Loa loa: A neglected NTDThomas B. Nutman, M.D.Head, Helminth Immunology Section andHead, Clinical Parasitology SectionLaboratory of Parasitic DiseasesNational Institute of Allergy and InfectiousDiseases
Loiasis• Ogranism-Loa loa• Vector - Chrysops spp. (deerfly)• Microfilariae: Blood-borne• Adult worms: subcutaneous• Prevalence - ?3-13 million• Geographic Distribution - West and Central Africa• Host range - Human
Loiasis: Diagnosis• Definintive diagnosis – Detection of microfilariae in daytime blood – Identification of adult worm in the subconjunctiva or subcutaneous tissue – PCR using Loa loa repeat sequence• Presumptive diagnosis – Compatible clinical picture + positive antifilarial antibodies • Problematic due to geographical, serologic and clinical overlap with other filarial infections
Loiasis: treatment• Diethylcarbamazine (DEC) – treatment of choice (8-10 mg/kg/d x 21 days) – mechanism of action unknown • immune system dependent • macro- and microfilaricidal – associated with severe side effects in patients with high levels of circulating microfilariae
Loiasis: adjunct therapy• Corticosteroids – decrease rate of microfilarial clearance – reduce severity of post-treatment reactions – DO NOT prevent severe CNS complications of treatment in patients with high microfilarial load• Apheresis – transient reduction of microfilarial load – ?decreased incidence of severe side effects
Loiasis response to therapyMedian years of follow-up: 4.5 years (range 2-15 years)Cure rates with DEC •1 course 38% (12/32) • 2 courses 54% (17/32) • ≥ 3 courses 90% (23/32)The remaining 3 patients were cured following a 3 weekcourse of albendazole. Klion A, Ottesen E, Nutman T. J Infect Dis. 1994 Mar;169(3):604-10.
Loiasis and ivermectin• Between 1989 and 1998, 76 million doses of ivermectin were distributed with 84 SAEs reported by passive surveillance (1 case/million) – 65/84 (75%) from Southern Cameroon – 37/65 (60%) were neurologic, 25% of which had high levels of Loa microfilaremia – the encephalopathy was temporally related to Mectizan™ (<5 d post-rx) and occurred in previously healthy individuals
Acknowledgements•Doran Fink • Past and present LPD•Amy Klion Clinical Staff•Peter Burbelo – LPD Clinical Fellows•Susan Leitman – Kate Spates•Jesica Christensen – Nicole Holland•Dan Fedorko – Amara Pabon•Gary Fahle – Melissa Law – Cheryl Talar-Williams