Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 35-34: Loiasis + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ Subcutaneous swellings; adult worms migrating across the eye Encephalitis, which may be brought on by treatment Microfilariae in the blood +++ General Considerations ++ This chronic filarial disease is caused by infection with Loa loa Transmitted by chrysops flies, which bite during the day Over 6–12 months after infection, larvae develop into adult worms, which migrate through subcutaneous tissues, including the subconjunctiva (leading to the term "eye worm") Adults can live for up to 17 years +++ Demographics ++ The infection occurs in humans and monkeys in rainforest areas of West and central Africa An estimated 3–13 million persons are infected + Clinical Findings Download Section PDF Listen +++ +++ Symptoms and Signs ++ Many infected persons are asymptomatic, but they may have high levels of microfilaremia and eosinophilia Transient subcutaneous swellings (Calabar swellings) Develop in symptomatic persons Are nonerythematous, up to 20 cm in diameter May be preceded by local pain or pruritus Usually resolve after 2–4 days but occasionally persist for several weeks Commonly seen around joints and may recur at the same or different sites Visitors from nonendemic areas are more likely to have allergic-type reactions, including pruritus, urticaria, and angioedema Adult worms may be seen migrating across the eye, with either no symptoms or conjunctivitis with pain and edema +++ Differential Diagnosis ++ Dracunculiasis Cutaneous larva migrans Gnathostomiasis Myiasis Filariasis Onchocerciasis (river blindness) Bacterial pyoderma Cysticercosis (with ophthalmic involvement) + Diagnosis Download Section PDF Listen +++ +++ Laboratory Tests ++ Obtain blood samples during the day to identify microfilariae in blood Failure to find microfilariae does not rule out the diagnosis Identification of a migrating eye worm is also diagnostic Serologic tests May be helpful in persons from nonendemic areas who may be acutely ill without detectable microfilaremia However, usefulness for residents of endemic areas is limited because most of them will have positive results Molecular methods, including field-friendly LAMP assays, are available to rule out loiasis before administration of ivermectin for the control of other filarial infections + Treatment Download Section PDF Listen +++ +++ Medications ++ Diethylcarbamazine Treatment of choice Eliminates microfilariae and has some activity against adult worms Dosage: 8–10 mg/kg/day for 21 days Repeat courses may be needed Mild side effects include fever, pruritus, arthralgias, nausea, diarrhea, and Calabar swellings Coadministration of antihistamines or corticosteroids can lessen side effects Ivermectin Highly active against microfilariae but not adult worms Entails a high risk of severe reactions To reduce the risk, pretreatment with corticosteroids and antihistamines and escalating dosage of diethylcarbamazine have been used, but this strategy does not prevent encephalitis Strategies to treat patients with high parasite loads include No treatment Apheresis, if available, to remove microfilariae prior to therapy with diethylcarbamazine Therapy with albendazole, which appears to be well tolerated due to its slow antiparasitic effects, prior to therapy with diethylcarbamazine or ivermectin + Outcome Download Section PDF Listen +++ +++ Complications ++ Encephalitis Most serious complication Most common in persons with high level microfilaremia and microfilariae in the cerebrospinal fluid May be triggered by treatment with diethylcarbamazine or ivermectin Symptoms may range from headache and insomnia to coma and death Other complications Kidney disease, with hematuria and proteinuria Endomyocardial fibrosis Peripheral neuropathy Patients with large worm burdens are at greater risk for serious complications of diethylcarbamazine therapy, including Kidney injury Shock Encephalitis Coma Death + References Download Section PDF Listen +++ + +Kamgno J et al. A test-and-not-treat strategy for onchocerciasis in Loa loa-endemic areas. N Engl J Med. 2017 Nov 23;377(21):2044–52. [PubMed: 29116890] + +Kamgno J et al. Effect of two or six doses 800 mg of albendazole every two months on Loa loa microfilaraemia: a double blind, randomized, placebo-controlled trial. PLoS Negl Trop Dis. 2016 Mar 11;10(3):3e. [PubMed: 26967331]