Enterobius vermicularis Department of Medical Parasitology
Enterobius vermicularis Department of Medical Parasitology
Introduction Enterobius vermicularis,commonly known as pinworm or seatworm E.vermicularis is parasitic only to humans Adults inhabit the ileocecus,that is,cecum and adjacent ascending colon and distal ileum. The infection of E.vermicularis may cause Enterobiasis World-wide distribution,it is commonly found in kindergarten and primary school students
Introduction • Enterobius vermicularis, commonly known as pinworm or seatworm • E. vermicularis is parasitic only to humans • Adults inhabit the ileocecus, that is, cecum and adjacent ascending colon and distal ileum. The infection of E. vermicularis may cause Enterobiasis • World-wide distribution, it is commonly found in kindergarten and primary school students
Classification Phylum Nemathelminthes Class Nematoda Order Oxyurata Family Oxyuridae
Phylum Nemathelminthes Class Nematoda Order Oxyurata Family Oxyuridae Classification
Morphology --Adult Female --fusiform body with a long,thin,tapering tail,8 to 13mm Male --"6"shape,curved tail,2 to 5mm.Males die right after mating,thus are rarely seen ·Vhite in color
Morphology -- Adult • Female -- fusiform body with a long, thin, tapering tail, 8 to 13mm • Male -- “6” shape, curved tail, 2 to 5mm. Males die right after mating, thus are rarely seen • White in color
·Cephalic alae The anterior end tapers and is flanked on each side by cuticular extensions of head ·Pharyngeal bulb The esophagus is slender, terminating in a prominent posterior bulb
• Cephalic alae The anterior end tapers and is flanked on each side by cuticular extensions of head • Pharyngeal bulb The esophagus is slender, terminating in a prominent posterior bulb
Morphology --Egg ·Oval in shape,50~60×25 um in average,a larva inside Clear,colorless and doubly refractive egg shell,flattened on one side
Morphology -- Egg • Oval in shape, 50~60×25μm in average, a larva inside • Clear, colorless and doubly refractive egg shell, flattened on one side
Life cycle AE & at night to lay eogs molt molt 3 times Adults---Newly laid- →Infective→Larvae-→Adults eggs 6h eggs
molt molt 3 times Adults Newly laid Infective Larvae Adults eggs 6h eggs Life cycle
Characteristics of life cycle Humans are the only host in nature No intermediate host (direct life cycle) No larval migration between organs
• Humans are the only host in nature • No intermediate host (direct life cycle) • No larval migration between organs Characteristics of life cycle
Infection Stage Infective eggs Type Self-infection: anus-hands-mouth route ·Cross-infection: contact transmission ·Inhalation ·Retroinfection
Infection Stage Infective eggs Type • Self-infection: anus-hands-mouth route • Cross-infection: contact transmission • Inhalation • Retroinfection
Residence Stage Adults Site Cecum and adjacent large and small intestines Mode Adhering to intestinal mucosa Feed Blood,tissue fluid,epithelial cells
Adults Cecum and adjacent large and small intestines Adhering to intestinal mucosa Residence Site Stage Mode Feed Blood, tissue fluid, epithelial cells