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Loa loa filariasis is a skin and eye disease caused by the nematode worm Loa loa. Humans contract this disease through the bite of a deer fly or mango fly, the vectors for Loa loa.[1] The disease is treated with the drug diethylcarbamazine , and when appropriate, surgical methods may be employed to remove adult worms from the conjunctiva.[2]Loa loa parasites are located in west and central Africa, and about 14 (point) 4 million people live in these areas of high infection.[3]

Signs and symptoms

In terms of the presentation we find that most people are asymptomatic, however Calabar swellings can develop anywhere on the individuals body and last 1 to 3 days. Additionally, worms can also roam subconjunctivally across the eyes. [4]


Loa loa is a filaria nematode that causes Loa loa filariasis. Loa loa means "worm worm", but is commonly known as the eye worm, as it localizes to the conjunctiva of the eye.[5]

Life cycle

The vector for Loa loa filariasis originates with flies from two hematophagous species of the genus Chrysops , C. silacea and C. dimidiata. During a blood meal, an infected fly introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound. The larvae develop into adults that commonly reside in subcutaneous tissue.[6]


Microscopic examination of microfilariae is a practical diagnostic procedure to find Loa loa. It is important to time the blood collection with the known periodicity of the microfilariae. The blood sample can be a thick smear, stained with Giemsa or haematoxylin and eosin. For increased sensitivity, concentration techniques can be used. These include centrifugation of the blood sample lyzed in 2 percent formalin.[7][8]


Treatment of loiasis involves in some cases, surgical removal of adult worms followed by systemic treatment. The current drug of choice for therapy is diethylcarbamazine , though albendazole use while not curative can substantially reduce the microfilarial load. The recommended dosage of DEC is 8 to 10 milligrams taken three times daily for 21 days per CDC. The pediatric dose is the same.[9]


As of 2009, loiasis is endemic to 11 countries, all in western or central Africa, and an estimated 12 to 13 million people have the disease. The highest incidence is seen in Cameroon, Republic of the Congo, Democratic Republic of Congo, Central African Republic, Nigeria, Gabon, and Equatorial Guinea.[10]


  1. John, David T. and William A. Petri, Jr. Markell and Voge's Medical Parasitology. 9th ed. 2006.
  2. Metzger, Wolfram Gottfried; Mordmüller, Benjamin (April 2014). "Loa loa—does it deserve to be neglected?". The Lancet Infectious Diseases. 14 (4): 353–357. doi:10.1016/S1473-3099(13)70263-9. Archived from the original on 2021-03-31. Retrieved 2023-11-24.
  3. Prevention, CDC-Centers for Disease Control and (22 September 2021). "CDC - Loiasis - Epidemiology & Risk Factors".
  4. "Loiasis - Infectious Diseases". MSD Manual Professional Edition.
  5. Schmidt, Gerald et al. "Foundations of Parasitology". 7th ed. McGraw Hill, New York, NY, 2005.
  6. "CDC - DPDx - Loiasis". 15 April 2019. Retrieved 6 May 2024.
  7. Parasites – Loiasis, Archived 2022-03-07 at the Wayback Machine
  8. "CDC - DPDx - Diagnostic Procedures - Blood Specimens". 4 November 2020. Archived from the original on 1 September 2023. Retrieved 7 December 2023.
  9. "CDC - Loiasis - Resources for Health Professionals". 24 November 2020. Retrieved 7 May 2024.
  10. The Gideon Online Archived 2022-04-05 at the Wayback Machine.