filariasis

filariasis

1. phylum nematode

2. ovoviviparous

   • egg>L1>L2>L3>L4>adult
     • this takes four months with developmental arrests at L1 and L3

3. nine species of filarial nematodes use humans as definitive host

   • the definitive dost is the one in which the sexually reproducing adult develops
   • they are transmitted by blood feeding insects: vectors
   • there are three groups according to the niche they occupy
     • lymphatic filariasis
       • emphatic system including nodes
         • can cause fillariases
       • eg Wuchereria bancrofti
       • stages of infection
         • mosquito takes a blood meal and L1 larvae enter skin
           • adult worm is in the lymphatics
             • adults produce sheathed microfillarae that reach the blood stream
               • microfilarae are the L1 larvae
                 • mosquito take a blood meal and ingest the L1 larvae
                   • microfillarae lose sheaths and penetrate mosquitos midgut
                     • from here they migrate to the thoracic muscle
                       • here the larvae develop from stage 1 to L3
                         • they then migrate to the head and mosquitos proboscis
                   • microfillarae presence in the blood stream is highest at night
               • the sheath is the eggshell
       • Wuchereria and Brugia fillarae are periodic: most present at night
     • subcutaneous fillariases
       • subcutaneous fat layer of the skin
       • eg Loa loa (African eye worm
     • serous cavity fillariases
       • serous cavity of the abdomen
       • eg Mansonella perstans