Nematoda PDF

Phylum Nematoda ▪ Nematodes (from Greek nema a thread) are long, thin often threadlike “worms.” ▪ The head is small and possesses only small sense organs and the overall appearance is of an organism that narrows at both ends.  1 mm long nematode htt...

Phylum Nematoda ▪ Nematodes (from Greek nema a thread) are long, thin often threadlike “worms.” ▪ The head is small and possesses only small sense organs and the overall appearance is of an organism that narrows at both ends.  1 mm long nematode http://www.ucmp.berkeley.edu/phyla/ecdys ozoa/nematoda.html Phylum Nematoda ▪ The nematodes are quite species diverse (about 15,000 species. ▪ Most nematodes are under 5cm and many are microscopic. Phylum Nematoda ▪ Nematodes use their pseudocoelom as a hydrostatic skeleton. Fliud filled cavity ▪ The body has a thick cuticle (made primarily of collagen) secreted by the underlying epidermis, which resists the high hydrostatic pressure exerted by the fluid in the pseudocoelom. Phylum Nematoda Beneath the epidermis is a layer of longitudinal muscles. Muscles in nematodes are not arranged in antagonistic pairs, the antagonistic role is played by the cuticle. Contraction of a longitudinal muscle on one side is transmitted through the hydrostatic skeleton and stretches the cuticle on the opposite side of the body. When the muscle relaxes, the cuticle contracts and the body returns to its resting position. Phylum Nematoda ▪ Nematodes have a complete gut with a mouth, muscular pharynx, intestine, rectum, and anus. ▪ Most nematodes males are smaller than females. Mail have tail. ▪ Fertilization is internal and juveniles go through several developmental stages, each time molting or shedding their cuticle. Free-living nematodes ▪ Free-living nematodes live in the sea, in fresh water, and in the soil. They occur worldwide in all environments and most live in the interstitial spaces of sediments and soils. Free-living nematode http://kentsimmons.uwinnipeg.ca/16cm05/16labman5bl/05pgmth.8 Figure 15.05a Male (top) and female Ascaris lumbricoides Free-living nematodes ▪ Most free-living nematodes are carnivorous. However, some feed on algae and fungi ,plants, especially the roots. Free-living nematodes ▪ Many root feeding nematodes are major agricultural pests. These species pierce root cells and suck out their contents. ▪ Nematodes are estimated to destroy 12% of the world’s cash crops annually. Parasitic nematodes ▪ There are a great many species of parasitic nematodes and they attack virtually all groups of animals and plants. ▪ Parasitic forms include ascarids, hookworms, Guinea worms, trichina worms, pinworms, and filarial worms. Ascaris lumbricoides: large roundworm of humans ▪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 200,00 eggs a day. ▪Infection occurs when parasite eggs are eaten with uncooked food or when soiled fingers are put into the mouth. Ascaris lumbricoides: large roundworm of humans ▪The ingestion of worm eggs via food and water contaminated with human feces.these eggs hatch in small 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. Ascaris lumbricoides: large roundworm of humans ▪In the intestines the worms cause abdominal symptoms and allergic reactions and may produce an intestinal blockage.  ascaris ▪ Disease: ASCARASIS ▪ Pathogensis and clinical findings: ▪ Larval migration is most lethal than presence of worm in intestine. ▪ Mostly affect lungs. ▪ Inflammation with an eosinophilic exduate. ▪ Usually children. ▪ Infection are asymptomatic. ▪ Ascaris pneumonia (fever,cough,abdominal pain and even intestinal obstruction.  ascaris ▪ Epideminlogy common disease in tropics. ▪ Laboratory diagonsis egg in stool oval irregular surface. ▪ Treatment mebendazole and pyrantel pamoate ▪ Prevention proper disposal of feces life cycle of ASCARIS  Hookworms Nector and Ancylostoma duodenale Hookworms are named for the dorsal curve in their anterior end. ▪ Hookworms are quite small, the commonest species Necator americanus is only 11mm long. However, because they feed on blood a heavy infection can produce severe anemia. http://www.virginmedia.com/images/hookworm.jpg  Hookworms ▪ Large plates in the hookworm’s mouth are used to cut the intestinal lining of the host. ▪ The parasite then pumps blood through its gut, partially digesting it before excreting it. ▪ Because hookworms suck more blood than they use, they can cause debilitating anemia. In children a hookworm infection can stunt growth and cause a general lack of energy. Figure 15.06 Section through hookworm attached to dog intestine  Hookworms ▪ Hookworms do not permanently attach in one spot, but move around the gut and reattach when they are ready to feed. ▪ Hookworms have evolved sophisticated anti- clotting factors that keep platelets from clumping and forming a clot while the hookworm is feeding.  Hookworms ▪ The life cycle of hookworms is similar to that of ascarids. ▪ Infection occurs after a larva hatches from an egg and penetrates the skin of a person. It then makes its way to the lungs where eventually it is coughed up and swallowed and travels to the intestines.  