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)

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

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

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

Enterobius vermicularis Enterobius vermicularis eggs Female Male Enterobius vermicularis egg Enterobius vermicularis eggs

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

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 15-30 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

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

Enterobius vermicularis

Ascaris lumbricoides

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

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

Hookworms

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

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

Common name Whipworm Length of adult worm Female 20-35, male 15-30 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

Trichuris trichiuria

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

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

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

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.

Life cycle of wuchereria bancrofti

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

b. Cutaneous Nematodes Dracunculus medinensis Loa loa Onchocrca volvulus

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: 33-50 cm, male 19-42 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

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

2. Loa loa

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

Dracunculus medinensis