Loa Loa cope by Dr. Nutman

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  • 1. 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

2. Loiasis Ogranism-Loa loa Vector - Chrysops spp. (deerfly) Microfilariae: Blood-borne Adult worms: subcutaneous Prevalence - ?3-13 million Geographic Distribution - West and CentralAfrica Host range - Human 3. Geographic distribution of loiasis 4. Lifecycle of Loa loa (EGG) L1 ADULTL4 L2L3 5. Loiasis - Clinical Manifestations Asymptomatic Non-specific urticaria, pruritus, myalgias Calabar swellings Eyeworm Complications Endomyocardial fibrosis, renal disease,encephalopathy, entrapment neuropathy 6. Loiasis Calabar Swellings Episodic angioedema Most common on extremities Duration -1-4 days 7. Parasite HostHyper- Responsive ResponsiveHypo-responsiveresponsive (appropriate)(inappropriate) (tolerant/suppressed)Unusual ImmunityPathology InfectedPathology 8. Loiasis: Diagnosis Definintive diagnosis Detection of microfilariae in daytime blood Identification of adult worm in thesubconjunctiva or subcutaneous tissue PCR using Loa loa repeat sequence Presumptive diagnosis Compatible clinical picture + positiveantifilarial antibodies Problematic due to geographical, serologic and clinical overlap with other filarial infections 9. Loiasis: extraction of adult worm 10. 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 11. Loiasis: adjunct therapy Corticosteroids decrease rate of microfilarial clearance reduce severity of post-treatment reactions DO NOT prevent severe CNS complications oftreatment in patients with high microfilarialload Apheresis transient reduction of microfilarial load ?decreased incidence of severe side effects 12. 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. 13. Loiasis and ivermectin Between 1989 and 1998, 76 million doses ofivermectin were distributed with 84 SAEsreported 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 (