Living site Adults in small intestine Diagnostic stage Undeveloped eggs in feces Infective stage Eggs embryonate in soil by 2-3 wks Method of infection Infective eggs are ingested Migration Larvae migrate though the lungs HOSTMAN
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.lumbricoides obstructing the intrahepatic and extrahepatic bile ducts.
Ascarid chronic pancreatitis
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 Hook worms
Ancylostoma duodenale Necator americanus Ancylostoma duodenale 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
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 Note : The large buccal capsule is open dorsally with one pair of cutting plate teeth.
Bursa of hookworms Lift A. duodenale; Right N. americanus
A.dN.a SizeLargerSmaller ShapeCS Buccal capsule 4 hooklets2 plates BursaRound Broader Dorsal ray Tridigitate at the terminus Bidigitate at the base SpiculesSeparatedFused at terminal MucronPresentAbsence
Enterobius vermicularis adult female cm.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.
Egg (indistinguishable between the 2 species) –Median size (like the ascaris egg) –Elliptical –Transparent –Thin shell –4-cell stage when discharge
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
Trichuris vulpis egg
Life Cycle Host -man No intermediate host : Egg Larva (free-living) Larvae migrate from skin to the lungs :Egg takes 6 hours to be infective stage : Similar to Ascaris but no pulmonary migration. There are reservoir hosts.
Parasitic site: : small intestinal : u pper small intestine; Duodenum, jejunum : colon Gravid female adult deposits its eggs on the anus and perianal skin. : ileo-caecal region
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: : fecal direct smear : Brine floatation Larva cultivation Egg counting(to estimate infection intensity) : Collect eggs from perianal region by anal swab on the cellophane tape. Search adult female in the perianal region when the child is sleeping. : Brine floatation
Prevention and Control : 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 Readily endemic in children concentrated units Should put the prevention in first Mebendazole (100mg repeated after 2 weeks) Principles same as for ascaris