Prepared by : Nada H. Lubbad Phylum Nematoda Prepared by : Nada H. Lubbad

General characteristic: Metazoa. Triploblastic : Pseudocoelomate. Bilaterally symmetrical, thread ,cylindrical (roundworms).the body wall is covered with smooth,non-chitinous cuticle . Free-living nematodes live in the sea, in fresh water, in the soil, on decaying organic matter or parasitic. Roundworms are also characterized by a complete digestive system. It opens by mouth and ends by anus. No vascular or respiratory systems. Sexes are separate, males are smaller than females. Ectoderm Mesoderm Endoderm

Phylum Nematoda Phasmidia Aphasmidia Wuchereria bancrofti Ascaris lumbricoides Trichinella spiralis strongyloides stercoralis Enterobius vermicularis Ancylostoma duodenale

Phasmidia 1. Ascaris lumbricoides : It’s estimated that worldwide as many as 1.4 billion people are infected with Ascaris lumbricoides which lives in the small intestine. Females may be a foot long and produce 200,000 eggs a day. Infection occurs when parasite eggs are eaten with uncooked food or when soiled fingers are put into the mouth. The larvae penetrates the intestinal wall and travel through the blood stream to the lungs where they break out of the alveoli (often causing pneumonia). Then they make their way up the trachea where they are swallowed and eventually settle in the small intestine. In the intestines the worms cause abdominal symptoms and allergic reactions and may produce an intestinal blockage. Pain , vomiting Liver abscess

Ascaris lumbricoides

Ascaris fertilized egg

2. Enterobius vermicularis: Pin worm. Female 8-13mm larger than male 2-5 mm. The infective stage is embryonated egg. It is a group infection especially common among children. Very often associated with low sanitation and hygiene. Mode of infection: by ingestion or autoinfection via nails scratching the perianus. Infection site: Large intestine. After copulation the males die. When the female is ready to lay eggs she crawls out تزحفof the anus and deposits the eggs on the perianal skin. A single female can produce more than 10,000 eggs. After laying her eggs, the female also dies. When ingested by another person the eggs hatch in the small intestine, and the juvenile worms grow into adult, sexually mature worms in about a month.

Enterobius vermicularis adult

Enterobius vermicularis egg

3. Ancylostoma duodenale Hookworms are named for the dorsal curve in their anterior end. Live in small intestine It has a Cephalic gland: it opens in the buccal cavity , their secretion prevents coagulation of the host’s blood. Hookworms are quite small, because they feed on blood a heavy infection can produce severe anemia. Infective stage: Filariform larva. Mode of transmission : Filariform larvae in moist soil penetrate skin through bare feet.

Ancylostoma duodenale egg

4. strongyloides stercoralis: It has a heterogenic life cycle , a parasitic generation interspersed with a free-living one.

5.Wuchereria bancrofti ( Tissue Nematodes ) Elephantiasis, a result of a parasitic infection of filarial nematodes. The nematodes that cause this are microscopic and cause a blockage of the lymphatic system and so fluid retention with tissue and skin thickening. The legs and genitals are particularly affected, the scrotum can swell to the size of a basketball in some unfortunate individuals.

Aphasmidia 6. Trichinella spiralis Trichinella spiralis is a tiny nematode that causes the potentially fatal disease trichinosis. Humans typically become infected by eating undercooked pork. Trichinella lives in cysts formed in individual muscle cells of the host. Larvae of Trichinella, freed from their cysts, typically coiled. Encysted larvae of Trichinella in pressed muscle tissue.