Nematode The intestinal nematodes –Ascaris –Hook worms –Pin worm –Whip worm The blood- and...
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Transcript of Nematode The intestinal nematodes –Ascaris –Hook worms –Pin worm –Whip worm The blood- and...
NematodeNematode
The intestinal nematodes– Ascaris
– Hook worms
– Pin worm
– Whip worm
The blood- and tissue dwelling nematodes
– The filaria
– Trichinella
Ascaris蛔虫
Ascaris lumbricoidesAscaris lumbricoides似蚓蛔线虫似蚓蛔线虫
IntroductionIntroduction
• The first representative and the most
common intestinal parasite
• Cosmopolitan in distribution
• Rural > urban
• Children > adults
MorphologyMorphology
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. Notice the vulvar waist(arrow)of the female worm and the coiled end of the male worm.
Ascaris female worm
A scanning electron micrograph of Ascaris showing the three prominent “lips”
Egg
• Fertilized egg
• Unfertilized egg
Albuminous layer
Egg shell
Ovum
A. lumbricoides, fertilized egg (6050 micrometer)
A. lumbricoides, fertilized egg
A. lumbricoides unfertilized egg
The life cycle of A. lumbricoides
Living site
Adults in small intestine
Diagnostic stage
Undeveloped eggs in feces
Infective stageEggs embryonate in soil by 2-3 wks
Method of infection
Infective eggs are ingested
Migration
Larvae migrate though the lungs
HOSTHOST
MANMAN
SymptomatologySymptomatology
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.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
DiagnosisDiagnosis
• Microscopic identification eggs in the stoola 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 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)
TreatmentTreatment
• Albendazolea single oral dose of 400 mg
• Mebenazole100 mg orally twice daily for 3 days
PreventionPrevention
• 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 wormsHook worms钩虫钩虫
Ancylostoma duodenaleAncylostoma duodenale十二指肠钩口线虫十二指肠钩口线虫
Necator americanusNecator americanus美洲板口线虫美洲板口线虫
PinwormPinworm蛲虫蛲虫
Enterobius vermicularisEnterobius vermicularis蠕形住肠线虫蠕形住肠线虫
Whip wormWhip worm鞭虫鞭虫
Trichuris trichiuraTrichuris trichiura毛首鞭形线虫毛首鞭形线虫
Adult worms of Ancylostoma duodenale
Adult worms of Necator americanus
MorphologyMorphology
• 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 americanusNote : The large buccal capsule is open dorsally with one pair
of cutting plate teeth.
Bursa of hookworms
Lift A. duodenale; Right N. americanus
A.d N.a
Size Larger Smaller
Shape “C” “S”
Buccal capsule
4 hooklets 2 plates
Bursa Round Broader
Dorsal ray Tridigitate at t
he terminusBidigitate at the b
ase
Spicules Separated Fused at terminal
Mucron Present Absence
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.
• 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 CycleLife 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, jej
unum
蛲虫 : colon
Gravid female adult deposits its eggs on th
e anus and perianal skin.
鞭虫 : ileo-caecal region
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
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 Anal itching (migration of gravid females)
Ectopic infection
Digestive disturbances
鞭虫 :adult worm Digestive disturbances Anemia
Trichuris trichiura in the large intestine. Many worms are present, each with its anterior end embedded in the intestinal mucos
a, 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 ControlPrevention 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 ControlPrevention and Control蛲虫• Readily endemic in children concentrated u
nits
• Should put the prevention in first
• Mebendazole(100mg repeated after 2 weeks)
鞭虫 Principles same as for ascaris
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)