Lymphatic filariasis

Back to DTMH temporary home

• ヒト体内でadultから生まれたmicrofilariaは吸血で蚊に移行し，蚊の体内で3回moltを繰り返してL3 larvaeに至る．

• L3は1.7mmまで体長を増し，吸血によって蚊の体外に放出され，蚊が生じた穿刺口等から皮内に侵入する

1.7mmもの体長のlarvaeがどうやって体長10mmに満たない蚊の体内で共存できるのか？

• Onchocerciasisのヒト体内の病態生理はmicrofilariaによるが，lymphatic filariasisはadultによる．

• Lymphatic filariasisでリンパ浮腫を生じている患者の下肢をエコーで観察すると，拡張したリンパ管内で蠢くadult filariaを観察できる．

Brugia malayi

Intermediate host
Category	mosquito, female
Latin	Mansonia spp., Aedes spp.
Inward infection	blood-feeding of human
Organ	midgut, thoracic muscle, proboscis
Reproduction
Course	microfilariae lose sheath migrate to thoracic muscle metamorphoses L1→L2→L3 in thoracic muscle L3 migrate to proboscis
Detection
Outward transmission	blood-feeding of human through proboscis

Definitive host
Category	HUMAN
Latin
Inward infection	blood-feeding by mosquito
Organ	lymphatics, blood stream
Reproduction	sexual
Course	L3 invade through cleavage on skin L3 migrate to lymphatics develop to adult female 43-55 mm, male 13-23 mm obstruct lymphatics resulted in elephantiasis and hydrocele in years mate in lymphatics produce sheathed microfilariae (no egg) 177-230 µm nocturnal periodicity microfilariae migrate to blood circulation mechanism unknown
Detection	microscopy, microfilariae, Giemsa stain, blood taken nocturnally concentration technique 2% formalin to blood (Knott's technique) polycarbonate membrane filtration
Outward transmission	blood-feeding by mosquito

Wuchereria bancrofti

Intermediate host
Category	mosquito, female
Latin	Aedes spp., Anopheles spp., Culex spp., Mansonia spp., Coquillettida juxtamansonia
Inward infection	blood-feeding of human
Organ	midgut, thoracic muscle, proboscis
Reproduction
Course	microfilariae lose sheath migrate to thoracic muscle metamorphoses L1→L2→L3 in thoracic muscle L3 migrate to proboscis
Detection
Outward transmission	blood-feeding of human through proboscis

Definitive host
Category	HUMAN
Latin
Inward infection	blood-feeding by mosquito
Organ	skin, lymphatics
Reproduction	sexual
Course	L3 invade through cleavage on skin L3 migrate to lymphatics develop to adult female 80-100 mm, male 40 mm obstruct lymphatics resulted in elephantiasis and hydrocele in years mate in lymphatics produce sheathed microfilariae (no egg) 244-296 µm nocturnal periodicity microfilariae migrate to blood circulation mechanism unknown
Detection	microscopy, microfilariae, Giemsa stain, blood taken nocturnally concentration technique 2% formalin to blood (Knott's technique) polycarbonate membrane filtration blood Ag RDT; rapid immunochromatographic antigen test (ICT card test) urine Ab ELISA; high sensitivity and specificity possible diurnally
Outward transmission	blood-feeding by mosquito

mass drug administration MDA

• Diethylcarbamazepine (DEC) 6mg/kg only once for all inhabitant in endemic area
  • repeated several consecutive years

Ottesen EA, Hooper PJ, Bradley M, Biswas G. The global programme to eliminate lymphatic filariasis: Health impact after 8 years. PLoS Negl Trop Dis. 2008;2(10). doi:10.1371/journal.pntd.0000317

Back to DTMH temporary home