Onchocerciasis

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Onchocerca volvulus

Intermediate host
Category	blackfly ブヨ, female
Latin	genus Simulium
Inward infection	blood-feeding of human
Organ	midgut
Reproduction	asexual
Course	microfilariae has no sheath migrate to thoracic muscle metamorphoses L1→L2→L3 in thoracic muscle L3 migrate to proboscis
Detection
Outward transmission	blood-feeding of human

Definitive host
Category	HUMAN
Latin
Inward infection	blood-feeding by female blackfly
Organ	skin, lymphatics, blood, urine
Reproduction	sexual
Course	L3 into adult in subcutaneous subcutaneous nodule female 33-50 cm (not mm), male 2-5 cm live 15 years Wolbachia spp. is endosymbiotic bacteria in female uterus, which is essential to survival of female adult female produce microfilariae 9 years 220-360 µm 2 years mainly skin, connective tissue, sometimes lymphatics, blood, urine, sputum allergy and inflammation resulting in serious skin pruritis (leopard skin, anterior tibia) and keratitis (river blindeness)
Detection	skin snipping no nocturnality, every time in a day available microfilariae has no sheath
Outward transmission	blood-feeding by female blackfly

Hall LR, Pearlman E. Pathogenesis of onchocercal keratitis (river blindness). Clin Microbiol Rev. 1999;12(3):445-453. doi:10.1128/cmr.12.3.445

診断

• Skin snipping による皮膚断片の培養と顕微鏡下観察
  • 高浸淫地では有用だが，低感度なので有病割合が低下すると有用性が劣る
• RDT
  • Onchocerca vulvolsのIgG4抗体および抗原をimmunochromatographで検出

treatment

• for microfilariae
  • ivermectin is effective only for microfilariae
  • only one dose of ivermectin 150 µg/kg (both for children and adults) significantly decrease microfilariae load that lasts a year or more
  • every 6 month repetition
• If use diethylcarbamazepine (DEC) for onchocerciasis it kills microfilariae inside skin and develops severe allergic reaction against dead microfilariae on skin
• for adult
  • doxycycline is effective for Wolbachia resulting in killing of 60% and sterlizing 80-90% of female adult

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