0521779407-07 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:10
572 Filariasis■Onchocerca volvulus (causes onchocerciasis, or “river blindness”),
transmitted by Simulium flies (black flies). Found in tropical Africa,
Guatemala, Ecuador, Venezuela.Signs & Symptoms
■Lymphatic filariasis: Many patients have no symptoms
➣Recurrent lymphadenitis with retrograde lymphangitis, gener-
ally from groin down thigh or to scrotum, or from axillary nodes
down arm
➣Hydrocele
➣In late stages, chronic edema of leg, arm or scrotum, chyluria
■Loa loa: early stage (usually seen in expatriates): arthralgias, myal-
gias, mild fatigue, urticaria or other migratory rash, recurrent edema-
tous non-tender swellings on extremities (Calabar swellings), migra-
tion of worm across conjunctiva or eyelid, or found in small removed
nodule
■Late, chronic stage: same as above but with less arthralgia, myal-
gia, and fatigue. In Africans with chronic infections, symptoms are
mainly migrating worms and Calabar swellings.
■Onchocerciasis: light infections: no symptoms
■Moderate to heavy infections: varying degrees of rash, pruritus, nod-
ules around pelvic girdle and waist (in Africa) or head and neck (W.
Hemisphere), keratitis, anterior (and later posterior) uveitis. Later
one sees blindness (corneal scarring), enlarged inguinal nodes, and
loss of elasticity of skin.tests
■Basic tests: blood: CBC shows eosinophilia, often high, in all clinical
types.
■Basic tests: urine: may see microfilaria in all clinical types
■Specific tests:
■Lymphatic filariasis: Draw blood sample at 11–12 PM. Either run
5cc through micropore filter to see microfilariae, or mix with forma-
lin, spin and examine for microfilariae (Knott concentration test).
Somewhat more sensitive is the ICT Filariasis Card Test (from ICI
Diagnostics), which detects W. bancrofti antigen in serum by mon-
oclonal antibody.
Circulating filarial antigen (CFA) test available for W. bancrofti
only; advantage: no diurnal variability