1. Nematodes General Features
Have elongated, cylindrical, smooth, unsegmented, flesh-colored bodies.
Body is usually tapered to a pointed posterior end, and to a rounded anterior end
The body is covered by a noncellular, highly resistant coating “the cuticle”
They have complete digestive system with mouth, oesophagus, midgut and anus.
All are separate sexes; the female is usually larger than the male.
They are classified into 2 main categories according to their primary location:
Intestinal nematodes
Tissue nematodes (filariae)

2. Main features of Nematodes
Intestinal Nematodes
Tissue Nematodes
Shape
Large size, Cylindrical
Elongated, Slender (slim)
Habitat
Most adult worms live in the intestinal tract
Inhabit either lymph vessels; or skin and subcutaneous tissues
Diseases
Diseases are diagnosed by identifying their characteristic eggs in stool
Diseases are diagnosed by demonstrating microfilariae in blood, in tissue or tissue fluids

3. Medically important Nematodes. Tissue (Filarial worms)
Intestinal Nematodes
Tissue (Filarial worms)
1. Enterobius vermicularis
I. Lymphatic filariae:
1. Wuchereria bancrofti
2. Burgia malayi
2. Ascaris lumbricoides
3. Hookworms
*Ancylostoma duodenale *Necator americanus
II. Cutaneous filariae:
1. Dracunculus medinensis
2. Loa loa
3. Onchocerca volvulus
4. Trichuris trichiuria
5. Trichinella spiralis

4. I. Intestinal Nematodes
Comparison between 1. Enterobius vermicularis and 2. Ascaris lumbricoides

5. Enterobius vermicularis Enterobius vermicularis eggs
Female
Male
Enterobius vermicularis egg
Enterobius vermicularis eggs

6. Ascaris lumbricoides Female Male
Ascaris unfertilized egg.
Ascaris egg containing a larva, which will be infective if ingested.
Ascaris fertilized egg.

7. Enterobius vermicularis Geographical distribution
Ascaris lumbricoides
Name
Pinworm, seat worm
Ascariasis, round worm
Size
Female 8-13 , male 2-5 mm
Female 20-35, male cm
Disease
Enterobiasis (oxyuriasis)
Ascariasis
Geographical distribution
Worldwide, most common in temperate regions and in crowded places
Worldwide; high prevalence in tropical and subtropical areas with inadequate sanitation, and where human feces are used as fertilizer
Infective stage
Embryonated egg
Mode of infection
Ingestion; or autoinfection via nails scratching the perianus
Ingestion of eggs in food contaminated with human feces
Infection site
Large intestine
Small intestine, lung

8. Enterobius vermicularis Ascaris lumbricoides
Symptoms
Perianal Pruritis, especially at night, appendicitis, abdominal pain,
*invasion of girls’ genital tract cause vaginitis, pelvic or peritoneal granulomas
Migrating worms cause occlusion of biliary tract or oral expulsion in lung it causes inflammation with pulmonary symptoms, e.g. cough, hemoptysis
Identification
Characteristic eggs collected mornings from perianal area using transparent adhesive tape adult worm may be found in perianal area or during vaginal examination
Characteristic eggs in feces, larvae identified in sputum or gastric aspirate adult worm may pass in stool.
Treatment
Pyrantel pamoate
Albendazole, Mebendazole, Pyrantel pamoate

9. Enterobius vermicularis

10. Ascaris lumbricoides

11. 3. Hookworms
Ancylostoma duodenale Old World hookworm Necator americanus New world hookworm

12. Geographical distribution
Worldwide, in areas with warm, moist climate
Ancylostoma duodnale: Middle East, North Africa
Necator americanus: America
Disease
Hookworm infection
Infective stage
Filariform larva
Mode of transmission
Filariform larvae in moist soil penetrate skin through bare feet
Site of infection
Small intestine, heart, lung
Diagnostic stage
Egg in feces; oval, colorless, thin- shelled, segmented
Clinical findings
Iron deficiency: Anemia due to loss of blood at site attachment in intestine
*cardiac problems
*local skin manifestations “ground itch”
*respiratory symptoms during larval pulmonary attack

13. Hookworms

14. oval or ellipsoidal shape
Treatment
Albendazole, Mebendazole, Pyrantel pamoate
Laboratory diagnosis:
Microscopic examination of characteristic egg in stool
Egg of hook worm:
oval or ellipsoidal shape
with thin shell
Hookworm larva

15. Trichuris trichiura adults in gut (preserved post mortem specimen)
4. Trichuris trichiuria
Trichuris trichiura adults in gut (preserved post mortem specimen)
Trichuris trichiura: a macroscopic view of a tangled mass of adults
Trichuris trichiuria egg a typical barrel shape with two polar plugs, that are unstained

16. Common name
Whipworm
Length of adult worm
Female 20-35, male mm
Geographical distribution
Worldwide; high prevalence in tropical and subtropical areas with inadequate sanitation, and where human feces are used as fertilizer as Ascaris
Disease
Trichuriasis, trichocephaliasis
Infective stage
Embryonated egg
Mode of transmission
Ingestion of eggs in food contaminated with human feces
Site of infection
Large intestine (cecum)
Diagnostic stage
Egg in feces; are brown, barrel-shaped with a plug at each pole ; contains a fertilized unsegmented ovum.
Clinical findings
heavy infection, especially in children can cause gastro-intestinal problems (abdominal pain, diarrhea, rectal prolapsed), and possibly growth retardation
Laboratory diagnosis
microscopic examination of characteristic egg in stool adult worm may be identified upon examination of rectal mucosa by proctoscopy
Treatment
Mebendazole; Albendazole as alternative

17. Trichuris trichiuria

18. 5.Trichinella spiralis
Encysted larvae of Trichinella in pressed muscle tissue. 
Larvae of Trichinella, freed from their cysts, typically coiled.