Hookworms ▪ Pathogensis and clinical finding excess loss of blood from intestine. ▪ 0.1to 0.3 mL/day ▪ Weakness and pallor may leads to microcystic anemia due to blood loss. ▪ Ground itch vesicles at site of entry of larva ▪ Pneumonia and eosinophilia at larval migration. Hook worm ▪ Epidemiology tropical area. ▪ Prediposing factor Walking barefooted on soil ▪ Labortory diagonsis ▪ Eggs in stool ,ocult blood in stool ,eosinophil. ▪ Treatment mebendazole and pyrantel pamoate ▪ Prevention sewage properly and wear shoes Hookworm life cycle  ENTEROBIUS VERMICULARIS Pin worm ▪Disease pinworm infection: enterobiasis ▪Pathogensis and clinical finding: effected site perianal pruritus. ▪Epidemiology: common in tropical area. ▪chidren younger than 12 years. ▪ Labortory diagonsis ▪ Eggs recovered from peroanal skin by using scotch tape techniques. ▪ There eggs are not found in stool. ▪ Small white adult found in the stoolnear anus of diapered children. ▪ Treatment mebendazole or pyrantel pamoate. ▪ Prevention no mean ▪ Infection in human no animal involve. ▪ Infection by ingestion the worm eggs in small intestine then change to larvae in colon. ▪ Male female meet at colon. ▪ In night female migrates from anus and reseales thousands of fertilized eggs on the perianal skin. Guinea worms ▪ Guinea worm infections (also referred to as Dracunculiasis) are now confined to sub- Saharan Africa. ▪ Humans become infected when they drink water containing the crustaceans. ▪ Guinea worms life cycle Larvae are consumed by copepod in water and undergoes two molts inside it. Guinea worms ▪ Human drinks unfiltered water containing copepods with larvae where they released when copepods die. ▪ The immature worm penetrates the gut wall and wanders through the body, maturing and growing. ▪ After mating, the male worms die and the females move through tissues under the skin usually legs. Guinea worms ▪ After about a year the female makes her way to the surface of the skin (usually in the legs) causing very painful blistering. ▪ To ease the pain, sufferers immerse their feet in water. This bursts the blisters and the female worm then protrudes from the sore and lays her eggs, thus continuing the life cycle.  Guinea worms ▪ There is no cure for Guinea worms and the only way to remove one is to slowly over the course of weeks wind the worm out on a stick. ▪ If the worm breaks, a serious bacterial infection results. Interestingly, the traditional symbols for medicine and healing the staff of Asclepias (showing a snake entwined around a staff) and the caduceus (which shows two snakes entwined about a winged staff) very likely are derived from the Guinea worm removal technique. Guinea worms ▪ Guinea worm infection is avoidable with relatively simple precautions such as preventing people walking in drinking water sources and boiling or filtering water before drinking it. Guinea worms ▪ Since the mid ’1980s a campaign to eradicate Guinea worms coordinated by the U.N. and the Carter Center has had tremendous success. ▪ In1986million people were infected, but by 2000 the number of cases had been reduced to about 75,000 and by 2006 to.11,000 Guinea worms ▪ Guinea worms have been eliminated from Pakistan, India, and Iran and infections greatly reduced over much of sub-Saharan Africa. ▪ The major barrier to elimination at this point is the ongoing conflict in southern Sudan where the majority of cases now occur.  Trichina worms http://en.wikipedia.org/wiki/File:Trichinella_larvGPJ.xDPD_1 ▪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. Trichina worms ▪ Trichinella when it hatches from an ingested cyst in its host’s gut drills through the wall of the gut where females produce living young. ▪ These juveniles travels in the circulatory system to a muscle. ▪ The juvenile penetrates an individual muscle cell and breaks the cell down so it can be remade. Trichina worms ▪ Trichinella, just as a virus does, manipulates the host cell’s DNA. It causes the cell to recruit a blood supply to supply food to the cell and also produce collagen to form a cyst around the cell. ▪ The Trichinella juvenile awaits ingestion by another host. When ingested it emerges from its cysts enters the mucosal lining of gut, develops into an adult and continues the life cycle.  Trichinella life cycle in humans www.trichinella.org/bio_lifecycle.htm Trichina worms ▪ Adults usually do not persist long in the gut before being expelled by the host’s immune system. ▪ Trichinella occurs commonly in wild animals such as foxes, wolves and bears. Smaller mammals such as skunks, raccoons and rats, which commonly associate with people, are the main sources of domestic pig infections. http://www.foodsafetyindia.nic.in/images/Trichinella_LifeCycle.gif Trichina worms ▪ Pigs may become infected by eating the bodies of animals infected with the parasite. Humans are an inadvertent host of Trichinella. ▪ In humans, infection with a few Trichinella parasites may cause no symptoms, but heavy infections can cause intense muscle pain and in some cases death.