae)
Examples of Class Nematoda
• Intestinal nematodes:
Trichuris trichiura
Ascaris lumbricoides
Enterobius vermicularis
Anclystoma duodenale
Trichinella spiralis
• Tissue nematodes: Lymphatic filariae
Wuchereria bancrofti
Trichuris trichiura (whip worm)
Adult male 4 cm long. Posterior end is curved and provided with 1 spicule (magnifier)
Adult female 5 cm long, larger than male. Posterior end is straight and blunt . (magnifier)
Egg: barrel shaped with 2 transparent mucoid plugs (H.P)
• Location of adult: large intestine of man
• Infective stage : embryonated egg
• Mode of transmission: ingestion of food contaminated with embryonated eggs
• Diagnosis: eggs in stool
• Disease: Trichuriasis
Trichuris trichiura
Ascaris lumbricoides
Anterior ends (ascaris lips): mouth surrounded with 3 lips and provided by sensory papillae (Magnifier)
Posterior end of male: curved with 2 spicules (Magnifier)
Egg :rounded with coarsly mamillated wall
Ascaris lumbricoides• Location of adult: Small intestine of
man
• Infective stage: embryonated egg
• Mode of transmission: ingestion of food (green vegetables) contaminated with embryonated egg
• Diagnosis: eggs in stool
• Disease: Ascariasis
Enterobius vermicularis (pin worm, oxyuris)
Male (5mm): Posterior end is curved with one spicule
Female (10mm) Posterior end is straight with,long pointed tail Egg:
Planoconvex or D shaped egg
Enterobius vermicularis (pin worm, oxyuris)
• Location: large intestine of man• Infective stage: embryonated egg• Mode of transmission: ingestion of food
contaminated with embryonated egg or autoinfection via nails scratching the perianal region
• Diagnosis: eggs in anal or perianal swab collected using transparent adhesive tape. rarely in stool
• Disease: Enterobiasis
Hook worms: Anclystoma duodenale
Posterior end of male ending with copulatory bursa which is supported with rays
Anterior end showing buccal capsule having 2 pairs of teeth, 2 dental plates
Anclystoma duodenale
• Location of adult: small intestine of man
• Infective stage: filariform larvae
• Mode of transmission: penetration of filariform larvae in skin through bare feet
• Diagnosis: eggs in stool
• Disease: Hook worm infection
Trichinella spiralis
Female: 3 mm long, posterior end blunt, vulva (genital organ) opens at the junction of the anterior fifth with the rest of the body
Encysted larva in muscle
Trichinella spiralis
• Location of adult: small intestine of man• Location of larvae: encysted in striated muscles• Infective stage: encysted larvae in striated
muscle • Mode of transmission: ingestion of undercooked
pork containing encysted larvae• Diagnosis: muscle biopsy to identify larvae in
striated muscles• Disease: Trichinosis
Wuchereria bancrofti
Microfilaria: sheathed body, curved, tapering tail, nuclear column are visualized individually and do not extend to the tip of tail
Wuchereria bancrofti
• Location of adult: lymphatics and lymph nodes• Infective stage: infective filariform larvae in the
mouth parts of mosquito• Vector (intermediate host):
mosquito ( Anopheles or Culex sp). • Mode of transmission: bite of mosquito having
infective filariform larvae • Diagnosis: Microfilaria in blood film• Disease: lymphatic filariasis