What are the Filarial Diseases?



oncho_map_2014Onchocerciasis (River Blindness)
Over 21 million infected
About 205 million people at risk
14.6 million people suffer from skin diseases
1.5 million people had vision loss




Loiasis – Loa loa
Nearly 30 million people at risk
About 13 million people infected





Onchocerciasis (River blindness) is almost exclusively confined to West and Central Africa where 31 countries are endemic, although there are localized infections in Yemen and some South American countries.

Loiasis (Loa loa infection) occurs in the rain forest and swamp areas of West Africa and in Central Africa where 10 countries are endemic.


Onchocerciasis (River blindness), Lymphatic filariasis (Elephantiasis) and Loiasis (Loa loa infection) are all caused by parasitic filarial nematode worms that are transmitted between humans by blood-sucking insects.

Onchocerciasis is caused by Onchocerca volvulus, transmitted by the bite of an infected female blackfly; Brugia malayi (most of the remainder) and Brugia timori, and is transmitted by various mosquito species; Loa loa worms are transmitted by the bites of Mango flies or by deer flies (Chrysops spp.).

Social and economic impact

Filarial diseases are the most devastating of the neglected tropical diseases in terms of social and economic impact. Families and communities have to bear the brunt of long-term healthcare, coupled with loss of productivity and earnings due to the incapacity to work. The disabling and disfiguring effects on the individual lead to social stigmatization and isolation.


Filarial disease is not particularly life-threatening, but onchocerciasis causes long-term suffering and chronic disease with life-long disabilities in millions of people worldwide, such as blindness, severe itching and dermatitis. Loiasis is usually considered asymptomatic but can cause localized swellings associated with localized and generalized itching.

Patient treatments needs

Programmes for the treatment and control of filarial diseases through mass drug administration (MDA) have been in place for over 20 years. However current treatments target the juvenile worm (microfilariae) and need to be repeated for 10-15 years in the case of onchocerciasis. Therefore, there is an unmet medical need for a drug that can kill the adult worms (macrofilaricide). A new, safe, short-course macrofilaricidal drug could be used in individual patient treatment and to help the elimination effort in MDA programmes and ideally also in patients with Loa loa co-infection.

DNDi aims to:

  • Deliver a safe, effective, affordable, and field-adapted drug that can kill adult filarial worms (a ‘macrofi laricide’) and be used for prevention or individual treatment.



Cover page filarial diseases factsheet

Filarial diseases factsheet

Disease brief

River blindness: Putting patient needs first
Developing a short-course treatment for onchocerciasis

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Visual patient story

Revealing the neglect: River blindness
Akoyo’s story