Class Nematoda

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) Egg: barrel shaped with 2 transparent mucoid plugs (H.P) 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)

Trichuris trichiura 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

Ascaris lumbricoides Anterior ends (ascaris lips): mouth surrounded with 3 lips and provided by sensory papillae (Magnifier) Egg :rounded with coarsly mamillated wall Posterior end of male: curved with 2 spicules (Magnifier)

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) Female (10mm) Posterior end is straight with,long pointed tail Egg: Planoconvex or D shaped egg Male (5mm): Posterior end is curved with one spicule

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