19. Common name
Trichinosis
Length of adult
Male 2.2, female 1.2 mm
Geog. distribution
Worldwide
Disease
Trichinillosis, trichinosis
Infective stage
Encysted larva
Transmission mode
Larvae in undercooked pork. Pigs are main reservoir
Site of infection
Striated muscles
Diagnostic stage
Larvae in muscles and tissues
Clinical findings
Larvae migration in muscular tissues cause facial and periorbital oedema, rash, muscle pain, conjunctivitis
Laboratory diagnosis
Muscle biopsy to identify larvae in striated muscles *indication of eosinophilia
*serologic tests
Treatment
Steroid plus Mebendazole in severe infections *thiabendazole

21. II. Tissue (Filarial) Nematodes
a. Lymphatic
Wuchereria bancrofti
Brugia malayi
b. Cutaneous
Dracunculus medinensis
Loa loa
Onchocrca volvulus

22. Wuchereria bancrofti Brugia malayi Elephantiasis Bancroft's filaria
Geo. Dist.
Worldwide in tropical areas
Limited to Asia (Malaysia)
Disease
Elephantiasis, Wuchereriasis Bancroftian filariasis, lymphatic filariasis
Malayan filariasis,
lymphatic filariasis
Mode of transmn
Mosquito (Anopheles sp. or Culex sp.)
Mosquito (Mansonia sp.,
or Aedes sp.)
Inf. stage
Motile microfilaria
Site of infection
Lymph nodes, lymphatic glands and vessels in legs, arms and genitalia (testes)
Lymph nodes, lymphatic glands and vessels in legs, arms but genitalia is not affected.
Clinical findings
Inflammation of vessels, rupture of lymphs, fibrosis, leading to obstruction. Thickening, hypertrophy of tissues, enlargement of tissues (especially extremities and genitalia)
Inflammation of vessels, rupture of lymphs, fibrosis, leading to obstruction. Thickening, hypertrophy of tissues, enlargement of tissues (especially extremities)
but genitalia enlargement is not seen.

23. Life cycle of wuchereria bancrofti

25. Treatment: Diethylcarbamazine, Surgery in elephantiasis
Diagnosis: Demonstration of microfilaria in blood molecular diagnosis using PCR
Wuchereria bancrofti
Brugia malayi
Treatment: Diethylcarbamazine,
Surgery in elephantiasis

26. b. Cutaneous Nematodes Dracunculus medinensis Loa loa
Onchocrca volvulus

27. Dracunculus medinensis Loa loa Onchocerca volvulus
Guinea fire worm
Eye worm
Blinding worm
Geog. distrib
Africa, Yemen, India, South America
Africa,
Africa, Latin America, and Middle East
Length
Female over 100 cm, male 2 cm
F: 40-70mm, m: 30-34mm
F: cm, male m
Vector
Cyclope
Fly of genus Chrysops (deerfly or mango fly)
Fly of genus Simulium (black fly )
Site of infectio
Spread from intestinal walls to tissues and subcutaneous tissues
Subcutaneous tissues, and muscles
Nodules in subcutaneous tissues
Disease
Dracunculosis, Guinea worm dis.
Loiasis, Calabar swelling
Onchocerciasis, River blindness
Symptoms
Urticaria, skin ulcer (the worm emerges as whitish filament in the center of a painful ulcer), rupture of worm during surgical removal
an anaphylactic reaction
Angioedema, swelling of various parts of body (Calabar swelling), conjunctivitis, irritation, oedema of eyelids, impaired vision
Pruritis, papule dermatitis with thickening, scaling and dryness of skin (lizard skin), fibrous onchocercoma subcutaneous nodules, ocular lesion blindness
Diagnosis
Demonstration in local lesion or fluid discharge of adult worm (head of worm) or rhabditiform larva seen under the skin
Demonstration of microfilaria in blood (since adult worm lives in subcutaneous tissue and microfilaria in blood)
Examination of nodule aspirate, histopathology of skin near nodule; adult lives in subcutaneous tissue, microfilaria in subcutaneous fluid
Treatment
Diethylcarbamazine, thiobenzadole, niridazole, surgery
Diethylcarbamazine for microfilaria and adult, soothing lotion for Calabar swelling
Ivermectin against microfilaria, Suramin (Bayer 205, antropyl) against adult, surgery

28. 1. Dracunculus medinensis
The female guinea worm (Dracunculus medinensis) induces a painful blister
Ruptured blister, the worm emerges as a whitish filament in the center of a painful ulcer which is often secondarily infected.
Rolling of the worm over a rod

29. 2. Loa loa

30. Black flies of the genus Simulium.
3. Onchocerca volvulus
Black flies of the genus Simulium.
Nodules containing Onchocerca volvulus on the head of a man in Guatemala

31. Dracunculus medinensis