Filariasis

Filariasis is a filarial infection caused by parasitic nematodes (roundworms) belonging to the superfamily Filarioidea. The disease is classified among the neglected tropical diseases and encompasses multiple clinical syndromes depending on the infecting species. The most prevalent form is lymphatic filariasis, caused by three species of Filaria transmitted by mosquitoes. Other significant types include onchocerciasis (river blindness) caused by Onchocerca volvulus, loiasis caused by Loa loa, mansonelliasis caused by Mansonella species, and dirofilariasis caused by Dirofilaria species. Eight filarial worm species are known to use humans as definitive hosts.

The most characteristic manifestation of lymphatic filariasis is elephantiasis, characterized by edema with thickening of the skin and underlying tissues, resulting from parasite lodgment in the lymphatic system. Acute inflammatory episodes present as 5- to 7-day fevers accompanied by lymph node inflammation, often with epididymitis and spermatic cord involvement. Secondary bacterial infections are common and tend to be more severe in previously unexposed individuals than in native residents of endemic areas. Chronic filarial disease develops gradually over years of infection. Lymphatic filariasis remains the leading cause of permanent disfigurement and the second most common cause of long-term disability worldwide.

In 2000, approximately 199 million lymphatic filariasis infection cases were estimated globally, with 3.1 million cases in the Americas and around 107 million in Southeast Asia. The four countries of Bangladesh, India, Indonesia, and Myanmar accounted for approximately 52% of global cases. African nations comprised roughly 21% of cases, with some evidence of decreasing trends between 2000 and 2018. Despite regional declines, the global disease burden remains concentrated in Southeast Asia. Wuchereria bancrofti accounts for more than 90% of filarial infections worldwide.

Filariasis is transmitted through the bites of infected mosquitoes belonging to the genera Aedes, Culex, Anopheles, and Mansonia. The parasite life cycle involves humans as the definitive host and mosquitoes as intermediate hosts. Female worms are ovoviviparous and produce thousands of juvenile microfilariae in infected humans. When mosquitoes ingest blood meals, they take up microfilariae, which then mature and migrate to the insect proboscis for transmission to new human hosts during subsequent bites. Recent evidence suggests climate change may influence the spread of the disease and its vectors.

Source-backed detail on specific high-risk demographic groups is not yet available from the provided sources.

Prevention strategies focus on interrupting transmission through mass drug administration in endemic communities, combined with vector control measures targeting the mosquito vectors. The World Health Organization recommends community-wide treatment with antiparasitic medications to reduce transmission. Source-backed detail on specific preventive drug regimens is not yet available from the provided sources.

Surveillance relies on detecting microfilariae in peripheral blood using Giemsa-stained thin and thick blood film smears, with the finger prick test representing the standard diagnostic approach. Blood collection timing must correspond to the feeding activity patterns of the relevant vector species. For Wuchereria bancrofti, nighttime blood collection is preferred, while daytime collection is indicated for Loa loa due to its deer fly vector. The specificity of timing requirements reflects the nocturnal or diurnal periodicity of microfilariae in peripheral circulation.

1. 1 WHO Fact Sheet. Detail.
2. 2 WHO Q&A. News.
3. 3 Wikidata. filariasis.
4. 4 Wikipedia. Filariasis - Wikipedia.

ICD-10

B74

ICD-11

1F60

Total cases

3

Peak month

2011-08

Coverage

1 reporting countries · 2010-01-01 → 2026-04-01