Nematode The intestinal nematodes Ascaris Hook worms Pin worm Whip worm The blood- and tissue dwelling nematodes The filaria Trichinella

Ascaris lumbricoides 似蚓蛔线虫

Introduction The first representative and the most common intestinal parasite Cosmopolitan in distribution Rural > urban Children > adults

Morphology Adult Looks like an earthworm Female (20-35 cm); Male (12-30 cm) 3 lips which carry minute teeth

A pair of female and male worms of A. lumbricoides A pair of female and male worms of A. lumbricoides. Notice the vulvar waist(arrow)of the female worm and the coiled end of the male worm.

http://www.dpd.cdc.gov/dpdx/HTML/Search_Choices.htm Ascaris female worm

http://www.biosci.ohio-state.edu/~parasite/ascaris.html A scanning electron micrograph of Ascaris showing the three prominent “lips”

Egg Fertilized egg Unfertilized egg

A. lumbricoides, fertilized egg (6050 micrometer) Egg shell Ovum Albuminous layer A. lumbricoides, fertilized egg (6050 micrometer)

A. lumbricoides, fertilized egg http://www.biosci.ohio-state.edu/~parasite/ascaris.html A. lumbricoides, fertilized egg

A. lumbricoides unfertilized egg http://www.biosci.ohio-state.edu/~parasite/ascaris.html A. lumbricoides unfertilized egg 

The life cycle of A. lumbricoides http://www.dpd.cdc.gov/dpdx/HTML/Search_Choices.htm The life cycle of A. lumbricoides

HOST MAN Living site Adults in small intestine Migration Larvae migrate though the lungs Diagnostic stage Undeveloped eggs in feces Method of infection Infective eggs are ingested Infective stage Eggs embryonate in soil by 2-3 wks

Symptomatology Larva Pneumonitis Asthma attacks Loeffler’s syndrome

Adult The presence of few worms may be asymptomatic (85%) The most common symptoms are vague abdominal pain Large numbers of worms may cause malnutrition and present signs and symptoms of obstruction

Migration of adult worms may cause signs and symptoms of perforation, peritonitis, appendicitis or extrahepatic biliary obstruction.

A.lumbricoides in common bile duct

Cross section of a liver specimen contains many adult worms of A Cross section of a liver specimen contains many adult worms of A.lumbricoides obstructing the intrahepatic and extrahepatic bile ducts.

Ascarid chronic pancreatitis

http://www.biosci.ohio-state.edu/~parasite/ascaris.html A large mass of Ascaris lumbricoides that was passed from the intestinal tract.  The ruler at the bottom of the image is 4 cm (about 1.5 inches) in length.

An autopsy specimen shows intestinal obstruction by many adult worms of A.lumbricoides. Notice the markedly distended intestinal loop, the thin intestinal wall with hemorrhage and worms protruding from the perforated wound.

Peritonitis caused by intestinal perforation due to Ascaris Resected bowel and the adult female from the peritoneal cavity

Diagnosis Microscopic identification eggs in the stool a direct wet mount examination of the specimen (200,000 eggs/female/day) Macroscopic identification of adults passed in stool or through the mouth or nose

Epidemiology Worldwide distribution, throughout the temperate and tropical areas 1,000,000,000 people in the world 40% population in Africa and Asia 600,000,000 in China (1992)

Treatment Albendazole a single oral dose of 400 mg Mebenazole 100 mg orally twice daily for 3 days

Prevention Avoid contacting soil that may be contaminated with human feces Do not defecate outdoors Dispose of diapers properly

Wash hands with soap and water before handling food When traveling to areas where sanitation and hygiene are poor, avoid water or food that may be contaminated Wash, peel or cook all raw vegetables and fruits before eating

Hook worms 钩虫

Ancylostoma duodenale 十二指肠钩口线虫 Necator americanus 美洲板口线虫

Pinworm 蛲虫 Enterobius vermicularis 蠕形住肠线虫

Whip worm 鞭虫 Trichuris trichiura 毛首鞭形线虫

Adult worms of Ancylostoma duodenale http://www.life.sci.qut.edu.au/LIFESCI/darben/figs/nematode/intnema/aduodmf.jpg Adult worms of Ancylostoma duodenale

Adult worms of Necator americanus http://www.life.sci.qut.edu.au/LIFESCI/darben/figs/nematode/intnema/aduodmf.jpg Adult worms of Necator americanus

Morphology Adult Cylindrical with the head bent sharply backwards Males are smaller than the females and possess a bursa at their posterior end

http://wwhttp://www. biosci. ohio-state. edu/~parasite/hookworm_adults http://wwhttp://www.biosci.ohio-state.edu/~parasite/hookworm_adults.html Scanning electron micrograph of the oral opening of Ancylostoma duodenale, another species of human hookworm.  Note the presence of four cutting "teeth," two on each side.

