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)

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