Filariasis

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    Filariases are helminthiases due to tissue-dwelling nematode worms (filariae). Human to human transmission takes place through the bite of an insect vector.

     

    The most important pathogens are outlined in the table below. Mixed infections are common in co-endemic regions.

     

    Each filarial species is found in 2 principal developmental stages: macrofilariae (adult worms) and microfilariae (larval offspring). The treatment depends on the pathogenic stage of the species considered and targets microfilariae for O. volvulus and macrofilariae for the other species.

     

    Species/Infections

    Location of
    macrofilariae

    Location of
    microfilariae

    Pathogenic
    stage

    Presence
    of
    Wolbachia

    Onchocerca volvulus
    (onchocerciasis)

    Subcutaneous nodules

    Skin and eye

    Microfilariae

    Yes

    Loa loa
    (loiasis)

    Subcutaneous tissue

    Blood

    Macrofilariae

    No

    Wuchereria bancrofti, Brugia malayi and Brugia timori
    (lymphatic filariasis)

    Lymph vessels

    Blood

    Macrofilariae

    Yes

     

    Classical antifilarial agents include diethylcarbamazine (DEC), ivermectin and albendazole. Doxycycline is used solely in the treatment of O. volvulus and lymphatic filarial worms, which harbour an endosymbiotic bacterium (Wolbachia) sensitive to doxycycline.