1. Pathology & Parasitology Practical Session 4
Class Nematoda

2. General characters
Cylindrical, unsegmented round worms with tapering ends
Separate sex, the female is usually larger than the male
No intermediate host except Wuchereria bancrofti
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:
1- Intestinal nematodes
2- Tissue nematodes (filariae)

3. Examples of Class Nematoda
Intestinal nematodes:
Trichuris trichiura
Ascaris lumbricoides
Enterobius vermicularis
Ancylostoma duodenale
Trichinella spiralis
Tissue nematodes: Lymphatic filariae
Wuchereria bancrofti

4. General life cycle of Intestinal Nematodes
Type A Type B
Infective larva
Ascaris lumbricoides
Trichuris trichiura
Enterobius vermicularis
Ancylostoma duodenale
Trichinella spiralis

5. 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

6. Trichuris trichiura (whip worm)
Adult male: 4 cm long. Posterior end is curved and provided with 2 spicules (magnifier)
Egg: barrel shaped with 2 transparent mucoid plugs (H.P)
Adult female: 5 cm long, larger than male. Posterior end is straight and blunt . (magnifier)

7. 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

8. Ascaris lumbricoides
Anterior ends (Ascaris lips): mouth surrounded with 3 lips and provided by sensory papillae (Magnifier)
Egg: rounded with coarsely mammillated wall (H.P)
Posterior end of male(15-31cm long): curved with 2 spicules (Magnifier)

9. Enterobius vermicularis (pin worm)
Location of adult: 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

10. Enterobius vermicularis (pin worm)
Female (10mm) Posterior end is straight with long pointed tail (4X)
Male (5mm): Posterior end is curved with one spicule
Egg: Planoconvex or D shaped egg (H.P)

11. Ancylostoma 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

12. Hook worms: Ancylostoma duodenale
Anterior end of both male and female showing buccal capsule having 2 pairs of teeth & 2 dentalplates(H.P)
Posterior end of male (8-11mm long) ending with copulatory bursa (L.P)
Posterior end of female (10-13 mm long) showing straight end

13. Ancylostoma duodenale egg (H.P)

14. Trichinella spiralis Location of adult: Small intestine of man
Location of larvae: Encysted in striated muscles
Infective stage: Encysted larvae in striated muscles
Mode of transmission: Ingestion of undercooked pork containing encysted larvae
Diagnosis: Muscle biopsy to identify larvae in striated muscles
Disease: Trichinosis

15. Trichinella spiralis Female (L.P): 3 mm long, posterior end is blunt
Encysted larva in muscle (L.P)

16. Tissue nematodes 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 spp).
Mode of transmission: Bite of mosquito having infective filariform larvae
Diagnosis: Microfilaria in blood film
Disease: Lymphatic filariasis (elephantiasis)

17. Wuchereria bancrofti
Microfilaria: sheathed body, curved, tapering tail, nuclear column are visualized individually (oil immersion lense). Female adult is 8-10 cm long.

18. Arthropods

19. Arthropods Class Insecta: Flea, louse, bed bug, mosquito
Class Arachnida: Hard and soft tick, mites
Class Crustacea: Cyclops
Question form: Medical importance, sex

20. 1- Insecta Flea Medical importance:
Composed of head with antenna, thorax carrying 3 pairs of legs, abdomen formed of 10 segments (magnifier)
Medical importance:
1- Vector for plague
2- Intermediate host for H.diminuta, D. caninum

21. 1- Insecta : Louse Medical importance:
Composed of head with antenna, thorax carrying 3 pairs of legs, abdomen formed of 9 segments (incompletely segmented) carrying respiratory spiracles, bifid end (magnifier)
Medical importance:
Pediculosis (heavy infestation with lice)

22. 1- Insecta Bed bug
Composed of head with antenna, thorax carrying 3 pairs of legs, abdomen formed of 8 segments, rounded end (magnifier)
Medical importance: Insomnia, irritation

23. 1- Insecta :Mouth parts of female Anopheles mosquito
2 hairy antenna
Mouth part (Proboscis) is for piercing and sucking in female (complex and strong)
Medical importance: Transmit malaria & elephantiasis

24. 2-Class Arachnida: Hard tick
Composed of false head without antenna, thorax fused with head (cephalothorax), abdomen is not segmented, 4 pairs of legs ending by claws (magnifier)

25. 2-Class Arachnida : Soft tick
The soft ticks have an oval or pear-shaped outline with the anterior body region broadly rounded. The mouthparts are difficult to see from a dorsal view. The soft ticks have a granulated leathery appearance.

26. Medical importance of Tick:
1- Mechanically: Bite, bleeding
2- Systemically: Tick paralysis

27. 2-Class Arachnida : Mite Sarcoptes scabei
Oval. Thorax fused with head (cephalothorax), abdomen is not segmented
4 pairs of legs ending with suckers or long bristles
Medical importance: Sarcoptes scabei cause scabies

28. 3- Class Crustacea : Cyclops
Male
Female
Composed of cephalothorax carrying 1 median eye, 2 pairs of antennae, abdomen is segmented into 4 or 5 segments, female carry 2 egg pouches, last segment carry legs.
Medical importance:
Intermediate host for: Diphylobothrium latum, Diphylobothrium mansoni & Dracunculus medinensis