Filariasis


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.