Adult mouthpart of Necator americanus http://www.medicine.cmu.ac.th/dept/parasite/official/nematode/framene.htm Adult mouthpart of Necator americanus Note : The large buccal capsule is open dorsally with one pair of cutting plate teeth.

Lift A. duodenale; Right N. americanus Bursa of hookworms Lift A. duodenale; Right N. americanus

Tridigitate at the terminus A.d N.a Size Larger Smaller Shape “C” “S” Buccal capsule 4 hooklets 2 plates Bursa Round Broader Dorsal ray Tridigitate at the terminus Bidigitate at the base Spicules Separated Fused at terminal Mucron Present Absence

Enterobius vermicularis adult female http://www.medicine.cmu.ac.th/dept/parasite/official/nematode/framene.htm 0.8-1.3 cm.in length , spindle-shaped with a long pointed posterior end. Anterior part has dorsoventral bladder-like expansions of cuticula (cervical alae). Rhabditiform esophagus. The greater part of the body is occupied by the uterus filled with eggs. Enterobius vermicularis adult female 0.8-1.3cm.in length , spindle-shaped with a long thin sharply tail. The greater part of the body is occupied by the uterus filled with eggs.

Trichuris trichiura adults. http://www.biosci.ohio-state.edu/~parasite/trichuris.html Trichuris trichiura adults. 

Egg (indistinguishable between the 2 species) Median size (like the ascaris egg) Elliptical Transparent Thin shell 4-cell stage when discharge

http://www.biosci.ohio-state.edu/~parasite/enterobius.html Enterobius vermicularis egg. Note the thick shell and characteristic shape; approximate length = 55 µm.

Egg < Ascaris egg Non-symmetrical ellipse; D shaped Transparent Thick transparent shell Tadpole-like embryo when discharged

http://www.biosci.ohio-state.edu/~parasite/trichuris.html Trichuris vulpis egg

http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Hookworm_il.htm The third stage larva initiates the infection by penetrating the shin and passing into the blood circulation,. Through the blood it is carried to the right heart and then to pulmonary blood vessels. It soon breaks out of the pulmonary blood vessels into the alveoli. It then crawls up the trachea and is is swallowed with saliva to re-enter the intestinal tract.

Life Cycle Host -man No intermediate host 钩虫: Egg Larva (free-living) Larvae migrate from skin to the lungs 蛲虫:Egg takes 6 hours to be infective stage 鞭虫: Similar to Ascaris but no pulmonary migration . There are reservoir hosts.

Parasitic site: 蛔虫: small intestinal 钩虫: upper small intestine; Duodenum, jejunum 蛲虫: colon Gravid female adult deposits its eggs on the anus and perianal skin. 鞭虫: ileo-caecal region

蛲虫: infective egg ( Egg takes 6 hours to be infective stage) Infection stage 蛔虫: infective egg 钩虫: infective larva 蛲虫: infective egg ( Egg takes 6 hours to be infective stage) infective mode: Anus-Hand-Mouth Auto-infection/Cross-infection 鞭虫: infective egg

Digestive disturbances /Allotriophagy Pathogenic stage: 蛔虫: adult worm /larva 钩虫:adult worm Digestive disturbances /Allotriophagy Microcytic hypochromic anemia (sucking, oozing, discharging) A.d. 0.15-0.4ml/d; N.a. 0.02-0.1ml/d larva:Dermatitis ‘ground itch’ Pneumonitis and Bronchitis

Pathogenic stage: 蛲虫:adult worm 鞭虫:adult worm Anal itching (migration of gravid females) Ectopic infection Digestive disturbances 鞭虫:adult worm Anemia

http://www.biosci.ohio-state.edu/~parasite/trichuris.html Erythema /eri’thi:ma/ 红斑 Trichuris trichiura in the large intestine.  Many worms are present, each with its anterior end embedded in the intestinal mucosa, resulting in the erythema. 

Etiologic dignosis: 蛔虫:fecal direct smear 钩虫:Brine floatation Larva cultivation Egg counting(to estimate infection intensity) 蛲虫: Collect eggs from perianal region by anal swab on the cellophane tape. Search adult female in the perianal region when the child is sleeping. 鞭虫: Brine floatation

Prevention and Control 钩虫:Distribution Cosmopolitan 0.4 billion humans are infected in China Natural factors Soil contamination Night soil as fertilizer Suitable climate dry-land vegetable- raising & mine

Prevention and Control 蛲虫 Readily endemic in children concentrated units Should put the prevention in first Mebendazole (100mg repeated after 2 weeks) 鞭虫 Principles same as for ascaris

Mebendazole 100mg/次 2次/d 连服3天 Drug: Albendazole 400mg/d 阿苯达唑/丙硫咪唑/肠虫清 Mebendazole 100mg/次 2次/d 连服3天 (600mg repeated after 2 weeks)